using System;
using System.Collections.Generic;
using System.Security.Cryptography;
using System.Text;
using static System.Net.WebRequestMethods;

namespace Vinno.vCloud.XunFeiAudio
{
    public class SkyNetAuth
    {
        //编码，使用UTF8
        private static Encoding CHARSET_UTF8 = Encoding.UTF8;
        //加密
        private static string DIGEST_NAME = "SHA-256";

        private static string AUTH_KEY = "Authorization";

        public static string generateAuthUrl(String apiKey, String apiSecret, String url)
        {
            AuthorizationData authorizationData = assemble(Http.Get, url, apiKey, apiSecret, null, null);

            string authBase = Convert.ToBase64String(CHARSET_UTF8.GetBytes(authorizationData.Authorization));

            authBase = string.Format("{0}?{1}={2}&host={3}&date={4}", url, AUTH_KEY.ToLower(), UrlEncode(authBase, Encoding.UTF8),
                     UrlEncode(authorizationData.Host, Encoding.UTF8), UrlEncode(authorizationData.Date, Encoding.UTF8));
            return authBase;
        }

        public static string generateAuthUrl(String apiKey, String apiSecret, String url, string body, String apiKeyKey)
        {
            AuthorizationData authorizationData = assemble(Http.Get, url, apiKey, apiSecret, body, apiKeyKey);

            string authBase = Convert.ToBase64String(CHARSET_UTF8.GetBytes(authorizationData.Authorization));

            authBase = string.Format("{0}?{1}={2}&host={3}&date={4}", url, AUTH_KEY.ToLower(), UrlEncode(authBase, Encoding.UTF8),
                     UrlEncode(authorizationData.Host, Encoding.UTF8), UrlEncode(authorizationData.Date, Encoding.UTF8));
            return authBase;
        }


        private static AuthorizationData assemble(string httpMethod, string requestUrl, string apiKey, string apiSecret, string body, string apiKeyKey)
        {
            if (string.IsNullOrEmpty(requestUrl))
            {
                throw new Exception("requestUr is empty.");
            }
            if (string.IsNullOrEmpty(apiKey))
            {
                throw new Exception("apiKey is empty.");
            }
            if (string.IsNullOrEmpty(apiSecret))
            {
                throw new Exception("apiSecret is empty.");
            }
            string httpRequestUrl = requestUrl.Replace("ws://", "http://").Replace("wss://", "https://");

            Uri uri = new Uri(httpRequestUrl);

            string dateStr = DateTime.UtcNow.GetDateTimeFormats('r')[0].ToString();

            string sha = getSignature(uri.Host, dateStr, getRequestLine(httpMethod, uri.AbsolutePath), apiSecret);

            string digest = null;

            if (!string.IsNullOrEmpty(body))
            {
                digest = signBody(body);
            }

            apiKeyKey = string.IsNullOrEmpty(apiKeyKey) ? "hmac api_key" : apiKeyKey;
            string authorization = string.Format("{0}=\"{1}\", algorithm=\"hmac-sha256\", headers=\"host date request-line{2}\", signature=\"{3}\"", apiKeyKey, apiKey, string.IsNullOrEmpty(digest) ? "" : " digest", sha);
            AuthorizationData authorizationData = new AuthorizationData();

            authorizationData.Date = dateStr;
            authorizationData.Host = uri.Host;
            authorizationData.Authorization = authorization;
            authorizationData.Digest = digest;
            return authorizationData;
        }

        private static string getRequestLine(string method, string path)
        {
            return string.Format("{0} {1} HTTP/1.1", method.ToUpper(), path);
        }

        private static string signBody(String body)
        {
            if (string.IsNullOrEmpty(body))
            {
                throw new Exception("body is empty.");
            }
            return signBody(CHARSET_UTF8.GetBytes(body));

        }

        private static string signBody(byte[] body)
        {
            if (null == body || body.Length == 0)
            {
                throw new Exception("body is empty.");
            }
            var sha256 = new SHA256Managed();
            byte[] hashmessage = sha256.ComputeHash(body);
            return Convert.ToBase64String(hashmessage);
        }

        private static string getSignature(string host, string date, string requestLine, string apiSecret)
        {

            if (string.IsNullOrEmpty(host))
            {
                throw new Exception("host is empty.");
            }
            if (string.IsNullOrEmpty(date))
            {
                throw new Exception("date is empty.");
            }
            if (string.IsNullOrEmpty(requestLine))
            {
                throw new Exception("requestLine is empty.");
            }
            if (string.IsNullOrEmpty(apiSecret))
            {
                throw new Exception("apiSecret is empty.");
            }

            StringBuilder builder = new StringBuilder("host: ").Append(host).Append("\n").Append("date: ").Append(date).Append("\n").Append(requestLine);

            byte[] keyByte = CHARSET_UTF8.GetBytes(apiSecret);
            byte[] messageBytes = System.Text.Encoding.UTF8.GetBytes(builder.ToString());
            using (var hmacsha256 = new HMACSHA256(keyByte))
            {
                byte[] hashmessage = hmacsha256.ComputeHash(messageBytes);
                return Convert.ToBase64String(hashmessage);
            }
        }

        private static string UrlEncode(string str, Encoding encoding)
        {
            StringBuilder sb = new StringBuilder();
            byte[] byStr = encoding.GetBytes(str);
            for (int i = 0; i < byStr.Length; i++)
            {
                sb.Append(@"%" + Convert.ToString(byStr[i], 16));
            }
            return (sb.ToString());
        }

        class AuthorizationData
        {
            public string Date { get; set; }
            public string Host { get; set; }
            public string Authorization { get; set; }
            public string Digest { get; set; }

            public Dictionary<string, string> GetHeader()
            {
                Dictionary<string, string> headers = new Dictionary<string, string>();
                headers.Add("Host", Host);
                headers.Add("Date", Date);
                if (!string.IsNullOrEmpty(Digest))
                {
                    headers.Add("Digest", string.Format("%s=%s", DIGEST_NAME, Digest));
                }
                headers.Add(AUTH_KEY, Authorization);
                return headers;
            }

        }
    }
}