'use client';

import Link from 'next/link';
import React, { useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState } from 'react';
import { Brain, Plus, Send, Trash2, X } from 'lucide-react';

import { ChatWorkbench } from '@/components/chat-workbench/ChatWorkbench';
import { ScrollArea } from '@/components/ui/scroll-area';
import {
  archiveSession,
  createSession,
  getActiveTask,
  getSession,
  getSessionProcess,
  listSessions,
  sendMessage,
  submitChatFeedback,
  uploadFile,
  wsManager,
} from '@/lib/api';
import { pickAppText } from '@/lib/i18n/core';
import { useAppI18n } from '@/lib/i18n/provider';
import { useChatStore } from '@/lib/store';
import type { ActiveTask, ChatMessage, FileAttachment, SessionUpdatedEvent, WsEvent } from '@/types';

function messageFingerprint(msg: ChatMessage): string {
  const attachmentKey = (msg.attachments ?? [])
    .map((a) => `${a.file_id ?? ''}:${a.name}:${a.content_type}:${a.size ?? ''}`)
    .join('|');
  return `${msg.role}::${String(msg.content)}::${attachmentKey}`;
}

function mergeServerWithPendingUsers(serverMessages: ChatMessage[], localMessages: ChatMessage[]): ChatMessage[] {
  const counts = new Map<string, number>();
  for (const message of serverMessages) {
    const key = messageFingerprint(message);
    counts.set(key, (counts.get(key) ?? 0) + 1);
  }

  const pendingUsers: ChatMessage[] = [];
  for (const message of localMessages) {
    const key = messageFingerprint(message);
    const count = counts.get(key) ?? 0;
    if (count > 0) {
      counts.set(key, count - 1);
      continue;
    }
    if (message.role === 'user') {
      pendingUsers.push(message);
    }
  }

  return [...serverMessages, ...pendingUsers];
}

function isSessionUpdatedEvent(data: WsEvent | Record<string, unknown>): data is SessionUpdatedEvent {
  return data.type === 'session_updated' && typeof data.session_id === 'string';
}

function activeTaskStatusLabel(status: string, locale: 'zh-CN' | 'en-US') {
  if (status === 'needs_revision') return pickAppText(locale, '待修改', 'Needs revision');
  if (status === 'awaiting_feedback') return pickAppText(locale, '待反馈', 'Awaiting feedback');
  if (status === 'running') return pickAppText(locale, '进行中', 'Running');
  return pickAppText(locale, '进行中', 'Active');
}

const THINKING_MODE_STORAGE_KEY = 'beaver_chat_thinking_enabled';

function loadThinkingModePreference(): boolean {
  if (typeof window === 'undefined') {
    return true;
  }
  const stored = window.localStorage.getItem(THINKING_MODE_STORAGE_KEY);
  return stored == null ? true : stored !== 'false';
}

export default function ChatPage() {
  const { locale } = useAppI18n();
  const {
    sessionId,
    messages,
    isLoading,
    isThinking,
    sessions,
    processRuns,
    processEvents,
    processArtifacts,
    selectedRunId,
    setSessionId,
    setMessages,
    addMessage,
    setIsLoading,
    clearMessages,
    setIsThinking,
    setSelectedRunId,
    setSessionProcess,
    updateMessageFeedback,
  } = useChatStore();

  const [input, setInput] = useState('');
  const [thinkingModeEnabled, setThinkingModeEnabled] = useState(loadThinkingModePreference);
  const [pendingFiles, setPendingFiles] = useState<Array<{ file: File; id?: string; progress: number; error?: string }>>([]);
  const [activeTask, setActiveTask] = useState<ActiveTask | null>(null);
  const messagesEndRef = useRef<HTMLDivElement>(null);
  const messageViewportRef = useRef<HTMLDivElement>(null);
  const textareaRef = useRef<HTMLTextAreaElement>(null);
  const fileInputRef = useRef<HTMLInputElement>(null);
  const loadSessionReqSeq = useRef(0);
  const refreshSessionOnReconnectRef = useRef(false);
  const hasConnectedRef = useRef(false);
  const shouldSnapToLatestRef = useRef(true);
  const wsStatus = useChatStore((state) => state.wsStatus);

  const sessionProcessRuns = useMemo(
    () => processRuns.filter((run) => run.session_id === sessionId),
    [processRuns, sessionId]
  );

