using System.Collections.Specialized;
using System.Net.Http.Headers;
using System.Text;
using DS.Module.Core.Extensions;
using Newtonsoft.Json;

namespace DS.Module.Core
{
    /// <summary>
    /// 提供对HTTP请求的低级别访问
    /// </summary>
    public class ApiFox
    {
        /// <summary>
        /// 基URI
        /// </summary>
        public Uri? BaseUri { get; set; }

        /// <summary>
        /// 默认请求头
        /// </summary>
        public IDictionary<string, string> DefaultHeaders { get; private set; }

        /// <summary>
        /// 在发送网络请求之前的事件
        /// </summary>
        public event EventHandler<BeforeSendEventArgs>? BeforeSend;

        /// <summary>
        /// 在发送网络请求完成时的事件
        /// </summary>
        public event EventHandler<CompleteEventArgs>? Completed;

        /// <summary>
        /// 初始化
        /// </summary>
        public ApiFox()
        {
            DefaultHeaders = new Dictionary<string, string>();
        }

        /// <summary>
        /// 发起<see cref="HttpMethod.Get"/>请求
        /// </summary>
        /// <typeparam name="T">请求结果的类型</typeparam>
        /// <param name="url">请求Url</param>
        /// <param name="keyValues">查询字符串的键值对</param>
        /// <returns></returns>
        /// <exception cref="ArgumentException"><paramref name="url"/>为null或空字符串</exception>
        public async Task<DataResult<T>> GetAsync<T>(string url, NameValueCollection? keyValues = null)
        {
            string queryString = string.Empty;
            if (keyValues != null && keyValues.Count > 0)
            {
                StringBuilder sb = new StringBuilder();
                foreach (string key in keyValues.Keys)
                {
                    var values = keyValues.GetValues(key);
                    if (values?.Length > 0)
                    {
                        for (int i = 0; i < values.Length; i++)
                        {
                            sb.Append($"&{key}={values[i]}");
                        }
                    }
                }

                if (sb.Length > 0) //移除首个&符
                    sb.Remove(0, 1);

                queryString = sb.ToString();
            }

            if (!queryString.IsNullOrEmpty())
                url = url.LastOrDefault() == '?' ? url + queryString : url + "?" + queryString;

            var result = await SendRequestAsync(HttpMethod.Get, url);
            if (!result.Succeeded)
                return DataResult<T>.Failed(result.Message, result.MultiCode);

            var response = result.Data;
            string json = await response.Content.ReadAsStringAsync();
            return DataResult<T>.Success(JsonConvert.DeserializeObject<T>(json));
        }

        /// <summary>
        /// 发起<see cref="HttpMethod.Post"/>请求
        /// </summary>
        /// <typeparam name="T">请求结果的类型</typeparam>
        /// <param name="url">请求Url</param>
        /// <param name="requestParams">请求参数对象</param>
        /// <returns></returns>
        /// <exception cref="ArgumentException"><paramref name="url"/>为null或空字符串</exception>
        public async Task<DataResult<T>> PostAsync<T>(string url, object? requestParams = null)
        {
            var result = await SendRequestAsync(HttpMethod.Post, url, requestParams);
            if (!result.Succeeded)
                return DataResult<T>.Failed(result.Message, result.MultiCode);

            var response = result.Data;
            string json = await response.Content.ReadAsStringAsync();
            return DataResult<T>.Success(JsonConvert.DeserializeObject<T>(json));
        }

        /// <summary>
        /// 发起HTTP请求
        /// </summary>
        /// <param name="method">请求方法</param>
        /// <param name="url">请求Url</param>
        /// <param name="requestParams">请求参数</param>
        /// <returns></returns>
        /// <exception cref="ArgumentNullException"><paramref name="method"/>为null</exception>
        /// <exception cref="ArgumentException"><paramref name="url"/>为null或空字符串</exception>
        public async Task<DataResult<HttpResponseMessage>> SendRequestAsync(HttpMethod method, string url, object? requestParams = null)
        {
            ArgumentNullException.ThrowIfNull(method);
            ArgumentException.ThrowIfNullOrEmpty(url);

