import { randomUUID } from 'node:crypto'
import fs from 'node:fs/promises'
import path from 'node:path'

import { agentChannelService as channelService } from '@data/services/AgentChannelService'
import { agentService } from '@data/services/AgentService'
import { agentSessionService } from '@data/services/AgentSessionService'
import { loggerService } from '@logger'
import { buildAgentSessionTopicId } from '@main/ai/agentSession/topic'
import {
  isAgentSessionWorkspaceError,
  prepareClaudeCodeWorkspaceDirectory
} from '@main/ai/runtime/claudeCode/settingsBuilder'
import { ChannelAdapterListener, type StreamListener } from '@main/ai/streamManager'
import { startAgentSessionRun } from '@main/ai/streamManager/api/startAgentSessionRun'
import { application } from '@main/core/application'
import type { FileAttachment, ImageAttachment } from '@main/utils/downloadAsBase64'
import type { AgentSessionEntity } from '@shared/data/api/schemas/agentSessions'

import type { ChannelAdapter, ChannelCommandEvent, ChannelMessageEvent } from './ChannelAdapter'
import { SLASH_COMMANDS } from './constants'
import { wrapExternalContent } from './security'

const logger = loggerService.withContext('ChannelMessageHandler')

const TYPING_INTERVAL_MS = 4000

/** Max number of entries in the session tracker before evicting oldest entries. */
const SESSION_TRACKER_MAX_SIZE = 500

/**
 * How long to wait for additional messages before flushing a batch.
 * IM users (especially on WeChat) often send multiple short messages in rapid
 * succession. Debouncing prevents each fragment from triggering a separate
 * agent round-trip and avoids concurrent stream interleaving.
 */
const MESSAGE_BATCH_DELAY_MS = 8000

type BatchResolver = {
  resolve: () => void
  reject: (err: unknown) => void
}

type PendingBatch = {
  adapter: ChannelAdapter
  messages: ChannelMessageEvent[]
  timer: ReturnType<typeof setTimeout>
  resolvers: BatchResolver[]
}

export class ChannelMessageHandler {
  // TODO: in v2 use cacheService
  private readonly sessionTracker = new Map<string, string>() // `${agentId}:${channelId}:${chatId}` -> sessionId
  private readonly pendingResolutions = new Map<string, Promise<AgentSessionEntity | null>>()
  /** Per-chat debounce buffer — accumulates rapid messages before flushing */
  private readonly pendingBatches = new Map<string, PendingBatch>()
  /** Per-chat serial queue — ensures only one stream runs at a time per chat */
  private readonly chatQueues = new Map<string, Promise<void>>()
  /** Active abort controllers per session — allows renderer to abort via IPC */
  private readonly activeAbortControllers = new Map<string, AbortController>()

  handleIncoming(adapter: ChannelAdapter, message: ChannelMessageEvent): Promise<void> {
    const batchKey = `${adapter.agentId}:${adapter.channelId}:${message.chatId}`

    return new Promise<void>((resolve, reject) => {
      const existing = this.pendingBatches.get(batchKey)
      if (existing) {
        // Append to existing batch and reset the debounce timer
        existing.messages.push(message)
        existing.resolvers.push({ resolve, reject })
        clearTimeout(existing.timer)
        existing.timer = setTimeout(() => this.flushBatch(batchKey), MESSAGE_BATCH_DELAY_MS)
        logger.debug('Message appended to pending batch', {
          batchKey,
          batchSize: existing.messages.length
        })
        return
      }

      // Start a new batch
      const batch: PendingBatch = {
        adapter,
        messages: [message],
        timer: setTimeout(() => this.flushBatch(batchKey), MESSAGE_BATCH_DELAY_MS),
        resolvers: [{ resolve, reject }]
      }
      this.pendingBatches.set(batchKey, batch)
    })
  }

  private flushBatch(batchKey: string): void {
    const batch = this.pendingBatches.get(batchKey)
    if (!batch) return
    this.pendingBatches.delete(batchKey)

    const merged = this.mergeMessages(batch.messages)
    const { resolvers } = batch

    if (batch.messages.length > 1) {
      logger.info('Flushing merged message batch', {
        batchKey,
        messageCount: batch.messages.length
      })
    }

    // Serialize with any in-flight stream to avoid interleaving
    const prev = this.chatQueues.get(batchKey) ?? Promise.resolve()
    const current = prev
      .then(() => this.processIncoming(batch.adapter, merged))
      .then(
        () => resolvers.forEach((r) => r.resolve()),
        (err) => resolvers.forEach((r) => r.reject(err))
      )
      .finally(() => {
        // Clean up queue entry when no newer work has been enqueued
        if (this.chatQueues.get(batchKey) === settled) {
          this.chatQueues.delete(batchKey)
        }
      })
    // Log errors but keep the queue chain intact
    const settled = current.catch((err) => {
      const errMsg = err instanceof Error ? err.message : String(err)
      logger.error('Channel message processing failed', { batchKey, error: errMsg })

