package helpers

import (
	"context"
	"strconv"

	"github.com/prysmaticlabs/prysm/api/grpc"
	"github.com/prysmaticlabs/prysm/beacon-chain/blockchain"
	"github.com/prysmaticlabs/prysm/beacon-chain/sync"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

// ValidateSync checks whether the node is currently syncing and returns an error if it is.
// It also appends syncing info to gRPC headers.
func ValidateSync(ctx context.Context, syncChecker sync.Checker, headFetcher blockchain.HeadFetcher, timeFetcher blockchain.TimeFetcher) error {
	if !syncChecker.Syncing() {
		return nil
	}
	headSlot := headFetcher.HeadSlot()
	syncDetailsContainer := &SyncDetailsContainer{
		SyncDetails: &SyncDetails{
			HeadSlot:     strconv.FormatUint(uint64(headSlot), 10),
			SyncDistance: strconv.FormatUint(uint64(timeFetcher.CurrentSlot()-headSlot), 10),
			IsSyncing:    true,
		},
	}
	err := grpc.AppendCustomErrorHeader(ctx, syncDetailsContainer)
	if err != nil {
		return status.Errorf(
			codes.InvalidArgument,
			"Syncing to latest head, not ready to respond. Could not prepare sync details: %v",
			err,
		)
	}
	return status.Error(codes.Unavailable, "Syncing to latest head, not ready to respond")
}