package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"strconv"

	"github.com/restic/restic/internal/errors"
	"github.com/restic/restic/internal/restic"
	"github.com/restic/restic/internal/ui"
	"github.com/spf13/cobra"
	"github.com/spf13/pflag"
)

func newForgetCommand() *cobra.Command {
	var opts ForgetOptions
	var pruneOpts PruneOptions

	cmd := &cobra.Command{
		Use:   "forget [flags] [snapshot ID] [...]",
		Short: "Remove snapshots from the repository",
		Long: `
The "forget" command removes snapshots according to a policy. All snapshots are
first divided into groups according to "--group-by", and after that the policy
specified by the "--keep-*" options is applied to each group individually.
If there are not enough snapshots to keep one for each duration related
"--keep-{within-,}*" option, the oldest snapshot in the group is kept
additionally.

Please note that this command really only deletes the snapshot object in the
repository, which is a reference to data stored there. In order to remove the
unreferenced data after "forget" was run successfully, see the "prune" command.

Please also read the documentation for "forget" to learn about some important
security considerations.

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

Exit status is 0 if the command was successful.
Exit status is 1 if there was any error.
Exit status is 3 if there was an error removing one or more snapshots.
Exit status is 10 if the repository does not exist.
Exit status is 11 if the repository is already locked.
Exit status is 12 if the password is incorrect.
`,
		GroupID:           cmdGroupDefault,
		DisableAutoGenTag: true,
		RunE: func(cmd *cobra.Command, args []string) error {
			term, cancel := setupTermstatus()
			defer cancel()
			return runForget(cmd.Context(), opts, pruneOpts, globalOptions, term, args)
		},
	}

	opts.AddFlags(cmd.Flags())
	pruneOpts.AddLimitedFlags(cmd.Flags())
	return cmd
}

type ForgetPolicyCount int

var ErrNegativePolicyCount = errors.New("negative values not allowed, use 'unlimited' instead")
var ErrFailedToRemoveOneOrMoreSnapshots = errors.New("failed to remove one or more snapshots")

func (c *ForgetPolicyCount) Set(s string) error {
	switch s {
	case "unlimited":
		*c = -1
	default:
		val, err := strconv.ParseInt(s, 10, 0)
		if err != nil {
			return err
		}
		if val < 0 {
			return ErrNegativePolicyCount
		}
		*c = ForgetPolicyCount(val)
	}

	return nil
}

func (c *ForgetPolicyCount) String() string {
	switch *c {
	case -1:
		return "unlimited"
	default:
		return strconv.FormatInt(int64(*c), 10)
	}
}

func (c *ForgetPolicyCount) Type() string {
	return "n"
}

// ForgetOptions collects all options for the forget command.
type ForgetOptions struct {
	Last          ForgetPolicyCount
	Hourly        ForgetPolicyCount
	Daily         ForgetPolicyCount
	Weekly        ForgetPolicyCount
	Monthly       ForgetPolicyCount
	Yearly        ForgetPolicyCount
	Within        restic.Duration
	WithinHourly  restic.Duration
	WithinDaily   restic.Duration
	WithinWeekly  restic.Duration
	WithinMonthly restic.Duration
	WithinYearly  restic.Duration
	KeepTags      restic.TagLists

