package experimental

import (
	"context"

	"github.com/tetratelabs/wazero/internal/ctxkey"
)

// MemoryAllocator is a memory allocation hook which is invoked
// to create a new MemoryBuffer, with the given specification:
// min is the initial and minimum length (in bytes) of the backing []byte,
// cap a suggested initial capacity, and max the maximum length
// that will ever be requested.
type MemoryAllocator func(min, cap, max uint64) MemoryBuffer

// MemoryBuffer is a memory buffer that backs a Wasm memory.
type MemoryBuffer interface {
	// Return the backing []byte for the memory buffer.
	Buffer() []byte
	// Grow the backing memory buffer to size bytes in length.
	// To back a shared memory, Grow can't change the address
	// of the backing []byte (only its length/capacity may change).
	Grow(size uint64) []byte
	// Free the backing memory buffer.
	Free()
}

// WithMemoryAllocator registers the given MemoryAllocator into the given
// context.Context.
func WithMemoryAllocator(ctx context.Context, allocator MemoryAllocator) context.Context {
	if allocator != nil {
		return context.WithValue(ctx, ctxkey.MemoryAllocatorKey{}, allocator)
	}
	return ctx
}