import { useState, useRef, useEffect, useMemo, useCallback } from "react";
import _ from "lodash";
import { toast } from "react-toastify";
import {
  useLazyQuery,
  useMutation,
  useQuery,
  useReactiveVar,
} from "@apollo/client";
import { useLocation, useNavigate } from "react-router-dom";
import {
  FileText,
  MessageSquare,
  Table,
  Factory,
  Brain,
  Settings,
  ArrowLeft,
  ChevronLeft,
  ChevronRight,
  Trophy,
  BarChart3,
  MoreVertical,
  Link2,
} from "lucide-react";
import { OS_LEGAL_COLORS } from "../assets/configurations/osLegalStyles";
import { motion, AnimatePresence } from "framer-motion";

import { ConfirmModal } from "../components/widgets/modals/ConfirmModal";
import { CreateExtractModal } from "../components/widgets/modals/CreateExtractModal";
import {
  CreateAndSearchBar,
  DropdownActionProps,
} from "../components/layout/CreateAndSearchBar";
import { CardLayout } from "../components/layout/CardLayout";
import {
  CorpusModal,
  CorpusFormData,
} from "../components/corpuses/CorpusModal";
import { CorpusListView } from "../components/corpuses/CorpusListView";

import {
  openedCorpus,
  selectedDocumentIds,
  corpusSearchTerm,
  deletingCorpus,
  showRemoveDocsFromCorpusModal,
  editingCorpus,
  viewingCorpus,
  documentSearchTerm,
  userObj,
  annotationContentSearchTerm,
  openedDocument,
  selectedMetaAnnotationId,
  filterToLabelId,
  analysisSearchTerm,
  exportingCorpus,
  showSelectCorpusAnalyzerOrFieldsetModal,
  selectedTab,
  selectedThreadId,
  corpusPowerUserMode,
  showCreateExtractModal,
  showImportCorpusModal,
  backendUserObj,
} from "../graphql/cache";
import { updateTabParam, updateModeParam } from "../utils/navigationUtils";
import {
  UPDATE_CORPUS,
  UpdateCorpusOutputs,
  UpdateCorpusInputs,
  CREATE_CORPUS,
  CreateCorpusOutputs,
  CreateCorpusInputs,
  DELETE_CORPUS,
  DeleteCorpusOutputs,
  DeleteCorpusInputs,
  REMOVE_DOCUMENTS_FROM_CORPUS,
  RemoveDocumentsFromCorpusOutputs,
  RemoveDocumentsFromCorpusInputs,
} from "../graphql/mutations";
import {
  GetCorpusesInputs,
  GetCorpusesOutputs,
  GetCorpusMetadataInputs,
  GetCorpusMetadataOutputs,
  GET_CORPUSES,
  GET_CORPUS_METADATA,
  GET_CORPUS_STATS,
  GET_CORPUS_FILTER_COUNTS,
  GetCorpusFilterCountsInputs,
  GetCorpusFilterCountsOutputs,
  RequestDocumentsInputs,
  RequestDocumentsOutputs,
  GET_DOCUMENTS,
} from "../graphql/queries";
import { CorpusType, LabelType } from "../types/graphql-api";
import { LooseObject, PermissionTypes } from "../components/types";
import { FilterToLabelSelector } from "../components/widgets/model-filters/FilterToLabelSelector";
import { ensureValidCorpusId } from "../utils/graphqlGuards";
import { CorpusAnnotationCards } from "../components/annotations/CorpusAnnotationCards";
import { CorpusDocumentCards } from "../components/documents/CorpusDocumentCards";
import {
  FolderDocumentBrowser,
  ViewMode,
} from "../components/corpuses/folders/FolderDocumentBrowser";
import { CorpusAnalysesCards } from "../components/analyses/CorpusAnalysesCards";
import { FilterToAnalysesSelector } from "../components/widgets/model-filters/FilterToAnalysesSelector";
import useWindowDimensions from "../components/hooks/WindowDimensionHook";
import { SelectExportTypeModal } from "../components/widgets/modals/SelectExportTypeModal";
import { ImportCorpusModal } from "../components/widgets/modals/ImportCorpusModal";
import { FilterToCorpusActionOutputs } from "../components/widgets/model-filters/FilterToCorpusActionOutputs";
import { getPermissions } from "../utils/transform";
import {
  MOBILE_VIEW_BREAKPOINT,
  DEBOUNCE,
} from "../assets/configurations/constants";
import { useEnv } from "../components/hooks/UseEnv";
import { CorpusDashboard } from "../components/corpuses/CorpusDashboard";
import { useCorpusState } from "../components/annotator/context/CorpusAtom";
import { CorpusSettings } from "../components/corpuses/CorpusSettings";
import { CorpusChat } from "../components/corpuses/CorpusChat";
import { ChatMessageSource } from "../components/annotator/context/ChatSourceAtom";
import {
  encodeTextBlock,
  textBlockFromSpan,
  textBlockFromTokensByPage,
} from "../utils/textBlockEncoding";
import { buildQueryParams } from "../utils/navigationUtils";
import { toGlobalId } from "../utils/idValidation";
import { CorpusDescriptionEditor } from "../components/corpuses/CorpusDescriptionEditor";
import { CamlArticleEditor } from "../components/corpuses/CamlArticleEditor";
import { CorpusDiscussionsView } from "../components/discussions/CorpusDiscussionsView";
import { BadgeManagement } from "../components/badges/BadgeManagement";
import { CorpusEngagementDashboard } from "../components/analytics/CorpusEngagementDashboard";
import { CorpusDocumentRelationships } from "../components/corpuses/CorpusDocumentRelationships";
import { CorpusQueryView } from "./CorpusQueryView";
import { ExtractsTabContent } from "./ExtractsTabContent";
import {
  BackNavButton,
  BottomSheetHandle,
  CleanViewContainer,
  CollapsedBadge,
  CorpusViewContainer,
  ExitPowerUserWrapper,
  MainContentArea,
  MobileBackButton,
  MobileKebabButton,
  MobileMenuBackdrop,
  NavigationHeader,
  NavigationItem,
  NavigationItems,
  NavigationSidebar,
  NavigationToggle,
  NavItemBadge,
  SearchBarContainer,
  SearchBarWithNav,
  TabNavigationHeader,
  TabTitle,
} from "./Corpuses.styles";

export const Corpuses = () => {
  const { width } = useWindowDimensions();

  const use_mobile_layout = width <= MOBILE_VIEW_BREAKPOINT;

  const show_remove_docs_from_corpus_modal = useReactiveVar(
    showRemoveDocsFromCorpusModal
  );
  const selected_metadata_id_to_filter_on = useReactiveVar(
    selectedMetaAnnotationId
  );

  // CRITICAL: Only call useCorpusState ONCE to avoid infinite re-renders
  // Calling it multiple times creates new object references each time
  const corpusState = useCorpusState();
  const {
    setCorpus,
    canUpdateCorpus,
    myPermissions: corpusAtomPermissions,
  } = corpusState;

  const selected_document_ids = useReactiveVar(selectedDocumentIds);
  const document_search_term = useReactiveVar(documentSearchTerm);
  const corpus_search_term = useReactiveVar(corpusSearchTerm);
  const analysis_search_term = useReactiveVar(analysisSearchTerm);
  const deleting_corpus = useReactiveVar(deletingCorpus);
  const corpus_to_edit = useReactiveVar(editingCorpus);
  const corpus_to_view = useReactiveVar(viewingCorpus);
  const opened_corpus = useReactiveVar(openedCorpus);

  const exporting_corpus = useReactiveVar(exportingCorpus);
  const opened_document = useReactiveVar(openedDocument);
  const filter_to_label_id = useReactiveVar(filterToLabelId);

  const currentUser = useReactiveVar(userObj);
  const backendUser = useReactiveVar(backendUserObj);
  const annotation_search_term = useReactiveVar(annotationContentSearchTerm);
  const show_create_extract_modal = useReactiveVar(showCreateExtractModal);

  const location = useLocation();
  const navigate = useNavigate();

  const [show_multi_delete_confirm, setShowMultiDeleteConfirm] =
    useState<boolean>(false);
  const [show_new_corpus_modal, setShowNewCorpusModal] =
    useState<boolean>(false);
  // Tab state is now URL-driven via CentralRouteManager
  const urlTab = useReactiveVar(selectedTab);
  const [showDescriptionEditor, setShowDescriptionEditor] =
    useState<boolean>(false);
  const [showArticleEditor, setShowArticleEditor] = useState<boolean>(false);
  const [sidebarExpanded, setSidebarExpanded] = useState<boolean>(false); // Collapsed by default, opens on hover
  const [mobileSidebarOpen, setMobileSidebarOpen] = useState<boolean>(false);

