use core::alloc::{GlobalAlloc, Layout};

pub struct Allocator;

#[cfg(all(unix, not(target_os = "macos")))]
unsafe impl GlobalAlloc for Allocator {
    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
        unsafe { libc::memalign(layout.align(), layout.size()) as *mut u8 }
    }

    unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
        unsafe { libc::free(ptr as *mut libc::c_void) }
    }

    unsafe fn realloc(&self, ptr: *mut u8, _layout: Layout, new_size: usize) -> *mut u8 {
        unsafe { libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8 }
    }
}

#[cfg(target_os = "macos")]
unsafe impl GlobalAlloc for Allocator {
    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
        let mut ptr: *mut libc::c_void = core::ptr::null_mut();
        let align = layout.align().max(8);
        let size = layout.size();
        let result = unsafe { libc::posix_memalign(&mut ptr, align, size) };
        if result != 0 {
            return core::ptr::null_mut();
        }
        ptr as *mut u8
    }

    unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
        unsafe { libc::free(ptr as *mut libc::c_void) }
    }

    unsafe fn realloc(&self, ptr: *mut u8, _layout: Layout, new_size: usize) -> *mut u8 {
        unsafe { libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8 }
    }
}

#[cfg(windows)]
unsafe impl GlobalAlloc for Allocator {
    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
        use windows_sys::Win32::System::Memory::*;
        unsafe { HeapAlloc(GetProcessHeap(), 0, layout.size()) as *mut u8 }
    }

    unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
        use windows_sys::Win32::System::Memory::*;
        unsafe { HeapFree(GetProcessHeap(), 0, ptr as *mut core::ffi::c_void) };
    }

    unsafe fn realloc(&self, ptr: *mut u8, _layout: Layout, new_size: usize) -> *mut u8 {
        use windows_sys::Win32::System::Memory::*;
        unsafe { HeapReAlloc(GetProcessHeap(), 0, ptr as *mut core::ffi::c_void, new_size) as *mut u8 }
    }
}