  const sessionRunIds = useMemo(
    () => new Set(sessionProcessRuns.map((run) => run.run_id)),
    [sessionProcessRuns]
  );

  const sessionProcessEvents = useMemo(
    () => processEvents.filter((event) => sessionRunIds.has(event.run_id)),
    [processEvents, sessionRunIds]
  );

  const sessionProcessArtifacts = useMemo(
    () => processArtifacts.filter((artifact) => sessionRunIds.has(artifact.run_id)),
    [processArtifacts, sessionRunIds]
  );

  const selectedSessionRunId = selectedRunId && sessionRunIds.has(selectedRunId) ? selectedRunId : null;

  const loadSessions = useCallback(async () => {
    try {
      const list = await listSessions();
      useChatStore.getState().setSessions(list);
    } catch {
      // backend may be offline during first render
    }
  }, []);

  const loadActiveTask = useCallback(async (key: string) => {
    try {
      if (useChatStore.getState().sessionId !== key) return;
      setActiveTask(await getActiveTask(key));
    } catch {
      if (useChatStore.getState().sessionId === key) {
        setActiveTask(null);
      }
    }
  }, []);

  const loadSessionMessages = useCallback(async (key: string) => {
    const reqSeq = ++loadSessionReqSeq.current;
    const localSnapshot = useChatStore.getState().messages;
    const waitingForReply = useChatStore.getState().isLoading || useChatStore.getState().isThinking;
    try {
      const [detail, process] = await Promise.all([
        getSession(key),
        getSessionProcess(key).catch(() => null),
      ]);
      if (reqSeq !== loadSessionReqSeq.current) return;
      if (useChatStore.getState().sessionId !== key) return;
      if (process) {
        setSessionProcess(key, process);
      }
      void loadActiveTask(key);
      const nextMessages = waitingForReply
        ? mergeServerWithPendingUsers(detail.messages, localSnapshot)
        : detail.messages;
      setMessages(nextMessages);
      shouldSnapToLatestRef.current = true;
      const last = nextMessages[nextMessages.length - 1];
      if (last?.role === 'assistant') {
        setIsThinking(false);
        setIsLoading(false);
      }
    } catch {
      if (reqSeq !== loadSessionReqSeq.current) return;
      if (useChatStore.getState().sessionId !== key) return;
    }
  }, [loadActiveTask, setIsLoading, setIsThinking, setMessages, setSessionProcess]);

  useEffect(() => {
    clearMessages();
    setIsLoading(false);
    setIsThinking(false);
    setActiveTask(null);
    void loadSessionMessages(sessionId);
    void loadActiveTask(sessionId);
  }, [clearMessages, loadActiveTask, loadSessionMessages, sessionId, setIsLoading, setIsThinking]);

  useEffect(() => {
    if (wsStatus === 'connected') {
      if (hasConnectedRef.current && refreshSessionOnReconnectRef.current) {
        refreshSessionOnReconnectRef.current = false;
        void loadSessionMessages(useChatStore.getState().sessionId);
      }
      hasConnectedRef.current = true;
      return;
    }

    if (wsStatus === 'disconnected' && hasConnectedRef.current) {
      refreshSessionOnReconnectRef.current = true;
    }
  }, [loadSessionMessages, wsStatus]);

  useEffect(() => {
    const unsubMessage = wsManager.onMessage((data) => {
      if (isSessionUpdatedEvent(data)) {
        void loadSessions();
        if (data.session_id === useChatStore.getState().sessionId) {
          void loadSessionMessages(data.session_id);
        }
        return;
      }

      if (data.type === 'status' && data.status === 'thinking') {
        setIsThinking(true);
      } else if (data.type === 'message' && data.role === 'assistant') {
        const validationResult = data.validation_result ?? data.metadata?.validation_result;
        const validationStatus = data.validation_status
          ? data.validation_status
          : validationResult
            ? ((validationResult as Record<string, unknown>).accepted === true ? 'passed' : 'failed')
            : 'unknown';
        setIsThinking(false);
        setIsLoading(false);
        addMessage({
          role: 'assistant',
          content: typeof data.content === 'string' ? data.content : '',
          timestamp: new Date().toISOString(),
          attachments: Array.isArray(data.attachments) ? data.attachments : undefined,
          run_id: typeof data.run_id === 'string' ? data.run_id : undefined,
          task_id: data.task_id ?? data.metadata?.task_id ?? null,
          task_status: data.task_status ?? data.metadata?.task_status ?? null,
          validation_status: validationStatus,
        });
        void loadSessionMessages(typeof data.session_id === 'string' ? data.session_id : useChatStore.getState().sessionId);
        void loadActiveTask(typeof data.session_id === 'string' ? data.session_id : useChatStore.getState().sessionId);
        loadSessions();
      }
    });

