package blocksync

import (
	"errors"
	"fmt"

	"github.com/cosmos/gogoproto/proto"

	bcproto "github.com/tendermint/tendermint/proto/tendermint/blocksync"
	"github.com/tendermint/tendermint/types"
)

const (
	// NOTE: keep up to date with bcproto.BlockResponse
	BlockResponseMessagePrefixSize   = 4
	BlockResponseMessageFieldKeySize = 1
	MaxMsgSize                       = types.MaxBlockSizeBytes +
		BlockResponseMessagePrefixSize +
		BlockResponseMessageFieldKeySize
)

// ValidateMsg validates a message.
func ValidateMsg(pb proto.Message) error {
	if pb == nil {
		return errors.New("message cannot be nil")
	}

	switch msg := pb.(type) {
	case *bcproto.BlockRequest:
		if msg.Height < 0 {
			return errors.New("negative Height")
		}
	case *bcproto.BlockResponse:
		_, err := types.BlockFromProto(msg.Block)
		if err != nil {
			return err
		}
	case *bcproto.NoBlockResponse:
		if msg.Height < 0 {
			return errors.New("negative Height")
		}
	case *bcproto.StatusResponse:
		if msg.Base < 0 {
			return errors.New("negative Base")
		}
		if msg.Height < 0 {
			return errors.New("negative Height")
		}
		if msg.Base > msg.Height {
			return fmt.Errorf("base %v cannot be greater than height %v", msg.Base, msg.Height)
		}
	case *bcproto.StatusRequest:
		return nil
	default:
		return fmt.Errorf("unknown message type %T", msg)
	}
	return nil
}