import "alloc.dby" as alloc

# Hosted and VM provider bridge. Raw operations remain private to this
# versioned runtime module; callers receive only the typed AllocatorRef.

static mut SYSTEM_VTABLE: alloc.AllocatorVTable

fn system_alloc_raw(size: usize, alignment: usize) -> ptr[u8]:
    return __dbyte_runtime.memory_alloc(size, alignment)

fn system_resize_raw(pointer: ptr[u8], old_size: usize, new_size: usize, alignment: usize) -> ptr[u8]:
    return __dbyte_runtime.memory_resize(pointer, old_size, new_size, alignment)

fn system_free_raw(pointer: ptr[u8], size: usize, alignment: usize) -> bool:
    return __dbyte_runtime.memory_free(pointer, size, alignment)

fn system_read8_raw(pointer: ptr[u8], offset: usize) -> u8:
    return __dbyte_runtime.memory_read8(pointer, offset)

fn system_write8_raw(pointer: ptr[u8], offset: usize, value: u8) -> unit:
    __dbyte_runtime.memory_write8(pointer, offset, value)
    return unit

fn provider_alloc(context: ptr[u8], size: usize, alignment: usize) -> Result[ptr[u8], alloc.AllocError]:
    let pointer = system_alloc_raw(size, alignment)
    if pointer == null:
        return Result[ptr[u8], alloc.AllocError].Err(alloc.AllocError.OutOfMemory())
    return Result[ptr[u8], alloc.AllocError].Ok(pointer)

fn provider_resize(context: ptr[u8], pointer: ptr[u8], old_size: usize, new_size: usize, alignment: usize) -> Result[ptr[u8], alloc.AllocError]:
    let replacement = system_resize_raw(pointer, old_size, new_size, alignment)
    if replacement == null:
        return Result[ptr[u8], alloc.AllocError].Err(alloc.AllocError.OutOfMemory())
    return Result[ptr[u8], alloc.AllocError].Ok(replacement)

fn provider_free(context: ptr[u8], pointer: ptr[u8], size: usize, alignment: usize) -> unit:
    let released = system_free_raw(pointer, size, alignment)
    return unit

pub fn system_allocator() -> alloc.AllocatorRef:
    SYSTEM_VTABLE.alloc = provider_alloc
    SYSTEM_VTABLE.resize = provider_resize
    SYSTEM_VTABLE.free = provider_free
    return alloc.AllocatorRef(context = null, vtable = &SYSTEM_VTABLE)