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

namespace OpenRa.FileFormats
{
	public class PackageEntry
	{
		public readonly uint Hash;
		public readonly uint Offset;
		public readonly uint Length;

		public PackageEntry(BinaryReader r)
		{
			Hash = r.ReadUInt32();
			Offset = r.ReadUInt32();
			Length = r.ReadUInt32();
		}

		public override string ToString()
		{
			string filename;
			if (Names.TryGetValue(Hash, out filename))
				return string.Format("{0} - offset 0x{1:x8} - length 0x{2:x8}", filename, Offset, Length);
			else
				return string.Format("0x{0:x8} - offset 0x{1:x8} - length 0x{2:x8}", Hash, Offset, Length);
		}

		public static uint HashFilename(string name)
		{
			if (name.Length > 12)
				name = name.Substring(0, 12);

			name = name.ToUpperInvariant();
			if (name.Length % 4 != 0)
				name = name.PadRight(name.Length + (4 - name.Length % 4), '\0');

			MemoryStream ms = new MemoryStream(Encoding.ASCII.GetBytes(name));
			BinaryReader reader = new BinaryReader(ms);

			uint result = 0;
			try
			{
				while(true)
					result = ((result << 1) | (result >> 31)) + reader.ReadUInt32();
			}
			catch (EndOfStreamException) { }

			return result;
		}

		static Dictionary<uint, string> Names = new Dictionary<uint,string>();
		
		public static void AddStandardName(string s)
		{
			uint hash = HashFilename(s);
			Names.Add(hash, s);
		}

		public const int Size = 12;
	}
}