      // Best-effort: notify the user with a generic message (no internal details)
      try {
        const adapter = batch.adapter
        const chatId = merged.chatId
        if (adapter && chatId) {
          adapter
            .sendMessage(chatId, '⚠️ An error occurred while processing your message. Please try again later.')
            .catch((sendErr) => {
              logger.debug('Failed to send error notification to channel', {
                chatId,
                error: sendErr instanceof Error ? sendErr.message : String(sendErr)
              })
            })
        }
      } catch {
        // Do not let error notification break the queue
      }
    })
    this.chatQueues.set(batchKey, settled)
  }

  private mergeMessages(messages: ChannelMessageEvent[]): ChannelMessageEvent {
    if (messages.length === 1) return messages[0]

    const first = messages[0]
    const mergedText = messages
      .map((m) => m.text)
      .filter(Boolean)
      .join('\n')
    const mergedImages = messages.flatMap((m) => m.images ?? [])
    const mergedFiles = messages.flatMap((m) => m.files ?? [])

    return {
      chatId: first.chatId,
      userId: first.userId,
      userName: first.userName,
      text: mergedText,
      ...(mergedImages.length > 0 ? { images: mergedImages } : {}),
      ...(mergedFiles.length > 0 ? { files: mergedFiles } : {})
    }
  }

  private async processIncoming(adapter: ChannelAdapter, message: ChannelMessageEvent): Promise<void> {
    const { agentId } = adapter

    try {
      const session = await this.resolveSession(agentId, adapter.channelId, adapter.channelType, message.chatId)
      if (!session) {
        logger.error('Failed to resolve session', { agentId })
        await adapter
          .sendMessage(message.chatId, '⚠️ Failed to resolve a session for this agent. Please try again later.')
          .catch((err) => {
            logger.debug('Failed to send session-error notification to channel', {
              chatId: message.chatId,
              error: err instanceof Error ? err.message : String(err)
            })
          })
        return
      }

      // Resolve agent for cognitive config (model / configuration / mcps / disabledTools).
      // Workspace is read from the session itself (CMA Environment binding).
      // An orphan session (`agentId === null`) cannot run; skip it.
      if (!session.agentId) {
        logger.error('Channel message hit an orphan session', { sessionId: session.id })
        return
      }
      const agent = await agentService.getAgent(session.agentId)
      if (!agent) {
        logger.error('Agent not found for session', { sessionId: session.id, agentId: session.agentId })
        return
      }

      // TODO(channel-perm-override): channel-level permission_mode used to mutate
      // session.configuration in-place; with config now living on agent, this
      // override needs to flow as a per-dispatch option instead. Tracked separately.

      const workDir = session.workspace?.path
      const hasAttachments = !!(message.images?.length || message.files?.length)
      if (hasAttachments) {
        try {
          await prepareClaudeCodeWorkspaceDirectory(session)
        } catch (error) {
          if (isAgentSessionWorkspaceError(error)) {
            await adapter.sendMessage(message.chatId, error.message).catch(() => {})
          }
          throw error
        }
      }

      // Save images to agent workspace so the agent can read them via the Read tool
      let imagePaths: string[] = []
      if (message.images && message.images.length > 0 && workDir) {
        try {
          imagePaths = await this.persistImages(workDir, message.images)
          logger.info('Persisted channel images to workspace', {
            agentId,
            count: imagePaths.length,
            dir: path.join(workDir, '.cherry-studio', 'channel-images')
          })
        } catch (error) {
          logger.warn('Failed to persist channel images', {
            agentId,
            error: error instanceof Error ? error.message : String(error)
          })
        }
      }

      // Save files to agent workspace so the agent can read them via the Read tool
      let filePaths: string[] = []
      if (message.files && message.files.length > 0 && workDir) {
        try {
          filePaths = await this.persistFiles(workDir, message.files)
          logger.info('Persisted channel files to workspace', {
            agentId,
            count: filePaths.length,
            dir: path.join(workDir, '.cherry-studio', 'channel-files')
          })
        } catch (error) {
          logger.warn('Failed to persist channel files', {
            agentId,
            error: error instanceof Error ? error.message : String(error)
          })
        }
      }

