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

namespace BizHawk.Emulation.Consoles.GB
{
	/// <summary>
	/// a gameboy/gameboy color emulator wrapped around native C++ libgambatte
	/// </summary>
	public class Gameboy : IEmulator, IVideoProvider, ISyncSoundProvider
	{
		/// <summary>
		/// internal gambatte state
		/// </summary>
		IntPtr GambatteState = IntPtr.Zero;

		/// <summary>
		/// keep a copy of the input callback delegate so it doesn't get GCed
		/// </summary>
		LibGambatte.InputGetter InputCallback;

		/// <summary>
		/// whatever keys are currently depressed
		/// </summary>
		LibGambatte.Buttons CurrentButtons = 0;

		public Gameboy(GameInfo game, byte[] romdata)
		{
			ThrowExceptionForBadRom(romdata);

			GambatteState = LibGambatte.gambatte_create();

			if (GambatteState == IntPtr.Zero)
				throw new Exception("gambatte_create() returned null???");

			LibGambatte.LoadFlags flags = 0;

			if (game["ForceDMG"])
				flags |= LibGambatte.LoadFlags.FORCE_DMG;
			if (game["GBACGB"])
				flags |= LibGambatte.LoadFlags.GBA_CGB;
			if (game["MulitcartCompat"])
				flags |= LibGambatte.LoadFlags.MULTICART_COMPAT;


			if (LibGambatte.gambatte_load(GambatteState, romdata, (uint)romdata.Length, flags) != 0)
				throw new Exception("gambatte_load() returned non-zero (is this not a gb or gbc rom?)");

			// set real default colors (before anyone mucks with them at all)
			ChangeDMGColors(new int[] { 10798341, 8956165, 1922333, 337157, 10798341, 8956165, 1922333, 337157, 10798341, 8956165, 1922333, 337157 });
			
			InitSound();

			Frame = 0;
			LagCount = 0;
			IsLagFrame = false;

			InputCallback = new LibGambatte.InputGetter(ControllerCallback);

			LibGambatte.gambatte_setinputgetter(GambatteState, InputCallback);

			InitMemoryDomains();

			GbOutputComm.RomStatusDetails = string.Format("{0}\r\nSHA1:{1}\r\nMD5:{2}\r\n",
				game.Name,
				Util.BytesToHexString(System.Security.Cryptography.SHA1.Create().ComputeHash(romdata)),
				Util.BytesToHexString(System.Security.Cryptography.MD5.Create().ComputeHash(romdata))
				);
		}

		public static readonly ControllerDefinition GbController = new ControllerDefinition
		{
			Name = "Gameboy Controller",
			BoolButtons =
			{
				"Up", "Down", "Left", "Right", "A", "B", "Select", "Start", "Power"
			}
		};

		public ControllerDefinition ControllerDefinition
		{
			get { return GbController; }
		}

		public IController Controller { get; set; }

		LibGambatte.Buttons ControllerCallback()
		{
			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
			IsLagFrame = false;
			return CurrentButtons;
		}

		/// <summary>
		/// true if the emulator is currently emulating CGB
		/// </summary>
		/// <returns></returns>
		public bool IsCGBMode()
		{
			return (LibGambatte.gambatte_iscgb(GambatteState));
		}

		public void FrameAdvance(bool render, bool rendersound)
		{
			uint nsamp = 35112; // according to gambatte docs, this is the nominal length of a frame in 2mhz clocks

			Controller.UpdateControls(Frame++);

			// update our local copy of the controller data
			CurrentButtons = 0;

			if (Controller["Up"])
				CurrentButtons |= LibGambatte.Buttons.UP;
			if (Controller["Down"])
				CurrentButtons |= LibGambatte.Buttons.DOWN;
			if (Controller["Left"])
				CurrentButtons |= LibGambatte.Buttons.LEFT;
			if (Controller["Right"])
				CurrentButtons |= LibGambatte.Buttons.RIGHT;
			if (Controller["A"])
				CurrentButtons |= LibGambatte.Buttons.A;
			if (Controller["B"])
				CurrentButtons |= LibGambatte.Buttons.B;
			if (Controller["Select"])
				CurrentButtons |= LibGambatte.Buttons.SELECT;
			if (Controller["Start"])
				CurrentButtons |= LibGambatte.Buttons.START;

			// the controller callback will set this to false if it actually gets called during the frame
			IsLagFrame = true;

			// download any modified data to the core
			foreach (var r in MemoryRefreshers)
				r.RefreshWrite();

			if (Controller["Power"])
				LibGambatte.gambatte_reset(GambatteState);

			RefreshMemoryCallbacks();

			LibGambatte.gambatte_runfor(GambatteState, VideoBuffer, 160, soundbuff, ref nsamp);