  // Power user mode: URL-driven via CentralRouteManager (?mode=power)
  const isPowerUserMode = useReactiveVar(corpusPowerUserMode);
  const { REACT_APP_ALLOW_IMPORTS } = useEnv();

  const [corpusSearchCache, setCorpusSearchCache] =
    useState<string>(corpus_search_term);
  const [analysesSearchCache, setAnalysesSearchCache] =
    useState<string>(analysis_search_term);
  const [documentSearchCache, setDocumentSearchCache] =
    useState<string>(document_search_term);
  const [annotationSearchCache, setAnnotationSearchCache] = useState<string>(
    annotation_search_term
  );

  // View mode state for the Documents tab
  const [documentsViewMode, setDocumentsViewMode] =
    useState<ViewMode>("modern-list");

  // Active tab on the Corpuses list view ("all" | "my" | "shared" | "public").
  // Lifted up here so it can drive the GET_CORPUSES query variables — the
  // server applies the tab filter and counts so pagination + badges stay
  // accurate regardless of how many pages have been loaded.
  const [corpusListActiveFilter, setCorpusListActiveFilter] =
    useState<string>("all");

  // Track whether CorpusChat is showing a conversation (vs the list view)
  // Used to hide parent navigation header when CorpusChat handles its own
  const [chatInConversation, setChatInConversation] = useState<boolean>(false);

  // Derive whether the discussions tab is showing a thread detail from URL state.
  // The ?thread= param is synced to selectedThreadId by CentralRouteManager.
  const currentSelectedThreadId = useReactiveVar(selectedThreadId);
  const discussionInThreadView = currentSelectedThreadId !== null;

  /**
   * Navigate to a source document with text block highlighting.
   * Called from CorpusChat when a user clicks a source citation.
   * Builds a deep link URL with ?tb= param and navigates to the document.
   *
   * Each silent-return path emits a console.warn so a user reporting "the
   * source link doesn't work" can immediately see which guard is firing in
   * DevTools instead of nothing happening on click.
   */
  const handleSourceNavigate = useCallback(
    (source: ChatMessageSource) => {
      if (!source.document_id) {
        console.warn(
          "[handleSourceNavigate] No-op: source has no document_id; backend payload may be missing it.",
          source
        );
        return;
      }
      if (!opened_corpus) {
        console.warn(
          "[handleSourceNavigate] No-op: opened_corpus is null; route resolution did not populate the openedCorpus reactive var."
        );
        return;
      }

      // Validate corpus has slug data. This should always be present when
      // viewing a corpus (resolved from a slug-based URL by CentralRouteManager).
      // Falling back to opened_corpus.id (a Relay global ID) would produce an
      // unresolvable URL like /d/user/Q29ycHVzVHlwZTo1/... that 404s.
      if (!opened_corpus.slug || !opened_corpus.creator?.slug) {
        console.warn(
          "[handleSourceNavigate] No-op: corpus missing slug data; cannot build canonical /d/<user-slug>/<corpus-slug>/<doc> URL.",
          {
            corpusSlug: opened_corpus.slug,
            creatorSlug: opened_corpus.creator?.slug,
            corpusId: opened_corpus.id,
          }
        );
        return;
      }

      // Build the text block encoding from source data.
      let textBlock: string | null = null;
      if (
        source.isTextBased &&
        typeof source.startIndex === "number" &&
        typeof source.endIndex === "number"
      ) {
        textBlock = encodeTextBlock(
          textBlockFromSpan(source.startIndex, source.endIndex)
        );
      } else if (
        source.tokensByPage &&
        Object.keys(source.tokensByPage).length > 0
      ) {
        textBlock = encodeTextBlock(
          textBlockFromTokensByPage(source.tokensByPage)
        );
      }

      // Build the navigation URL. We only have the document's raw DB id from
      // the WebSocket source, not its slug, so we use a Relay global ID for
      // the document segment. CentralRouteManager Phase 1 detects this as a
      // GraphQL ID and resolves it via resolveDocumentById, then redirects to
      // the canonical slug URL. The corpus segment uses validated slugs from
      // the already-resolved corpus.
      const docGraphQLId = toGlobalId("DocumentType", source.document_id);

      // Prefer the precise text-block highlight when we have one. If the
      // text-block could not be built (most often a PDF source whose multipage
      // annotation_json has page keys but empty tokensJsons arrays — we have
      // the annotation but not the per-token indices), fall back to selecting
      // the annotation by its global ID via the existing ?ann= URL convention.
      // Synthetic search-result annotations use negative IDs (see
      // search.py); those are not real Annotation rows, so skip the ?ann=
      // fallback and at least navigate to the document without a highlight
      // rather than silently doing nothing.
      const hasRealAnnotationId =
        typeof source.annotation_id === "number" && source.annotation_id > 0;

      let queryString: string;
      if (textBlock) {
        queryString = buildQueryParams({ textBlock });
      } else if (hasRealAnnotationId) {
        const annGlobalId = toGlobalId("AnnotationType", source.annotation_id);
        queryString = buildQueryParams({ annotationIds: [annGlobalId] });
        console.debug(
          "[handleSourceNavigate] No text-block reference available; falling back to ?ann= deep-link.",
          { annotationId: source.annotation_id, annGlobalId }
        );
      } else {
        // Last-ditch: open the document with no highlight rather than no-op.
        queryString = "";
        console.warn(
          "[handleSourceNavigate] No text-block AND no real annotation_id; navigating to document without a highlight.",
          {
            isTextBased: source.isTextBased,
            startIndex: source.startIndex,
            endIndex: source.endIndex,
            tokensByPageCounts: source.tokensByPage
              ? Object.fromEntries(
                  Object.entries(source.tokensByPage).map(([page, tokens]) => [
                    page,
                    tokens.length,
                  ])
                )
              : {},
            annotationId: source.annotation_id,
          }
        );
      }

      const targetUrl = `/d/${opened_corpus.creator.slug}/${opened_corpus.slug}/${docGraphQLId}${queryString}`;

      console.debug("[handleSourceNavigate] Navigating to source:", {
        targetUrl,
        documentId: source.document_id,
        annotationId: source.annotation_id,
      });

      navigate(targetUrl);
    },
    [opened_corpus, navigate]
  );

  const handleViewModeChange = useCallback((mode: ViewMode) => {
    setDocumentsViewMode(mode);
  }, []);

  const opened_corpus_id = opened_corpus?.id ? opened_corpus.id : null;
  const corpus_exit_path = opened_corpus?.isPersonal
    ? "/documents"
    : "/corpuses";
  const corpus_exit_label = opened_corpus?.isPersonal
    ? "Documents"
    : "Corpuses";
  let raw_permissions = opened_corpus?.myPermissions;
  if (opened_corpus && raw_permissions !== undefined) {
    raw_permissions = getPermissions(raw_permissions);
  }

