use std::ffi::c_void;
use xserv_tensor::{DType, Device, Tensor};

unsafe extern "C" {
    fn launch_gelu_f32(x: *const c_void, out: *mut c_void, n: i32, stream: *mut c_void);
    fn launch_gelu_bf16(x: *const c_void, out: *mut c_void, n: i32, stream: *mut c_void);
    fn launch_silu_f32(x: *const c_void, out: *mut c_void, n: i32, stream: *mut c_void);
    fn launch_silu_bf16(x: *const c_void, out: *mut c_void, n: i32, stream: *mut c_void);
    fn launch_scale_f32(x: *const c_void, out: *mut c_void, scale: f32, n: i32, stream: *mut c_void);
    fn launch_scale_bf16(x: *const c_void, out: *mut c_void, scale: f32, n: i32, stream: *mut c_void);
    fn launch_add_f32(a: *const c_void, b: *const c_void, out: *mut c_void, n: i32, stream: *mut c_void);
    fn launch_add_bf16(a: *const c_void, b: *const c_void, out: *mut c_void, n: i32, stream: *mut c_void);
    fn launch_mul_f32(a: *const c_void, b: *const c_void, out: *mut c_void, n: i32, stream: *mut c_void);
    fn launch_mul_bf16(a: *const c_void, b: *const c_void, out: *mut c_void, n: i32, stream: *mut c_void);
}

fn dispatch_unary(x: &Tensor, f32_fn: unsafe extern "C" fn(*const c_void, *mut c_void, i32, *mut c_void),
                  bf16_fn: unsafe extern "C" fn(*const c_void, *mut c_void, i32, *mut c_void)) -> Tensor {
    assert!(x.is_contiguous() && matches!(x.device(), Device::Cuda(_)));
    let out = Tensor::zeros(x.shape(), x.dtype(), x.device());
    let n = x.numel() as i32;
    unsafe {
        match x.dtype() {
            DType::F32 => f32_fn(x.data_ptr() as _, out.data_ptr() as *mut c_void, n, std::ptr::null_mut()),
            DType::BF16 => bf16_fn(x.data_ptr() as _, out.data_ptr() as *mut c_void, n, std::ptr::null_mut()),
            _ => panic!("unsupported dtype"),
        }
    }
    xserv_cuda::device::synchronize().unwrap();
    out
}

fn dispatch_binary(a: &Tensor, b: &Tensor,
                   f32_fn: unsafe extern "C" fn(*const c_void, *const c_void, *mut c_void, i32, *mut c_void),
                   bf16_fn: unsafe extern "C" fn(*const c_void, *const c_void, *mut c_void, i32, *mut c_void)) -> Tensor {
    assert_eq!(a.shape(), b.shape());
    assert!(a.is_contiguous() && b.is_contiguous());
    assert!(matches!(a.device(), Device::Cuda(_)));
    assert_eq!(a.dtype(), b.dtype());
    let out = Tensor::zeros(a.shape(), a.dtype(), a.device());
    let n = a.numel() as i32;
    unsafe {
        match a.dtype() {
            DType::F32 => f32_fn(a.data_ptr() as _, b.data_ptr() as _, out.data_ptr() as *mut c_void, n, std::ptr::null_mut()),
            DType::BF16 => bf16_fn(a.data_ptr() as _, b.data_ptr() as _, out.data_ptr() as *mut c_void, n, std::ptr::null_mut()),
            _ => panic!("unsupported dtype"),
        }
    }
    xserv_cuda::device::synchronize().unwrap();
    out
}

pub fn gelu(x: &Tensor) -> Tensor { dispatch_unary(x, launch_gelu_f32, launch_gelu_bf16) }
pub fn silu(x: &Tensor) -> Tensor { dispatch_unary(x, launch_silu_f32, launch_silu_bf16) }

pub fn scale(x: &Tensor, scale_val: f32) -> Tensor {
    assert!(x.is_contiguous() && matches!(x.device(), Device::Cuda(_)));
    let out = Tensor::zeros(x.shape(), x.dtype(), x.device());
    let n = x.numel() as i32;
    unsafe {
        match x.dtype() {
            DType::F32 => launch_scale_f32(x.data_ptr() as _, out.data_ptr() as *mut c_void, scale_val, n, std::ptr::null_mut()),
            DType::BF16 => launch_scale_bf16(x.data_ptr() as _, out.data_ptr() as *mut c_void, scale_val, n, std::ptr::null_mut()),
            _ => panic!("unsupported dtype for scale"),
        }
    }
    xserv_cuda::device::synchronize().unwrap();
    out
}

pub fn add(a: &Tensor, b: &Tensor) -> Tensor { dispatch_binary(a, b, launch_add_f32, launch_add_bf16) }
pub fn mul(a: &Tensor, b: &Tensor) -> Tensor { dispatch_binary(a, b, launch_mul_f32, launch_mul_bf16) }