			// upload any modified data to the memory domains

			foreach (var r in MemoryRefreshers)
				r.RefreshRead();

			if (rendersound)
				soundbuffcontains = (int)nsamp;
			else
				soundbuffcontains = 0;

			if (IsLagFrame)
				LagCount++;

		}

		/// <summary>
		/// throw exception with intelligible message on some kinds of bad rom
		/// </summary>
		/// <param name="romdata"></param>
		static void ThrowExceptionForBadRom(byte[] romdata)
		{
			if (romdata.Length < 0x148)
				throw new Exception("ROM is far too small to be a valid GB\\GBC rom!");

			switch (romdata[0x147])
			{
				case 0x00: break;
				case 0x01: break;
				case 0x02: break;
				case 0x03: break;
				case 0x05: break;
				case 0x06: break;
				case 0x08: break;
				case 0x09: break;

				case 0x0b: throw new Exception("\"MM01\" Mapper not supported!");
				case 0x0c: throw new Exception("\"MM01\" Mapper not supported!");
				case 0x0d: throw new Exception("\"MM01\" Mapper not supported!");

				case 0x0f: break;
				case 0x10: break;
				case 0x11: break;
				case 0x12: break;
				case 0x13: break;

				case 0x15: throw new Exception("\"MBC4\" Mapper not supported!");
				case 0x16: throw new Exception("\"MBC4\" Mapper not supported!");
				case 0x17: throw new Exception("\"MBC4\" Mapper not supported!");

				case 0x19: break;
				case 0x1a: break;
				case 0x1b: break;
				case 0x1c: break; // rumble
				case 0x1d: break; // rumble
				case 0x1e: break; // rumble

				case 0x20: throw new Exception("\"MBC6\" Mapper not supported!");
				case 0x22: throw new Exception("\"MBC7\" Mapper not supported!");

				case 0xfc: throw new Exception("\"Pocket Camera\" Mapper not supported!");
				case 0xfd: throw new Exception("\"Bandai TAMA5\" Mapper not supported!");
				case 0xfe: throw new Exception("\"HuC3\" Mapper not supported!");
				case 0xff: break;
				default: throw new Exception(string.Format("Unknown mapper: {0:x2}", romdata[0x147]));
			}
			return;
		}

		public int Frame { get; set; }

		public int LagCount { get; set; }

		public bool IsLagFrame { get; private set; }

		public string SystemId
		{
			get { return "GB"; }
		}

		public bool DeterministicEmulation { get { return true; } }

		#region saveram

		public byte[] ReadSaveRam()
		{
			int length = LibGambatte.gambatte_savesavedatalength(GambatteState);

			if (length > 0)
			{
				byte[] ret = new byte[length];
				LibGambatte.gambatte_savesavedata(GambatteState, ret);
				return ret;
			}
			else
				return new byte[0];
		}

		public void StoreSaveRam(byte[] data)
		{
			if (data.Length != LibGambatte.gambatte_savesavedatalength(GambatteState))
				throw new ArgumentException("Size of saveram data does not match expected!");
			LibGambatte.gambatte_loadsavedata(GambatteState, data);
		}

		/// <summary>
		/// reset cart save ram, if any, to initial state
		/// </summary>
		public void ClearSaveRam()
		{
			int length = LibGambatte.gambatte_savesavedatalength(GambatteState);
			if (length == 0)
				return;

			byte[] clear = new byte[length];
			for (int i = 0; i < clear.Length; i++)
				clear[i] = 0xff; // this exactly matches what gambatte core does

			StoreSaveRam(clear);
		}


		public bool SaveRamModified
		{
			get
			{
				if (LibGambatte.gambatte_savesavedatalength(GambatteState) == 0)
					return false;
				else
					return true; // need to wire more stuff into the core to actually know this
			}
			set { }
		}

		#endregion

		public void ResetFrameCounter()
		{
			// is this right?
			Frame = 0;
			LagCount = 0;
		}

		#region savestates

		/// <summary>
		/// handles the core-portion of savestating
		/// </summary>
		/// <returns>private binary data corresponding to a savestate</returns>
		byte[] SaveCoreBinary()
		{
			uint nlen = 0;
			IntPtr ndata = IntPtr.Zero;

			if (!LibGambatte.gambatte_savestate(GambatteState, VideoBuffer, 160, ref ndata, ref nlen))
				throw new Exception("Gambatte failed to save the savestate!");

			if (nlen == 0)
				throw new Exception("Gambatte returned a 0-length savestate?");

			byte[] data = new byte[nlen];
			System.Runtime.InteropServices.Marshal.Copy(ndata, data, 0, (int)nlen);
			LibGambatte.gambatte_savestate_destroy(ndata);