    return () => {
      unsubMessage();
    };
  }, [addMessage, loadActiveTask, loadSessionMessages, loadSessions, setIsLoading, setIsThinking]);

  useEffect(() => {
    if (!isLoading && !isThinking) {
      return;
    }
    const timer = setInterval(() => {
      loadSessionMessages(useChatStore.getState().sessionId);
    }, 1500);
    return () => clearInterval(timer);
  }, [isLoading, isThinking, loadSessionMessages]);

  const scrollMessagesToLatest = useCallback((behavior: ScrollBehavior) => {
    const viewport = messageViewportRef.current;
    if (!viewport) return;
    messagesEndRef.current?.scrollIntoView({ block: 'end', behavior });
    viewport.scrollTo({ top: viewport.scrollHeight, behavior });
  }, []);

  const scheduleScrollToLatest = useCallback((behavior: ScrollBehavior) => {
    if (typeof window === 'undefined') {
      scrollMessagesToLatest(behavior);
      return;
    }
    window.requestAnimationFrame(() => {
      window.requestAnimationFrame(() => {
        scrollMessagesToLatest(behavior);
      });
    });
  }, [scrollMessagesToLatest]);

  useEffect(() => {
    shouldSnapToLatestRef.current = true;
  }, [sessionId]);

  useLayoutEffect(() => {
    if (messages.length === 0 && !isThinking && sessionProcessEvents.length === 0) {
      return;
    }

    scheduleScrollToLatest(shouldSnapToLatestRef.current ? 'auto' : 'smooth');
    shouldSnapToLatestRef.current = false;
  }, [isThinking, messages.length, scheduleScrollToLatest, sessionProcessEvents.length]);

  const handleSend = useCallback(async () => {
    const text = input.trim();
    if ((!text && pendingFiles.length === 0) || isLoading) return;

    const readyFiles = pendingFiles.filter((p) => p.id && !p.error);
    const attachments: FileAttachment[] = readyFiles.map((item) => ({
      file_id: item.id!,
      name: item.file.name,
      content_type: item.file.type || 'application/octet-stream',
      size: item.file.size,
    }));

    setInput('');
    setPendingFiles([]);

    const msgContent = text || pickAppText(locale, '（仅附件）', '(Attachments only)');
    addMessage({
      role: 'user',
      content: msgContent,
      timestamp: new Date().toISOString(),
      attachments: attachments.length > 0 ? attachments : undefined,
    });
    setIsLoading(true);
    setIsThinking(false);

    if (wsManager.getStatus() === 'connected') {
      const wsPayload: Record<string, unknown> = {
        type: 'message',
        content: msgContent,
        thinking_enabled: thinkingModeEnabled,
      };
      if (attachments.length > 0) {
        wsPayload.attachments = attachments;
      }
      wsManager.sendRaw(wsPayload);
    } else {
      try {
        const result = await sendMessage(msgContent, sessionId, attachments.length > 0 ? attachments : undefined, {
          thinkingEnabled: thinkingModeEnabled,
        });
        setIsThinking(false);
        setIsLoading(false);
        if (result.response) {
          if (useChatStore.getState().sessionId !== sessionId) {
            await loadSessions();
            return;
          }
          addMessage({
            role: 'assistant',
            content: result.response,
            timestamp: new Date().toISOString(),
            run_id: result.run_id,
            task_id: result.task_id,
            task_status: result.task_status,
            validation_status: result.validation_result
              ? (result.validation_result.accepted === true ? 'passed' : 'failed')
              : 'unknown',
          });
          void getSessionProcess(sessionId).then((process) => setSessionProcess(sessionId, process)).catch(() => null);
          void loadActiveTask(sessionId);
          loadSessions();
        } else {
          await loadSessionMessages(sessionId);
          void loadActiveTask(sessionId);
          loadSessions();
        }
      } catch {
        setIsThinking(false);
        setIsLoading(false);
        if (useChatStore.getState().sessionId !== sessionId) {
          return;
        }
        addMessage({
          role: 'assistant',
          content: pickAppText(locale, '发送失败，请检查后端服务是否正在运行。', 'Send failed. Please check whether the backend service is running.'),
          timestamp: new Date().toISOString(),
        });
      }
    }
  }, [addMessage, input, isLoading, loadActiveTask, loadSessionMessages, loadSessions, locale, pendingFiles, sessionId, setIsLoading, setIsThinking, setSessionProcess, thinkingModeEnabled]);

