{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE RecordWildCards #-}

-- |
-- Module      : WGPU.Internal.CommandEncoder
-- Description : Command encoding.
module WGPU.Internal.CommandEncoder
  ( -- * Types
    CommandEncoder (..),

    -- * Functions
    createCommandEncoder,
    commandEncoderFinish,
  )
where

import Control.Monad.IO.Class (MonadIO, liftIO)
import Data.Text (Text)
import Foreign (nullPtr)
import WGPU.Internal.CommandBuffer (CommandBuffer (CommandBuffer))
import WGPU.Internal.Device (Device, deviceInst, wgpuDevice)
import WGPU.Internal.Instance (Instance, wgpuHsInstance)
import WGPU.Internal.Memory
  ( ToRaw,
    evalContT,
    raw,
    rawPtr,
    showWithPtr,
    withCZeroingAfter,
  )
import qualified WGPU.Raw.Generated.Fun as RawFun
import WGPU.Raw.Generated.Struct.WGPUCommandBufferDescriptor (WGPUCommandBufferDescriptor)
import qualified WGPU.Raw.Generated.Struct.WGPUCommandBufferDescriptor as WGPUCommandBufferDescriptor
import qualified WGPU.Raw.Generated.Struct.WGPUCommandEncoderDescriptor as WGPUCommandEncoderDescriptor
import WGPU.Raw.Types (WGPUCommandEncoder (WGPUCommandEncoder))

-------------------------------------------------------------------------------

-- | Handle to an encoder for a series of GPU operations.
--
-- A command encoder can record render passes, compute passes, and transfer
-- operations between driver-managed resources like buffers and textures.
data CommandEncoder = CommandEncoder
  { commandEncoderInst :: !Instance,
    wgpuCommandEncoder :: !WGPUCommandEncoder
  }

instance Show CommandEncoder where
  show e =
    let CommandEncoder _ (WGPUCommandEncoder ptr) = e
     in showWithPtr "CommandEncoder" ptr

instance Eq CommandEncoder where
  (==) e1 e2 =
    let CommandEncoder _ (WGPUCommandEncoder e1_ptr) = e1
        CommandEncoder _ (WGPUCommandEncoder e2_ptr) = e2
     in e1_ptr == e2_ptr

instance ToRaw CommandEncoder WGPUCommandEncoder where
  raw = pure . wgpuCommandEncoder

-------------------------------------------------------------------------------

-- | Create an empty command encoder.
createCommandEncoder ::
  MonadIO m =>
  -- | Device for which to create the command encoder.
  Device ->
  -- | Debug label for the command encoder.
  Text ->
  -- | IO action that returns the command encoder.
  m CommandEncoder
createCommandEncoder device label = liftIO . evalContT $ do
  let inst = deviceInst device
  label_ptr <- rawPtr label
  commandEncoderDescriptor_ptr <-
    withCZeroingAfter $
      WGPUCommandEncoderDescriptor.WGPUCommandEncoderDescriptor
        { nextInChain = nullPtr,
          label = label_ptr
        }
  commandEncoderRaw <-
    RawFun.wgpuDeviceCreateCommandEncoder
      (wgpuHsInstance inst)
      (wgpuDevice device)
      commandEncoderDescriptor_ptr
  pure (CommandEncoder inst commandEncoderRaw)

-- | Finish encoding commands, returning a command buffer.
commandEncoderFinish ::
  MonadIO m =>
  -- | Command encoder to finish.
  CommandEncoder ->
  -- | Debugging label for the command buffer.
  Text ->
  -- | IO action which returns the command buffer.
  m CommandBuffer
commandEncoderFinish commandEncoder label = liftIO . evalContT $ do
  let inst = commandEncoderInst commandEncoder
  commandBufferDescriptor_ptr <- rawPtr (CommandBufferDescriptor label)
  commandBufferRaw <-
    RawFun.wgpuCommandEncoderFinish
      (wgpuHsInstance inst)
      (wgpuCommandEncoder commandEncoder)
      commandBufferDescriptor_ptr
  pure (CommandBuffer commandBufferRaw)

-------------------------------------------------------------------------------

newtype CommandBufferDescriptor = CommandBufferDescriptor
  {commandBufferLabel :: Text}
  deriving (Eq, Show)

instance ToRaw CommandBufferDescriptor WGPUCommandBufferDescriptor where
  raw CommandBufferDescriptor {..} = do
    label_ptr <- rawPtr commandBufferLabel
    pure
      WGPUCommandBufferDescriptor.WGPUCommandBufferDescriptor
        { nextInChain = nullPtr,
          label = label_ptr
        }