  /**
   * Set up the debounced search handling for the two SearchBars (Corpus search is rendered first by this component,
   * but it will switch to doc search if you select a corpus, as this will navigate to show the corpus' docs)
   */
  const debouncedCorpusSearch = useRef(
    _.debounce((searchTerm) => {
      corpusSearchTerm(searchTerm);
    }, DEBOUNCE.SEARCH_MS)
  );

  const debouncedDocumentSearch = useRef(
    _.debounce((searchTerm) => {
      documentSearchTerm(searchTerm);
    }, DEBOUNCE.SEARCH_MS)
  );

  const debouncedAnnotationSearch = useRef(
    _.debounce((searchTerm) => {
      annotationContentSearchTerm(searchTerm);
    }, DEBOUNCE.SEARCH_MS)
  );

  const debouncedAnalysisSearch = useRef(
    _.debounce((searchTerm) => {
      analysisSearchTerm(searchTerm);
    }, DEBOUNCE.SEARCH_MS)
  );

  const handleCorpusSearchChange = (value: string) => {
    setCorpusSearchCache(value);
    debouncedCorpusSearch.current(value);
  };

  const handleDocumentSearchChange = (value: string) => {
    setDocumentSearchCache(value);
    debouncedDocumentSearch.current(value);
  };

  const handleAnnotationSearchChange = (value: string) => {
    setAnnotationSearchCache(value);
    debouncedAnnotationSearch.current(value);
  };

  const handleAnalysisSearchChange = (value: string) => {
    setAnalysesSearchCache(value);
    debouncedAnalysisSearch.current(value);
  };

  // Check for ?create=true query param to open the create corpus modal
  // This allows linking directly to corpus creation from other pages (e.g., Discover page)
  useEffect(() => {
    const searchParams = new URLSearchParams(location.search);
    if (searchParams.get("create") === "true") {
      setShowNewCorpusModal(true);
      // Strip the trigger param via React Router so the routing system stays
      // in sync (avoids bypassing CentralRouteManager's URL observer).
      searchParams.delete("create");
      const remaining = searchParams.toString();
      navigate(
        {
          pathname: location.pathname,
          search: remaining ? `?${remaining}` : "",
        },
        { replace: true }
      );
    }
  }, [location.search, location.pathname, navigate]);

  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  // Query to get corpuses
  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  // CRITICAL: Memoize corpus_variables to prevent infinite re-renders
  // Creating new object on every render causes Apollo to refetch → cache update → re-render → new object → LOOP
  const corpus_variables = useMemo<GetCorpusesInputs>(() => {
    const vars: GetCorpusesInputs = {};
    if (corpus_search_term) {
      vars.textSearch = corpus_search_term;
    }
    // Map active tab to backend filter args. Only one tab flag at a time —
    // "all" sends no flag so the server returns the full visible set.
    if (corpusListActiveFilter === "my") {
      vars.mine = true;
    } else if (corpusListActiveFilter === "shared") {
      vars.sharedWithMe = true;
    } else if (corpusListActiveFilter === "public") {
      vars.isPublic = true;
    }
    return vars;
  }, [corpus_search_term, corpusListActiveFilter]);

  // Now that auth is guaranteed to be ready before this component renders,
  // we can use a regular useQuery
  const {
    refetch: refetchCorpuses,
    loading: loading_corpuses,
    networkStatus: corpus_network_status,
    error: corpus_load_error,
    data: corpus_response,
    fetchMore: fetchMoreCorpusesOrig,
  } = useQuery<GetCorpusesOutputs, GetCorpusesInputs>(GET_CORPUSES, {
    variables: corpus_variables,
    // CHANGED from "network-only" to "cache-and-network" to prevent infinite refetch loops
    // "network-only" bypasses cache and refetches on EVERY render, causing infinite loops
    // "cache-and-network" uses cache immediately and fetches in background for updates
    fetchPolicy: "cache-and-network",
    notifyOnNetworkStatusChange: true, // required to get loading signal on fetchMore
  });

  // Tab counts for the Corpuses list view. Server-computed so they reflect
  // the user's actual visible set (and the current text search) without
  // needing every page paginated in.
  const corpus_filter_counts_variables = useMemo<GetCorpusFilterCountsInputs>(
    () => (corpus_search_term ? { textSearch: corpus_search_term } : {}),
    [corpus_search_term]
  );
  const {
    data: corpus_filter_counts_data,
    refetch: refetchCorpusFilterCounts,
  } = useQuery<GetCorpusFilterCountsOutputs, GetCorpusFilterCountsInputs>(
    GET_CORPUS_FILTER_COUNTS,
    {
      variables: corpus_filter_counts_variables,
      fetchPolicy: "cache-and-network",
    }
  );
  const corpus_filter_counts =
    corpus_filter_counts_data?.corpusFilterCounts ?? {
      all: 0,
      mine: 0,
      shared: 0,
      public: 0,
    };

  /* --------------------------------------------------------------------------------------------------
   * Entity resolution is now handled by CentralRouteManager
   * - When user navigates to /c/:user/:corpus → CentralRouteManager fetches and sets openedCorpus
   * - This component just reads openedCorpus reactive var and displays appropriate view
   * -------------------------------------------------------------------------------------------------- */

  if (corpus_load_error) {
    toast.error("ERROR\nUnable to fetch corpuses.");
  }

  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  // Query to get Metadata for Selected Corpus
  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  const [
    fetchMetadata,
    {
      called: metadata_called,
      loading: metadata_loading,
      data: metadata_data,
      refetch: refetchMetadata,
    },
  ] = useLazyQuery<GetCorpusMetadataOutputs, GetCorpusMetadataInputs>(
    GET_CORPUS_METADATA
  );

  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  // Query to refetch documents if dropdown action is used to delink a doc from corpus
  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  const [
    fetchDocumentsLazily,
    { error: documents_error, refetch: refetch_documents },
  ] = useLazyQuery<RequestDocumentsOutputs, RequestDocumentsInputs>(
    GET_DOCUMENTS,
    {
      variables: {
        ...(opened_corpus_id
          ? {
              annotateDocLabels: true,
              includeMetadata: true,
              inCorpusWithId: opened_corpus_id,
              includeCaml: true,
            }
          : { annotateDocLabels: false, includeMetadata: false }),
        ...(filter_to_label_id ? { hasLabelWithId: filter_to_label_id } : {}),
        ...(selected_metadata_id_to_filter_on
          ? { hasAnnotationsWithIds: selected_metadata_id_to_filter_on }
          : {}),
        ...(document_search_term ? { textSearch: document_search_term } : {}),
      },
      notifyOnNetworkStatusChange: true, // necessary in order to trigger loading signal on fetchMore
    }
  );
  if (documents_error) {
    toast.error("ERROR\nCould not fetch documents for corpus.");
  }

  useEffect(() => {
    // console.log("Corpuses.tsx - Loading Corpuses changed...");
  }, [loading_corpuses]);

  const fetchMoreCorpuses = (args: any) => {
    // console.log("Corpuses.txt - fetchMoreCorpuses()");
    fetchMoreCorpusesOrig(args);
  };

  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  // Effects to reload data on certain changes
  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  // Handle metadata refetch when auth changes and corpus is open
  useEffect(() => {
    if (currentUser && metadata_called && opened_corpus?.id) {
      // Only refetch if we have previously called the query successfully
      if (metadata_data || metadata_loading) {
        refetchMetadata();
      } else {
        // Re-fetch with current corpus ID if we haven't fetched before
        const { id: validId, isValid } = ensureValidCorpusId(opened_corpus);
        if (isValid && validId) {
          fetchMetadata({ variables: { metadataForCorpusId: validId } });
        }
      }
    }
  }, [currentUser]); // Re-run when user changes

  // Search term effect - needed because fetchPolicy is "network-only"
  useEffect(() => {
    refetchCorpuses();
  }, [corpus_search_term]);

  // REMOVED: location-based refetch - was hammering server on every navigation
  // Component already refetches on mount and when search term changes

  // Sync opened_corpus to CorpusAtom and fetch metadata when corpus selected
  // CRITICAL: Use stable ID as dependency to avoid infinite loops
  // Apollo reactive vars return new object references even when data unchanged
  const openedCorpusId = opened_corpus?.id;

  useEffect(() => {
    if (opened_corpus) {
      const corpus_permissions = getPermissions(opened_corpus.myPermissions);
      setCorpus({
        selectedCorpus: opened_corpus,
        myPermissions: corpus_permissions,
      });

