package sync

import (
	"context"
	"github.com/anytypeio/go-anytype-infrastructure-experiments/pkg/acl/acltree"
	"github.com/anytypeio/go-anytype-infrastructure-experiments/pkg/acl/treestorage"
	"github.com/anytypeio/go-anytype-infrastructure-experiments/service/sync/syncpb"
	"github.com/anytypeio/go-anytype-infrastructure-experiments/service/treecache"
	"github.com/anytypeio/go-anytype-infrastructure-experiments/util/slice"
)

type requestHander struct {
	treeCache treecache.Service
	client    SyncClient
}

func (r *requestHander) HandleHeadUpdate(ctx context.Context, senderId string, update *syncpb.SyncHeadUpdate) (err error) {
	var (
		fullRequest  *syncpb.SyncFullRequest
		snapshotPath []string
		result       acltree.AddResult
	)

	err = r.treeCache.Do(ctx, update.TreeId, func(tree acltree.ACLTree) error {
		// TODO: check if we already have those changes
		result, err = tree.AddRawChanges(ctx, update.Changes...)
		if err != nil {
			return err
		}
		shouldFullSync := !slice.UnsortedEquals(update.Heads, tree.Heads())
		snapshotPath = tree.SnapshotPath()
		if shouldFullSync {
			fullRequest, err = r.prepareFullSyncRequest(update.TreeId, update.SnapshotPath, tree)
			if err != nil {
				return err
			}
		}
		return nil
	})
	// if there are no such tree
	if err == treestorage.ErrUnknownTreeId {
		fullRequest = &syncpb.SyncFullRequest{
			TreeId: update.TreeId,
		}
	}
	// if we have incompatible heads, or we haven't seen the tree at all
	if fullRequest != nil {
		return r.client.RequestFullSync(senderId, fullRequest)
	}
	// if error or nothing has changed
	if err != nil || len(result.Added) == 0 {
		return err
	}
	// otherwise sending heads update message
	newUpdate := &syncpb.SyncHeadUpdate{
		Heads:        result.Heads,
		Changes:      result.Added,
		SnapshotPath: snapshotPath,
		TreeId:       update.TreeId,
	}
	err = r.client.NotifyHeadsChanged(newUpdate)
	return
}

func (r *requestHander) HandleFullSyncRequest(ctx context.Context, senderId string, request *syncpb.SyncFullRequest) error {
	// TODO: add case of new tree
	return nil
}

func (r *requestHander) HandleFullSyncResponse(ctx context.Context, senderId string, request *syncpb.SyncFullRequest) error {
	// TODO: add case of new tree
	return nil
}

func (r *requestHander) prepareFullSyncRequest(treeId string, theirPath []string, tree acltree.ACLTree) (*syncpb.SyncFullRequest, error) {
	ourChanges, err := tree.ChangesAfterCommonSnapshot(theirPath)
	if err != nil {
		return nil, err
	}
	return &syncpb.SyncFullRequest{
		Heads:        tree.Heads(),
		Changes:      ourChanges,
		TreeId:       treeId,
		SnapshotPath: tree.SnapshotPath(),
	}, nil
}