package main

import (
	"context"
	"fmt"

	"github.com/spf13/cobra"
	"golang.org/x/sync/errgroup"

	"github.com/restic/restic/internal/backend"
	"github.com/restic/restic/internal/debug"
	"github.com/restic/restic/internal/errors"
	"github.com/restic/restic/internal/repository"
	"github.com/restic/restic/internal/restic"
	"github.com/restic/restic/internal/walker"
)

var cmdRewrite = &cobra.Command{
	Use:   "rewrite [flags] [snapshotID ...]",
	Short: "Rewrite existing snapshots",
	Long: `
The "rewrite" command excludes files from existing snapshots.

By default 'rewrite' will create new snapshots that will contains same data as
the source snapshots but without excluded files. All metadata (time, host, tags)
will be preserved. The special tag 'rewrite' will be added to new snapshots to
distinguish it from the source (unless --inplace is used).

If --inplace option is used, old snapshot will be removed from repository.

Snapshots to rewrite are specified using --host, --tag, --path or by providing
a list of snapshot ids. Not specifying a snapshot id will rewrite all snapshots.

Please note, that this command only creates new snapshots. In order to delete
data from the repository use 'prune' command.

EXIT STATUS
===========

Exit status is 0 if the command was successful, and non-zero if there was any error.
`,
	DisableAutoGenTag: true,
	RunE: func(cmd *cobra.Command, args []string) error {
		return runRewrite(cmd.Context(), rewriteOptions, globalOptions, args)
	},
}

// RewriteOptions collects all options for the rewrite command.
type RewriteOptions struct {
	Hosts   []string
	Paths   []string
	Tags    restic.TagLists
	Inplace bool
	DryRun  bool

	excludePatternOptions
}

var rewriteOptions RewriteOptions

func init() {
	cmdRoot.AddCommand(cmdRewrite)

	f := cmdRewrite.Flags()
	f.StringArrayVarP(&rewriteOptions.Hosts, "host", "H", nil, "only consider snapshots for this `host`, when no snapshot ID is given (can be specified multiple times)")
	f.Var(&rewriteOptions.Tags, "tag", "only consider snapshots which include this `taglist`, when no snapshot-ID is given")
	f.StringArrayVar(&rewriteOptions.Paths, "path", nil, "only consider snapshots which include this (absolute) `path`, when no snapshot-ID is given")
	f.BoolVarP(&rewriteOptions.Inplace, "inplace", "", false, "replace existing snapshots")
	f.BoolVarP(&rewriteOptions.DryRun, "dry-run", "n", false, "do not do anything, just print what would be done")

	initExcludePatternOptions(f, &rewriteOptions.excludePatternOptions)
}

func rewriteSnapshot(ctx context.Context, repo *repository.Repository, sn *restic.Snapshot, opts RewriteOptions) (bool, error) {
	if sn.Tree == nil {
		return false, errors.Errorf("snapshot %v has nil tree", sn.ID().Str())
	}

	rejectByNameFuncs, err := collectExcludePatterns(opts.excludePatternOptions)
	if err != nil {
		return false, err
	}

	selectByName := func(nodepath string) bool {
		for _, reject := range rejectByNameFuncs {
			if reject(nodepath) {
				return false
			}
		}
		return true
	}

	wg, wgCtx := errgroup.WithContext(ctx)
	repo.StartPackUploader(wgCtx, wg)

	var filteredTree restic.ID
	wg.Go(func() error {
		filteredTree, err = walker.FilterTree(wgCtx, repo, "/", *sn.Tree, &walker.TreeFilterVisitor{
			SelectByName: selectByName,
			PrintExclude: func(path string) { Verbosef(fmt.Sprintf("excluding %s\n", path)) },
		})
		if err != nil {
			return err
		}

		return repo.Flush(wgCtx)
	})
	err = wg.Wait()
	if err != nil {
		return false, err
	}

	if filteredTree == *sn.Tree {
		debug.Log("Snapshot %v not modified", sn)
		return false, nil
	}

	debug.Log("Snapshot %v modified", sn)
	if opts.DryRun {
		Verbosef("would save new snapshot\n")
		return true, nil
	}

	// Retain the original snapshot id over all tag changes.
	if sn.Original == nil {
		sn.Original = sn.ID()
	}
	*sn.Tree = filteredTree

	if !opts.Inplace {
		sn.AddTags([]string{"rewrite"})
	}

	// Save the new snapshot.
	id, err := restic.SaveSnapshot(ctx, repo, sn)
	if err != nil {
		return false, err
	}

	if opts.Inplace {
		h := restic.Handle{Type: restic.SnapshotFile, Name: sn.ID().String()}
		if err = repo.Backend().Remove(ctx, h); err != nil {
			return false, err
		}

		debug.Log("old snapshot %v removed", sn.ID())
	}
	Verbosef("new snapshot saved as %v\n", id)
	return true, nil
}

func runRewrite(ctx context.Context, opts RewriteOptions, gopts GlobalOptions, args []string) error {

	if len(opts.ExcludeFiles) == 0 && len(opts.Excludes) == 0 && len(opts.InsensitiveExcludes) == 0 {
		return errors.Fatal("Nothing to do: no excludes provided")
	}

	repo, err := OpenRepository(ctx, gopts)
	if err != nil {
		return err
	}

	if !opts.DryRun {
		var lock *restic.Lock
		var err error
		if opts.Inplace {
			Verbosef("create exclusive lock for repository\n")
			lock, ctx, err = lockRepoExclusive(ctx, repo)
		} else {
			lock, ctx, err = lockRepo(ctx, repo)
		}
		defer unlockRepo(lock)
		if err != nil {
			return err
		}
	} else {
		repo.SetDryRun()
	}

	snapshotLister, err := backend.MemorizeList(ctx, repo.Backend(), restic.SnapshotFile)
	if err != nil {
		return err
	}

	if err = repo.LoadIndex(ctx); err != nil {
		return err
	}

	changedCount := 0
	for sn := range FindFilteredSnapshots(ctx, snapshotLister, repo, opts.Hosts, opts.Tags, opts.Paths, args) {
		Verbosef("\nsnapshot %s of %v at %s)\n", sn.ID().Str(), sn.Paths, sn.Time)
		changed, err := rewriteSnapshot(ctx, repo, sn, opts)
		if err != nil {
			return errors.Fatalf("unable to rewrite snapshot ID %q: %v", sn.ID().Str(), err)
		}
		if changed {
			changedCount++
		}
	}

	Verbosef("\n")
	if changedCount == 0 {
		Verbosef("no snapshots were modified\n")
	} else {
		if !opts.DryRun {
			Verbosef("modified %v snapshots\n", changedCount)
		} else {
			Verbosef("would modify %v snapshots\n", changedCount)
		}
	}

	return nil
}