package integration

import (
	"context"
	"errors"
	"github.com/tetratelabs/wazero/api"
)

type Message interface {
	MarshalVT() (dAtA []byte, err error)
	UnmarshalVT(dAtA []byte) error
}

func newMemoryManager(mod api.Module) *memoryManager {
	return &memoryManager{
		allocate:   mod.ExportedFunction("malloc"),
		deallocate: mod.ExportedFunction("free"),
	}
}

type memoryManager struct {
	allocate            api.Function
	deallocate          api.Function
	danglingAllocations []uint64
}

func (m *memoryManager) Deallocate(ctx context.Context, ptr uint64) error {
	_, err := m.deallocate.Call(ctx, ptr)
	return err
}

func (m *memoryManager) WriteMessage(ctx context.Context, mod api.Module, msg Message) (uint64, error) {
	data, err := msg.MarshalVT()
	if err != nil {
		return 0, err
	}
	ptr, err := m.Allocate(ctx, uint64(len(data)))
	if err != nil {
		return 0, err
	}

	if !mod.Memory().Write(uint32(ptr), data) {
		return 0, errors.New("failed to write message to memory")
	}

	return (ptr << uint64(32)) | uint64(len(data)), nil
}

func (m *memoryManager) Allocate(ctx context.Context, size uint64) (ptr uint64, err error) {
	results, err := m.allocate.Call(ctx, size)
	if err != nil {
		return 0, err
	}

	m.danglingAllocations = append(m.danglingAllocations, results[0])

	return results[0], nil
}

func (m *memoryManager) WithMem(ctx context.Context, size uint64, delegate func(ptr uint64) error) error {
	results, err := m.allocate.Call(ctx, size)
	if err != nil {
		return err
	}

	defer m.deallocate.Call(ctx, results[0])

	return delegate(results[0])
}

func (m *memoryManager) Close() (err error) {
	ctx := context.Background()

	for i := range m.danglingAllocations {
		_, e := m.deallocate.Call(ctx, m.danglingAllocations[i])
		err = errors.Join(err, e)
	}

	return err
}