using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace CampusErrand.Services;

/// <summary>
/// 微信开放平台服务实现
/// </summary>
public class WeChatService : IWeChatService
{
    private readonly HttpClient _httpClient;
    private readonly string _appId;
    private readonly string _appSecret;

    public WeChatService(HttpClient httpClient, IConfiguration configuration)
    {
        _httpClient = httpClient;
        var weChatConfig = configuration.GetSection("WeChat");
        _appId = weChatConfig["AppId"]!;
        _appSecret = weChatConfig["AppSecret"]!;
    }

    /// <inheritdoc />
    public async Task<WeChatSessionResult> Code2SessionAsync(string code)
    {
        var url = $"https://api.weixin.qq.com/sns/jscode2session?appid={_appId}&secret={_appSecret}&js_code={code}&grant_type=authorization_code";

        var response = await _httpClient.GetAsync(url);
        if (!response.IsSuccessStatusCode)
        {
            return new WeChatSessionResult
            {
                Success = false,
                ErrorMessage = "微信接口调用失败"
            };
        }

        var json = await response.Content.ReadAsStringAsync();
        Console.WriteLine($"[WeChat] code2session 响应: {json}");
        var result = JsonSerializer.Deserialize<WeChatCode2SessionResponse>(json);

        if (result == null || result.ErrCode != 0)
        {
            Console.WriteLine($"[WeChat] code2session 失败: errcode={result?.ErrCode}, errmsg={result?.ErrMsg}");
            return new WeChatSessionResult
            {
                Success = false,
                ErrorMessage = result?.ErrMsg ?? "微信接口返回异常"
            };
        }

        return new WeChatSessionResult
        {
            Success = true,
            SessionKey = result.SessionKey,
            OpenId = result.OpenId
        };
    }

    /// <inheritdoc />
    public string DecryptPhoneNumber(string sessionKey, string encryptedData, string iv)
    {
        var keyBytes = Convert.FromBase64String(sessionKey);
        var ivBytes = Convert.FromBase64String(iv);
        var dataBytes = Convert.FromBase64String(encryptedData);

        using var aes = Aes.Create();
        aes.Key = keyBytes;
        aes.IV = ivBytes;
        aes.Mode = CipherMode.CBC;
        aes.Padding = PaddingMode.PKCS7;

        using var decryptor = aes.CreateDecryptor();
        var decryptedBytes = decryptor.TransformFinalBlock(dataBytes, 0, dataBytes.Length);
        var decryptedJson = Encoding.UTF8.GetString(decryptedBytes);

        var phoneInfo = JsonSerializer.Deserialize<WeChatPhoneInfo>(decryptedJson);
        return phoneInfo?.PhoneNumber ?? throw new InvalidOperationException("解密手机号失败");
    }
}

/// <summary>
/// 微信 code2Session 响应
/// </summary>
internal class WeChatCode2SessionResponse
{
    [JsonPropertyName("session_key")]
    public string? SessionKey { get; set; }

    [JsonPropertyName("openid")]
    public string? OpenId { get; set; }

    [JsonPropertyName("errcode")]
    public int ErrCode { get; set; }

    [JsonPropertyName("errmsg")]
    public string? ErrMsg { get; set; }
}

/// <summary>
/// 微信解密后的手机号信息
/// </summary>
internal class WeChatPhoneInfo
{
    [JsonPropertyName("phoneNumber")]
    public string? PhoneNumber { get; set; }

    [JsonPropertyName("purePhoneNumber")]
    public string? PurePhoneNumber { get; set; }

    [JsonPropertyName("countryCode")]
    public string? CountryCode { get; set; }
}