      // Fetch metadata when corpus is selected
      const { id: validId, isValid } = ensureValidCorpusId(opened_corpus);
      if (isValid && validId) {
        try {
          fetchMetadata({ variables: { metadataForCorpusId: validId } });
          refetchStats(); // Refresh stats when corpus changes
        } catch (error) {
          console.error("Error fetching corpus metadata:", error);
        }
      } else {
        console.warn(
          "Skipping metadata fetch - invalid corpus ID:",
          opened_corpus.id
        );
      }
    } else {
      setCorpus({
        selectedCorpus: opened_corpus,
        myPermissions: [],
      });
    }
    // REMOVED: refetchCorpuses on opened_corpus null - unnecessary, query already has data
  }, [openedCorpusId]); // Only depend on ID, not full object

  // Update CorpusAtom when metadata is fetched
  // IMPORTANT: Only depend on corpus ID, not the whole object, to avoid infinite loops
  // GraphQL returns new object references on every render even if data unchanged
  const metadataCorpusId = metadata_data?.corpus?.id;

  useEffect(() => {
    if (metadata_data?.corpus && metadataCorpusId) {
      const corpus = metadata_data.corpus;
      const corpus_permissions = getPermissions(corpus.myPermissions || []);
      setCorpus({
        selectedCorpus: corpus,
        myPermissions: corpus_permissions,
      });
    }
  }, [metadataCorpusId]); // Only depend on ID, not the full object

  // NOTE: A previous version of this effect called ``refetch_documents()``
  // whenever ``selected_metadata_id_to_filter_on`` changed. ``refetch_documents``
  // is the ``refetch`` of a ``useLazyQuery`` that fires the query *immediately*
  // — including on mount, when the dependency starts as ``undefined``. That
  // produced a duplicate ``GET_DOCUMENTS`` network call on every corpus open
  // (with no ``inFolderId``), racing against the per-folder ``GET_DOCUMENTS``
  // already issued by ``CorpusDocumentCards``. The list there is authoritative
  // and re-runs on its own when ``selected_metadata_id_to_filter_on`` changes
  // (its variables include ``hasAnnotationsWithIds``), so this effect is
  // redundant — and the duplicate response merging into the same cache nodes
  // was contributing to the document-list reload loop.

  // Fetch corpus stats - with proper ID validation
  // Handle both string and number IDs, convert to string for GraphQL
  const validCorpusId = opened_corpus?.id
    ? String(opened_corpus.id)
    : undefined;

  const {
    data: statsData,
    loading: statsLoading,
    error: statsError,
    refetch: refetchStats,
  } = useQuery(GET_CORPUS_STATS, {
    variables: { corpusId: validCorpusId || "" }, // Provide empty string as fallback
    skip: !validCorpusId, // Skip if we don't have a valid ID
    // REMOVED pollInterval - was hammering server every 5 seconds
    // Stats are not real-time critical and will update when corpus changes
  });

  // Log stats errors for debugging
  useEffect(() => {
    if (statsError) {
      console.error("Error fetching corpus stats:", statsError);
    }
  }, [statsError]);

  // CRITICAL: Memoize stats object to prevent new object reference on every render
  // New object reference would cause navigationItems useMemo to re-run infinitely
  // Depend on primitive values, not the object itself, as Apollo returns new object refs
  const stats = useMemo(() => {
    return (
      statsData?.corpusStats || {
        totalDocs: 0,
        totalAnnotations: 0,
        totalAnalyses: 0,
        totalExtracts: 0,
        totalThreads: 0,
        totalChats: 0,
        totalRelationships: 0,
      }
    );
  }, [
    statsData?.corpusStats?.totalDocs,
    statsData?.corpusStats?.totalAnnotations,
    statsData?.corpusStats?.totalAnalyses,
    statsData?.corpusStats?.totalExtracts,
    statsData?.corpusStats?.totalThreads,
    statsData?.corpusStats?.totalChats,
    statsData?.corpusStats?.totalRelationships,
  ]);

  // When query is skipped (no valid corpus ID), treat as not loading
  const effectiveStatsLoading = validCorpusId ? statsLoading : false;

  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  // Query to shape item data
  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  const corpus_data = corpus_response?.corpuses?.edges
    ? corpus_response.corpuses.edges
    : [];
  const corpus_items = corpus_data
    .map((edge) => {
      if (!edge || !edge.node) return undefined;

      // Create a copy of the node
      const node = { ...edge.node };

      // Don't transform permissions here - let CorpusItem handle it
      // to avoid double transformation

      return node;
    })
    .filter((item): item is CorpusType => !!item);

  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  // Query to mutate corpus
  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  const [tryMutateCorpus, { loading: update_corpus_loading }] = useMutation<
    UpdateCorpusOutputs,
    UpdateCorpusInputs
  >(UPDATE_CORPUS, {
    onCompleted: (data) => {
      refetchCorpuses();
      refetchStats(); // Refresh stats after corpus update
      refetchCorpusFilterCounts();
      editingCorpus(null);
    },
  });

  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  // Query to delete corpus
  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  const [tryDeleteCorpus, { loading: delete_corpus_loading }] = useMutation<
    DeleteCorpusOutputs,
    DeleteCorpusInputs
  >(DELETE_CORPUS, {
    // Remove the deleted corpus from every cached connection (every tab,
    // every search term) so the list updates instantly without waiting on
    // the refetch round-trip.
    update: (cache, { data }, { variables }) => {
      if (!data?.deleteCorpus?.ok || !variables?.id) return;
      const cacheId = cache.identify({
        __typename: "CorpusType",
        id: variables.id,
      });
      if (cacheId) {
        cache.evict({ id: cacheId });
        cache.gc();
      }
    },
    onCompleted: () => {
      // cache.evict gives instant removal in every cached page; the refetch
      // is still load-bearing because deleting a corpus shifts every
      // server-side pagination cursor that comes after it, so subsequent
      // fetchMore calls would otherwise skip or duplicate items.
      refetchCorpuses();
      refetchCorpusFilterCounts();
    },
  });

  const [removeDocumentsFromCorpus, {}] = useMutation<
    RemoveDocumentsFromCorpusOutputs,
    RemoveDocumentsFromCorpusInputs
  >(REMOVE_DOCUMENTS_FROM_CORPUS, {
    onCompleted: () => {
      fetchDocumentsLazily();
      refetchStats(); // Refresh stats after removing documents
    },
  });

  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  // Query to delete corpus
  ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  const [tryCreateCorpus, { loading: create_corpus_loading }] = useMutation<
    CreateCorpusOutputs,
    CreateCorpusInputs
  >(CREATE_CORPUS, {
    onCompleted: (data) => {
      refetchCorpuses();
      refetchStats(); // Refresh stats after corpus creation
      refetchCorpusFilterCounts();
      setShowNewCorpusModal(false);
    },
  });

  // Handle corpus update with properly typed form data
  const handleUpdateCorpus = (formData: CorpusFormData) => {
    const variables: UpdateCorpusInputs = {
      id: formData.id!,
    };

    // Only include changed fields
    if (formData.title !== undefined) variables.title = formData.title;
    if (formData.description !== undefined)
      variables.description = formData.description;
    if (formData.slug !== undefined) variables.slug = formData.slug;
    if (formData.labelSet !== undefined)
      variables.labelSet = formData.labelSet ?? undefined;
    if (formData.preferredEmbedder !== undefined)
      variables.preferredEmbedder = formData.preferredEmbedder ?? undefined;
    if (formData.icon !== undefined && formData.icon !== null) {
      variables.icon = formData.icon;
    }
    if (formData.categories !== undefined) {
      variables.categories = formData.categories;
    }
    if (formData.license !== undefined) {
      variables.license = formData.license;
    }
    if (formData.licenseLink !== undefined) {
      variables.licenseLink = formData.licenseLink;
    }

    tryMutateCorpus({ variables });
  };

  const handleDeleteCorpus = (corpus_id: string | undefined) => {
    if (corpus_id) {
      // console.log("handleDeleteCorpus", corpus_id)
      tryDeleteCorpus({ variables: { id: corpus_id } })
        .then(({ data }) => {
          if (data?.deleteCorpus?.ok) {
            toast.success("SUCCESS! Deleted corpus.");
          } else {
            toast.error(
              data?.deleteCorpus?.message ?? "ERROR! Could not delete corpus."
            );
          }
        })
        .catch((err) => {
          toast.error("ERROR! Could not delete corpus.");
        });
    }
  };

  const handleRemoveContracts = (delete_ids: string[]) => {
    // console.log("handleRemoveContracts", delete_ids);
    removeDocumentsFromCorpus({
      variables: {
        corpusId: opened_corpus?.id ? opened_corpus.id : "",
        documentIdsToRemove: delete_ids,
      },
    })
      .then(() => {
        selectedDocumentIds([]);
        toast.success("SUCCESS! Contracts removed.");
      })
      .catch(() => {
        selectedDocumentIds([]);
        toast.error("ERROR! Contract removal failed.");
      });
  };

