package cli

import (
	"context"
	"path/filepath"
	"strings"
	"time"

	"github.com/pkg/errors"

	"github.com/kopia/kopia/repo"
	"github.com/kopia/kopia/snapshot"
	"github.com/kopia/kopia/snapshot/policy"
	"github.com/kopia/kopia/snapshot/snapshotfs"
)

const (
	maxSnapshotDescriptionLength = 1024
)

var (
	snapshotCreateCommand = snapshotCommands.Command("create", "Creates a snapshot of local directory or file.").Default()

	snapshotCreateSources                 = snapshotCreateCommand.Arg("source", "Files or directories to create snapshot(s) of.").ExistingFilesOrDirs()
	snapshotCreateAll                     = snapshotCreateCommand.Flag("all", "Create snapshots for files or directories previously backed up by this user on this computer").Bool()
	snapshotCreateCheckpointUploadLimitMB = snapshotCreateCommand.Flag("upload-limit-mb", "Stop the backup process after the specified amount of data (in MB) has been uploaded.").PlaceHolder("MB").Default("0").Int64()
	snapshotCreateDescription             = snapshotCreateCommand.Flag("description", "Free-form snapshot description.").String()
	snapshotCreateForceHash               = snapshotCreateCommand.Flag("force-hash", "Force hashing of source files for a given percentage of files [0..100]").Default("0").Int()
	snapshotCreateParallelUploads         = snapshotCreateCommand.Flag("parallel", "Upload N files in parallel").PlaceHolder("N").Default("0").Int()
)

func runBackupCommand(ctx context.Context, rep *repo.Repository) error {
	sources := *snapshotCreateSources

	if *snapshotCreateAll {
		local, err := getLocalBackupPaths(ctx, rep)
		if err != nil {
			return err
		}

		sources = append(sources, local...)
	}

	if len(sources) == 0 {
		return errors.New("no backup sources")
	}

	u := snapshotfs.NewUploader(rep)
	u.MaxUploadBytes = *snapshotCreateCheckpointUploadLimitMB << 20 //nolint:gomnd
	u.ForceHashPercentage = *snapshotCreateForceHash
	u.ParallelUploads = *snapshotCreateParallelUploads
	onCtrlC(u.Cancel)

	u.Progress = cliProgress

	if len(*snapshotCreateDescription) > maxSnapshotDescriptionLength {
		return errors.New("description too long")
	}

	var finalErrors []string

	for _, snapshotDir := range sources {
		log.Debugf("Backing up %v", snapshotDir)

		dir, err := filepath.Abs(snapshotDir)
		if err != nil {
			return errors.Errorf("invalid source: '%s': %s", snapshotDir, err)
		}

		sourceInfo := snapshot.SourceInfo{Path: filepath.Clean(dir), Host: getHostName(), UserName: getUserName()}

		log.Infof("snapshotting %v", sourceInfo)

		if err := snapshotSingleSource(ctx, rep, u, sourceInfo); err != nil {
			finalErrors = append(finalErrors, err.Error())
		}
	}

	if len(finalErrors) == 0 {
		return nil
	}

	return errors.Errorf("encountered %v errors:\n%v", len(finalErrors), strings.Join(finalErrors, "\n"))
}

func snapshotSingleSource(ctx context.Context, rep *repo.Repository, u *snapshotfs.Uploader, sourceInfo snapshot.SourceInfo) error {
	t0 := time.Now()

	rep.Content.ResetStats()

	localEntry, err := getLocalFSEntry(sourceInfo.Path)
	if err != nil {
		return errors.Wrap(err, "unable to get local filesystem entry")
	}

	previous, err := findPreviousSnapshotManifest(ctx, rep, sourceInfo, nil)
	if err != nil {
		return err
	}

	policyTree, err := policy.TreeForSource(ctx, rep, sourceInfo)
	if err != nil {
		return errors.Wrap(err, "unable to get policy tree")
	}

	log.Infof("uploading %v using %v previous manifests", sourceInfo, len(previous))

	manifest, err := u.Upload(ctx, localEntry, policyTree, sourceInfo, previous...)
	if err != nil {
		return err
	}

	manifest.Description = *snapshotCreateDescription

	snapID, err := snapshot.SaveSnapshot(ctx, rep, manifest)
	if err != nil {
		return errors.Wrap(err, "cannot save manifest")
	}

	printStderr("uploaded snapshot %v (root %v) in %v\n", snapID, manifest.RootObjectID(), time.Since(t0))

	_, err = policy.ApplyRetentionPolicy(ctx, rep, sourceInfo, true)

	return err
}

// findPreviousSnapshotManifest returns the list of previous snapshots for a given source, including
// last complete snapshot and possibly some number of incomplete snapshots following it.
func findPreviousSnapshotManifest(ctx context.Context, rep *repo.Repository, sourceInfo snapshot.SourceInfo, noLaterThan *time.Time) ([]*snapshot.Manifest, error) {
	man, err := snapshot.ListSnapshots(ctx, rep, sourceInfo)
	if err != nil {
		return nil, errors.Wrap(err, "error listing previous snapshots")
	}

	// phase 1 - find latest complete snapshot.
	var previousComplete *snapshot.Manifest

	var previousCompleteStartTime time.Time

	var result []*snapshot.Manifest

	for _, p := range man {
		if noLaterThan != nil && p.StartTime.After(*noLaterThan) {
			continue
		}

		if p.IncompleteReason == "" && (previousComplete == nil || p.StartTime.After(previousComplete.StartTime)) {
			previousComplete = p
			previousCompleteStartTime = p.StartTime
		}
	}

	if previousComplete != nil {
		result = append(result, previousComplete)
	}

	// add all incomplete snapshots after that
	for _, p := range man {
		if noLaterThan != nil && p.StartTime.After(*noLaterThan) {
			continue
		}

		if p.IncompleteReason != "" && p.StartTime.After(previousCompleteStartTime) {
			result = append(result, p)
		}
	}

	return result, nil
}

func getLocalBackupPaths(ctx context.Context, rep *repo.Repository) ([]string, error) {
	h := getHostName()
	u := getUserName()
	log.Debugf("Looking for previous backups of '%v@%v'...", u, h)

	sources, err := snapshot.ListSources(ctx, rep)
	if err != nil {
		return nil, errors.Wrap(err, "unable to list sources")
	}

	var result []string

	for _, src := range sources {
		if src.Host == h && src.UserName == u {
			result = append(result, src.Path)
		}
	}

	return result, nil
}

func init() {
	addUserAndHostFlags(snapshotCreateCommand)
	snapshotCreateCommand.Action(repositoryAction(runBackupCommand))
}