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

// Find-or-create DM channel between two users
export const openDM = mutation({
  args: {
    userId: v.id("userProfiles"),
    targetUserId: v.id("userProfiles"),
  },
  returns: v.object({
    channelId: v.id("channels"),
    created: v.boolean(),
  }),
  handler: async (ctx, args) => {
    if (args.userId === args.targetUserId) {
      throw new Error("Cannot DM yourself");
    }

    // Deterministic channel name
    const sorted = [args.userId, args.targetUserId].sort();
    const dmName = `dm-${sorted[0]}-${sorted[1]}`;

    // Check if already exists
    const existing = await ctx.db
      .query("channels")
      .withIndex("by_name", (q) => q.eq("name", dmName))
      .unique();

    if (existing) {
      return { channelId: existing._id, created: false };
    }

    // Create DM channel
    const channelId = await ctx.db.insert("channels", {
      name: dmName,
      type: "dm",
    });

    // Add participants
    await ctx.db.insert("dmParticipants", {
      channelId,
      userId: args.userId,
    });
    await ctx.db.insert("dmParticipants", {
      channelId,
      userId: args.targetUserId,
    });

    return { channelId, created: true };
  },
});

// List user's DM channels with other user info
export const listDMs = query({
  args: { userId: v.id("userProfiles") },
  returns: v.array(
    v.object({
      channel_id: v.id("channels"),
      channel_name: v.string(),
      other_user_id: v.string(),
      other_username: v.string(),
    })
  ),
  handler: async (ctx, args) => {
    // Get all DM participations for this user
    const myParticipations = await ctx.db
      .query("dmParticipants")
      .withIndex("by_user", (q) => q.eq("userId", args.userId))
      .collect();

    const result: Array<{
      channel_id: typeof myParticipations[0]["channelId"];
      channel_name: string;
      other_user_id: string;
      other_username: string;
    }> = [];

    for (const part of myParticipations) {
      const channel = await ctx.db.get(part.channelId);
      if (!channel || channel.type !== "dm") continue;

      // Find other participant
      const otherParts = await ctx.db
        .query("dmParticipants")
        .withIndex("by_channel", (q) => q.eq("channelId", part.channelId))
        .collect();

      const otherPart = otherParts.find((p) => p.userId !== args.userId);
      if (!otherPart) continue;

      const otherUser = await ctx.db.get(otherPart.userId);
      if (!otherUser) continue;

      result.push({
        channel_id: part.channelId,
        channel_name: channel.name,
        other_user_id: otherUser._id,
        other_username: otherUser.username,
      });
    }

    return result;
  },
});