	UnsafeAllowRemoveAll bool

	restic.SnapshotFilter
	Compact bool

	// Grouping
	GroupBy restic.SnapshotGroupByOptions
	DryRun  bool
	Prune   bool
}

func (opts *ForgetOptions) AddFlags(f *pflag.FlagSet) {
	f.VarP(&opts.Last, "keep-last", "l", "keep the last `n` snapshots (use 'unlimited' to keep all snapshots)")
	f.VarP(&opts.Hourly, "keep-hourly", "H", "keep the last `n` hourly snapshots (use 'unlimited' to keep all hourly snapshots)")
	f.VarP(&opts.Daily, "keep-daily", "d", "keep the last `n` daily snapshots (use 'unlimited' to keep all daily snapshots)")
	f.VarP(&opts.Weekly, "keep-weekly", "w", "keep the last `n` weekly snapshots (use 'unlimited' to keep all weekly snapshots)")
	f.VarP(&opts.Monthly, "keep-monthly", "m", "keep the last `n` monthly snapshots (use 'unlimited' to keep all monthly snapshots)")
	f.VarP(&opts.Yearly, "keep-yearly", "y", "keep the last `n` yearly snapshots (use 'unlimited' to keep all yearly snapshots)")
	f.VarP(&opts.Within, "keep-within", "", "keep snapshots that are newer than `duration` (eg. 1y5m7d2h) relative to the latest snapshot")
	f.VarP(&opts.WithinHourly, "keep-within-hourly", "", "keep hourly snapshots that are newer than `duration` (eg. 1y5m7d2h) relative to the latest snapshot")
	f.VarP(&opts.WithinDaily, "keep-within-daily", "", "keep daily snapshots that are newer than `duration` (eg. 1y5m7d2h) relative to the latest snapshot")
	f.VarP(&opts.WithinWeekly, "keep-within-weekly", "", "keep weekly snapshots that are newer than `duration` (eg. 1y5m7d2h) relative to the latest snapshot")
	f.VarP(&opts.WithinMonthly, "keep-within-monthly", "", "keep monthly snapshots that are newer than `duration` (eg. 1y5m7d2h) relative to the latest snapshot")
	f.VarP(&opts.WithinYearly, "keep-within-yearly", "", "keep yearly snapshots that are newer than `duration` (eg. 1y5m7d2h) relative to the latest snapshot")
	f.Var(&opts.KeepTags, "keep-tag", "keep snapshots with this `taglist` (can be specified multiple times)")
	f.BoolVar(&opts.UnsafeAllowRemoveAll, "unsafe-allow-remove-all", false, "allow deleting all snapshots of a snapshot group")

	f.StringArrayVar(&opts.Hosts, "hostname", nil, "only consider snapshots with the given `hostname` (can be specified multiple times)")
	err := f.MarkDeprecated("hostname", "use --host")
	if err != nil {
		// MarkDeprecated only returns an error when the flag is not found
		panic(err)
	}
	// must be defined after `--hostname` to not override the default value from the environment
	initMultiSnapshotFilter(f, &opts.SnapshotFilter, false)

	f.BoolVarP(&opts.Compact, "compact", "c", false, "use compact output format")
	opts.GroupBy = restic.SnapshotGroupByOptions{Host: true, Path: true}
	f.VarP(&opts.GroupBy, "group-by", "g", "`group` snapshots by host, paths and/or tags, separated by comma (disable grouping with '')")
	f.BoolVarP(&opts.DryRun, "dry-run", "n", false, "do not delete anything, just print what would be done")
	f.BoolVar(&opts.Prune, "prune", false, "automatically run the 'prune' command if snapshots have been removed")

	f.SortFlags = false
}

func verifyForgetOptions(opts *ForgetOptions) error {
	if opts.Last < -1 || opts.Hourly < -1 || opts.Daily < -1 || opts.Weekly < -1 ||
		opts.Monthly < -1 || opts.Yearly < -1 {
		return errors.Fatal("negative values other than -1 are not allowed for --keep-*")
	}

	for _, d := range []restic.Duration{opts.Within, opts.WithinHourly, opts.WithinDaily,
		opts.WithinMonthly, opts.WithinWeekly, opts.WithinYearly} {
		if d.Hours < 0 || d.Days < 0 || d.Months < 0 || d.Years < 0 {
			return errors.Fatal("durations containing negative values are not allowed for --keep-within*")
		}
	}

	return nil
}

func runForget(ctx context.Context, opts ForgetOptions, pruneOptions PruneOptions, gopts GlobalOptions, term ui.Terminal, args []string) error {
	err := verifyForgetOptions(&opts)
	if err != nil {
		return err
	}

	err = verifyPruneOptions(&pruneOptions)
	if err != nil {
		return err
	}

	if gopts.NoLock && !opts.DryRun {
		return errors.Fatal("--no-lock is only applicable in combination with --dry-run for forget command")
	}

