<?php
/**
 * 检查数据库版本是否需要升级
 * 返回 JSON: {needs_upgrade: bool, current: string, target: string}
 */

require_once __DIR__ . '/../config.php';

header('Content-Type: application/json; charset=utf-8');

// 只有班主任才能检查升级
if (!isset($_SESSION['user_id']) || $_SESSION['user_type'] !== 'admin') {
    echo json_encode(['error' => '未授权']);
    exit();
}

$role = $_SESSION['role'] ?? '';
if ($role !== '班主任') {
    echo json_encode(['needs_upgrade' => false]);
    exit();
}

// 读取后端 .env 获取数据库配置
$envPath = __DIR__ . '/../../backend/.env';
if (!file_exists($envPath)) {
    echo json_encode(['error' => '数据库配置文件不存在']);
    exit();
}

$lines = file($envPath, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
$dbConfig = [];
foreach ($lines as $line) {
    $line = trim($line);
    if ($line === '' || strpos($line, '#') === 0) {
        continue;
    }
    if (strpos($line, '=') !== false) {
        list($key, $value) = explode('=', $line, 2);
        $dbConfig[trim($key)] = trim($value);
    }
}

$required = ['DB_HOST', 'DB_PORT', 'DB_USER', 'DB_PASSWORD', 'DB_NAME'];
foreach ($required as $key) {
    if (!isset($dbConfig[$key]) || $dbConfig[$key] === '') {
        echo json_encode(['error' => "缺少数据库配置: {$key}"]);
        exit();
    }
}

try {
    $dsn = "mysql:host={$dbConfig['DB_HOST']};port={$dbConfig['DB_PORT']};dbname={$dbConfig['DB_NAME']};charset=utf8mb4";
    $pdo = new PDO($dsn, $dbConfig['DB_USER'], $dbConfig['DB_PASSWORD'], [
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
    ]);

    // 检测当前版本
    $currentVersion = '0.0.0';
    try {
        $stmt = $pdo->query("SELECT setting_value FROM system_settings WHERE setting_key = 'db_version'");
        $row = $stmt->fetch(PDO::FETCH_ASSOC);
        if ($row) {
            $currentVersion = $row['setting_value'];
        }
    } catch (PDOException $e) {
        // 表不存在，使用默认值
    }

    // 读取目标版本
    $versionFile = __DIR__ . '/../../VERSION';
    if (!file_exists($versionFile)) {
        echo json_encode(['error' => 'VERSION 文件不存在']);
        exit();
    }
    $targetVersion = trim(file_get_contents($versionFile));

    $needsUpgrade = version_compare($targetVersion, $currentVersion, '>');

    $allVersions = [
        '1.7'   => 'v1.7.sql',
        '1.8'   => 'v1.8.sql',
        '2.0'   => 'v2.0.sql',
        '2.0.1' => 'v2.0.1.sql',
        '2.1'   => 'v2.1.sql',
    ];
    $steps = [];
    foreach ($allVersions as $version => $file) {
        if (version_compare($version, $currentVersion, '>') &&
            version_compare($version, $targetVersion, '<=')) {
            $steps[] = ['version' => $version, 'file' => $file];
        }
    }
    usort($steps, function($a, $b) { return version_compare($a['version'], $b['version']); });

    echo json_encode([
        'needs_upgrade' => $needsUpgrade,
        'current' => $currentVersion,
        'target' => $targetVersion,
        'steps' => $steps
    ]);
} catch (PDOException $e) {
    echo json_encode(['error' => '数据库连接失败: ' . $e->getMessage()]);
}