import { Router } from 'express';
import type { ActiveChat } from '../../services/chat.js';
import type { WebContext } from '../context.js';
import {
  buildConversationState,
  chooseConversationIntent,
  mergeConversationState,
} from '../../services/conversation-state.js';

export function createConversationsRouter(ctx: WebContext): Router {
  const router = Router();

  async function findConversation(id: string): Promise<ActiveChat | undefined> {
    if (!ctx.services.chat) return undefined;
    const conversations = await ctx.services.chat.getCachedConversations();
    return conversations.find(
      (c) => c.roomId === id || c.username === id || c.roomName === id,
    );
  }

  function getConversationIntelligence(conversation: ActiveChat, requestedIntent?: 'media-ask') {
    const messages = (conversation.messages ?? []).map((message) => ({
      sender: message.sender,
      text: message.text,
      isSelf: message.isSelf,
    }));
    const saved = conversation.roomId ? ctx.services.conversationState?.get(conversation.roomId) : undefined;
    const state = mergeConversationState(saved, buildConversationState(messages));
    if (conversation.roomId) ctx.services.conversationState?.save(conversation.roomId, state);
    return { messages, state, intent: chooseConversationIntent(messages, state, requestedIntent) };
  }

  router.get('/conversations', async (req, res) => {
    if (!ctx.services.chat) {
      res.status(503).json({ error: 'Chat service not initialized' });
      return;
    }
    try {
      const conversations = await ctx.services.chat.getCachedConversations();
      if (req.query.includeImageMetadata !== 'true') {
        res.json(conversations);
        return;
      }
      const receivedMediaRooms = new Set<string>();
      const receivedMediaUsers = new Set<string>();

      if (ctx.services.media) {
        try {
          const mediaItems = await ctx.services.media.getMediaItems();
          for (const item of mediaItems) {
            if (item.sender.toLowerCase() === 'me') continue;
            if (item.chatRoomId) receivedMediaRooms.add(item.chatRoomId);
            if (item.chatUsername) receivedMediaUsers.add(item.chatUsername.toLowerCase());
          }
        } catch (error) {
          ctx.logger.warn('Failed to read media index for conversation markers:', error);
        }
      }

      res.json(conversations.map((conversation) => ({
        ...conversation,
        hasReceivedImages:
          receivedMediaRooms.has(conversation.roomId ?? '')
          || receivedMediaUsers.has(conversation.username.toLowerCase())
          || (conversation.messages ?? []).some(
            (message) => !message.isSelf && (message.media?.length ?? 0) > 0,
          ),
      })));
    } catch (error) {
      ctx.logger.error('Failed to fetch conversations:', error);
      res.status(500).json({ error: 'Failed to fetch conversations' });
    }
  });

  router.get('/conversations/:id', async (req, res) => {
    if (!ctx.services.chat) {
      res.status(404).json({ error: 'Chat service not initialized' });
      return;
    }
    try {
      // Conversation reads never initiate a sync. Sync lifecycle events can
      // invalidate this query, so starting a sync here would create a loop.
      const syncStatus = ctx.services.chat.getSyncStatus();
      const syncInFlight = syncStatus.syncing;
      const conversation = await findConversation(decodeURIComponent(req.params.id));
      if (!conversation) {
        res.status(404).json({ error: 'Conversation not found' });
        return;
      }
      // Delta sync only populates room summaries — full message history is
      // fetched on demand the first time a conversation is opened, and
      // re-fetched when the summary's last-activity timestamp is newer than
      // anything we have cached (i.e. they've replied since we last loaded).
      const cachedLastTs = conversation.messages?.length
        ? conversation.messages[conversation.messages.length - 1].timestamp
        : 0;
      const hasNewerActivity = (conversation.lastMessageTime ?? 0) > cachedLastTs;
      const needsLazyLoad =
        !conversation.messages || conversation.messages.length === 0 || hasNewerActivity;
      if (needsLazyLoad && !syncInFlight) {
        try {
          await ctx.services.chat.loadConversationDetails(conversation);
          await ctx.services.chat.saveCacheExternal();
        } catch (err) {
          ctx.logger.warn(`Lazy-load failed for conversation ${conversation.roomId}:`, err);
        }
      }