  const handleFeedback = useCallback(async (runId: string, feedbackType: 'satisfied' | 'revise' | 'abandon', comment?: string) => {
    updateMessageFeedback(runId, feedbackType);
    try {
      await submitChatFeedback({
        sessionId,
        runId,
        feedbackType,
        comment,
      });
      void loadSessionMessages(sessionId);
      void getSessionProcess(sessionId).then((process) => setSessionProcess(sessionId, process)).catch(() => null);
      void loadActiveTask(sessionId);
      void loadSessions();
    } catch (err: any) {
      updateMessageFeedback(runId, undefined, err?.message || pickAppText(locale, '反馈提交失败', 'Feedback failed'));
    }
  }, [loadActiveTask, loadSessionMessages, loadSessions, locale, sessionId, setSessionProcess, updateMessageFeedback]);

  const handleKeyDown = (e: React.KeyboardEvent) => {
    if (e.key === 'Enter' && !e.shiftKey && !e.nativeEvent.isComposing) {
      e.preventDefault();
      handleSend();
    }
  };

  const handleFileSelect = useCallback(async (e: React.ChangeEvent<HTMLInputElement>) => {
    const files = Array.from(e.target.files || []);
    if (!files.length) return;
    e.target.value = '';

    for (const file of files) {
      if (file.size > 50 * 1024 * 1024) {
        setPendingFiles((prev) => [...prev, { file, progress: 0, error: pickAppText(locale, '文件过大（最大 50MB）', 'File is too large (max 50MB)') }]);
        continue;
      }

      setPendingFiles((prev) => [...prev, { file, progress: 0 }]);
      try {
        const result = await uploadFile(file, sessionId, (pct) => {
          setPendingFiles((prev) => prev.map((item) => (item.file === file ? { ...item, progress: pct } : item)));
        });
        setPendingFiles((prev) => prev.map((item) => (item.file === file ? { ...item, id: result.file_id, progress: 100 } : item)));
      } catch (err: any) {
        setPendingFiles((prev) => prev.map((item) => (item.file === file ? { ...item, error: err.message || pickAppText(locale, '上传失败', 'Upload failed') } : item)));
      }
    }
  }, [locale, sessionId]);

  const handleNewSession = async () => {
    const id = `web:${Date.now()}`;
    setSessionId(id);
    setSelectedRunId(null);
    setActiveTask(null);
    clearMessages();
    useChatStore.getState().resetProcessState();
    try {
      await createSession(id);
    } catch {
      // ignore transient create failures; first message can still create the session server-side
    }
    void loadSessions();
  };

  const handleArchiveSession = async (key: string, e: React.MouseEvent) => {
    e.stopPropagation();
    try {
      await archiveSession(key);
      useChatStore.getState().setSessions(useChatStore.getState().sessions.filter((session) => session.key !== key));
      if (key === sessionId) {
        setSessionId('web:default');
        setActiveTask(null);
        clearMessages();
        useChatStore.getState().resetProcessState();
      }
      void loadSessions();
    } catch {
      addMessage({
        role: 'assistant',
        content: pickAppText(locale, '归档会话失败，请稍后重试。', 'Failed to archive the session. Please try again later.'),
        timestamp: new Date().toISOString(),
      });
    }
  };

  const handleSelectSession = (key: string) => {
    setSelectedRunId(null);
    setActiveTask(null);
    setSessionId(key);
  };

  const removePendingFile = useCallback((file: File) => {
    setPendingFiles((prev) => prev.filter((item) => item.file !== file));
  }, []);

