package wire

import (
	"fmt"

	"github.com/theater/picomap/lib/halfsiphash"
	"github.com/theater/picomap/lib/msgpack"
)

var HashKey = [8]byte{}

type ResponseBOOTSEL struct{}
type RequestBOOTSEL struct{}

type Envelope struct {
	Checksum uint32
	Payload  []byte
}

func init() {
	msgpack.RegisterExt(0, (*Envelope)(nil))
	msgpack.RegisterExt(1, (*ResponseBOOTSEL)(nil))
	msgpack.RegisterExt(2, (*RequestBOOTSEL)(nil))
}

func EncodeMessage(msg any) ([]byte, error) {
	payload, err := msgpack.Marshal(msg)
	if err != nil {
		return nil, fmt.Errorf("encode inner: %w", err)
	}

	checksum := halfsiphash.Sum32(payload, HashKey)
	env := Envelope{Checksum: checksum, Payload: payload}
	data, err := msgpack.Marshal(&env)
	if err != nil {
		return nil, fmt.Errorf("encode envelope: %w", err)
	}
	return data, nil
}

func DecodeMessage(data []byte) (any, error) {
	var env Envelope
	if err := msgpack.Unmarshal(data, &env); err != nil {
		return nil, fmt.Errorf("decode envelope: %w", err)
	}

	expected := halfsiphash.Sum32(env.Payload, HashKey)
	if env.Checksum != expected {
		return nil, fmt.Errorf("checksum mismatch: got %08x, want %08x", env.Checksum, expected)
	}

	var inner any
	if err := msgpack.Unmarshal(env.Payload, &inner); err != nil {
		return nil, fmt.Errorf("decode inner: %w", err)
	}
	return inner, nil
}