use crate::{AllocationEntry, Allocator, DropFn};
use boxcar::Vec;
use std::alloc::Layout;

#[derive(Default)]
pub struct GlobalAllocator {
    allocations: Vec<AllocationEntry>,
}

impl Allocator for GlobalAllocator {
    unsafe fn alloc_unsafe(&self, data: *const u8, layout: Layout, drop_fn: DropFn) -> *mut u8 {
        unsafe {
            let ptr = std::alloc::alloc(layout);
            std::ptr::copy_nonoverlapping(data, ptr, layout.size());
            self.allocations.push(AllocationEntry {
                ptr,
                layout,
                drop_fn,
            });
            ptr
        }
    }
}

impl Drop for GlobalAllocator {
    fn drop(&mut self) {
        unsafe {
            for AllocationEntry {
                ptr,
                layout,
                drop_fn,
            } in std::mem::take(&mut self.allocations)
            {
                if let Some(drop) = drop_fn {
                    drop(ptr);
                }
                std::alloc::dealloc(ptr, layout);
            }
        }
    }
}