<?php
require_once __DIR__ . '/../../includes/auth.php';
header('Content-Type: application/json');

if (!isLoggedIn()) { echo json_encode(['success'=>false,'error'=>'Not authenticated']); exit; }

$action = $_GET['action'] ?? '';
$userId = $_SESSION['user_id'];
$isAdmin = !empty($_SESSION['is_admin']);

switch ($action) {

    // ── User: get own messages ─────────────────────────────
    case 'messages':
        $since = (int)($_GET['since'] ?? 0); // last message id for polling
        $stmt = db()->prepare("
            SELECT id, sender, message, is_read, created_at
            FROM chat_messages
            WHERE user_id = ? AND id > ?
            ORDER BY id ASC
            LIMIT 100
        ");
        $stmt->execute([$userId, $since]);
        $msgs = $stmt->fetchAll();

        // Mark admin messages as read
        db()->prepare("UPDATE chat_messages SET is_read=1 WHERE user_id=? AND sender='admin' AND is_read=0")->execute([$userId]);

        echo json_encode(['success'=>true, 'messages'=>$msgs]);
        break;

    // ── User: send message to admin ───────────────────────
    case 'send':
        if ($_SERVER['REQUEST_METHOD'] !== 'POST') { echo json_encode(['success'=>false]); exit; }
        $data = json_decode(file_get_contents('php://input'), true);
        $msg  = trim($data['message'] ?? '');
        if (empty($msg) || mb_strlen($msg) > 2000) { echo json_encode(['success'=>false,'error'=>'Invalid message']); exit; }

        $stmt = db()->prepare("INSERT INTO chat_messages (user_id, sender, message) VALUES (?, 'user', ?)");
        $stmt->execute([$userId, $msg]);
        echo json_encode(['success'=>true, 'id'=>db()->lastInsertId()]);
        break;

    // ── Admin: get inbox list (one row per user, latest msg) ──
    case 'admin_inbox':
        if (!$isAdmin) { echo json_encode(['success'=>false,'error'=>'Forbidden']); exit; }
        $rows = db()->query("
            SELECT
                u.id AS user_id,
                u.username,
                u.alias,
                cm.message AS last_message,
                cm.sender  AS last_sender,
                cm.created_at AS last_time,
                SUM(CASE WHEN cm2.sender='user' AND cm2.is_read=0 THEN 1 ELSE 0 END) AS unread_count
            FROM users u
            JOIN chat_messages cm ON cm.id = (
                SELECT id FROM chat_messages
                WHERE user_id = u.id
                ORDER BY id DESC LIMIT 1
            )
            LEFT JOIN chat_messages cm2 ON cm2.user_id = u.id
            GROUP BY u.id, u.username, u.alias, cm.message, cm.sender, cm.created_at
            ORDER BY cm.created_at DESC
        ")->fetchAll();
        echo json_encode(['success'=>true, 'inbox'=>$rows]);
        break;

    // ── Admin: get all messages for a specific user ────────
    case 'admin_thread':
        if (!$isAdmin) { echo json_encode(['success'=>false,'error'=>'Forbidden']); exit; }
        $tid   = (int)($_GET['user_id'] ?? 0);
        $since = (int)($_GET['since']   ?? 0);
        if (!$tid) { echo json_encode(['success'=>false,'error'=>'user_id required']); exit; }

        $stmt = db()->prepare("
            SELECT id, sender, message, is_read, created_at
            FROM chat_messages
            WHERE user_id = ? AND id > ?
            ORDER BY id ASC LIMIT 200
        ");
        $stmt->execute([$tid, $since]);
        $msgs = $stmt->fetchAll();

        // Mark user messages as read
        db()->prepare("UPDATE chat_messages SET is_read=1 WHERE user_id=? AND sender='user' AND is_read=0")->execute([$tid]);

        // Get user info
        $uStmt = db()->prepare("SELECT id, username, alias, tokens FROM users WHERE id=?");
        $uStmt->execute([$tid]);
        $user = $uStmt->fetch();

        echo json_encode(['success'=>true, 'messages'=>$msgs, 'user'=>$user]);
        break;

    // ── Admin: reply to a user ────────────────────────────
    case 'admin_send':
        if (!$isAdmin) { echo json_encode(['success'=>false,'error'=>'Forbidden']); exit; }
        if ($_SERVER['REQUEST_METHOD'] !== 'POST') { echo json_encode(['success'=>false]); exit; }
        $data   = json_decode(file_get_contents('php://input'), true);
        $tid    = (int)($data['user_id'] ?? 0);
        $msg    = trim($data['message'] ?? '');
        if (!$tid || empty($msg) || mb_strlen($msg) > 2000) { echo json_encode(['success'=>false,'error'=>'Invalid']); exit; }

        $stmt = db()->prepare("INSERT INTO chat_messages (user_id, sender, message) VALUES (?, 'admin', ?)");
        $stmt->execute([$tid, $msg]);
        echo json_encode(['success'=>true, 'id'=>db()->lastInsertId()]);
        break;

    // ── Unread count (for badge) ──────────────────────────
    case 'unread':
        if ($isAdmin) {
            $count = db()->query("SELECT COUNT(*) FROM chat_messages WHERE sender='user' AND is_read=0")->fetchColumn();
        } else {
            $stmt = db()->prepare("SELECT COUNT(*) FROM chat_messages WHERE user_id=? AND sender='admin' AND is_read=0");
            $stmt->execute([$userId]);
            $count = $stmt->fetchColumn();
        }
        echo json_encode(['success'=>true, 'count'=>(int)$count]);
        break;

    default:
        echo json_encode(['success'=>false,'error'=>'Unknown action']);
}