import { query, mutation } from "./_generated/server";
import { v } from "convex/values";
import { paginationOptsValidator } from "convex/server";

export const listByUser = query({
  args: { token: v.string() },
  handler: async (ctx, args) => {
    const session = await ctx.db
      .query("sessions")
      .withIndex("by_token", (q) => q.eq("token", args.token))
      .first();
    if (!session) return [];

    const allChats = await ctx.db.query("chats").order("desc").collect();
    const userChats = allChats.filter((chat) =>
      chat.participantIds.includes(session.userId)
    );

    const enriched = await Promise.all(
      userChats.map(async (chat) => {
        const otherId = chat.participantIds.find(
          (id) => id !== session.userId
        )!;
        const otherUser = await ctx.db.get(otherId);
        const lastMessage = await ctx.db
          .query("messages")
          .withIndex("by_chat", (q) => q.eq("chatId", chat._id))
          .order("desc")
          .first();

        return {
          _id: chat._id,
          otherUser: otherUser
            ? {
                _id: otherUser._id,
                name: otherUser.name,
                avatarId: otherUser.avatarId ?? null,
              }
            : null,
          lastMessage: lastMessage
            ? {
                content: lastMessage.content,
                createdAt: lastMessage.createdAt,
                senderId: lastMessage.senderId,
              }
            : null,
          lastMessageAt: chat.lastMessageAt,
        };
      })
    );

    return enriched.sort((a, b) => b.lastMessageAt - a.lastMessageAt);
  },
});

export const listByUserPaginated = query({
  args: { token: v.string(), paginationOpts: paginationOptsValidator },
  handler: async (ctx, args) => {
    const session = await ctx.db
      .query("sessions")
      .withIndex("by_token", (q) => q.eq("token", args.token))
      .first();
    if (!session) {
      return { page: [], continuationCursor: null, isDone: true };
    }

    const result = await ctx.db
      .query("chats")
      .order("desc")
      .paginate(args.paginationOpts);

    const filtered = result.page.filter((chat) =>
      chat.participantIds.includes(session.userId)
    );

    const enriched = await Promise.all(
      filtered.map(async (chat) => {
        const otherId = chat.participantIds.find(
          (id) => id !== session.userId
        )!;
        const otherUser = await ctx.db.get(otherId);
        const lastMessage = await ctx.db
          .query("messages")
          .withIndex("by_chat", (q) => q.eq("chatId", chat._id))
          .order("desc")
          .first();

        return {
          _id: chat._id,
          otherUser: otherUser
            ? {
                _id: otherUser._id,
                name: otherUser.name,
                avatarId: otherUser.avatarId ?? null,
              }
            : null,
          lastMessage: lastMessage
            ? {
                content: lastMessage.content,
                createdAt: lastMessage.createdAt,
                senderId: lastMessage.senderId,
              }
            : null,
          lastMessageAt: chat.lastMessageAt,
        };
      })
    );

    return {
      page: enriched.sort((a, b) => b.lastMessageAt - a.lastMessageAt),
      continueCursor: result.continueCursor,
      isDone: result.isDone,
    };
  },
});

export const getOrCreate = mutation({
  args: {
    token: v.string(),
    partnerId: v.id("users"),
  },
  handler: async (ctx, args) => {
    const session = await ctx.db
      .query("sessions")
      .withIndex("by_token", (q) => q.eq("token", args.token))
      .first();
    if (!session) throw new Error("Неавторизиран");

    const allChats = await ctx.db.query("chats").collect();
    const existing = allChats.find(
      (c) =>
        c.participantIds.includes(session.userId) &&
        c.participantIds.includes(args.partnerId) &&
        c.participantIds.length === 2
    );

    if (existing) return existing._id;

    const chatId = await ctx.db.insert("chats", {
      participantIds: [session.userId, args.partnerId],
      lastMessageAt: Date.now(),
      createdBy: session.userId,
    });

    return chatId;
  },
});

export const getById = query({
  args: { token: v.string(), chatId: v.id("chats") },
  handler: async (ctx, args) => {
    const session = await ctx.db
      .query("sessions")
      .withIndex("by_token", (q) => q.eq("token", args.token))
      .first();
    if (!session) throw new Error("Неавторизиран");

    const chat = await ctx.db.get(args.chatId);
    if (!chat) throw new Error("Разговорот не е пронајден");

    if (!chat.participantIds.includes(session.userId)) {
      throw new Error("Немате пристап до овој разговор");
    }

    const otherId = chat.participantIds.find(
      (id) => id !== session.userId
    )!;
    const otherUser = await ctx.db.get(otherId);

    return {
      _id: chat._id,
      participantIds: chat.participantIds,
      otherUser: otherUser
        ? {
            _id: otherUser._id,
            name: otherUser.name,
            avatarId: otherUser.avatarId ?? null,
          }
        : null,
      lastMessageAt: chat.lastMessageAt,
    };
  },
});