using System;
using System.IO;
using System.Net;
using System.Text;
using System.Security.Cryptography;

namespace com.rwmanila
{
    public class api
    {
        private const string AuthenticationHeaderName = "Authentication";
        private const string TimestampHeaderName = "Timestamp";

        private const string serverUrl = "http://apps-02.rwmanila.com/api";
        private const string publicUserId = "public";
        private const string publicAPIKey = "7CE766FE1473813B97C148EB9F7BD49514B9ECD0";

        public string userId { get; private set; }
        public string apiKey { get; private set; }
        public Uri server { get; private set; }

        public api(string userId = api.publicUserId,
            string apiKey = api.publicAPIKey,
            string server = api.serverUrl)
        {
            this.userId = userId;
            this.apiKey = apiKey;
            this.server = new Uri(server);
        }
        public string send(string request, string contentType)
        {
            string r = string.Empty;
            string t = DateTime.Now.ToString("U");

            try
            {
                HttpWebRequest req = (HttpWebRequest)
                    WebRequest.Create(this.server);
                req.Method = "POST";
                req.ContentType = contentType;
                req.Headers.Add(api.TimestampHeaderName, t);
                req.Headers.Add(api.AuthenticationHeaderName,
                    this.userId + ":" +
                    api.genSignature(this.apiKey,
                        string.Join(" ", req.Method, t, this.server.AbsolutePath).Trim()));
                byte[] postData = Encoding.UTF8.GetBytes(request);
                req.ContentLength = postData.Length;
                using (Stream sreq = req.GetRequestStream())
                    sreq.Write(postData, 0, postData.Length);
                using (Stream sres = req.GetResponse().GetResponseStream())
                using (StreamReader sread = new StreamReader(sres))
                    r = sread.ReadToEnd();
            }
            catch (Exception ex) { r = ex.Message; }
            return r;
        }
        
        private static string genSignature(string apikey, string message)
        {
            var key = Encoding.UTF8.GetBytes(apikey.ToUpper());
            string hashString;

            using (var hmac = new HMACSHA256(key))
            {
                var hash = hmac.ComputeHash(Encoding.UTF8.GetBytes(message.Trim()));
                hashString = Convert.ToBase64String(hash);
            }

            return hashString;
        }
    }
}