      // Build text with attachment file paths appended so the agent knows where they are saved
      let textWithAttachments = message.text
      if (imagePaths.length > 0) {
        textWithAttachments += `\n\n[Attached images saved to workspace]\n${imagePaths.map((p) => `- ${p}`).join('\n')}`
      }
      if (filePaths.length > 0) {
        textWithAttachments += `\n\n[Attached files saved to workspace]\n${filePaths.map((p) => `- ${p}`).join('\n')}`
      }

      // Wrap untrusted channel input with security boundary markers
      const securedContent = wrapExternalContent(textWithAttachments, {
        chatId: message.chatId,
        userId: message.userId,
        userName: message.userName,
        channelType: adapter.channelType
      })

      const abortController = new AbortController()
      this.activeAbortControllers.set(session.id, abortController)

      // Show typing indicator immediately and keep refreshing every 4s
      adapter.sendTypingIndicator(message.chatId).catch(() => {})
      const typingInterval = setInterval(
        () => adapter.sendTypingIndicator(message.chatId).catch(() => {}),
        TYPING_INTERVAL_MS
      )

      try {
        // Delivery (streaming updates + the sanitized finalize) is owned by the
        // `ChannelAdapterListener` registered inside `collectStreamResponse`; we only await
        // turn completion here. (The old post-hoc finalize was dead — the sentinel's `c.text`
        // read never accumulated — and reviving it would double-send.)
        await this.collectStreamResponse(session, securedContent, abortController, adapter, message.chatId)
      } catch (streamError) {
        const streamErrorMessage = streamError instanceof Error ? streamError.message : String(streamError)
        if (isAgentSessionWorkspaceError(streamError)) {
          // Thrown before streaming starts (validateSession), so no controller exists yet and
          // onStreamError is a no-op on most adapters — send a plain message so the inbound
          // message isn't silently dropped on Telegram/WeChat/QQ/Discord/Slack.
          adapter.sendMessage(message.chatId, streamErrorMessage).catch(() => {})
        } else {
          // Mid-stream error: let the adapter update its streaming UI.
          adapter.onStreamError(message.chatId, streamErrorMessage).catch(() => {})
        }
        throw streamError
      } finally {
        this.activeAbortControllers.delete(session.id)
        clearInterval(typingInterval)
      }
    } catch (error) {
      logger.error('Error handling incoming message', {
        agentId,
        chatId: message.chatId,
        error: error instanceof Error ? error.message : String(error)
      })
    }
  }

  async handleCommand(adapter: ChannelAdapter, command: ChannelCommandEvent): Promise<void> {
    const { agentId } = adapter
    try {
      switch (command.command) {
        case 'new': {
          // TODO(channel-perm-override): channel.permissionMode no longer
          // applied here — config lives on agent now. Tracked separately.
          const newSession = await this.createSessionForChannel(agentId, adapter.channelId)
          await channelService.updateChannel(adapter.channelId, { sessionId: newSession.id })
          const trackerKey = `${agentId}:${adapter.channelId}:${command.chatId}`
          this.sessionTracker.set(trackerKey, newSession.id)
          this.evictSessionTracker()
          await adapter.sendMessage(command.chatId, 'New session created.')
          break
        }
        case 'compact': {
          const session = await this.resolveSession(agentId, adapter.channelId, adapter.channelType, command.chatId)
          if (!session) {
            await adapter.sendMessage(command.chatId, 'No active session.')
            return
          }
          const abortController = new AbortController()
          adapter.sendTypingIndicator(command.chatId).catch(() => {})
          const typingInterval = setInterval(
            () => adapter.sendTypingIndicator(command.chatId).catch(() => {}),
            TYPING_INTERVAL_MS
          )
          try {
            const response = await this.collectStreamResponse(
              session,
              '/compact',
              abortController,
              adapter,
              command.chatId
            )
            // The `ChannelAdapterListener` registered inside `collectStreamResponse` already
            // delivered any non-empty output; only send an explicit fallback when compact
            // produced no text, so we don't double-send.
            if (!response) {
              await adapter.sendMessage(command.chatId, 'Session compacted.')
            }
          } finally {
            clearInterval(typingInterval)
          }
          break
        }
        case 'help': {
          const agent = await agentService.getAgent(agentId)
          const name = agent?.name ?? 'CherryClaw'
          const description = agent?.description ?? ''
          const helpText = [
            `*${name}*`,
            description ? `_${description}_` : '',
            '',
            'Available commands:',
            ...SLASH_COMMANDS.map((cmd) => `/${cmd.name} - ${cmd.description}`)
          ]
            .filter(Boolean)
            .join('\n')
          await adapter.sendMessage(command.chatId, helpText)
          break
        }
        case 'whoami': {
          await adapter.sendMessage(
            command.chatId,
            [
              `Current chat ID: \`${command.chatId}\``,
              '',
              'Add this value to `allow_ids` in settings to receive notifications.'
            ].join('\n')
          )
          break
        }
      }
    } catch (error) {
      logger.error('Error handling command', {
        agentId,
        command: command.command,
        error: error instanceof Error ? error.message : String(error)
      })
      adapter
        .sendMessage(command.chatId, '⚠️ An error occurred while processing the command. Please try again later.')
        .catch((sendErr) => {
          logger.debug('Failed to send error notification to channel', {
            chatId: command.chatId,
            error: sendErr instanceof Error ? sendErr.message : String(sendErr)
          })
        })
    }
  }

