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

type OwnedActiveChat = ActiveChat & { owner?: { accountId: string; redditUsername: string } };

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

  function currentOwner() {
    const snapshot = ctx.services.accountAuth?.getSnapshot();
    return snapshot?.accountId && snapshot.redditUsername
      ? { accountId: snapshot.accountId, redditUsername: snapshot.redditUsername }
      : undefined;
  }

  function parseOwnedId(id: string): { accountId: string; conversationId: string } | null {
    const separator = id.indexOf('~');
    if (separator < 1) return null;
    try {
      return {
        accountId: decodeURIComponent(id.slice(0, separator)),
        conversationId: decodeURIComponent(id.slice(separator + 1)),
      };
    } catch { return null; }
  }

  async function findConversation(id: string): Promise<{
    conversation: ActiveChat;
    runtime: NonNullable<ReturnType<NonNullable<WebContext['services']['accountRuntimes']>['get']>> | null;
  } | undefined> {
    const owned = parseOwnedId(id);
    if (!owned && (ctx.services.accountRuntimes?.list().length ?? 0) > 0) return undefined;
    const runtime = owned ? ctx.services.accountRuntimes?.get(owned.accountId) ?? null : null;
    if (owned && (!runtime || runtime.snapshot().state !== 'running')) return undefined;
    const chat = runtime?.resources.chatService ?? ctx.services.chat;
    if (!chat) return undefined;
    const conversations = await chat.getCachedConversations();
    const conversationId = owned?.conversationId ?? id;
    const conversation = conversations.find(
      (c) => c.roomId === conversationId || c.username === conversationId || c.roomName === conversationId,
    );
    return conversation ? { conversation, runtime } : undefined;
  }

  function getConversationIntelligence(
    conversation: ActiveChat,
    stateRepo = ctx.services.conversationState,
    requestedIntent?: 'media-ask',
  ) {
    const messages = (conversation.messages ?? []).map((message) => ({
      sender: message.sender,
      text: message.text,
      isSelf: message.isSelf,
    }));
    const saved = conversation.roomId ? stateRepo?.get(conversation.roomId) : undefined;
    const state = mergeConversationState(saved, buildConversationState(messages));
    if (conversation.roomId) stateRepo?.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 runtimes = ctx.services.accountRuntimes?.list().filter((runtime) => runtime.state === 'running') ?? [];
      const conversations: OwnedActiveChat[] = runtimes.length > 0
        ? (await Promise.all(runtimes.map(async (snapshot) => {
            const runtime = ctx.services.accountRuntimes!.get(snapshot.accountId)!;
            return (await runtime.resources.chatService.getCachedConversations()).map((conversation) => ({
              ...conversation,
              owner: { accountId: snapshot.accountId, redditUsername: snapshot.redditUsername },
            }));
          }))).flat()
        : await ctx.services.chat.getCachedConversations();
      if (req.query.includeImageMetadata !== 'true') {
        res.json(conversations.map((conversation) => ({ ...conversation, owner: conversation.owner ?? currentOwner() })));
        return;
      }
      const receivedMediaRooms = new Set<string>();
      const receivedMediaUsers = new Set<string>();

      if (ctx.services.media) {
        try {
          const mediaByAccount = runtimes.length > 0
            ? await Promise.all(runtimes.map(async (snapshot) => ({
                accountId: snapshot.accountId,
                items: await ctx.services.accountRuntimes!.get(snapshot.accountId)!.resources.mediaService.getMediaItems(),
              })))
            : [{ accountId: currentOwner()?.accountId ?? 'legacy', items: await ctx.services.media.getMediaItems() }];
          for (const source of mediaByAccount) {
            for (const item of source.items) {
              if (item.sender.toLowerCase() === 'me') continue;
              if (item.chatRoomId) receivedMediaRooms.add(`${source.accountId}:${item.chatRoomId}`);
              if (item.chatUsername) receivedMediaUsers.add(`${source.accountId}:${item.chatUsername.toLowerCase()}`);
            }
          }
        } catch (error) {
          ctx.logger.warn('Failed to read media index for conversation markers:', error);
        }
      }

