package sync

import (
	"cloudsave/pkg/data"
	"cloudsave/pkg/remote"
	"cloudsave/pkg/remote/client"
	"cloudsave/pkg/repository"
	"errors"
	"fmt"
)

type (
	ConflictResolution int
	State              int
	decision           int

	Syncer struct {
		cli     *client.Client
		service *data.Service

		stateCallback    func(s State, g repository.Metadata)
		errorCallback    func(err error, g repository.Metadata)
		conflictCallback func(a, b repository.Metadata) ConflictResolution
	}
)

const (
	Their ConflictResolution = iota
	Mine
	None
)

const (
	ignore decision = iota
	push
	pull
)

const (
	FetchingMetdata State = iota
	Pushing
	Pulling
	Pushed
	Pulled
	UpToDate
)

var (
	ErrFetching  error = errors.New("failed to fetch the metadata")
	ErrPushing   error = errors.New("failed to push data")
	ErrPulling   error = errors.New("failed to pull data")
	ErrDatastore error = errors.New("failed to get data from local datastore")
)

func NewSyncer(cli *client.Client, service *data.Service) *Syncer {
	return &Syncer{
		cli:     cli,
		service: service,
	}
}

func (s *Syncer) SetStateCallback(fn func(s State, g repository.Metadata)) {
	s.stateCallback = fn
}

func (s *Syncer) SetErrorCallback(fn func(err error, g repository.Metadata)) {
	s.errorCallback = fn
}

func (s *Syncer) SetConflictCallback(fn func(a, b repository.Metadata) ConflictResolution) {
	s.conflictCallback = fn
}

func (s *Syncer) Sync() {
	games, err := s.service.AllGames()
	if err != nil {
		s.errorCallback(fmt.Errorf("failed to get all games: %w", err), repository.Metadata{})
		return
	}

	for _, g := range games {
		r, err := remote.One(g.ID)
		if err != nil {
			s.errorCallback(fmt.Errorf("%w: %s", ErrDatastore, err), g)
		}
		if r.URL != s.cli.BaseURL() {
			continue
		}
		if err := s.sync(g); err != nil {
			s.errorCallback(err, g)
		}
	}
}

func (s *Syncer) sync(g repository.Metadata) error {
	s.stateCallback(FetchingMetdata, g)

	remoteMetadata, err := s.cli.Metadata(g.ID)
	if err != nil {
		if errors.Is(err, client.ErrNotFound) {
			s.stateCallback(Pushing, g)
			if err := s.push(g); err != nil {
				return fmt.Errorf("%w: %s", ErrPushing, err)
			}
			s.stateCallback(Pushed, g)
			return nil
		}
		return fmt.Errorf("%w: %s", ErrFetching, err)
	}

	if g.MD5 == remoteMetadata.MD5 {
		s.stateCallback(UpToDate, g)
		return nil
	}

	d := ignore

	if g.Version > remoteMetadata.Version {
		d = push
	}

	if g.Version < remoteMetadata.Version {
		d = pull
	}

	if g.Version == remoteMetadata.Version {
		r := s.conflictCallback(g, remoteMetadata)
		switch r {
		case Mine:
			{
				d = push
			}
		case Their:
			{
				d = pull
			}
		}
		return nil
	}

	switch d {
	case push:
		{
			s.stateCallback(Pushing, g)
			if err := s.push(g); err != nil {
				return fmt.Errorf("%w: %s", ErrPushing, err)
			}
			s.stateCallback(Pushed, g)
			return nil
		}
	case pull:
		{
			s.stateCallback(Pulling, g)
			if err := s.pull(g, remoteMetadata); err != nil {
				return fmt.Errorf("%w: %s", ErrPulling, err)
			}
			s.stateCallback(Pulled, g)
			return nil
		}
	}

	return nil
}

func (s *Syncer) push(g repository.Metadata) error {
	if err := s.service.PushArchive(g.ID, "", s.cli); err != nil {
		return err
	}

	// manage backup
	bs, err := s.service.AllBackups(g.ID)
	if err != nil {
		return err
	}

	for _, b := range bs {
		binfo, err := s.cli.ArchiveInfo(g.ID, b.UUID)
		if err != nil {
			if !errors.Is(err, client.ErrNotFound) {
				return fmt.Errorf("failed to get remote information about the backup file: %w", err)
			}
		}

		if binfo.MD5 != b.MD5 {
			if err := s.cli.PushBackup(b, g); err != nil {
				return fmt.Errorf("failed to push backup: %w", err)
			}
		}

	}
	return nil
}

func (s *Syncer) pull(g, r repository.Metadata) error {
	g.Version = r.Version
	g.Date = r.Date

	if err := s.service.UpdateMetadata(g.ID, g); err != nil {
		return err
	}

	if err := s.service.PullArchive(g.ID, "", s.cli); err != nil {
		return err
	}

	if err := s.service.ApplyCurrent(g.ID); err != nil {
		return err
	}

	// manage backup
	bs, err := s.cli.ListArchives(g.ID)
	if err != nil {
		return err
	}

	for _, uuid := range bs {
		rinfo, err := s.cli.ArchiveInfo(g.ID, uuid)
		if err != nil {
			return err
		}

		linfo, err := s.service.Backup(g.ID, uuid)
		if err != nil {
			return err
		}

		if linfo.MD5 != rinfo.MD5 {
			if err := s.service.PullBackup(g.ID, uuid, s.cli); err != nil {
				return err
			}
		}
	}

	return nil
}