/**
 * Copyright (c) 2019 Razeware LLC
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * Notwithstanding the foregoing, you may not use, copy, modify, merge, publish,
 * distribute, sublicense, create a derivative work, and/or sell copies of the
 * Software in any work that is designed, intended, or marketed for pedagogical or
 * instructional purposes related to programming, coding, application development,
 * or information technology.  Permission for such use, copying, modification,
 * merger, publication, distribution, sublicensing, creation of derivative works,
 * or sale is expressly withheld.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

import MetalKit

public typealias float2 = SIMD2<Float>
public typealias float3 = SIMD3<Float>
public typealias float4 = SIMD4<Float>

public class Renderer: NSObject, MTKViewDelegate {
    
  public let device: MTLDevice!
  let commandQueue: MTLCommandQueue!
  
  override public init() {
    let initialized = Renderer.initializeMetal()
    device = initialized?.device
    commandQueue = initialized?.commandQueue
    
    super.init()
  }
  
  private static func initializeMetal() -> (
    device: MTLDevice, commandQueue: MTLCommandQueue)?
  {
    guard let device = MTLCreateSystemDefaultDevice(),
      let commandQueue = device.makeCommandQueue() else { return nil }
    
    return (device, commandQueue)
  }
  
  func makeRenderCommandEncoder(_ commandBuffer: MTLCommandBuffer, _ texture: MTLTexture) -> MTLRenderCommandEncoder {
    let descriptor = MTLRenderPassDescriptor()
    let color = MTLClearColor(red: 0.5, green: 0.5, blue: 0.5, alpha: 1)
    descriptor.colorAttachments[0].texture = texture
    descriptor.colorAttachments[0].clearColor = color
    descriptor.colorAttachments[0].loadAction = .clear
    guard let renderCommandEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: descriptor) else {
      fatalError("Cannot create a render command encoder.")
    }
    return renderCommandEncoder
  }
  
  public func draw(in view: MTKView) {
    guard let commandBuffer = commandQueue.makeCommandBuffer(),
          let drawable = view.currentDrawable else {
      return
    }
    
    // first command encoder
    let renderEncoder = makeRenderCommandEncoder(commandBuffer, drawable.texture)
    renderEncoder.endEncoding()
    
    // second command encoder
    
    commandBuffer.present(drawable)
    commandBuffer.commit()
  }
  
  public func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {}
}