/*

 Copyright (C) 2015-2016 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 Utility class for creating a render state pipeline.

 */

#import "MetalNBodyRenderPipeline.h"

@implementation MetalNBodyRenderPipeline

{

@private

    BOOL _blend;

    BOOL _haveDescriptor;

    id<MTLFunction>  _vertex;

    id<MTLFunction>  _fragment;

    id<MTLRenderPipelineState> _render;

}

- (instancetype) init

{

    self = [super init];

    if(self)

    {

        _blend          = NO;

        _haveDescriptor = NO;

        _fragment = nil;

        _vertex   = nil;

        _render   = nil;

    } // if

    return self;

} // init

- (BOOL) _acquire:(nullable id<MTLDevice>) device

{

    if(device)

    {

        if(!_vertex)

        {

            NSLog(@">> ERROR: Vertex stage object is nil!");

            return NO;

        } // if

        if(!_fragment)

        {

            NSLog(@">> ERROR: Fragment stage object is nil!");

            return NO;

        } // if

        MTLRenderPipelineDescriptor* pDescriptor = [MTLRenderPipelineDescriptor new];

        if(!pDescriptor)

        {

            NSLog(@">> ERROR: Failed to instantiate render pipeline descriptor!");

            return NO;

        } // if

        [pDescriptor setVertexFunction:_vertex];

        [pDescriptor setFragmentFunction:_fragment];

        pDescriptor.colorAttachments[0].pixelFormat         = MTLPixelFormatBGRA8Unorm;

        pDescriptor.colorAttachments[0].blendingEnabled     = YES;

        pDescriptor.colorAttachments[0].rgbBlendOperation   = MTLBlendOperationAdd;

        pDescriptor.colorAttachments[0].alphaBlendOperation = MTLBlendOperationAdd;

        if(_blend)

        {

            pDescriptor.colorAttachments[0].sourceRGBBlendFactor        = MTLBlendFactorOne;

            pDescriptor.colorAttachments[0].sourceAlphaBlendFactor      = MTLBlendFactorOne;

            pDescriptor.colorAttachments[0].destinationRGBBlendFactor   = MTLBlendFactorOneMinusSourceAlpha;

            pDescriptor.colorAttachments[0].destinationAlphaBlendFactor = MTLBlendFactorOneMinusSourceAlpha;

        } // if

        else

        {

            pDescriptor.colorAttachments[0].sourceRGBBlendFactor        = MTLBlendFactorSourceAlpha;

            pDescriptor.colorAttachments[0].sourceAlphaBlendFactor      = MTLBlendFactorSourceAlpha;

            pDescriptor.colorAttachments[0].destinationRGBBlendFactor   = MTLBlendFactorOne;

            pDescriptor.colorAttachments[0].destinationAlphaBlendFactor = MTLBlendFactorOne;

        } // else

        NSError* pError = nil;

        _render = [device newRenderPipelineStateWithDescriptor:pDescriptor

                                                         error:&pError];

        if(!_render)

        {

            NSString* pDescription = [pError description];

            if(pDescription)

            {

                NSLog(@">> ERROR: Failed to instantiate render pipeline: {%@}", pDescription);

            } // if

            else

            {

                NSLog(@">> ERROR: Failed to instantiate render pipeline!");

            } // else

            return NO;

        } // if

        return YES;

    } // if

    else

    {

        NSLog(@">> ERROR: Metal device is nil!");

    } // if

    return NO;

} // acquire

// Generate render pipeline state using a default system

// device, fragment and vertex stages

- (void) acquire:(nullable id<MTLDevice>)device

{

    if(!_haveDescriptor)

    {

        _haveDescriptor = [self _acquire:device];

    } // if

} // acquire

@end