      // Attach the post that triggered this outreach so the modal can link to it.
      let triggeringPost: {
        id: string;
        subreddit?: string;
        title?: string;
        url: string;
        imageUrl: string | null;
        sentAt: number;
      } | null = null;
      try {
        const sent = conversation.roomId
          ? ctx.repos.messages.getByChatRoomId(conversation.roomId)
            ?? ctx.repos.messages.getLatestByRecipient(conversation.username)
          : ctx.repos.messages.getLatestByRecipient(conversation.username);
        if (sent && sent.postId) {
          const url = sent.postUrl ?? (sent.subreddit
            ? `https://www.reddit.com/r/${sent.subreddit}/comments/${sent.postId}/`
            : `https://redd.it/${sent.postId}`);
          triggeringPost = {
            id: sent.postId,
            subreddit: sent.subreddit,
            title: sent.postTitle,
            url,
            imageUrl: sent.postImageUrl ?? null,
            sentAt: sent.sentAt,
          };
        }
      } catch (err) {
        ctx.logger.warn(`Failed to look up triggering post for ${conversation.username}:`, err);
      }

      res.json({
        ...conversation,
        triggeringPost,
        syncInProgress: syncInFlight
          ? {
              kind: syncStatus.syncingKind,
              progress: syncStatus.progress,
              staleMessages: needsLazyLoad,
            }
          : null,
      });
    } catch (error) {
      ctx.logger.error('Failed to fetch conversation:', error);
      res.status(500).json({ error: String(error) });
    }
  });

  router.post('/conversations/:id/suggest-reply', async (req, res) => {
    if (!ctx.services.chat) {
      res.status(500).json({ error: 'Chat service not initialized' });
      return;
    }
    if (!ctx.services.ai) {
      res.status(500).json({ error: 'AI client not initialized' });
      return;
    }
    try {
      const conversation = await findConversation(decodeURIComponent(req.params.id));
      if (!conversation) {
        res.status(404).json({ error: 'Conversation not found' });
        return;
      }
      if (!conversation.messages || conversation.messages.length === 0) {
        res.status(400).json({ error: 'No messages in conversation to generate a reply from' });
        return;
      }
      if (!conversation.messages.some((m) => !m.isSelf)) {
        res.status(400).json({ error: 'No reply from user yet - nothing to respond to' });
        return;
      }

      const intelligence = getConversationIntelligence(conversation);
      const suggestedReply = await ctx.services.ai.generateReply(
        intelligence.messages,
        conversation.username,
        intelligence.state,
        intelligence.intent,
      );
      res.json({ suggestedReply, intent: intelligence.intent, conversationState: intelligence.state });
    } catch (error) {
      ctx.logger.error('Failed to generate suggested reply:', error);
      res.status(500).json({ error: String(error) });
    }
  });

  router.post('/conversations/:id/suggest-media-ask', async (req, res) => {
    if (!ctx.services.chat) {
      res.status(500).json({ error: 'Chat service not initialized' });
      return;
    }
    if (!ctx.services.ai) {
      res.status(500).json({ error: 'AI client not initialized' });
      return;
    }
    try {
      const conversation = await findConversation(decodeURIComponent(req.params.id));
      if (!conversation) {
        res.status(404).json({ error: 'Conversation not found' });
        return;
      }
      if (!conversation.messages || conversation.messages.length === 0) {
        res.status(400).json({ error: 'No messages in conversation to generate from' });
        return;
      }
      if (!conversation.messages.some((m) => !m.isSelf)) {
        res.status(400).json({ error: 'No reply from user yet - nothing to respond to' });
        return;
      }