  // Handle corpus creation with properly typed form data
  const handleCreateNewCorpus = (formData: CorpusFormData) => {
    // Runtime validation for required fields
    if (!formData.title || !formData.description) {
      toast.error("Title and description are required");
      return;
    }

    const variables: CreateCorpusInputs = {
      title: formData.title,
      description: formData.description,
    };

    // Include optional fields if provided
    if (formData.labelSet) variables.labelSet = formData.labelSet;
    if (formData.preferredEmbedder)
      variables.preferredEmbedder = formData.preferredEmbedder;
    if (formData.icon) {
      variables.icon = formData.icon;
    }
    if (formData.categories && formData.categories.length > 0) {
      variables.categories = formData.categories;
    }
    // Create path: only send license fields when non-empty (server defaults apply).
    // Update path (above) uses !== undefined to allow sending empty strings to clear values.
    if (formData.license) {
      variables.license = formData.license;
    }
    if (formData.licenseLink) {
      variables.licenseLink = formData.licenseLink;
    }

    tryCreateCorpus({ variables })
      .then((data) => {
        if (data.data?.createCorpus.ok) {
          toast.success("SUCCESS. Created corpus.");
        } else {
          toast.error(`FAILED on server: ${data.data?.createCorpus.message}`);
        }
        refetchCorpuses();
        setShowNewCorpusModal(false);
      })
      .catch((err) => {
        toast.error("ERROR. Could not create corpus.");
      });
  };

  let corpus_actions: DropdownActionProps[] = [];
  if (currentUser) {
    corpus_actions = [
      ...corpus_actions,
      {
        icon: "plus",
        title: "Create Corpus",
        key: `Corpus_action_${0}`,
        color: "blue",
        action_function: () => setShowNewCorpusModal(true),
      },
    ];

    // Imports are gated by a global env kill-switch (used to disable for the
    // public demo) AND by the server-derived `canImportCorpus` permission on
    // the authenticated user. Mirrors the backend check in
    // UploadCorpusImportZip / ImportZipToCorpus.
    if (REACT_APP_ALLOW_IMPORTS && backendUser?.canImportCorpus) {
      corpus_actions.push({
        icon: "cloud upload",
        title: "Import Corpus",
        key: `Corpus_action_${1}`,
        color: "green",
        action_function: () => showImportCorpusModal(true),
      });
    }
  }

  let contract_actions: DropdownActionProps[] = [];
  if (selected_document_ids.length > 0 && currentUser) {
    contract_actions.push({
      icon: "remove circle",
      title: "Remove Contract(s)",
      key: `Corpus_action_${corpus_actions.length}`,
      color: "blue",
      action_function: () => setShowMultiDeleteConfirm(true),
    });
  }

  // Actions for analyzer pane (if user is signed in)
  if (
    currentUser &&
    raw_permissions?.includes(PermissionTypes.CAN_UPDATE) &&
    raw_permissions?.includes(PermissionTypes.CAN_READ)
  ) {
    corpus_actions.push({
      icon: "factory",
      title: "Start New Analysis",
      key: `Analysis_action_${corpus_actions.length}`,
      color: "blue",
      action_function: () => showSelectCorpusAnalyzerOrFieldsetModal(true),
    });
  }

  // NOTE: canUpdateCorpus and corpusAtomPermissions are already destructured above
  // Removed duplicate useCorpusState() call that was causing infinite re-renders

  // Tab IDs for URL-based navigation (order matches navigationItems array)
  const TAB_IDS = [
    "home",
    "documents",
    "annotations",
    "analyses",
    "extracts",
    "relationships",
    "discussions",
    "chats",
    "analytics",
    "settings",
    "badges",
  ] as const;

  // Helper to navigate to a tab by index or ID
  const setActiveTab = (tabIndexOrId: number | string) => {
    const tabId =
      typeof tabIndexOrId === "number" ? TAB_IDS[tabIndexOrId] : tabIndexOrId;
    // Use null for "home" to keep URLs clean (home is default)
    updateTabParam(location, navigate, tabId === "home" ? null : tabId);
    // Refresh stats on tab switch to ensure counts are up to date
    if (validCorpusId) {
      refetchStats();
    }
  };

  // Derive active tab index from URL
  const active_tab = useMemo(() => {
    if (!urlTab) return 0; // Default to home
    const index = TAB_IDS.indexOf(urlTab as (typeof TAB_IDS)[number]);
    if (index < 0) {
      console.warn(
        `[Corpuses] Invalid tab ID "${urlTab}" in URL, defaulting to home. Valid tabs: ${TAB_IDS.join(
          ", "
        )}`
      );
    }
    return index >= 0 ? index : 0;
  }, [urlTab]);