      res.json(conversations.map((conversation) => ({
        ...conversation,
        owner: conversation.owner ?? currentOwner(),
        hasReceivedImages:
          receivedMediaRooms.has(`${conversation.owner?.accountId ?? currentOwner()?.accountId ?? 'legacy'}:${conversation.roomId ?? ''}`)
          || receivedMediaUsers.has(`${conversation.owner?.accountId ?? currentOwner()?.accountId ?? 'legacy'}:${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 resolved = await findConversation(decodeURIComponent(req.params.id));
      if (!resolved) {
        res.status(404).json({ error: 'Conversation not found' });
        return;
      }
      const chatService = resolved.runtime?.resources.chatService ?? ctx.services.chat;
      const syncStatus = chatService.getSyncStatus();
      const syncInFlight = syncStatus.syncing;
      const conversation = resolved.conversation;
      // 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 chatService.loadConversationDetails(conversation);
          await chatService.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;
        postedAt?: number;
        sentAt: number;
      } | null = null;
      let automatedOpener: string | null = null;
      try {
        const messagesRepo = resolved.runtime?.resources.messagesRepo ?? ctx.repos.messages;
        const sent = conversation.roomId
          ? messagesRepo.getByChatRoomId(conversation.roomId)
            ?? messagesRepo.getLatestByRecipient(conversation.username)
          : messagesRepo.getLatestByRecipient(conversation.username);
        automatedOpener = sent?.message ?? null;
        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,
            ...(sent.postCreatedAt ? { postedAt: sent.postCreatedAt } : {}),
            sentAt: sent.sentAt,
          };
        }
      } catch (err) {
        ctx.logger.warn(`Failed to look up triggering post for ${conversation.username}:`, err);
      }

      const stateRepo = resolved.runtime?.resources.conversationStateRepo ?? ctx.services.conversationState;
      const intelligence = getConversationIntelligence(conversation, stateRepo);
      const receivedImage = (conversation.messages ?? []).some(
        (message) => !message.isSelf && (message.media?.length ?? 0) > 0,
      );
      if (intelligence.state.automation.status === 'active' && receivedImage) {
        intelligence.state.automation.status = 'image-received';
        intelligence.state.automation.handoffReason = 'The user shared an image.';
      } else if (intelligence.state.automation.status === 'active' && intelligence.state.boundaries.length > 0) {
        intelligence.state.automation.status = 'boundary';
        intelligence.state.automation.handoffReason = intelligence.state.boundaries.join('; ');
      }
      if (conversation.roomId) stateRepo?.save(conversation.roomId, intelligence.state);
      const aiFingerprints = new Map<string, number>();
      if (automatedOpener) {
        aiFingerprints.set(conversationMessageFingerprint(automatedOpener), 1);
      }
      for (const fingerprint of intelligence.state.automation.aiMessageFingerprints) {
        aiFingerprints.set(fingerprint, (aiFingerprints.get(fingerprint) ?? 0) + 1);
      }
      const annotatedMessages = conversation.messages?.map((message) => {
        if (!message.isSelf) return message;
        const fingerprint = conversationMessageFingerprint(message.text);
        const remainingMatches = aiFingerprints.get(fingerprint) ?? 0;
        if (remainingMatches === 0) return message;
        aiFingerprints.set(fingerprint, remainingMatches - 1);
        return { ...message, isAi: true };
      });

