const express = require("express");
const mongoose = require("mongoose");
const Comment = require("../models/Comment");
const Post = require("../models/Post");
const auth = require("../middleware/auth");
const { paginate, buildPaginatedResponse } = require("../middleware/pagination");
const { asyncHandler } = require("../middleware/errorHandler");

const router = express.Router();

/**
 * GET /api/posts/:postId/comments
 * Get all comments for a post (paginated)
 */
router.get(
  "/:postId/comments",
  paginate,
  asyncHandler(async (req, res) => {
    const { postId } = req.params;
    const { skip, limit, page } = req.pagination;

    // Verify post exists
    const post = await Post.findById(postId);
    if (!post) {
      return res.status(404).json({ msg: "Post not found" });
    }

    // Get comments with pagination
    const comments = await Comment.find({ post: postId })
      .sort({ createdAt: -1 })
      .skip(skip)
      .limit(limit)
      .populate("user", ["name", "profilePicture"]);

    const totalCount = await Comment.countDocuments({ post: postId });

    res.json(buildPaginatedResponse(comments, totalCount, page, limit));
  })
);

/**
 * POST /api/posts/:postId/comments
 * Create a new comment on a post
 */
router.post(
  "/:postId/comments",
  auth,
  asyncHandler(async (req, res) => {
    const { postId } = req.params;
    const { content } = req.body;

    // Validate content
    if (!content || content.trim().length === 0) {
      return res.status(400).json({ msg: "Comment content is required" });
    }

    if (content.length > 500) {
      return res
        .status(400)
        .json({ msg: "Comment content must be 500 characters or less" });
    }

    // Verify post exists
    const post = await Post.findById(postId);
    if (!post) {
      return res.status(404).json({ msg: "Post not found" });
    }

    // Create comment
    const newComment = new Comment({
      user: req.user.id,
      post: postId,
      content: content.trim(),
    });

    const comment = await newComment.save();

    // Update post's comment count
    await Post.findByIdAndUpdate(postId, {
      $inc: { commentsCount: 1 },
    });

    // Populate user data before sending response
    await comment.populate("user", ["name", "profilePicture"]);

    // Emit Socket.IO event for new comment
    const io = req.app.get("io");
    if (io) {
      io.to(`post_${postId}`).emit("newComment", {
        postId,
        comment,
      });
    }

    res.status(201).json(comment);
  })
);

/**
 * DELETE /api/posts/:postId/comments/:commentId
 * Delete own comment
 */
router.delete(
  "/:postId/comments/:commentId",
  auth,
  asyncHandler(async (req, res) => {
    const { postId, commentId } = req.params;

    // Find comment
    const comment = await Comment.findById(commentId);
    if (!comment) {
      return res.status(404).json({ msg: "Comment not found" });
    }

    // Verify comment belongs to the post
    if (comment.post.toString() !== postId) {
      return res.status(400).json({ msg: "Comment does not belong to this post" });
    }

    // Verify user owns the comment
    if (comment.user.toString() !== req.user.id) {
      return res.status(403).json({ msg: "Not authorized to delete this comment" });
    }

    // Delete comment
    await Comment.findByIdAndDelete(commentId);

    // Update post's comment count
    await Post.findByIdAndUpdate(postId, {
      $inc: { commentsCount: -1 },
    });

    // Emit Socket.IO event for deleted comment
    const io = req.app.get("io");
    if (io) {
      io.to(`post_${postId}`).emit("commentDeleted", {
        postId,
        commentId,
      });
    }

    res.json({ msg: "Comment deleted successfully" });
  })
);

module.exports = router;