  // Navigation items configuration
  // Memoize to prevent recreating on every render
  const navigationItems = useMemo(() => {
    return [
      {
        id: "home",
        label: "Home",
        icon: <Brain />,
        component: (
          <CorpusQueryView
            opened_corpus={opened_corpus}
            setShowDescriptionEditor={setShowDescriptionEditor}
            setShowArticleEditor={setShowArticleEditor}
            onNavigate={(tabIndex) => setActiveTab(tabIndex)}
            onBack={() => navigate(corpus_exit_path)}
            navigateBackLabel={corpus_exit_label}
            canUpdate={canUpdateCorpus}
            stats={stats}
            statsLoading={effectiveStatsLoading}
            onOpenMobileMenu={() => setMobileSidebarOpen(true)}
            onSourceNavigate={handleSourceNavigate}
            isPowerUserMode={isPowerUserMode}
            onModeToggle={
              currentUser
                ? () =>
                    updateModeParam(
                      location,
                      navigate,
                      isPowerUserMode ? null : "power"
                    )
                : undefined
            }
          />
        ),
      },
      {
        id: "documents",
        label: "Documents",
        icon: <FileText />,
        badge: stats.totalDocs,
        component: (
          <div style={{ display: "flex", flexDirection: "column" }}>
            <TabNavigationHeader>
              <BackNavButton
                onClick={() => setActiveTab(0)}
                whileHover={{ scale: 1.05 }}
                whileTap={{ scale: 0.95 }}
                title="Back to Home"
              >
                <ArrowLeft />
              </BackNavButton>
              <TabTitle>Documents</TabTitle>
              <MobileKebabButton
                onClick={() => setMobileSidebarOpen(true)}
                aria-label="Open navigation menu"
              >
                <MoreVertical />
              </MobileKebabButton>
            </TabNavigationHeader>
            <div>
              {opened_corpus_id && (
                <FolderDocumentBrowser
                  corpusId={opened_corpus_id}
                  viewMode={documentsViewMode}
                  onViewModeChange={handleViewModeChange}
                >
                  <CorpusDocumentCards
                    opened_corpus_id={opened_corpus_id}
                    viewMode={documentsViewMode}
                    onOpenArticleEditor={() => setShowArticleEditor(true)}
                    canUpdate={canUpdateCorpus}
                  />
                </FolderDocumentBrowser>
              )}
            </div>
          </div>
        ),
      },
      {
        id: "annotations",
        label: "Annotations",
        icon: <MessageSquare />,
        badge: stats.totalAnnotations,
        component: (
          <div style={{ display: "flex", flexDirection: "column" }}>
            <TabNavigationHeader>
              <BackNavButton
                onClick={() => setActiveTab(0)}
                whileHover={{ scale: 1.05 }}
                whileTap={{ scale: 0.95 }}
                title="Back to Home"
              >
                <ArrowLeft />
              </BackNavButton>
              <TabTitle>Annotations</TabTitle>
              <MobileKebabButton
                onClick={() => setMobileSidebarOpen(true)}
                aria-label="Open navigation menu"
              >
                <MoreVertical />
              </MobileKebabButton>
            </TabNavigationHeader>
            <div>
              <CorpusAnnotationCards opened_corpus_id={opened_corpus_id} />
            </div>
          </div>
        ),
      },
      {
        id: "analyses",
        label: "Analyses",
        icon: <Factory />,
        badge: stats.totalAnalyses,
        component: (
          <div style={{ display: "flex", flexDirection: "column" }}>
            <TabNavigationHeader>
              <BackNavButton
                onClick={() => setActiveTab(0)}
                whileHover={{ scale: 1.05 }}
                whileTap={{ scale: 0.95 }}
                title="Back to Home"
              >
                <ArrowLeft />
              </BackNavButton>
              <TabTitle>Analyses</TabTitle>
              <MobileKebabButton
                onClick={() => setMobileSidebarOpen(true)}
                aria-label="Open navigation menu"
              >
                <MoreVertical />
              </MobileKebabButton>
            </TabNavigationHeader>
            <div>
              <CorpusAnalysesCards />
            </div>
          </div>
        ),
      },
      {
        id: "extracts",
        label: "Extracts",
        icon: <Table />,
        badge: stats.totalExtracts,
        component: (
          <ExtractsTabContent
            setActiveTab={setActiveTab}
            onOpenMobileMenu={() => setMobileSidebarOpen(true)}
          />
        ),
      },
      {
        id: "relationships",
        label: "Relationships",
        icon: <Link2 />,
        badge: stats.totalRelationships,
        component: opened_corpus?.id ? (
          <div style={{ display: "flex", flexDirection: "column" }}>
            <TabNavigationHeader>
              <BackNavButton
                onClick={() => setActiveTab(0)}
                whileHover={{ scale: 1.05 }}
                whileTap={{ scale: 0.95 }}
                title="Back to Home"
              >
                <ArrowLeft />
              </BackNavButton>
              <TabTitle>Document Relationships</TabTitle>
              <MobileKebabButton
                onClick={() => setMobileSidebarOpen(true)}
                aria-label="Open navigation menu"
              >
                <MoreVertical />
              </MobileKebabButton>
            </TabNavigationHeader>
            <div>
              <CorpusDocumentRelationships corpusId={opened_corpus.id} />
            </div>
          </div>
        ) : null,
      },
      {
        id: "discussions",
        label: "Discussions",
        icon: <MessageSquare />,
        badge: stats.totalThreads || 0,
        component: opened_corpus?.id ? (
          <div style={{ display: "flex", flexDirection: "column" }}>
            {/* Only show parent header when viewing thread list */}
            {/* When viewing inline thread detail, CorpusDiscussionsView handles its own */}
            {!discussionInThreadView && (
              <TabNavigationHeader>
                <BackNavButton
                  onClick={() => setActiveTab(0)}
                  whileHover={{ scale: 1.05 }}
                  whileTap={{ scale: 0.95 }}
                  title="Back to Home"
                >
                  <ArrowLeft />
                </BackNavButton>
                <TabTitle>Discussions</TabTitle>
                <MobileKebabButton
                  onClick={() => setMobileSidebarOpen(true)}
                  aria-label="Open navigation menu"
                >
                  <MoreVertical />
                </MobileKebabButton>
              </TabNavigationHeader>
            )}
            <div>
              <CorpusDiscussionsView corpusId={opened_corpus.id} hideHeader />
            </div>
          </div>
        ) : null,
      },
      {
        id: "chats",
        label: "Chats",
        icon: <Brain />,
        badge: stats.totalChats,
        component: opened_corpus?.id ? (
          // Bound the chat tab to viewport-minus-navbar so MessagesArea's
          // internal overflow-y:auto kicks in and the input stays pinned to
          // the bottom. The surrounding shell (root, CorpusViewContainer,
          // MainContentArea) all use min-height for natural document flow,
          // so without an explicit bound here the chat would expand to fit
          // every message instead of scrolling. CardLayout's outer padding
          // is zeroed above for this tab, so we don't have to subtract it.
          <div
            style={{
              display: "flex",
              flexDirection: "column",
              height:
                "calc(var(--oc-visible-viewport-height, 100vh) - var(--oc-navbar-height, 4.5rem))",
              maxHeight:
                "calc(var(--oc-visible-viewport-height, 100vh) - var(--oc-navbar-height, 4.5rem))",
              minHeight: 0,
              overflow: "hidden",
            }}
          >
            {/* Only show parent header when CorpusChat is in list view */}
            {/* When in conversation view, CorpusChat renders its own navigation */}
            {!chatInConversation && (
              <TabNavigationHeader>
                <BackNavButton
                  onClick={() => setActiveTab(0)}
                  whileHover={{ scale: 1.05 }}
                  whileTap={{ scale: 0.95 }}
                  title="Back to Home"
                >
                  <ArrowLeft />
                </BackNavButton>
                <TabTitle>Chat History</TabTitle>
                <MobileKebabButton
                  onClick={() => setMobileSidebarOpen(true)}
                  aria-label="Open navigation menu"
                >
                  <MoreVertical />
                </MobileKebabButton>
              </TabNavigationHeader>
            )}
            <div
              style={{
                flex: 1,
                minHeight: 0,
                display: "flex",
                flexDirection: "column",
              }}
            >
              <CorpusChat
                corpusId={opened_corpus.id}
                showLoad={true}
                onMessageSelect={() => {}}
                onSourceNavigate={handleSourceNavigate}
                setShowLoad={() => {}}
                onViewModeChange={setChatInConversation}
                onNavigateHome={() => setActiveTab(0)}
                // The chats tab's TabNavigationHeader (rendered above when in
                // list view) already provides Back navigation on every screen
                // size, so suppress the inner filter-bar Back to avoid the
                // duplicate-back-button UX bug.
                hideListBackButton
              />
            </div>
          </div>
        ) : null,
      },
      {
        id: "analytics",
        label: "Analytics",
        icon: <BarChart3 />,
        component: opened_corpus?.id ? (
          <CorpusEngagementDashboard corpusId={opened_corpus.id} />
        ) : null,
      },
      ...(opened_corpus && canUpdateCorpus
        ? [
            {
              id: "settings",
              label: "Settings",
              icon: <Settings />,
              component: opened_corpus?.title ? (
                <div style={{ display: "flex", flexDirection: "column" }}>
                  <TabNavigationHeader>
                    <BackNavButton
                      onClick={() => setActiveTab(0)}
                      whileHover={{ scale: 1.05 }}
                      whileTap={{ scale: 0.95 }}
                      title="Back to Home"
                    >
                      <ArrowLeft />
                    </BackNavButton>
                    <TabTitle>Settings</TabTitle>
                    <MobileKebabButton
                      onClick={() => setMobileSidebarOpen(true)}
                      aria-label="Open navigation menu"
                    >
                      <MoreVertical />
                    </MobileKebabButton>
                  </TabNavigationHeader>
                  <div>
                    <CorpusSettings
                      corpus={{
                        id: opened_corpus.id,
                        title: opened_corpus.title,
                        description: opened_corpus.description || "",
                        mdDescription: opened_corpus.mdDescription,
                        allowComments: opened_corpus.allowComments || false,
                        preferredEmbedder: opened_corpus.preferredEmbedder,
                        slug: (opened_corpus as any).slug || null,
                        creator: opened_corpus.creator,
                        created: opened_corpus.created,
                        modified: opened_corpus.modified,
                        isPublic: opened_corpus.isPublic,
                        myPermissions: corpusAtomPermissions,
                      }}
                    />
                  </div>
                </div>
              ) : null,
            },
            {
              id: "badges",
              label: "Badges",
              icon: <Trophy />,
              component: opened_corpus?.id ? (
                <div style={{ display: "flex", flexDirection: "column" }}>
                  <TabNavigationHeader>
                    <BackNavButton
                      onClick={() => setActiveTab(0)}
                      whileHover={{ scale: 1.05 }}
                      whileTap={{ scale: 0.95 }}
                      title="Back to Home"
                    >
                      <ArrowLeft />
                    </BackNavButton>
                    <TabTitle>Badges</TabTitle>
                    <MobileKebabButton
                      onClick={() => setMobileSidebarOpen(true)}
                      aria-label="Open navigation menu"
                    >
                      <MoreVertical />
                    </MobileKebabButton>
                  </TabNavigationHeader>
                  <div style={{ flex: 1, overflow: "auto" }}>
                    <BadgeManagement corpusId={opened_corpus.id} />
                  </div>
                </div>
              ) : null,
            },
          ]
        : []),
    ];
  }, [
    openedCorpusId, // Use stable ID instead of full object
    opened_corpus_id,
    opened_corpus?.isPersonal,
    stats.totalDocs,
    stats.totalAnnotations,
    stats.totalAnalyses,
    stats.totalExtracts,
    stats.totalThreads,
    stats.totalChats,
    stats.totalRelationships,
    canUpdateCorpus,
    documentsViewMode, // Required for view mode toggle to work
    chatInConversation, // Required for chat tab header visibility
    currentSelectedThreadId, // Required for discussions tab header visibility (URL-driven)
    isPowerUserMode, // Required for mode toggle button label and callback
    // Note: corpusAtomPermissions is an array that changes, but canUpdateCorpus is derived from it
    // and is a stable boolean, so we don't need corpusAtomPermissions in deps
  ]);