      res.json({
        ...conversation,
        ...(annotatedMessages ? { messages: annotatedMessages } : {}),
        owner: resolved.runtime
          ? { accountId: resolved.runtime.session.accountId, redditUsername: resolved.runtime.session.redditUsername }
          : currentOwner(),
        triggeringPost,
        automation: {
          turnsUsed: intelligence.state.automation.turnsUsed,
          remainingTurns: remainingAutomationTurns(intelligence.state),
          status: intelligence.state.automation.status,
          handoffReason: intelligence.state.automation.handoffReason,
        },
        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 resolved = await findConversation(decodeURIComponent(req.params.id));
      if (!resolved) {
        res.status(404).json({ error: 'Conversation not found' });
        return;
      }
      const conversation = resolved.conversation;
      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, resolved.runtime?.resources.conversationStateRepo);
      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 resolved = await findConversation(decodeURIComponent(req.params.id));
      if (!resolved) {
        res.status(404).json({ error: 'Conversation not found' });
        return;
      }
      const conversation = resolved.conversation;
      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, resolved.runtime?.resources.conversationStateRepo, '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 resolved = await findConversation(decodeURIComponent(req.params.id));
      if (!resolved) {
        res.status(404).json({ error: 'Conversation not found' });
        return;
      }
      const conversation = resolved.conversation;
      const chatService = resolved.runtime?.resources.chatService ?? ctx.services.chat;
      const stateRepo = resolved.runtime?.resources.conversationStateRepo ?? ctx.services.conversationState;
      if (!conversation.url) {
        res.status(400).json({ error: 'No chat URL for this conversation' });
        return;
      }

      const success = await chatService.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 = stateRepo?.get(conversation.roomId);
          const updatedState = mergeConversationState(
            saved,
            buildConversationState([...currentMessages, { sender: 'Me', text: message.trim(), isSelf: true }]),
          );
          updatedState.automation.status = 'user-overridden';
          updatedState.automation.handoffReason = 'A manual reply was sent in this conversation.';
          stateRepo?.save(conversation.roomId, updatedState);
        }
        if (resolved.runtime) {
          resolved.runtime.resources.activityLogRepo.insert({
            timestamp: Date.now(), type: 'sent',
            message: `Sent chat reply to u/${conversation.username}`,
            recipient: conversation.username,
          });
        } else {
          ctx.activity.push('sent', `Sent chat reply to u/${conversation.username}`, conversation.username);
        }
        ctx.broadcaster.push('info', `Chat reply sent to u/${conversation.username}`);
        try {
          // Wait for Matrix /sync to merge the sent event into the cached
          // message history. The dashboard invalidates its queries when this
          // request completes, so returning earlier can immediately re-read
          // the stale pre-send conversation.
          await chatService.refreshTopChats(5);
        } catch (err) {
          // Delivery is already confirmed by Matrix's send response. A sync
          // failure must not turn a successful send into a reported failure.
          ctx.logger.error('Failed to refresh chats after send-reply:', err);
        }
        res.json({ success: true });
      } 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 { accountId, username, message } = req.body ?? {};
      if (!accountId || typeof accountId !== 'string') {
        res.status(400).json({ error: 'accountId is required' });
        return;
      }
      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 runtime = ctx.services.accountRuntimes?.get(accountId);
      if (!runtime || runtime.snapshot().state !== 'running') {
        res.status(409).json({ error: 'Selected Reddit account is not running' });
        return;
      }
      const chat = await runtime.resources.chatService.startConversation(username, message.trim());
      if (!chat) {
        res.status(500).json({ error: 'Failed to start conversation (unknown user or send failed)' });
        return;
      }
      runtime.resources.activityLogRepo.insert({
        timestamp: Date.now(), type: 'sent',
        message: `Started chat with u/${chat.username}`,
        recipient: chat.username,
      });
      if (chat.roomId) {
        runtime.resources.conversationStateRepo.save(
          chat.roomId,
          buildConversationState(chat.messages ?? [{ sender: 'Me', text: message.trim(), isSelf: true }]),
        );
      }
      ctx.broadcaster.push('info', `Started new chat with u/${chat.username}`);
      res.json({ success: true, chat: { ...chat, owner: { accountId, redditUsername: runtime.session.redditUsername } } });
    } catch (error) {
      ctx.logger.error('Failed to start conversation:', error);
      res.status(500).json({ error: String(error) });
    }
  });

  return router;
}