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

if (!isset($_SESSION['user_id']) || !isset($_SESSION['user_type'])) {
    http_response_code(401);
    echo json_encode(['error' => 'Unauthorized']);
    exit;
}

$action = $_GET['action'] ?? null;
$userId = $_SESSION['user_id'];
$userType = $_SESSION['user_type'];

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

switch ($action) {
    case 'get_conversations':
        $db = db();
        // This query is complex. It gets the last message for each conversation.
        $stmt = $db->prepare("
            SELECT 
                other_user.id as user_id,
                other_user.type as user_type,
                other_user.name,
                last_message.message,
                last_message.created_at,
                (SELECT COUNT(*) FROM messages WHERE receiver_id = :user_id AND receiver_type = :user_type AND sender_id = other_user.id AND sender_type = other_user.type AND is_read = 0) as unread_count
            FROM (
                SELECT 
                    CASE WHEN sender_id = :user_id AND sender_type = :user_type THEN receiver_id ELSE sender_id END as other_id,
                    CASE WHEN sender_id = :user_id AND sender_type = :user_type THEN receiver_type ELSE sender_type END as other_type,
                    MAX(id) as last_message_id
                FROM messages
                WHERE (sender_id = :user_id AND sender_type = :user_type) OR (receiver_id = :user_id AND receiver_type = :user_type)
                GROUP BY other_id, other_type
            ) as conversations
            JOIN messages as last_message ON last_message.id = conversations.last_message_id
            JOIN (
                SELECT id, name, 'coach' as type FROM coaches
                UNION ALL
                SELECT id, name, 'client' as type FROM clients
            ) as other_user ON other_user.id = conversations.other_id AND other_user.type = conversations.other_type
            ORDER BY last_message.created_at DESC
        ");

        $stmt->execute(['user_id' => $userId, 'user_type' => $userType]);
        $conversations = $stmt->fetchAll(PDO::FETCH_ASSOC);

        echo json_encode($conversations);
        break;

    case 'get_messages':
        $peerId = $_GET['user_id'] ?? null;
        $peerType = $_GET['user_type'] ?? null;

        if (empty($peerId) || empty($peerType)) {
            http_response_code(400);
            echo json_encode(['error' => 'Missing user_id or user_type']);
            exit;
        }

        $db = db();
        // Mark messages as read
        $updateStmt = $db->prepare("UPDATE messages SET is_read = 1 WHERE sender_id = ? AND sender_type = ? AND receiver_id = ? AND receiver_type = ?");
        $updateStmt->execute([$peerId, $peerType, $userId, $userType]);

        // Fetch messages
        $stmt = $db->prepare("SELECT * FROM messages WHERE (sender_id = ? AND sender_type = ? AND receiver_id = ? AND receiver_type = ?) OR (sender_id = ? AND sender_type = ? AND receiver_id = ? AND receiver_type = ?) ORDER BY created_at ASC");
        $stmt->execute([$userId, $userType, $peerId, $peerType, $peerId, $peerType, $userId, $userType]);
        $messages = $stmt->fetchAll(PDO::FETCH_ASSOC);

        echo json_encode($messages);
        break;

    case 'send_message':
        $data = json_decode(file_get_contents('php://input'), true);
        if (empty($data['receiver_id']) || empty($data['receiver_type']) || empty($data['message'])) {
            http_response_code(400);
            echo json_encode(['error' => 'Missing required fields']);
            exit;
        }

        $db = db();
        $stmt = $db->prepare("INSERT INTO messages (sender_id, sender_type, receiver_id, receiver_type, message) VALUES (?, ?, ?, ?, ?)");
        if ($stmt->execute([$userId, $userType, $data['receiver_id'], $data['receiver_type'], $data['message']])) {
            // Send email notification
            require_once __DIR__ . '/../mail/MailService.php';

            $receiverTable = $data['receiver_type'] === 'coach' ? 'coaches' : 'clients';
            $stmt = $db->prepare("SELECT email FROM {$receiverTable} WHERE id = ?");
            $stmt->execute([$data['receiver_id']]);
            $recipient = $stmt->fetch(PDO::FETCH_ASSOC);

            if ($recipient && !empty($recipient['email'])) {
                $to = $recipient['email'];
                $subject = 'You have a new message';
                $messageBody = 'You have received a new message. Click here to view: <a href="http://' . $_SERVER['HTTP_HOST'] . '/messages.php">View Messages</a>';
                MailService::sendMail($to, $subject, $messageBody, strip_tags($messageBody));
            }
            echo json_encode(['success' => true]);
        } else {
            http_response_code(500);
            echo json_encode(['error' => 'Failed to send message']);
        }
        break;

    default:
        http_response_code(400);
        echo json_encode(['error' => 'Invalid action']);
        break;
}