using System.Collections.Generic;
using System.Runtime.InteropServices;
namespace Aiwaz.Contracts
{
    public enum CommandFlags : byte
    {
	    None = 0x00,
	    SubChainStart = 0x01,	// Command will start a new command chain (UseShader for example)
	    SubChainEnd = 0x02,		// Command will end a command chain (Render)
	    Unique = 0x04,			// Similar commands should not be reduced to one Command
	    StartChain = 0x08,		// Command will generate a new command chain		
	    EndChain = 0x10,		// Command will end the command chain (RenderGeometry for example)
	    FlushChain = 0x20,		// Command will end the command chain (RenderGeometry for example)
    }

    public class Command
    {
        [StructLayout(LayoutKind.Explicit)]
        public struct CommandInfoUnion
        {
            [FieldOffset(0)]
            public uint RawValue;
            [FieldOffset(0)]
            public byte Priority;
            [FieldOffset(1)]
            public byte SubPriority;
            [FieldOffset(2)]
            public CommandFlags Flags;
            [FieldOffset(3)]
            public byte Type;
        }

        public Command(ICommandUser argOwner, CommandFlags argFlags, byte argType)
            : this(argOwner, argFlags, argType, 0, 0)
        {
        }

        public Command(ICommandUser argOwner, CommandFlags argFlags, byte argType, byte argPriority)
            : this(argOwner, argFlags, argType, argPriority, 0)
        {
        }

        public Command(ICommandUser argOwner, CommandFlags argFlags, byte argType, byte argPriority, byte argSubPriority)
	    {
            CommandInfo.RawValue = 0;
		    Owner = argOwner;
            Flags = argFlags;
            Priority = argPriority;
            SubPriority = argSubPriority;
            Type = argType;
        }


        public CommandInfoUnion CommandInfo;
        public byte Priority { get { return CommandInfo.Priority; } set { CommandInfo.Priority = value; } }
        public byte SubPriority { get { return CommandInfo.SubPriority; } set { CommandInfo.SubPriority = value; } }
        public CommandFlags Flags { get { return CommandInfo.Flags; } set { CommandInfo.Flags = value; } }
        public byte Type { get { return CommandInfo.Type; } set { CommandInfo.Type = value; } }

        public ICommandUser Owner;
    };

    public enum CommandExecuteResult
    {
	    None,		// Execution done, proceed to the next Command
	    RetrySubChain,	// Execution should start from a previous "SubChainStart"-flagged Command
	    RetrySubChainSkipHead // Equal to the above result but skips the as "SubChainStart"-flagged Command
    };

    public interface ICommandUser
    {
        List<Command> Commands { get; }

	    CommandExecuteResult ExecuteCommand(byte argCommandType, ICommandBuffer argCurrentBuffer, int argCurrentPositon);

	    void AssignToRenderCommandNode(IRenderCommandNode argNode);
	    void UnassignFromRenderCommandNode(IRenderCommandNode argNode);

	    // Commands should be applied before all following commands
        bool IsPreconditionForNextCommands { get; set; }
    };


    public interface ICommandBuffer
    {
	    void Clear();
	    void Perform(bool argUseOptimizedList);
	    void Optimize();
	    void AddChildCommandBuffer(ICommandBuffer argCommandBuffer);
	    void RemoveChildCommandBuffer(ICommandBuffer argCommandBuffer);

	    List<Command> BufferedCommands { get; }
	    List<ICommandBuffer> ChildCommandBuffers { get; }
	    ICommandBuffer ParentBuffer { get; set; }
    };

}