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

namespace Nexi
{
    public class Packet
    {
        /// <summary>
        /// How interesting is this packet?  Between 0 and 1.
        /// </summary>
        public double Interest;

        public string TextContents;

        public static Packet FromText(TextReader src)
        {
            Reader rdr = new Reader(src);
            rdr.ReadHeaders();
            rdr.ReadBody();
            return rdr.Packet;
        }

        private class Reader
        {
            private readonly TextReader _src;
            private Packet pack = new Packet();

            public Packet Packet { get { return pack; } }

            private string _contentType;

            public Reader(TextReader src)
            {
                _src = src;
            }

            public void ReadHeaders()
            {
                while (true)
                {
                    string line = _src.ReadLine();

                    if (line == "")
                        // end of headers
                        return;

                    if (line.StartsWith(" ") || line.StartsWith("\t"))
                        // we don't handle continued headers yet
                        throw new NotImplementedException("Continued headers aren't supported");

                    int colonpos = line.IndexOf(':');
                    if (colonpos == -1)
                        throw new ArgumentException(String.Format("Bad header '{0}': missing colon", line));

                    string header = line.Substring(0, colonpos).ToLowerInvariant().Trim();
                    string value = line.Substring(colonpos + 1).Trim();

                    if (header == "interest")
                        pack.Interest = double.Parse(value);
                    else if (header == "content-type")
                        _contentType = value;
                    else
                        // eventually we should ignore unknown headers
                        throw new ArgumentException(String.Format("Unknown header {0}", header));
                }
            }

            public void ReadBody()
            {
                StringBuilder bob = new StringBuilder();

                while (true)
                {
                    string line = _src.ReadLine();

                    if (line == null)
                    {
                        // end of text
                        assignBody(bob.ToString());
                        return;
                    }

                    bob.AppendLine(line);
                }
            }

            private void assignBody(string p)
            {
                if (_contentType == "text/plain")
                {
                    pack.TextContents = p;
                }
                else
                {
                    throw new ArgumentException(string.Format("Unknown content type {0}", _contentType));
                }
            }
        }
    }
}