using BenchmarkTools 
using WGPUCompute

# Kernel definition
function cast_kernel(x::WgpuArray{T, N}, out::WgpuArray{S, N}) where {T, S, N}
	xdim = workgroupDims.x
	ydim = workgroupDims.y
	gIdx = workgroupId.x*xdim + localId.x
	gIdy = workgroupId.y*ydim + localId.y
	gId = xDims.x*gIdy + gIdx
	out[gId] = S(ceil(x[gId]))
end

# wrapper function
function cast(S::DataType, x::WgpuArray{T, N}) where {T, N}
	y = WgpuArray{S}(undef, size(x))
	@wgpukernel launch=true workgroupSizes=(4, 4) workgroupCount=(2, 2) shmem=() cast_kernel(x, y)
	return y
end

x = WgpuArray{Float32}(rand(Float32, 8, 8) .- 0.5f0)
z = cast(UInt32, x)

function tiled_matmul_kernel(x::WgpuArray{T, N}, y::WgpuArray{T, N}, out::WgpuArray{T, N}) where {T, N}
	#set out matrix to zero
	gId = xDims.x*globalId.y + globalId.x
	out[gId] = 0.0
	
	# set local variable = 0.0
	sum = 0.0
	
	for tileId in 0:numWorkgroups.y
		# copy block from x to shared memory
		xId = workgroupId.x*workgroupDims.x + localId.x
		yId = tileId*workgroupDims.y + localId.y
		sId = localId.y*workgroupDims.x + localId.x
		shmem1[sId] = x[yId*xDims.x + xId]
		
		# copy block from y to shared memory
		xId = tileId*workgroupDims.x + localId.x
		yId = workgroupId.y*workgroupDims.y + localId.y
		shmem2[sId] = y[yId*yDims.x + xId]
		synchronize()
				
		# block sums for each tid
		for i in 0:xDims.y/numWorkgroups.y
			sum = sum + shmem1[i*workgroupDims.x + localId.x]*shmem2[localId.y*workgroupDims.x + i]
		end
		synchronize()
	end
	
	out[gId] = sum
end

# For now valid only for square matrices of size powers of 2 and base size 16 to keep it simple.
function tiled_matmul_heuristics(x::WgpuArray{T, N}, y::WgpuArray{T, N}) where {T, N}
	aSize = size(x)
	bSize = size(y)
	@assert last(aSize) == first(bSize)
	outSize = (first(aSize), last(bSize))
	@assert eltype(x) == eltype(y)
	wgSize = (16, 16) # This can be fixed for now
	wgCount = div.((outSize[1], outSize[2]), 16, RoundUp)
	return (outSize, wgSize, wgCount)
end

function tiled_matmul(x::WgpuArray{T, N}, y::WgpuArray{T, N}) where {T, N}
	(outSize, wgSize, wgCount) = tiled_matmul_heuristics(x, y)
	out = WgpuArray{eltype(x), ndims(x)}(undef, outSize)
	@wgpukernel(
		launch=true,
		workgroupSizes=wgSize,
		workgroupCount=wgCount,
		shmem=(:shmem1=>(Float32, wgSize), :shmem2=>(Float32, wgSize)),
		tiled_matmul_kernel(x, y, out)
	)
	return out
end

Base.:*(x::WgpuArray{T, N}, y::WgpuArray{T, N})  where {T, N} = tiled_matmul(x, y)

x = WgpuArray{Float32, 2}(rand(2048, 2048));
y = WgpuArray{Float32, 2}(rand(2048, 2048));

z = x*y

z_cpu = (x |> collect)*(y |> collect)

@test z_cpu ≈ (z |> collect)

using WGPUCompute
using BenchmarkTools

aArray = WgpuArray{Float32}(undef, (1024, 1024, 100)) 
bArray = WgpuArray{Float32}(rand(Float32, (1024, 1024, 100)))

@benchmark copyto!(aArray, 1, bArray, 1, prod(size(aArray)))

using WGPUCompute

y = WgpuArray((rand(4, 4) .-0.5) .|> Float32)

function relu_kernel(x::WgpuArray{T, N}, out::WgpuArray{T, N}) where {T, N}
	gId = xDims.x*globalId.y + globalId.x
	value = x[gId]
	out[gId] = max(value, 0.0)
end

function relu(x::WgpuArray{T, N}) where {T, N}
	y = similar(x)
	@wgpukernel launch=true workgroupSizes=(4,4) workgroupCount=(1,1) shmem=() relu_kernel(x, y)
	return y
end

relu(y)