<?php
// 接受数据，并且提取出action
$data = json_decode(file_get_contents('php://input'), true);
$action = $data['action'] ?? '';

// 处理与用户相关的操作
include 'db.php';

// 如果数据库连接失败，则返回错误信息
/** @var mysqli $conn */
if (!isset($conn)) {
    echo json_encode(['code' => 10004, 'status' => 'error', 'message' => '数据库连接失败']);
    exit;
}

// 测试用户名是否已存在
function testUsername(mysqli $conn, string $username): bool
{
    $sql = "select * from users where username = '$username'"; // sql注入风险
    $result = mysqli_query($conn, $sql);
    if (mysqli_num_rows($result) > 0) {
        return true;
    } else {
        return false;
    }
}

// 如果action是register，则注册用户
if ($action == 'register') {
    $username = $data['username'];
    $password = $data['password'];
    $email = $data['email'];
    if (testUsername($conn, $username)) {
        echo json_encode(['code' => 10001, 'status' => 'error', 'message' => '用户名已存在']);
    } else {
        $sql = "insert into users (username, password, email) values ('$username', '$password', '$email')";
        $result = mysqli_query($conn, $sql);
        if ($result) {
            echo json_encode(['code' => 0, 'status' => 'success', 'message' => '注册成功']);
        } else {
            echo json_encode(['code' => 10002, 'status' => 'error', 'message' => '注册失败']);
        }
    }
}

// login的逻辑
if ($action == 'login') {
    $username = $data['username'];
    $password = $data['password'];
    $sql = "select * from users where username = '$username' and password = '$password'";
    $result = mysqli_query($conn, $sql);
    if (mysqli_num_rows($result) > 0) {
        echo json_encode(['code' => 0, 'status' => 'success', 'message' => '登录成功']);
    } else {
        echo json_encode(['code' => 10003, 'status' => 'error', 'message' => '用户名或密码错误']);
    }
}