using System;
using System.Runtime.InteropServices;
using WellspringCS;

namespace MoonWorks.Graphics.Font
{
	public unsafe class TextBatch : IDisposable
	{
		public const int MAX_CHARS = 4096;
		public const int MAX_VERTICES = MAX_CHARS * 4;
		public const int MAX_INDICES = MAX_CHARS * 6;

		private GraphicsDevice GraphicsDevice { get; }
		public IntPtr Handle { get; }

		public Buffer VertexBuffer { get; protected set; } = null;
		public Buffer IndexBuffer { get; protected set; } = null;
		public uint PrimitiveCount { get; protected set; }

		public Font CurrentFont { get; private set; }

		private byte* StringBytes;
		private int StringBytesLength;

		private bool IsDisposed;

		public TextBatch(GraphicsDevice graphicsDevice)
		{
			GraphicsDevice = graphicsDevice;
			Handle = Wellspring.Wellspring_CreateTextBatch();

			StringBytesLength = 128;
			StringBytes = (byte*) NativeMemory.Alloc((nuint) StringBytesLength);

			VertexBuffer = Buffer.Create<Vertex>(GraphicsDevice, BufferUsageFlags.Vertex, MAX_VERTICES);
			IndexBuffer = Buffer.Create<uint>(GraphicsDevice, BufferUsageFlags.Index, MAX_INDICES);
		}

		public void Start(Font font)
		{
			Wellspring.Wellspring_StartTextBatch(Handle, font.Handle);
			CurrentFont = font;
			PrimitiveCount = 0;
		}

		public unsafe bool Add(
			string text,
			float x,
			float y,
			int pixelSize,
			float depth,
			Color color,
			HorizontalAlignment horizontalAlignment = HorizontalAlignment.Left,
			VerticalAlignment verticalAlignment = VerticalAlignment.Baseline
		) {
			var byteCount = System.Text.Encoding.UTF8.GetByteCount(text);

			if (StringBytesLength < byteCount)
			{
				StringBytes = (byte*) NativeMemory.Realloc(StringBytes, (nuint) byteCount);
			}

			fixed (char* chars = text)
			{
				System.Text.Encoding.UTF8.GetBytes(chars, text.Length, StringBytes, byteCount);

				var result = Wellspring.Wellspring_Draw(
					Handle,
					x,
					y,
					pixelSize,
					depth,
					new Wellspring.Color { R = color.R, G = color.G, B = color.B, A = color.A },
					(Wellspring.HorizontalAlignment) horizontalAlignment,
					(Wellspring.VerticalAlignment) verticalAlignment,
					(IntPtr) StringBytes,
					(uint) byteCount
				);

				if (result == 0)
				{
					Logger.LogWarn("Could not decode string: " + text);
					return false;
				}
			}

			return true;
		}

		// Call this after you have made all the Draw calls you want.
		public unsafe void UploadBufferData(CommandBuffer commandBuffer)
		{
			Wellspring.Wellspring_GetBufferData(
				Handle,
				out uint vertexCount,
				out IntPtr vertexDataPointer,
				out uint vertexDataLengthInBytes,
				out IntPtr indexDataPointer,
				out uint indexDataLengthInBytes
			);

			if (vertexDataLengthInBytes > 0 && indexDataLengthInBytes > 0)
			{
				commandBuffer.SetBufferData(VertexBuffer, vertexDataPointer, 0, vertexDataLengthInBytes);
				commandBuffer.SetBufferData(IndexBuffer, indexDataPointer, 0, indexDataLengthInBytes);
			}

			PrimitiveCount = vertexCount / 2; // FIXME: is this jank?
		}

		protected virtual void Dispose(bool disposing)
		{
			if (!IsDisposed)
			{
				if (disposing)
				{
					VertexBuffer.Dispose();
					IndexBuffer.Dispose();
				}

				NativeMemory.Free(StringBytes);
				Wellspring.Wellspring_DestroyTextBatch(Handle);

				IsDisposed = true;
			}
		}

		~TextBatch()
		{
			// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
			Dispose(disposing: false);
		}

		public void Dispose()
		{
			// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
			Dispose(disposing: true);
			GC.SuppressFinalize(this);
		}
	}
}