using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace UMP.Services.Helpers
{
    internal static class HttpUtility
    {
        public static IEnumerable<string> GetUrisFromManifest(string source)
        {
            var opening = "<BaseURL>";
            var closing = "</BaseURL>";
            var start = source.IndexOf(opening);

            if (start != -1)
            {
                var temp = source.Substring(start);
                var uris = temp.Split(new string[] { opening }, StringSplitOptions.RemoveEmptyEntries)
                    .Select(v => v.Substring(0, v.IndexOf(closing)));

                return uris;
            }

            throw new NotSupportedException();
        }

        public static string UrlDecode(string str)
        {
            return UrlDecode(str, Encoding.UTF8);
        }

        public static string UrlDecode(string s, Encoding e)
        {
            if (null == s)
                return null;

            if (s.IndexOf('%') == -1 && s.IndexOf('+') == -1)
                return s;

            if (e == null)
                e = Encoding.UTF8;

            long len = s.Length;
            var bytes = new List<byte>();
            int xchar;
            char ch;

            for (int i = 0; i < len; i++)
            {
                ch = s[i];
                if (ch == '%' && i + 2 < len && s[i + 1] != '%')
                {
                    if (s[i + 1] == 'u' && i + 5 < len)
                    {
                        // unicode hex sequence
                        xchar = GetChar(s, i + 2, 4);
                        if (xchar != -1)
                        {
                            WriteCharBytes(bytes, (char)xchar, e);
                            i += 5;
                        }
                        else
                            WriteCharBytes(bytes, '%', e);
                    }
                    else if ((xchar = GetChar(s, i + 1, 2)) != -1)
                    {
                        WriteCharBytes(bytes, (char)xchar, e);
                        i += 2;
                    }
                    else
                    {
                        WriteCharBytes(bytes, '%', e);
                    }
                    continue;
                }

                if (ch == '+')
                    WriteCharBytes(bytes, ' ', e);
                else
                    WriteCharBytes(bytes, ch, e);
            }

            var buf = bytes.ToArray();
            bytes.Clear();
            bytes = null;
            return e.GetString(buf);

        }

        private static void WriteCharBytes(IList buf, char ch, Encoding e)
        {
            if (ch > 255)
            {
                foreach (byte b in e.GetBytes(new char[] { ch }))
                    buf.Add(b);
            }
            else
                buf.Add((byte)ch);
        }

        private static int GetChar(string str, int offset, int length)
        {
            int val = 0;
            int end = length + offset;
            for (int i = offset; i < end; i++)
            {
                char c = str[i];
                if (c > 127)
                    return -1;

                int current = GetInt((byte)c);
                if (current == -1)
                    return -1;
                val = (val << 4) + current;
            }

            return val;
        }

        private static int GetInt(byte b)
        {
            char c = (char)b;
            if (c >= '0' && c <= '9')
                return c - '0';

            if (c >= 'a' && c <= 'f')
                return c - 'a' + 10;

            if (c >= 'A' && c <= 'F')
                return c - 'A' + 10;

            return -1;
        }
    }
}