  const currentView = navigationItems[active_tab];

  let content = <></>;
  if (
    (opened_corpus === null || opened_corpus === undefined) &&
    (opened_document === null || opened_document === undefined)
  ) {
    content = (
      <CorpusListView
        corpuses={corpus_items}
        pageInfo={corpus_response?.corpuses?.pageInfo}
        loading={
          loading_corpuses ||
          delete_corpus_loading ||
          update_corpus_loading ||
          create_corpus_loading
        }
        networkStatus={corpus_network_status}
        fetchMore={fetchMoreCorpuses}
        onCreateCorpus={() => setShowNewCorpusModal(true)}
        onImportCorpus={() => showImportCorpusModal(true)}
        searchValue={corpusSearchCache}
        onSearchChange={handleCorpusSearchChange}
        allowImport={
          REACT_APP_ALLOW_IMPORTS && Boolean(backendUser?.canImportCorpus)
        }
        activeFilter={corpusListActiveFilter}
        onFilterChange={setCorpusListActiveFilter}
        filterCounts={corpus_filter_counts}
      />
    );
  } else if (
    opened_corpus && // Corpus selected
    !opened_document // No document selected
  ) {
    // Determine the content to display in the main area
    const mainContent = isPowerUserMode
      ? currentView?.component
      : navigationItems.find((item) => item.id === "home")?.component;

    content = isPowerUserMode ? (
      <CorpusViewContainer id="corpus-view-container">
        {/* Mobile backdrop */}
        <AnimatePresence>
          {mobileSidebarOpen && (
            <MobileMenuBackdrop
              initial={{ opacity: 0 }}
              animate={{ opacity: 1 }}
              exit={{ opacity: 0 }}
              onClick={() => setMobileSidebarOpen(false)}
            />
          )}
        </AnimatePresence>

        {/* Navigation Sidebar */}
        <NavigationSidebar
          data-testid="navigation-sidebar"
          $isExpanded={use_mobile_layout ? mobileSidebarOpen : sidebarExpanded}
          initial={{
            width: use_mobile_layout ? "0" : sidebarExpanded ? "280px" : "80px",
          }}
          animate={{
            width: use_mobile_layout
              ? mobileSidebarOpen
                ? "280px"
                : "0"
              : sidebarExpanded
              ? "280px"
              : "80px",
          }}
          transition={{ duration: 0.3, ease: "easeInOut" }}
          onMouseEnter={() => !use_mobile_layout && setSidebarExpanded(true)}
          onMouseLeave={() => !use_mobile_layout && setSidebarExpanded(false)}
        >
          <BottomSheetHandle
            onClick={() => use_mobile_layout && setMobileSidebarOpen(false)}
          />
          <NavigationHeader
            $isExpanded={
              use_mobile_layout ? mobileSidebarOpen : sidebarExpanded
            }
          >
            {(use_mobile_layout ? mobileSidebarOpen : sidebarExpanded) && (
              <motion.div
                initial={{ opacity: 0, x: -10 }}
                animate={{ opacity: 1, x: 0 }}
                transition={{ duration: 0.3, delay: 0.1 }}
                style={{
                  display: "flex",
                  flexDirection: "column",
                  gap: "0.25rem",
                  flex: 1,
                }}
              >
                <div
                  style={{
                    fontSize: "0.6875rem",
                    fontWeight: 500,
                    color: OS_LEGAL_COLORS.textMuted,
                    textTransform: "uppercase",
                    letterSpacing: "0.05em",
                  }}
                >
                  {opened_corpus ? "Corpus" : "Navigation"}
                </div>
                <div
                  style={{
                    fontSize: "1rem",
                    fontWeight: 600,
                    color: OS_LEGAL_COLORS.textPrimary,
                    letterSpacing: "-0.015em",
                    overflow: "hidden",
                    textOverflow: "ellipsis",
                    whiteSpace: "nowrap",
                  }}
                >
                  {opened_corpus ? opened_corpus.title : "Menu"}
                </div>
              </motion.div>
            )}
            {!use_mobile_layout && (
              <NavigationToggle
                data-testid="sidebar-toggle"
                onClick={() => setSidebarExpanded(!sidebarExpanded)}
                whileHover={{ scale: 1.05 }}
                whileTap={{ scale: 0.95 }}
                style={{
                  marginLeft: sidebarExpanded ? "0" : "auto",
                  marginRight: sidebarExpanded ? "0" : "auto",
                }}
              >
                {sidebarExpanded ? <ChevronLeft /> : <ChevronRight />}
              </NavigationToggle>
            )}
          </NavigationHeader>

          <NavigationItems id="nav-items">
            {navigationItems.map((item, index) => (
              <NavigationItem
                data-item-id={item.id}
                key={item.id}
                $isActive={active_tab === index}
                $isExpanded={
                  use_mobile_layout ? mobileSidebarOpen : sidebarExpanded
                }
                onClick={() => {
                  setActiveTab(index);
                  if (use_mobile_layout) {
                    setMobileSidebarOpen(false);
                  }
                  // Refresh stats when switching tabs
                  refetchStats();
                }}
                whileHover={{ x: 2 }}
                whileTap={{ scale: 0.98 }}
              >
                <div style={{ position: "relative" }}>
                  {item.icon}
                  {item.badge !== undefined &&
                    !sidebarExpanded &&
                    !use_mobile_layout && (
                      <CollapsedBadge $isZero={item.badge === 0}>
                        {item.badge > 0 ? item.badge : "–"}
                      </CollapsedBadge>
                    )}
                </div>
                {(use_mobile_layout ? mobileSidebarOpen : sidebarExpanded) && (
                  <>
                    <span style={{ flex: "1", textAlign: "left" }}>
                      {item.label}
                    </span>
                    {item.badge !== undefined && (
                      <NavItemBadge
                        $isActive={active_tab === index}
                        $isZero={item.badge === 0}
                      >
                        {item.badge > 0 ? item.badge : "–"}
                      </NavItemBadge>
                    )}
                  </>
                )}
              </NavigationItem>
            ))}
          </NavigationItems>

