/**
 * Copyright 2026 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

'use client';

import { Button } from '@/components/ui/button';
import { ButtonGroup, ButtonGroupText } from '@/components/ui/button-group';
import {
  Tooltip,
  TooltipContent,
  TooltipProvider,
  TooltipTrigger,
} from '@/components/ui/tooltip';
import { cn } from '@/lib/utils';
import { cjk } from '@streamdown/cjk';
import { code } from '@streamdown/code';
import { math } from '@streamdown/math';
import { mermaid } from '@streamdown/mermaid';
import type { UIMessage } from 'ai';
import { ChevronLeftIcon, ChevronRightIcon } from 'lucide-react';
import type { ComponentProps, HTMLAttributes, ReactElement } from 'react';
import {
  createContext,
  memo,
  useCallback,
  useContext,
  useEffect,
  useMemo,
  useState,
} from 'react';
import { Streamdown } from 'streamdown';

export type MessageProps = HTMLAttributes<HTMLDivElement> & {
  from: UIMessage['role'];
};

export const Message = ({ className, from, ...props }: MessageProps) => (
  <div
    className={cn(
      'group flex w-full max-w-[95%] flex-col gap-2',
      from === 'user' ? 'is-user ml-auto justify-end' : 'is-assistant',
      className
    )}
    {...props}
  />
);

export type MessageContentProps = HTMLAttributes<HTMLDivElement>;

export const MessageContent = ({
  children,
  className,
  ...props
}: MessageContentProps) => (
  <div
    className={cn(
      'is-user:dark flex w-fit min-w-0 max-w-full flex-col gap-2 overflow-hidden text-sm',
      'group-[.is-user]:ml-auto group-[.is-user]:rounded-lg group-[.is-user]:bg-secondary group-[.is-user]:px-4 group-[.is-user]:py-3 group-[.is-user]:text-foreground',
      'group-[.is-assistant]:text-foreground',
      className
    )}
    {...props}>
    {children}
  </div>
);

export type MessageActionsProps = ComponentProps<'div'>;

export const MessageActions = ({
  className,
  children,
  ...props
}: MessageActionsProps) => (
  <div className={cn('flex items-center gap-1', className)} {...props}>
    {children}
  </div>
);

export type MessageActionProps = ComponentProps<typeof Button> & {
  tooltip?: string;
  label?: string;
};

export const MessageAction = ({
  tooltip,
  children,
  label,
  variant = 'ghost',
  size = 'icon-sm',
  ...props
}: MessageActionProps) => {
  const button = (
    <Button size={size} type="button" variant={variant} {...props}>
      {children}
      <span className="sr-only">{label || tooltip}</span>
    </Button>
  );

  if (tooltip) {
    return (
      <TooltipProvider>
        <Tooltip>
          <TooltipTrigger asChild>{button}</TooltipTrigger>
          <TooltipContent>
            <p>{tooltip}</p>
          </TooltipContent>
        </Tooltip>
      </TooltipProvider>
    );
  }

  return button;
};

interface MessageBranchContextType {
  currentBranch: number;
  totalBranches: number;
  goToPrevious: () => void;
  goToNext: () => void;
  branches: ReactElement[];
  setBranches: (branches: ReactElement[]) => void;
}

const MessageBranchContext = createContext<MessageBranchContextType | null>(
  null
);

const useMessageBranch = () => {
  const context = useContext(MessageBranchContext);

  if (!context) {
    throw new Error(
      'MessageBranch components must be used within MessageBranch'
    );
  }

  return context;
};

export type MessageBranchProps = HTMLAttributes<HTMLDivElement> & {
  defaultBranch?: number;
  onBranchChange?: (branchIndex: number) => void;
};

export const MessageBranch = ({
  defaultBranch = 0,
  onBranchChange,
  className,
  ...props
}: MessageBranchProps) => {
  const [currentBranch, setCurrentBranch] = useState(defaultBranch);
  const [branches, setBranches] = useState<ReactElement[]>([]);

  const handleBranchChange = useCallback(
    (newBranch: number) => {
      setCurrentBranch(newBranch);
      onBranchChange?.(newBranch);
    },
    [onBranchChange]
  );

  const goToPrevious = useCallback(() => {
    const newBranch =
      currentBranch > 0 ? currentBranch - 1 : branches.length - 1;
    handleBranchChange(newBranch);
  }, [currentBranch, branches.length, handleBranchChange]);

  const goToNext = useCallback(() => {
    const newBranch =
      currentBranch < branches.length - 1 ? currentBranch + 1 : 0;
    handleBranchChange(newBranch);
  }, [currentBranch, branches.length, handleBranchChange]);