  /** Evict oldest session tracker entries when the map exceeds the size limit. */
  private evictSessionTracker(): void {
    if (this.sessionTracker.size <= SESSION_TRACKER_MAX_SIZE) return
    const excess = this.sessionTracker.size - SESSION_TRACKER_MAX_SIZE
    const iter = this.sessionTracker.keys()
    for (let i = 0; i < excess; i++) {
      const { value } = iter.next()
      if (value) this.sessionTracker.delete(value)
    }
  }

  /** Clear session tracking for an agent (used when agent is deleted/updated) */
  clearSessionTracker(agentId: string): void {
    // Abort any in-flight stream owned by a tracked session of this agent
    // before dropping the tracker entries — otherwise the stream keeps
    // running on a deleted agent and `sendMessage` to a now-detached
    // channel will throw.
    const sessionIdsToAbort: string[] = []
    for (const [key, sessionId] of this.sessionTracker.entries()) {
      if (key.startsWith(`${agentId}:`)) {
        sessionIdsToAbort.push(sessionId)
        this.sessionTracker.delete(key)
      }
    }
    for (const sessionId of sessionIdsToAbort) {
      this.abortSessionStream(sessionId, 'agent-cleared')
    }
    for (const [key, batch] of this.pendingBatches.entries()) {
      if (key.startsWith(`${agentId}:`)) {
        clearTimeout(batch.timer)
        this.pendingBatches.delete(key)
        // Settle the discarded batch's callers so their .catch handlers fire
        // instead of leaving handleIncoming promises hanging forever.
        batch.resolvers.forEach((r) => r.reject(new Error('Agent removed; batch discarded')))
      }
    }
    for (const key of this.chatQueues.keys()) {
      if (key.startsWith(`${agentId}:`)) {
        this.chatQueues.delete(key)
      }
    }
  }

  /** Abort an active stream for the given session. Returns true if a stream was in flight. */
  abortSession(sessionId: string): boolean {
    if (!this.activeAbortControllers.has(sessionId)) return false
    this.abortSessionStream(sessionId, 'channel-session-aborted')
    return true
  }

  /**
   * Stop the upstream agent-session turn for a session. The local `AbortController`
   * is never passed to the running stream — it only flips a listener's `isAlive()`,
   * which (because the manager prunes dead listeners before firing their terminal
   * callback) would strand the completion sentinel. So abort through the manager,
   * which settles the turn as `paused` and lets the still-alive sentinel resolve.
   */
  private abortSessionStream(sessionId: string, reason: string): void {
    application.get('AiStreamManager').abort(buildAgentSessionTopicId(sessionId), reason)
  }

  private async resolveSession(
    agentId: string,
    channelId: string,
    channelType: string,
    chatId: string
  ): Promise<AgentSessionEntity | null> {
    const trackerKey = `${agentId}:${channelId}:${chatId}`

    // Coalesce concurrent resolutions for the same chat to avoid duplicate sessions
    const pending = this.pendingResolutions.get(trackerKey)
    if (pending) return pending

    const resolution = this.doResolveSession(agentId, channelId, channelType, chatId, trackerKey)
    this.pendingResolutions.set(trackerKey, resolution)
    try {
      return await resolution
    } finally {
      this.pendingResolutions.delete(trackerKey)
    }
  }

  private async doResolveSession(
    agentId: string,
    channelId: string,
    _channelType: string,
    _chatId: string,
    trackerKey: string
  ): Promise<AgentSessionEntity | null> {
    const channelRow = await channelService.getChannel(channelId)
    const lookup = async (sessionId: string) => agentSessionService.getById(sessionId).catch(() => null)

    // Check tracker first
    const trackedId = this.sessionTracker.get(trackerKey)
    if (trackedId) {
      const session = await lookup(trackedId)
      if (session && session.agentId === agentId) {
        if (channelRow && channelRow.sessionId !== session.id) {
          channelService
            .updateChannel(channelId, { sessionId: session.id })
            .catch((err) =>
              logger.warn('Failed to sync channel-session link', err instanceof Error ? err : new Error(String(err)))
            )
        }
        return session
      }
      this.sessionTracker.delete(trackerKey)
    }