			return data;
		}

		/// <summary>
		/// handles the core portion of loadstating
		/// </summary>
		/// <param name="data">private binary data previously returned from SaveCoreBinary()</param>
		void LoadCoreBinary(byte[] data)
		{
			if (!LibGambatte.gambatte_loadstate(GambatteState, data, (uint)data.Length))
				throw new Exception("Gambatte failed to load the savestate!");
			// since a savestate has been loaded, all memory domain data is now dirty
			foreach (var r in MemoryRefreshers)
				r.RefreshRead();
		}
	
		public void SaveStateText(System.IO.TextWriter writer)
		{
			var temp = SaveStateBinary();
			temp.SaveAsHex(writer);
			// write extra copy of stuff we don't use
			writer.WriteLine("Frame {0}", Frame);
		}

		public void LoadStateText(System.IO.TextReader reader)
		{
			string hex = reader.ReadLine();
			byte[] state = new byte[hex.Length / 2];
			state.ReadFromHex(hex);
			LoadStateBinary(new BinaryReader(new MemoryStream(state)));
		}

		public void SaveStateBinary(System.IO.BinaryWriter writer)
		{
			byte[] data = SaveCoreBinary();

			writer.Write(data.Length);
			writer.Write(data);

			// other variables
			writer.Write(IsLagFrame);
			writer.Write(LagCount);
			writer.Write(Frame);
		}

		public void LoadStateBinary(System.IO.BinaryReader reader)
		{
			int length = reader.ReadInt32();
			byte[] data = reader.ReadBytes(length);

			LoadCoreBinary(data);

			// other variables
			IsLagFrame = reader.ReadBoolean();
			LagCount = reader.ReadInt32();
			Frame = reader.ReadInt32();
		}

		public byte[] SaveStateBinary()
		{
			MemoryStream ms = new MemoryStream();
			BinaryWriter bw = new BinaryWriter(ms);
			SaveStateBinary(bw);
			bw.Flush();
			return ms.ToArray();
		}

		#endregion

		#region memorycallback

		LibGambatte.MemoryCallback readcb;
		LibGambatte.MemoryCallback writecb;

		void RefreshMemoryCallbacks()
		{
			var mcs = CoreInputComm.MemoryCallbackSystem;

			// we RefreshMemoryCallbacks() after the triggers in case the trigger turns itself off at that point

			if (mcs.HasRead)
				readcb = delegate(uint addr) { mcs.TriggerRead((int)addr); RefreshMemoryCallbacks(); };
			else
				readcb = null;
			if (mcs.HasWrite)
				writecb = delegate(uint addr) { mcs.TriggerWrite((int)addr); RefreshMemoryCallbacks(); };
			else
				writecb = null;

			LibGambatte.gambatte_setreadcallback(GambatteState, readcb);
			LibGambatte.gambatte_setwritecallback(GambatteState, writecb);
		}
	


		#endregion

		public CoreInputComm CoreInputComm { get; set; }

		CoreOutputComm GbOutputComm = new CoreOutputComm
		{
			VsyncNum = 262144,
			VsyncDen = 4389,
			RomStatusAnnotation = null, //"Bizwhackin it up",
			RomStatusDetails = null, //"LEVAR BURTON",
		};

		public CoreOutputComm CoreOutputComm
		{
			get { return GbOutputComm; }
		}

		#region MemoryDomains

		class MemoryRefresher
		{
			IntPtr data;
			int length;

			byte[] CachedMemory;

			public MemoryRefresher(IntPtr data, int length)
			{
				this.data = data;
				this.length = length;
				CachedMemory = new byte[length];

				writeneeded = false;
				// needs to be true in case a read is attempted before the first frame advance
				readneeded = true;
			}
	
			bool readneeded;
			bool writeneeded;

			/// <summary>
			/// reads data from native core to managed buffer
			/// </summary>
			public void RefreshRead()
			{
				readneeded = true;
			}

			/// <summary>
			/// writes data from managed buffer back to core
			/// </summary>
			public void RefreshWrite()
			{
				if (writeneeded)
				{
					System.Runtime.InteropServices.Marshal.Copy(CachedMemory, 0, data, length);
					writeneeded = false;
				}
			}

			public byte Peek(int addr)
			{
				if (readneeded)
				{
					System.Runtime.InteropServices.Marshal.Copy(data, CachedMemory, 0, length);
					readneeded = false;
				}
				return CachedMemory[addr];
			}
			public void Poke(int addr, byte val)
			{
				// a poke without any peek is certainly legal.  we need to update read, because writeneeded = true means that
				// all of this data will be downloaded before the next frame.  so everything but that which was poked needs to
				// be up to date.
				if (readneeded)
				{
					System.Runtime.InteropServices.Marshal.Copy(data, CachedMemory, 0, length);
					readneeded = false;
				}
				CachedMemory[addr] = val;
				writeneeded = true;
			}
		}


		void CreateMemoryDomain(LibGambatte.MemoryAreas which, string name)
		{
			IntPtr data = IntPtr.Zero;
			int length = 0;

			if (!LibGambatte.gambatte_getmemoryarea(GambatteState, which, ref data, ref length))
				throw new Exception("gambatte_getmemoryarea() failed!");

