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

using UnityEngine;

namespace UniLua
{
	internal class LuaFile
	{
		private static readonly string LUA_ROOT = System.IO.Path.Combine(Application.streamingAssetsPath, "LuaRoot");

		public static FileLoadInfo OpenFile( string filename )
		{
			var path = System.IO.Path.Combine(LUA_ROOT, filename);
            return new FileLoadInfo(LuaFile.GetStream(path));
		}

		public static bool Readable( string filename )
		{
			var path = System.IO.Path.Combine(LUA_ROOT, filename);
			try {
				using( var stream = File.Open( path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite ) ) {
					return true;
				}
			}
			catch( Exception ) {
				return false;
			}
		}

        private static Stream GetStream(string path, float timeOut = 0.5f)
        {
            if (Application.platform == RuntimePlatform.Android)
            {
                WWW www = new WWW(path);
                while (!www.isDone) ;
                if (!string.IsNullOrEmpty(www.error))
                {
                    return null;
                }
                return new MemoryStream(www.bytes);
            }

            return File.Open(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
        }
	}

	internal class FileLoadInfo : ILoadInfo, IDisposable
	{
		public FileLoadInfo( Stream stream )
		{
			Stream = stream;
			Buf = new Queue<byte>();
		}

		public int ReadByte()
		{
			if( Buf.Count > 0 )
				return (int)Buf.Dequeue();
			else
				return Stream.ReadByte();
		}

		public int PeekByte()
		{
			if( Buf.Count > 0 )
				return (int)Buf.Peek();
			else
			{
				var c = Stream.ReadByte();
				if( c == -1 )
					return c;
				Save( (byte)c );
				return c;
			}
		}

		public void Dispose()
		{
			Stream.Dispose();
		}

		private const string UTF8_BOM = "\u00EF\u00BB\u00BF";
		private Stream 	Stream;
		private Queue<byte>	Buf;

		private void Save( byte b )
		{
			Buf.Enqueue( b );
		}

		private void Clear()
		{
			Buf.Clear();
		}

		private int SkipBOM()
		{
			for( var i=0; i<UTF8_BOM.Length; ++i )
			{
				var c = Stream.ReadByte();
				if(c == -1 || c != (byte)UTF8_BOM[i])
					return c;
				Save( (byte)c );
			}
			// perfix matched; discard it
			Clear();
			return Stream.ReadByte();
		}

		public void SkipComment()
		{
			var c = SkipBOM();

			// first line is a comment (Unix exec. file)?
			if( c == '#' )
			{
				do {
					c = Stream.ReadByte();
				} while( c != -1 && c != '\n' );
				Save( (byte)'\n' ); // fix line number
			}
			else if( c != -1 )
			{
				Save( (byte)c );
			}
		}
	}

}