<?php
session_start();
require_once 'db/config.php';

header('Content-Type: application/json');

if (!isset($_SESSION['user_id'])) {
    echo json_encode(['success' => false, 'error' => 'User not logged in.']);
    exit();
}

if (!isset($_GET['post_id']) || !isset($_GET['action'])) {
    echo json_encode(['success' => false, 'error' => 'Invalid request.']);
    exit();
}

$postId = (int)$_GET['post_id'];
$action = $_GET['action'];
$userId = $_SESSION['user_id'];
$vote = ($action === 'like') ? 1 : -1;

$pdo = db();

try {
    $pdo->beginTransaction();

    // Check for existing vote
    $stmt = $pdo->prepare('SELECT vote FROM post_votes WHERE user_id = :user_id AND post_id = :post_id');
    $stmt->execute(['user_id' => $userId, 'post_id' => $postId]);
    $existingVote = $stmt->fetchColumn();

    if ($existingVote) {
        if ($existingVote == $vote) {
            // User is undoing their vote
            $stmt = $pdo->prepare('DELETE FROM post_votes WHERE user_id = :user_id AND post_id = :post_id');
            $stmt->execute(['user_id' => $userId, 'post_id' => $postId]);
        } else {
            // User is changing their vote
            $stmt = $pdo->prepare('UPDATE post_votes SET vote = :vote WHERE user_id = :user_id AND post_id = :post_id');
            $stmt->execute(['vote' => $vote, 'user_id' => $userId, 'post_id' => $postId]);
        }
    } else {
        // New vote
        $stmt = $pdo->prepare('INSERT INTO post_votes (user_id, post_id, vote) VALUES (:user_id, :post_id, :vote)');
        $stmt->execute(['user_id' => $userId, 'post_id' => $postId, 'vote' => $vote]);
    }

    $pdo->commit();

    // Fetch new like/dislike counts
    $stmt = $pdo->prepare('SELECT 
        (SELECT COUNT(*) FROM post_votes WHERE post_id = :post_id AND vote = 1) as likes,
        (SELECT COUNT(*) FROM post_votes WHERE post_id = :post_id AND vote = -1) as dislikes
    ');
    $stmt->execute(['post_id' => $postId]);
    $counts = $stmt->fetch(PDO::FETCH_ASSOC);

    echo json_encode(['success' => true, 'likes' => $counts['likes'], 'dislikes' => $counts['dislikes']]);

} catch (Exception $e) {
    $pdo->rollBack();
    echo json_encode(['success' => false, 'error' => 'Database error: ' . $e->getMessage()]);
}