  const toggleThinkingMode = useCallback(() => {
    setThinkingModeEnabled((current) => {
      const next = !current;
      if (typeof window !== 'undefined') {
        window.localStorage.setItem(THINKING_MODE_STORAGE_KEY, String(next));
      }
      return next;
    });
  }, []);

  const formatSessionName = (key: string) => {
    if (key.startsWith('web:')) {
      const id = key.slice(4);
      if (id === 'default') return pickAppText(locale, '默认', 'Default');
      const numeric = Number(id);
      if (!Number.isNaN(numeric)) {
        return new Date(numeric).toLocaleDateString(locale, {
          month: 'short',
          day: 'numeric',
          hour: '2-digit',
          minute: '2-digit',
        });
      }
      return id;
    }
    return key;
  };

  return (
    <div className="flex h-[calc(100vh-4rem)] bg-background">
      <aside className="flex w-[280px] shrink-0 flex-col border-r border-[#E6E1DE] bg-[#F7F6F5]">
        <div className="px-5 pb-5 pt-6">
          <button
            type="button"
            onClick={handleNewSession}
            className="flex h-11 w-full items-center justify-center gap-2 rounded-full bg-primary px-4 text-sm font-medium text-primary-foreground transition-colors hover:bg-[#342E2B]"
          >
            <Plus className="h-4 w-4" />
            {pickAppText(locale, '新对话', 'New chat')}
          </button>
        </div>
        <ScrollArea className="flex-1">
          <div className="space-y-3 px-3 pb-6">
            <div className="px-3 pb-2 text-[14px] text-muted-foreground">{pickAppText(locale, '最近对话', 'Recent chats')}</div>
            {sessions.length === 0 && (
              <p className="px-3 py-4 text-sm text-muted-foreground">{pickAppText(locale, '暂无对话记录', 'No chat history yet')}</p>
            )}
            {sessions.map((session) => (
              <div
                key={session.key}
                onClick={() => handleSelectSession(session.key)}
                className={`group flex cursor-pointer items-center justify-between rounded-xl px-4 py-3 text-[15px] transition-colors ${
                  session.key === sessionId
                    ? 'bg-[#EFEEED] text-foreground'
                    : 'text-foreground hover:bg-[#EFEEED]/70'
                }`}
              >
                <div className="truncate">
                  <span className="truncate">{formatSessionName(session.key)}</span>
                </div>
                  <button
                  onClick={(event) => handleArchiveSession(session.key, event)}
                  className="opacity-0 group-hover:opacity-100 p-0.5 hover:text-destructive transition-opacity"
                  title={pickAppText(locale, '归档会话', 'Archive session')}
                  aria-label={pickAppText(locale, '归档会话', 'Archive session')}
                >
                  <Trash2 className="w-3.5 h-3.5" />
                </button>
              </div>
            ))}
          </div>
        </ScrollArea>
      </aside>

      <div className="flex-1 flex flex-col min-w-0">
        <div className="flex-1 min-h-0">
          <ChatWorkbench
            messages={messages}
            isThinking={isThinking || (isLoading && messages[messages.length - 1]?.role === 'user')}
            messagesEndRef={messagesEndRef}
            messageViewportRef={messageViewportRef}
            processRuns={sessionProcessRuns}
            processEvents={sessionProcessEvents}
            processArtifacts={sessionProcessArtifacts}
            selectedRunId={selectedSessionRunId}
            onSelectRun={(runId) => setSelectedRunId(selectedSessionRunId === runId ? null : runId)}
            onFeedback={handleFeedback}
          />
        </div>