            Uri? reqUri = default;
            if (BaseUri == null)
            {
                if (!Uri.TryCreate(url, UriKind.RelativeOrAbsolute, out Uri? uri))
                    throw new ArgumentException("给定的URL格式无效", nameof(url));

                reqUri = new Uri(url);
            }
            else
            {
                reqUri = new(BaseUri, url);
            }

            HttpClient http = new();
            http.DefaultRequestHeaders.Add("User-Agent", $"X-{nameof(ApiFox)}");

            if (DefaultHeaders.Count > 0)
                foreach (var header in DefaultHeaders)
                    http.DefaultRequestHeaders.Add(header.Key, header.Value);

            if (!http.DefaultRequestHeaders.Contains("Accept"))
                http.DefaultRequestHeaders.Add("Accept", "application/json, text/plain");

            OnBeforeSend(new BeforeSendEventArgs
            {
                RequestHeaders = http.DefaultRequestHeaders,
                RequestParameter = requestParams,
                RequestUri = reqUri
            });

            try
            {
                HttpResponseMessage? response = null;
                if (method == HttpMethod.Get)
                {
                    response = await http.GetAsync(reqUri);
                }
                else if (method == HttpMethod.Post)
                {
                    var jsonRequest = new StringContent(JsonConvert.SerializeObject(requestParams), Encoding.UTF8, "application/json");
                    response = await http.PostAsync(reqUri, jsonRequest);
                }
                else if (method == HttpMethod.Put)
                {
                    var jsonRequest = new StringContent(JsonConvert.SerializeObject(requestParams), Encoding.UTF8, "application/json");
                    response = await http.PutAsync(reqUri, jsonRequest);
                }
                else if (method == HttpMethod.Delete)
                {
                    response = await http.DeleteAsync(reqUri);
                }
                else
                {
                    throw new NotSupportedException($"不支持的请求方法：{method.Method}");
                }

                OnCompleted(new CompleteEventArgs 
                {
                    RequestUri = reqUri,
                    Response = response
                });

                if (!response.IsSuccessStatusCode)
                    return DataResult<HttpResponseMessage>.FailedData(response, string.Format(MultiLanguageConst.HttpRequestFailed, $"{response.StatusCode}"));

                return DataResult<HttpResponseMessage>.Success(response);
            }
            finally
            {
                http?.Dispose();
            }
        }

        /// <summary>
        /// 在发送网络请求之前调用
        /// </summary>
        /// <param name="e">事件参数</param>
        protected virtual void OnBeforeSend(BeforeSendEventArgs e)
        {
            BeforeSend?.Invoke(this, e);
        }

        /// <summary>
        /// 在发送网络请求完成时调用
        /// </summary>
        /// <param name="e">事件参数</param>
        protected virtual void OnCompleted(CompleteEventArgs e)
        {
            Completed?.Invoke(this, e);
        }
    }

    /// <summary>
    /// 发送网络请求之前的事件参数
    /// </summary>
    public class BeforeSendEventArgs : EventArgs
    {
        /// <summary>
        /// 远程请求的URI
        /// </summary>
        public Uri RequestUri { get; internal set; }

        /// <summary>
        /// 请求标头
        /// </summary>
        public HttpRequestHeaders RequestHeaders { get; internal set; }

        /// <summary>
        /// 请求参数
        /// </summary>
        public object? RequestParameter { get; set; }
    }

    /// <summary>
    /// 发送网络请求完成的事件参数
    /// </summary>
    public class CompleteEventArgs : EventArgs
    {
        /// <summary>
        /// 远程请求的URI
        /// </summary>
        public Uri RequestUri { get; internal set; }

        /// <summary>
        /// 网络响应对象
        /// </summary>
        public HttpResponseMessage Response { get; internal set; }
    }
}