          {/* Exit to Explore mode button */}
          <ExitPowerUserWrapper>
            <NavigationItem
              $isActive={false}
              $isExpanded={
                use_mobile_layout ? mobileSidebarOpen : sidebarExpanded
              }
              onClick={() => updateModeParam(location, navigate, null)}
              whileHover={{ x: 2 }}
              whileTap={{ scale: 0.98 }}
              data-testid="exit-power-user"
              style={{ opacity: 0.7 }}
            >
              <ArrowLeft />
              {(use_mobile_layout ? mobileSidebarOpen : sidebarExpanded) && (
                <span style={{ flex: "1", textAlign: "left" }}>Explore</span>
              )}
            </NavigationItem>
          </ExitPowerUserWrapper>
        </NavigationSidebar>

        {/* Main content area */}
        <MainContentArea id="main-corpus-content-area">
          {mainContent}
        </MainContentArea>
      </CorpusViewContainer>
    ) : (
      <CleanViewContainer id="corpus-clean-view">
        {mainContent}
      </CleanViewContainer>
    );
  } else if (
    opened_corpus !== null &&
    opened_corpus !== undefined &&
    opened_document !== null &&
    opened_document !== undefined
  ) {
    content = <></>;
  }

  /* ------------------------------------------------------------------ */
  /* Entity resolution is now handled by CentralRouteManager            */
  /* - /corpuses route → shows list (no entity)                         */
  /* - /c/:user/:corpus route → CentralRouteManager sets openedCorpus   */
  /* This component just reads openedCorpus and renders appropriately   */
  /* ------------------------------------------------------------------ */

  return (
    <CardLayout
      style={{
        flex: 1,
        display: "flex",
        flexDirection: "column",
        minHeight: 0,
        // The chats tab owns a viewport-bounded layout (input pinned to
        // bottom, messages scroll internally). CardLayout's default outer
        // padding would push the chat past the viewport and shrink-wrap
        // the input area awkwardly, so we drop the padding for this tab.
        ...(currentView?.id === "chats" ? { padding: 0 } : {}),
      }}
      Modals={
        <>
          {opened_corpus && showDescriptionEditor && (
            <CorpusDescriptionEditor
              corpusId={opened_corpus.id}
              isOpen={showDescriptionEditor}
              onClose={() => setShowDescriptionEditor(false)}
              onUpdate={() => {
                const { id: validId, isValid } =
                  ensureValidCorpusId(opened_corpus);
                if (isValid && validId) {
                  fetchMetadata({
                    variables: { metadataForCorpusId: validId },
                  });
                }
                refetchStats(); // Refresh stats after description update
                setShowDescriptionEditor(false);
              }}
            />
          )}
          {opened_corpus && showArticleEditor && (
            <CamlArticleEditor
              corpusId={opened_corpus.id}
              isOpen={showArticleEditor}
              onClose={() => setShowArticleEditor(false)}
              onUpdate={() => {
                refetchStats();
              }}
            />
          )}
          <ConfirmModal
            message={`Are you sure you want to delete corpus?`}
            yesAction={() => handleDeleteCorpus(deleting_corpus?.id)}
            noAction={() => deletingCorpus(null)}
            toggleModal={() => deletingCorpus(null)}
            visible={Boolean(deleting_corpus)}
          />
          <ConfirmModal
            message={"Remove selected contracts?"}
            yesAction={() => handleRemoveContracts(selected_document_ids)}
            noAction={() => setShowMultiDeleteConfirm(false)}
            toggleModal={() => setShowMultiDeleteConfirm(false)}
            visible={show_multi_delete_confirm}
          />
          <ConfirmModal
            message={`Are you sure you want to remove contract(s) from corpus?`}
            yesAction={() => handleRemoveContracts(selected_document_ids)}
            noAction={() =>
              showRemoveDocsFromCorpusModal(!show_remove_docs_from_corpus_modal)
            }
            toggleModal={() =>
              showRemoveDocsFromCorpusModal(!show_remove_docs_from_corpus_modal)
            }
            visible={show_remove_docs_from_corpus_modal}
          />
          <CorpusModal
            open={corpus_to_edit !== null}
            mode="EDIT"
            corpus={corpus_to_edit}
            onSubmit={handleUpdateCorpus}
            onClose={() => editingCorpus(null)}
            loading={update_corpus_loading}
          />
          <SelectExportTypeModal
            open={exporting_corpus !== null}
            onClose={() => exportingCorpus(null)}
          />
          {corpus_to_view !== null ? (
            <CorpusModal
              open={corpus_to_view !== null}
              mode="VIEW"
              corpus={corpus_to_view}
              onClose={() => viewingCorpus(null)}
            />
          ) : (
            <></>
          )}

          {show_new_corpus_modal ? (
            <CorpusModal
              open={show_new_corpus_modal}
              mode="CREATE"
              onSubmit={handleCreateNewCorpus}
              onClose={() => setShowNewCorpusModal(false)}
              loading={create_corpus_loading}
            />
          ) : (
            <></>
          )}

          <CreateExtractModal
            open={show_create_extract_modal}
            onClose={() => showCreateExtractModal(false)}
            corpusId={opened_corpus?.id}
          />
        </>
      }
      SearchBar={
        opened_corpus === null ||
        currentView?.id === "home" ||
        // Chats own their viewport-bounded layout; rendering a search bar
        // above adds vertical overhead that pushes the chat past the
        // viewport and forces the page navbar offscreen.
        currentView?.id === "chats" ? null : currentView?.id === "documents" ? (
          <SearchBarWithNav>
            <MobileBackButton
              onClick={() => {
                navigate(corpus_exit_path); // CentralRouteManager will clear openedCorpus
              }}
              title={`Back to ${corpus_exit_label}`}
            >
              <ArrowLeft />
            </MobileBackButton>
            <SearchBarContainer>
              <CreateAndSearchBar
                onChange={handleDocumentSearchChange}
                actions={contract_actions}
                placeholder="Search for document in corpus..."
                value={documentSearchCache}
                filters={
                  opened_corpus ? (
                    <>
                      {/* <FilterToMetadataSelector
                        selected_corpus_id={opened_corpus.id}
                      /> Temporarily disabled - not working and not really in-use*/}
                      <FilterToLabelSelector
                        only_labels_for_labelset_id={
                          opened_corpus.labelSet?.id
                            ? opened_corpus.labelSet.id
                            : ""
                        }
                        label_type={LabelType.DocTypeLabel}
                      />
                    </>
                  ) : (
                    <></>
                  )
                }
              />
            </SearchBarContainer>
          </SearchBarWithNav>
        ) : currentView?.id === "annotations" ? (
          <CreateAndSearchBar
            onChange={handleAnnotationSearchChange}
            actions={corpus_actions}
            placeholder="Search for annotated text in corpus..."
            value={annotationSearchCache}
            filters={
              opened_corpus ? (
                <>
                  <FilterToCorpusActionOutputs />
                  <FilterToAnalysesSelector corpus={opened_corpus} />
                  <FilterToLabelSelector
                    only_labels_for_labelset_id={
                      opened_corpus.labelSet?.id
                        ? opened_corpus.labelSet.id
                        : ""
                    }
                    label_type={LabelType.TokenLabel}
                  />
                </>
              ) : (
                <></>
              )
            }
          />
        ) : currentView?.id === "analyses" || currentView?.id === "extracts" ? (
          <SearchBarWithNav>
            <MobileBackButton
              onClick={() => {
                navigate(corpus_exit_path); // CentralRouteManager will clear openedCorpus
              }}
              title={`Back to ${corpus_exit_label}`}
            >
              <ArrowLeft />
            </MobileBackButton>
            <SearchBarContainer>
              <CreateAndSearchBar
                onChange={handleAnalysisSearchChange}
                actions={corpus_actions}
                placeholder="Search for analyses..."
                value={analysesSearchCache}
                filters={
                  <>
                    <FilterToCorpusActionOutputs />
                    <FilterToAnalysesSelector corpus={opened_corpus} />
                  </>
                }
              />
            </SearchBarContainer>
          </SearchBarWithNav>
        ) : (
          // Default search bar for any other views (like settings)
          <CreateAndSearchBar
            onChange={() => {}}
            actions={[]}
            placeholder="Search..."
            value=""
          />
        )
      }
      BreadCrumbs={null}
    >
      <ImportCorpusModal />
      {content}
    </CardLayout>
  );
};