        <div className="bg-background px-8 pb-8 pt-4">
          <div className="mx-auto max-w-5xl">
            {activeTask && (
              <div className="mb-2 flex">
                <Link
                  href={`/tasks/${encodeURIComponent(activeTask.task_id)}`}
                  className="inline-flex max-w-full items-center gap-2 rounded-full border border-[#D8D2CE] bg-[#F7F6F5] px-3 py-1.5 text-xs text-foreground transition-colors hover:bg-[#EFEEED]"
                  title={activeTask.description}
                >
                  <span className="shrink-0 text-muted-foreground">{pickAppText(locale, '当前任务', 'Current task')}:</span>
                  <span className="truncate font-medium">{activeTask.short_title}</span>
                  <span className="shrink-0 rounded-full bg-white px-2 py-0.5 text-[11px] text-muted-foreground">
                    {activeTaskStatusLabel(activeTask.status, locale)}
                  </span>
                </Link>
              </div>
            )}
            {pendingFiles.length > 0 && (
              <div className="mb-2 space-y-1">
                {pendingFiles.map((item, index) => (
                  <div key={`${item.file.name}:${index}`} className="flex items-center gap-2 px-3 py-1.5 bg-muted rounded-md text-sm">
                    <span className="truncate flex-1">
                      {item.file.name}{' '}
                      <span className="text-muted-foreground">({(item.file.size / 1024).toFixed(0)}KB)</span>
                    </span>
                    {item.error ? (
                      <span className="text-destructive text-xs">{item.error}</span>
                    ) : item.progress < 100 ? (
                      <div className="w-20 h-1.5 bg-muted-foreground/20 rounded-full overflow-hidden">
                        <div className="h-full bg-primary rounded-full transition-all" style={{ width: `${item.progress}%` }} />
                      </div>
                    ) : (
                      <span className="text-[#657162] text-xs">{pickAppText(locale, '就绪', 'Ready')}</span>
                    )}
                    <button onClick={() => removePendingFile(item.file)} className="text-muted-foreground hover:text-foreground">
                      <X className="w-3.5 h-3.5" />
                    </button>
                  </div>
                ))}
              </div>
            )}

            <div className="relative rounded-[28px] border border-[#E6E1DE] bg-white p-4 shadow-[0_8px_24px_rgba(0,0,0,0.08)]">
              <input ref={fileInputRef} type="file" multiple className="hidden" onChange={handleFileSelect} />

              <textarea
                ref={textareaRef}
                value={input}
                onChange={(e) => setInput(e.target.value)}
                onKeyDown={handleKeyDown}
                placeholder={pickAppText(locale, '今天想聊什么？', 'What would you like to talk about today?')}
                rows={1}
                className="block w-full resize-none border-0 bg-transparent px-2 pb-8 pt-1 text-[17px] leading-7 placeholder:text-muted-foreground focus:outline-none disabled:cursor-not-allowed disabled:opacity-50"
                style={{ minHeight: '72px', maxHeight: '200px' }}
                onInput={(e) => {
                  const target = e.target as HTMLTextAreaElement;
                  target.style.height = 'auto';
                  target.style.height = `${Math.min(target.scrollHeight, 200)}px`;
                }}
              />

              <div className="flex items-center justify-between">
                <div className="flex items-center gap-5 text-[15px] text-muted-foreground">
                  <button
                    onClick={() => fileInputRef.current?.click()}
                    className="inline-flex items-center gap-2 text-foreground transition-colors hover:text-muted-foreground"
                    title={pickAppText(locale, '添加附件', 'Add attachment')}
                  >
                    <Plus className="h-5 w-5" />
                  </button>
                  <button
                    type="button"
                    onClick={toggleThinkingMode}
                    className={`inline-flex h-8 items-center gap-2 rounded-full border px-3 text-sm transition-colors ${
                      thinkingModeEnabled
                        ? 'border-primary/40 bg-[#F1EFEE] text-foreground'
                        : 'border-[#E6E1DE] bg-white text-muted-foreground hover:text-foreground'
                    }`}
                    title={
                      thinkingModeEnabled
                        ? pickAppText(locale, '思考模式已开启', 'Thinking mode is on')
                        : pickAppText(locale, '思考模式已关闭', 'Thinking mode is off')
                    }
                    aria-pressed={thinkingModeEnabled}
                  >
                    <Brain className="h-4 w-4" />
                    {pickAppText(locale, '思考', 'Think')}
                  </button>
                </div>
                <button
                  type="button"
                  onClick={handleSend}
                  disabled={(!input.trim() && pendingFiles.filter((item) => item.id && !item.error).length === 0) || isLoading}
                  className="flex h-12 w-12 items-center justify-center rounded-full bg-[#85817E] text-white transition-colors hover:bg-primary disabled:opacity-40"
                  aria-label={pickAppText(locale, '发送', 'Send')}
                >
                  <Send className="h-5 w-5" />
                </button>
              </div>
            </div>
          </div>
        </div>
      </div>
    </div>
  );
}