			// if length == 0, it's an empty block; (usually rambank on some carts); that's ok
			// TODO: when length == 0, should we simply not add the memory domain at all?
			if (data == IntPtr.Zero && length > 0)
				throw new Exception("bad return from gambatte_getmemoryarea()");

			var refresher = new MemoryRefresher(data, length);

			MemoryRefreshers.Add(refresher);

			MemoryDomains.Add(new MemoryDomain(name, length, Endian.Little, refresher.Peek, refresher.Poke));
		}

		void InitMemoryDomains()
		{
			MemoryDomains = new List<MemoryDomain>();
			MemoryRefreshers = new List<MemoryRefresher>();

			CreateMemoryDomain(LibGambatte.MemoryAreas.wram, "WRAM");
			CreateMemoryDomain(LibGambatte.MemoryAreas.rom, "ROM");
			CreateMemoryDomain(LibGambatte.MemoryAreas.vram, "VRAM");
			CreateMemoryDomain(LibGambatte.MemoryAreas.cartram, "Cart RAM");
			CreateMemoryDomain(LibGambatte.MemoryAreas.oam, "OAM");
			CreateMemoryDomain(LibGambatte.MemoryAreas.hram, "HRAM");

			// also add a special memory domain for the system bus, where calls get sent directly to the core each time

			MemoryDomains.Add(new MemoryDomain("System Bus", 65536, Endian.Little,
				delegate(int addr)
				{
					return LibGambatte.gambatte_cpuread(GambatteState, (ushort)addr);
				},
				delegate(int addr, byte val)
				{
					LibGambatte.gambatte_cpuwrite(GambatteState, (ushort)addr, val);
				}));

			// this is the wram area and matches the bizhawk convention for what MainMemory means
			MainMemory = MemoryDomains[0];
		}

		public IList<MemoryDomain> MemoryDomains { get; private set; }

		public MemoryDomain MainMemory { get; private set; }

		List <MemoryRefresher> MemoryRefreshers;

		#endregion

		public void Dispose()
		{
			LibGambatte.gambatte_destroy(GambatteState);
			GambatteState = IntPtr.Zero;
			DisposeSound();
		}

		#region IVideoProvider

		public IVideoProvider VideoProvider
		{
			get { return this; }
		}

		/// <summary>
		/// stored image of most recent frame
		/// </summary>
		int[] VideoBuffer = new int[160 * 144];

		public int[] GetVideoBuffer()
		{
			return VideoBuffer;
		}

		public int VirtualWidth
		{
			// only sgb changes this, which we don't emulate here
			get { return 160; }
		}

		public int BufferWidth
		{
			get { return 160; }
		}

		public int BufferHeight
		{
			get { return 144; }
		}

		public int BackgroundColor
		{
			get { return 0; }
		}

		#endregion

		#region palette

		/// <summary>
		/// update gambatte core's internal colors
		/// </summary>
		public void ChangeDMGColors(int[] colors)
		{
			for (int i = 0; i < 12; i++)
				LibGambatte.gambatte_setdmgpalettecolor(GambatteState, (LibGambatte.PalType)(i / 4), (uint)i % 4, (uint)colors[i]);
		}

		#endregion

		#region ISoundProvider

		public ISoundProvider SoundProvider
		{
			get { return null; }
		}
		public ISyncSoundProvider SyncSoundProvider { get { return dcfilter; } }
		public bool StartAsyncSound() { return false; }
		public void EndAsyncSound() { }

		/// <summary>
		/// sample pairs before resampling
		/// </summary>
		short[] soundbuff = new short[(35112 + 2064) * 2];
		/// <summary>
		/// how many sample pairs are in soundbuff
		/// </summary>
		int soundbuffcontains = 0;

		Sound.Utilities.SpeexResampler resampler;
		Sound.Utilities.DCFilter dcfilter;

		void InitSound()
		{
			resampler = new Sound.Utilities.SpeexResampler(2, 2097152, 44100, 2097152, 44100, null, this);
			dcfilter = new Sound.Utilities.DCFilter(resampler, 65536);
		}

		void DisposeSound()
		{
			resampler.Dispose();
			resampler = null;
		}

		public void DiscardSamples()
		{
			soundbuffcontains = 0;
		}

		public void GetSamples(out short[] samples, out int nsamp)
		{
			samples = soundbuff;
			nsamp = soundbuffcontains;
		}
		#endregion

	}
}