use std::ffi::c_void;
use std::os::raw::c_char;

pub type CudaStream = *mut c_void;
pub type CudaEvent = *mut c_void;

pub const CUDA_MEMCPY_H2D: i32 = 1;
pub const CUDA_MEMCPY_D2H: i32 = 2;
pub const CUDA_MEMCPY_D2D: i32 = 3;

pub const CUDA_SUCCESS: i32 = 0;
pub const CUDA_ERROR_OUT_OF_MEMORY: i32 = 2;

#[repr(C)]
pub struct CudaDeviceProp {
    pub name: [c_char; 256],
    pub total_global_mem: usize,
    pub shared_mem_per_block: usize,
    pub regs_per_block: i32,
    pub warp_size: i32,
    pub max_threads_per_block: i32,
    pub max_threads_dim: [i32; 3],
    pub max_grid_size: [i32; 3],
    pub clock_rate: i32,
    pub total_const_mem: usize,
    pub major: i32,
    pub minor: i32,
    // There are many more fields; we only read up to what we need.
    // cudaDeviceProp is a large struct (~1KB). We pad the rest.
    _pad: [u8; 4096],
}

unsafe extern "C" {
    // --- Device ---
    pub fn cudaGetDeviceCount(count: *mut i32) -> i32;
    pub fn cudaSetDevice(device: i32) -> i32;
    pub fn cudaGetDevice(device: *mut i32) -> i32;
    pub fn cudaGetDeviceProperties(prop: *mut CudaDeviceProp, device: i32) -> i32;
    pub fn cudaDeviceSynchronize() -> i32;

    // --- Memory ---
    pub fn cudaMalloc(devptr: *mut *mut u8, size: usize) -> i32;
    pub fn cudaFree(devptr: *mut u8) -> i32;
    pub fn cudaMallocHost(ptr: *mut *mut u8, size: usize) -> i32;
    pub fn cudaFreeHost(ptr: *mut u8) -> i32;
    pub fn cudaMemcpy(dst: *mut u8, src: *const u8, count: usize, kind: i32) -> i32;
    pub fn cudaMemcpyAsync(
        dst: *mut u8,
        src: *const u8,
        count: usize,
        kind: i32,
        stream: CudaStream,
    ) -> i32;
    pub fn cudaMemset(devptr: *mut u8, value: i32, count: usize) -> i32;

    // --- Stream ---
    pub fn cudaStreamCreate(stream: *mut CudaStream) -> i32;
    pub fn cudaStreamDestroy(stream: CudaStream) -> i32;
    pub fn cudaStreamSynchronize(stream: CudaStream) -> i32;

    // --- Error ---
    pub fn cudaGetLastError() -> i32;
    pub fn cudaGetErrorString(error: i32) -> *const c_char;

    // --- Our test kernel ---
    pub fn launch_vecadd_f32(
        a: *const f32,
        b: *const f32,
        c: *mut f32,
        n: i32,
        stream: CudaStream,
    );
}