<?php
/**
 * Simple session-based authentication.
 * Supports registration, login, SSO callback, and role checks.
 */

// Set secure session cookie params before starting
session_set_cookie_params([
    'lifetime' => 0,
    'path' => '/',
    'httponly' => true,
    'samesite' => 'Lax',
    'secure' => !empty($_SERVER['HTTPS']) || getenv('FORCE_HTTPS'),
]);
session_start();

function current_user(): ?array {
    if (!isset($_SESSION['user_id'])) return null;
    $user = db_one("SELECT id, username, display_name, bio, role, created_at FROM users WHERE id = ?", [$_SESSION['user_id']]);
    return $user ?: null;
}

function require_auth(): array {
    $user = current_user();
    if (!$user) {
        http_response_code(401);
        echo json_encode(['error' => 'Authentication required']);
        exit;
    }
    return $user;
}

function require_admin(): array {
    $user = require_auth();
    if ($user['role'] !== 'admin') {
        http_response_code(403);
        echo json_encode(['error' => 'Admin access required']);
        exit;
    }
    return $user;
}

function require_member(): array {
    $user = require_auth();
    if ($user['role'] === 'viewer') {
        http_response_code(403);
        echo json_encode(['error' => 'Member access required']);
        exit;
    }
    return $user;
}

// --- CSRF protection ---
function check_csrf(): void {
    $method = $_SERVER['REQUEST_METHOD'] ?? 'GET';
    if (!in_array($method, ['POST', 'PUT', 'DELETE'])) return;

    $origin = $_SERVER['HTTP_ORIGIN'] ?? '';
    $referer = $_SERVER['HTTP_REFERER'] ?? '';
    $expected_host = $_SERVER['HTTP_HOST'] ?? '';

    if ($origin) {
        $origin_host = parse_url($origin, PHP_URL_HOST);
        if ($origin_host !== $expected_host) {
            http_response_code(403);
            echo json_encode(['error' => 'Cross-origin requests are not allowed']);
            exit;
        }
    } elseif ($referer) {
        $referer_host = parse_url($referer, PHP_URL_HOST);
        if ($referer_host !== $expected_host) {
            http_response_code(403);
            echo json_encode(['error' => 'Cross-origin requests are not allowed']);
            exit;
        }
    }
}

// --- Rate limiting for login ---
function check_login_rate(string $username): void {
    $ip = $_SERVER['REMOTE_ADDR'] ?? 'unknown';
    $key = 'login_attempts_' . md5($ip . $username);
    $file = sys_get_temp_dir() . '/' . $key;
    $attempts = file_exists($file) ? (int)file_get_contents($file) : 0;
    if ($attempts >= 10) {
        http_response_code(429);
        echo json_encode(['error' => 'Too many login attempts. Try again later.']);
        exit;
    }
}

function record_login_failure(string $username): void {
    $ip = $_SERVER['REMOTE_ADDR'] ?? 'unknown';
    $key = 'login_attempts_' . md5($ip . $username);
    $file = sys_get_temp_dir() . '/' . $key;
    $attempts = file_exists($file) ? (int)file_get_contents($file) : 0;
    file_put_contents($file, ($attempts + 1));
    touch($file, time() + 900);
}

function clear_login_rate(string $username): void {
    $ip = $_SERVER['REMOTE_ADDR'] ?? 'unknown';
    $key = 'login_attempts_' . md5($ip . $username);
    $file = sys_get_temp_dir() . '/' . $key;
    if (file_exists($file)) unlink($file);
}

function handle_register(): void {
    $data = json_body();
    $username = trim($data['username'] ?? '');
    $password = $data['password'] ?? '';
    $display_name = trim($data['display_name'] ?? '');

    if (!preg_match('/^[a-zA-Z0-9_]{3,32}$/', $username)) {
        respond(400, ['error' => 'Username must be 3-32 characters: letters, numbers, underscore']);
        return;
    }
    if (strlen($password) < 8 || strlen($password) > 72) {
        respond(400, ['error' => 'Password must be 8-72 characters']);
        return;
    }
    if (db_one("SELECT id FROM users WHERE username = ?", [$username])) {
        respond(409, ['error' => 'Username already taken']);
        return;
    }

    $user_count = (int) db_one("SELECT COUNT(*) as c FROM users")['c'];
    $role = 'member';

    if ($user_count === 0) {
        $bootstrap_token = getenv('ADMIN_BOOTSTRAP_TOKEN');
        if ($bootstrap_token) {
            $provided = $data['bootstrap_token'] ?? '';
            if ($provided !== $bootstrap_token) {
                respond(403, ['error' => 'First registration requires an admin bootstrap token. Set ADMIN_BOOTSTRAP_TOKEN env var and include it in the registration request.']);
                return;
            }
            $role = 'admin';
        } else {
            error_log('Protocol Droid: First user registered as admin without bootstrap token. Set ADMIN_BOOTSTRAP_TOKEN for production.');
            $role = 'admin';
        }
    }

    if ($user_count > 0) {
        $reg_enabled = db_one("SELECT value FROM config WHERE `key` = 'registration_enabled'");
        if ($reg_enabled && $reg_enabled['value'] !== 'true') {
            respond(403, ['error' => 'Registration is disabled on this instance']);
            return;
        }
        $require_approval = config_get('require_approval', 'false') === 'true';
        if ($require_approval) {
            $role = 'viewer';
        }
    }

    $id = db_insert('users', [
        'username' => $username,
        'display_name' => $display_name ?: $username,
        'password_hash' => password_hash($password, PASSWORD_DEFAULT),
        'role' => $role,
    ]);

    session_regenerate_id(true);
    $_SESSION['user_id'] = $id;
    respond(201, [
        'id' => $id,
        'username' => $username,
        'display_name' => $display_name ?: $username,
        'role' => $role,
    ]);
}

function handle_login(): void {
    $data = json_body();
    $username = trim($data['username'] ?? '');
    $password = $data['password'] ?? '';

    check_login_rate($username);

    $user = db_one("SELECT * FROM users WHERE username = ?", [$username]);
    if (!$user || !password_verify($password, $user['password_hash'] ?? '')) {
        record_login_failure($username);
        respond(401, ['error' => 'Invalid username or password']);
        return;
    }

    clear_login_rate($username);
    session_regenerate_id(true);
    $_SESSION['user_id'] = $user['id'];
    respond(200, [
        'id' => $user['id'],
        'username' => $user['username'],
        'display_name' => $user['display_name'],
        'role' => $user['role'],
    ]);
}

function handle_logout(): void {
    $_SESSION = [];
    session_destroy();
    if (ini_get('session.use_cookies')) {
        $params = session_get_cookie_params();
        setcookie(session_name(), '', time() - 42000,
            $params['path'], $params['domain'],
            $params['secure'], $params['httponly']
        );
    }
    respond(200, ['ok' => true]);
}

function handle_me(): void {
    $user = current_user();
    if (!$user) {
        respond(200, ['user' => null]);
        return;
    }
    respond(200, ['user' => $user]);
}

function handle_sso_callback(): void {
    respond(501, ['error' => 'SSO not configured on this instance. Configure SSO in api/auth.php']);
}