/**
 * 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 { cn } from '@/lib/utils';
import type { UIMessage } from 'ai';
import { ArrowDownIcon, DownloadIcon } from 'lucide-react';
import type { ComponentProps } from 'react';
import { useCallback } from 'react';
import { StickToBottom, useStickToBottomContext } from 'use-stick-to-bottom';

export type ConversationProps = ComponentProps<typeof StickToBottom>;

export const Conversation = ({ className, ...props }: ConversationProps) => (
  <StickToBottom
    className={cn('relative flex-1 overflow-y-hidden', className)}
    initial="smooth"
    resize="smooth"
    role="log"
    {...props}
  />
);

export type ConversationContentProps = ComponentProps<
  typeof StickToBottom.Content
>;

export const ConversationContent = ({
  className,
  ...props
}: ConversationContentProps) => (
  <StickToBottom.Content
    className={cn('flex flex-col gap-8 p-4', className)}
    {...props}
  />
);

export type ConversationEmptyStateProps = ComponentProps<'div'> & {
  title?: string;
  description?: string;
  icon?: React.ReactNode;
};

export const ConversationEmptyState = ({
  className,
  title = 'No messages yet',
  description = 'Start a conversation to see messages here',
  icon,
  children,
  ...props
}: ConversationEmptyStateProps) => (
  <div
    className={cn(
      'flex size-full flex-col items-center justify-center gap-3 p-8 text-center',
      className
    )}
    {...props}>
    {children ?? (
      <>
        {icon && <div className="text-muted-foreground">{icon}</div>}
        <div className="space-y-1">
          <h3 className="font-medium text-sm">{title}</h3>
          {description && (
            <p className="text-muted-foreground text-sm">{description}</p>
          )}
        </div>
      </>
    )}
  </div>
);

export type ConversationScrollButtonProps = ComponentProps<typeof Button>;

export const ConversationScrollButton = ({
  className,
  ...props
}: ConversationScrollButtonProps) => {
  const { isAtBottom, scrollToBottom } = useStickToBottomContext();

  const handleScrollToBottom = useCallback(() => {
    scrollToBottom();
  }, [scrollToBottom]);

  return (
    !isAtBottom && (
      <Button
        className={cn(
          'absolute bottom-4 left-[50%] translate-x-[-50%] rounded-full dark:bg-background dark:hover:bg-muted',
          className
        )}
        onClick={handleScrollToBottom}
        size="icon"
        type="button"
        variant="outline"
        {...props}>
        <ArrowDownIcon className="size-4" />
      </Button>
    )
  );
};

const getMessageText = (message: UIMessage): string =>
  message.parts
    .filter((part) => part.type === 'text')
    .map((part) => part.text)
    .join('');

export type ConversationDownloadProps = Omit<
  ComponentProps<typeof Button>,
  'onClick'
> & {
  messages: UIMessage[];
  filename?: string;
  formatMessage?: (message: UIMessage, index: number) => string;
};

const defaultFormatMessage = (message: UIMessage): string => {
  const roleLabel =
    message.role.charAt(0).toUpperCase() + message.role.slice(1);
  return `**${roleLabel}:** ${getMessageText(message)}`;
};

export const messagesToMarkdown = (
  messages: UIMessage[],
  formatMessage: (
    message: UIMessage,
    index: number
  ) => string = defaultFormatMessage
): string => messages.map((msg, i) => formatMessage(msg, i)).join('\n\n');

export const ConversationDownload = ({
  messages,
  filename = 'conversation.md',
  formatMessage = defaultFormatMessage,
  className,
  children,
  ...props
}: ConversationDownloadProps) => {
  const handleDownload = useCallback(() => {
    const markdown = messagesToMarkdown(messages, formatMessage);
    const blob = new Blob([markdown], { type: 'text/markdown' });
    const url = URL.createObjectURL(blob);
    const link = document.createElement('a');
    link.href = url;
    link.download = filename;
    document.body.append(link);
    link.click();
    link.remove();
    URL.revokeObjectURL(url);
  }, [messages, filename, formatMessage]);

  return (
    <Button
      className={cn(
        'absolute top-4 right-4 rounded-full dark:bg-background dark:hover:bg-muted',
        className
      )}
      onClick={handleDownload}
      size="icon"
      type="button"
      variant="outline"
      {...props}>
      {children ?? <DownloadIcon className="size-4" />}
    </Button>
  );
};
