#include <torch/extension.h>


torch::Tensor moe_dispatch_cuda_forward(
    int s, int ec, int h,
    torch::Tensor batch_tokens,
    torch::Tensor mask,
    torch::Tensor dest_idx);

torch::Tensor moe_dispatch_cuda_backward(
    int s, int ec, int h,
    torch::Tensor expert_grad,
    torch::Tensor mask,
    torch::Tensor dest_idx);

torch::Tensor moe_combine_cuda_forward(
    int s, int e, int c, int h,
    torch::Tensor expert_tokens,
    torch::Tensor logits,
    torch::Tensor mask,
    torch::Tensor dest_idx);

std::vector<torch::Tensor> moe_combine_cuda_backward(
    int s, int e, int c, int h,
    torch::Tensor tokens_grad,
    torch::Tensor expert_tokens,
    torch::Tensor logits,
    torch::Tensor mask,
    torch::Tensor dest_idx);

torch::Tensor cumsum_sub_one_in_dim0(torch::Tensor mask);

#define CHECK_CUDA(x) TORCH_CHECK(x.device().is_cuda(), #x " must be a CUDA tensor")
#define CHECK_CONTIGUOUS(x) TORCH_CHECK(x.is_contiguous(), #x " must be contiguous")
#define CHECK_INPUT(x) CHECK_CUDA(x); CHECK_CONTIGUOUS(x)

torch::Tensor moe_dispatch_forward(
    int s, int ec, int h,
    torch::Tensor batch_tokens,
    torch::Tensor mask,
    torch::Tensor dest_idx) {

    CHECK_INPUT(batch_tokens);
    CHECK_CUDA(mask);
    CHECK_CUDA(dest_idx);

    return moe_dispatch_cuda_forward(
        s, ec, h,
        batch_tokens, mask, dest_idx);
}

torch::Tensor moe_dispatch_backward(
    int s, int ec, int h,
    torch::Tensor expert_grad,
    torch::Tensor mask,
    torch::Tensor dest_idx) {

    CHECK_INPUT(expert_grad);
    CHECK_CUDA(mask);
    CHECK_CUDA(dest_idx);

    return moe_dispatch_cuda_backward(
        s, ec, h,
        expert_grad, mask, dest_idx);
}

torch::Tensor moe_combine_forward(
    int s, int e, int c, int h,
    torch::Tensor expert_tokens,
    torch::Tensor logits,
    torch::Tensor mask,
    torch::Tensor dest_idx) {

    CHECK_INPUT(expert_tokens);
    CHECK_INPUT(logits);
    CHECK_CUDA(mask);
    CHECK_CUDA(dest_idx);

    return moe_combine_cuda_forward(
        s, e, c, h,
        expert_tokens, logits, mask, dest_idx);
}

std::vector<torch::Tensor> moe_combine_backward(
    int s, int e, int c, int h,
    torch::Tensor tokens_grad,
    torch::Tensor expert_tokens,
    torch::Tensor logits,
    torch::Tensor mask,
    torch::Tensor dest_idx) {

    CHECK_INPUT(tokens_grad);
    CHECK_INPUT(logits);
    CHECK_CUDA(mask);
    CHECK_CUDA(dest_idx);

    return moe_combine_cuda_backward(
        s, e, c, h,
        tokens_grad, expert_tokens, logits, mask, dest_idx);
}

torch::Tensor moe_cumsum(torch::Tensor mask) {
    CHECK_INPUT(mask);
    return cumsum_sub_one_in_dim0(mask);
}

PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
    m.def("cumsum_sub_one", &moe_cumsum,
        "Fast cumsum operation in dim0");
    m.def("dispatch_forward", &moe_dispatch_forward, 
        "Forward operation in MoE dispatch function");
    m.def("dispatch_backward", &moe_dispatch_backward,
        "Backward operation in MoE dispatch function");
    m.def("combine_forward", &moe_combine_forward,
        "Combine operation in MoE combine function");
    m.def("combine_backward", &moe_combine_backward,
        "Combine operation in MoE combine function");
}