    // Look up existing session via channel's session_id
    if (channelRow?.sessionId) {
      const existingSession = await lookup(channelRow.sessionId)
      if (existingSession && existingSession.agentId === agentId) {
        this.sessionTracker.set(trackerKey, existingSession.id)
        this.evictSessionTracker()
        return existingSession
      }
    }

    // No existing session found — create a new one
    logger.info('No existing session for channel, creating new session', {
      agentId,
      channelId,
      channelSessionId: channelRow?.sessionId ?? null,
      trackerKey
    })

    const newSession = await this.createSessionForChannel(agentId, channelId, channelRow ?? undefined)
    await channelService.updateChannel(channelId, { sessionId: newSession.id })
    this.sessionTracker.set(trackerKey, newSession.id)
    this.evictSessionTracker()
    return newSession
  }

  private async createSessionForChannel(
    agentId: string,
    channelId: string,
    channel?: NonNullable<Awaited<ReturnType<typeof channelService.getChannel>>>
  ): Promise<AgentSessionEntity> {
    const channelRow = channel ?? (await channelService.getChannel(channelId))
    if (!channelRow) {
      throw new Error(`Channel not found: ${channelId}`)
    }
    return await agentSessionService.create({
      agentId,
      name: 'Channel session',
      workspace: channelRow.workspace
    })
  }

  private async collectStreamResponse(
    session: AgentSessionEntity,
    content: string,
    abortController: AbortController,
    adapter: ChannelAdapter,
    chatId: string
  ): Promise<string> {
    if (!session.agentId) {
      throw new Error(`Cannot stream on orphan session ${session.id} — its agent was deleted`)
    }

    let resolveExecution!: (text: string) => void
    let rejectExecution!: (err: unknown) => void
    const executionDone = new Promise<string>((resolve, reject) => {
      resolveExecution = resolve
      rejectExecution = reject
    })
    let accumulatedText = ''
    const sentinel: StreamListener = {
      id: `channel-completion:${chatId}`,
      onChunk(chunk) {
        // `text-delta`'s field is `delta`, not `text` (AI SDK `UIMessageChunk`).
        if (chunk.type === 'text-delta') accumulatedText += chunk.delta
      },
      onDone() {
        resolveExecution(accumulatedText.trim())
      },
      onPaused() {
        resolveExecution(accumulatedText.trim())
      },
      onError(result) {
        rejectExecution(new Error(result.error.message ?? 'Execution failed'))
      },
      isAlive: () => !abortController.signal.aborted
    }

    await startAgentSessionRun({
      sessionId: session.id,
      userParts: [{ type: 'text', text: content }],
      listeners: [sentinel, new ChannelAdapterListener(adapter, chatId)]
    })

    return executionDone
  }

  /**
   * Save images to the agent's workspace so the agent can read them via the Read tool.
   * Returns the list of absolute file paths written.
   */
  private async persistImages(workDir: string, images: ImageAttachment[]): Promise<string[]> {
    const dir = path.join(workDir, '.cherry-studio', 'channel-images')
    await fs.mkdir(dir, { recursive: true })

    const paths: string[] = []
    for (const img of images) {
      const ext = img.media_type.split('/')[1]?.replace('jpeg', 'jpg') || 'png'
      const filename = `${Date.now()}-${randomUUID().slice(0, 8)}.${ext}`
      const filePath = path.join(dir, filename)
      await fs.writeFile(filePath, Buffer.from(img.data, 'base64'))
      paths.push(filePath)
    }

    return paths
  }

  /**
   * Save files to the agent's workspace so the agent can read them via the Read tool.
   * Returns the list of absolute file paths written.
   */
  private async persistFiles(workDir: string, files: FileAttachment[]): Promise<string[]> {
    const dir = path.join(workDir, '.cherry-studio', 'channel-files')
    await fs.mkdir(dir, { recursive: true })

    const paths: string[] = []
    for (const file of files) {
      // Prefix with timestamp to avoid collisions, preserve original filename for readability
      const safeName = file.filename.replace(/[/\\:*?"<>|]/g, '_')
      const filename = `${Date.now()}-${safeName}`
      const filePath = path.join(dir, filename)
      await fs.writeFile(filePath, Buffer.from(file.data, 'base64'))
      paths.push(filePath)
    }

    return paths
  }
}

export const channelMessageHandler = new ChannelMessageHandler()