  const contextValue = useMemo<MessageBranchContextType>(
    () => ({
      branches,
      currentBranch,
      goToNext,
      goToPrevious,
      setBranches,
      totalBranches: branches.length,
    }),
    [branches, currentBranch, goToNext, goToPrevious]
  );

  return (
    <MessageBranchContext.Provider value={contextValue}>
      <div
        className={cn('grid w-full gap-2 [&>div]:pb-0', className)}
        {...props}
      />
    </MessageBranchContext.Provider>
  );
};

export type MessageBranchContentProps = HTMLAttributes<HTMLDivElement>;

export const MessageBranchContent = ({
  children,
  ...props
}: MessageBranchContentProps) => {
  const { currentBranch, setBranches, branches } = useMessageBranch();
  const childrenArray = useMemo(
    () => (Array.isArray(children) ? children : [children]),
    [children]
  );

  // Use useEffect to update branches when they change
  useEffect(() => {
    if (branches.length !== childrenArray.length) {
      setBranches(childrenArray);
    }
  }, [childrenArray, branches, setBranches]);

  return childrenArray.map((branch, index) => (
    <div
      className={cn(
        'grid gap-2 overflow-hidden [&>div]:pb-0',
        index === currentBranch ? 'block' : 'hidden'
      )}
      key={branch.key}
      {...props}>
      {branch}
    </div>
  ));
};

export type MessageBranchSelectorProps = ComponentProps<typeof ButtonGroup>;

export const MessageBranchSelector = ({
  className,
  ...props
}: MessageBranchSelectorProps) => {
  const { totalBranches } = useMessageBranch();

  // Don't render if there's only one branch
  if (totalBranches <= 1) {
    return null;
  }

  return (
    <ButtonGroup
      className={cn(
        '[&>*:not(:first-child)]:rounded-l-md [&>*:not(:last-child)]:rounded-r-md',
        className
      )}
      orientation="horizontal"
      {...props}
    />
  );
};

export type MessageBranchPreviousProps = ComponentProps<typeof Button>;

export const MessageBranchPrevious = ({
  children,
  ...props
}: MessageBranchPreviousProps) => {
  const { goToPrevious, totalBranches } = useMessageBranch();

  return (
    <Button
      aria-label="Previous branch"
      disabled={totalBranches <= 1}
      onClick={goToPrevious}
      size="icon-sm"
      type="button"
      variant="ghost"
      {...props}>
      {children ?? <ChevronLeftIcon size={14} />}
    </Button>
  );
};

export type MessageBranchNextProps = ComponentProps<typeof Button>;

export const MessageBranchNext = ({
  children,
  ...props
}: MessageBranchNextProps) => {
  const { goToNext, totalBranches } = useMessageBranch();

  return (
    <Button
      aria-label="Next branch"
      disabled={totalBranches <= 1}
      onClick={goToNext}
      size="icon-sm"
      type="button"
      variant="ghost"
      {...props}>
      {children ?? <ChevronRightIcon size={14} />}
    </Button>
  );
};

export type MessageBranchPageProps = HTMLAttributes<HTMLSpanElement>;

export const MessageBranchPage = ({
  className,
  ...props
}: MessageBranchPageProps) => {
  const { currentBranch, totalBranches } = useMessageBranch();

  return (
    <ButtonGroupText
      className={cn(
        'border-none bg-transparent text-muted-foreground shadow-none',
        className
      )}
      {...props}>
      {currentBranch + 1} of {totalBranches}
    </ButtonGroupText>
  );
};

export type MessageResponseProps = ComponentProps<typeof Streamdown>;

const streamdownPlugins = { cjk, code, math, mermaid };

export const MessageResponse = memo(
  ({ className, ...props }: MessageResponseProps) => (
    <Streamdown
      className={cn(
        'size-full [&>*:first-child]:mt-0 [&>*:last-child]:mb-0',
        className
      )}
      plugins={streamdownPlugins}
      {...props}
    />
  ),
  (prevProps, nextProps) =>
    prevProps.children === nextProps.children &&
    nextProps.isAnimating === prevProps.isAnimating
);

MessageResponse.displayName = 'MessageResponse';

export type MessageToolbarProps = ComponentProps<'div'>;

export const MessageToolbar = ({
  className,
  children,
  ...props
}: MessageToolbarProps) => (
  <div
    className={cn(
      'mt-4 flex w-full items-center justify-between gap-4',
      className
    )}
    {...props}>
    {children}
  </div>
);