      const intelligence = getConversationIntelligence(conversation, 'media-ask');
      if (intelligence.intent.kind !== 'media-ask') {
        res.status(409).json({ error: intelligence.intent.reason, intent: intelligence.intent, conversationState: intelligence.state });
        return;
      }
      const suggestedReply = await ctx.services.ai.generateMediaAsk(
        intelligence.messages,
        conversation.username,
        intelligence.state,
        intelligence.intent,
      );
      res.json({ suggestedReply, intent: intelligence.intent, conversationState: intelligence.state });
    } catch (error) {
      ctx.logger.error('Failed to generate media-ask message:', error);
      res.status(500).json({ error: String(error) });
    }
  });

  router.post('/conversations/:id/send-reply', async (req, res) => {
    if (!ctx.services.chat) {
      res.status(500).json({ error: 'Chat service not initialized' });
      return;
    }
    try {
      const { message } = req.body;
      if (!message || typeof message !== 'string' || message.trim().length === 0) {
        res.status(400).json({ error: 'Message is required' });
        return;
      }

      const conversation = await findConversation(decodeURIComponent(req.params.id));
      if (!conversation) {
        res.status(404).json({ error: 'Conversation not found' });
        return;
      }
      if (!conversation.url) {
        res.status(400).json({ error: 'No chat URL for this conversation' });
        return;
      }

      const success = await ctx.services.chat.sendChatMessage(conversation.url, message.trim());
      if (success) {
        if (conversation.roomId) {
          const currentMessages = (conversation.messages ?? []).map((item) => ({
            sender: item.sender,
            text: item.text,
            isSelf: item.isSelf,
          }));
          const saved = ctx.services.conversationState?.get(conversation.roomId);
          const updatedState = mergeConversationState(
            saved,
            buildConversationState([...currentMessages, { sender: 'Me', text: message.trim(), isSelf: true }]),
          );
          ctx.services.conversationState?.save(conversation.roomId, updatedState);
        }
        ctx.activity.push('sent', `Sent chat reply to u/${conversation.username}`, conversation.username);
        ctx.broadcaster.push('info', `Chat reply sent to u/${conversation.username}`);
        res.json({ success: true });

        ctx.services.chat.refreshTopChats(5).catch((err) =>
          ctx.logger.error('Failed to refresh chats after send-reply:', err),
        );
      } else {
        res.status(500).json({ error: 'Failed to send chat message' });
      }
    } catch (error) {
      ctx.logger.error('Failed to send chat reply:', error);
      res.status(500).json({ error: String(error) });
    }
  });

  /**
   * Start a brand-new DM with a Reddit user and send the opening message.
   * Body: { username: string, message: string }
   */
  router.post('/conversations/start', async (req, res) => {
    if (!ctx.services.chat) {
      res.status(500).json({ error: 'Chat service not initialized' });
      return;
    }
    try {
      const { username, message } = req.body ?? {};
      if (!username || typeof username !== 'string') {
        res.status(400).json({ error: 'username is required' });
        return;
      }
      if (!message || typeof message !== 'string' || message.trim().length === 0) {
        res.status(400).json({ error: 'message is required' });
        return;
      }
      const chat = await ctx.services.chat.startConversation(username, message.trim());
      if (!chat) {
        res.status(500).json({ error: 'Failed to start conversation (unknown user or send failed)' });
        return;
      }
      ctx.activity.push('sent', `Started chat with u/${chat.username}`, chat.username);
      if (chat.roomId) {
        ctx.services.conversationState?.save(
          chat.roomId,
          buildConversationState(chat.messages ?? [{ sender: 'Me', text: message.trim(), isSelf: true }]),
        );
      }
      ctx.broadcaster.push('info', `Started new chat with u/${chat.username}`);
      res.json({ success: true, chat });
    } catch (error) {
      ctx.logger.error('Failed to start conversation:', error);
      res.status(500).json({ error: String(error) });
    }
  });

  return router;
}