	printer := newTerminalProgressPrinter(gopts.JSON, gopts.verbosity, term)
	ctx, repo, unlock, err := openWithExclusiveLock(ctx, gopts, opts.DryRun && gopts.NoLock, printer)
	if err != nil {
		return err
	}
	defer unlock()

	var snapshots restic.Snapshots
	removeSnIDs := restic.NewIDSet()

	for sn := range FindFilteredSnapshots(ctx, repo, repo, &opts.SnapshotFilter, args, printer) {
		snapshots = append(snapshots, sn)
	}
	if ctx.Err() != nil {
		return ctx.Err()
	}

	var jsonGroups []*ForgetGroup

	if len(args) > 0 {
		// When explicit snapshots args are given, remove them immediately.
		for _, sn := range snapshots {
			removeSnIDs.Insert(*sn.ID())
		}
	} else {
		snapshotGroups, _, err := restic.GroupSnapshots(snapshots, opts.GroupBy)
		if err != nil {
			return err
		}

		policy := restic.ExpirePolicy{
			Last:          int(opts.Last),
			Hourly:        int(opts.Hourly),
			Daily:         int(opts.Daily),
			Weekly:        int(opts.Weekly),
			Monthly:       int(opts.Monthly),
			Yearly:        int(opts.Yearly),
			Within:        opts.Within,
			WithinHourly:  opts.WithinHourly,
			WithinDaily:   opts.WithinDaily,
			WithinWeekly:  opts.WithinWeekly,
			WithinMonthly: opts.WithinMonthly,
			WithinYearly:  opts.WithinYearly,
			Tags:          opts.KeepTags,
		}

		if policy.Empty() {
			if opts.UnsafeAllowRemoveAll {
				if opts.SnapshotFilter.Empty() {
					return errors.Fatal("--unsafe-allow-remove-all is not allowed unless a snapshot filter option is specified")
				}
				// UnsafeAllowRemoveAll together with snapshot filter is fine
			} else {
				return errors.Fatal("no policy was specified, no snapshots will be removed")
			}
		}

		printer.P("Applying Policy: %v\n", policy)

		for k, snapshotGroup := range snapshotGroups {
			if ctx.Err() != nil {
				return ctx.Err()
			}

			if gopts.Verbose >= 1 && !gopts.JSON {
				err = PrintSnapshotGroupHeader(globalOptions.stdout, k)
				if err != nil {
					return err
				}
			}

			var key restic.SnapshotGroupKey
			if json.Unmarshal([]byte(k), &key) != nil {
				return err
			}

			var fg ForgetGroup
			fg.Tags = key.Tags
			fg.Host = key.Hostname
			fg.Paths = key.Paths

			keep, remove, reasons := restic.ApplyPolicy(snapshotGroup, policy)

			if !policy.Empty() && len(keep) == 0 {
				return fmt.Errorf("refusing to delete last snapshot of snapshot group \"%v\"", key.String())
			}
			if len(keep) != 0 && !gopts.Quiet && !gopts.JSON {
				printer.P("keep %d snapshots:\n", len(keep))
				if err := PrintSnapshots(globalOptions.stdout, keep, reasons, opts.Compact); err != nil {
					return err
				}
				printer.P("\n")
			}
			fg.Keep = asJSONSnapshots(keep)

			if len(remove) != 0 && !gopts.Quiet && !gopts.JSON {
				printer.P("remove %d snapshots:\n", len(remove))
				if err := PrintSnapshots(globalOptions.stdout, remove, nil, opts.Compact); err != nil {
					return err
				}
				printer.P("\n")
			}
			fg.Remove = asJSONSnapshots(remove)

			fg.Reasons = asJSONKeeps(reasons)

			jsonGroups = append(jsonGroups, &fg)

			for _, sn := range remove {
				removeSnIDs.Insert(*sn.ID())
			}
		}
	}

	if ctx.Err() != nil {
		return ctx.Err()
	}

	// these are the snapshots that failed to be removed
	failedSnIDs := restic.NewIDSet()
	if len(removeSnIDs) > 0 {
		if !opts.DryRun {
			bar := printer.NewCounter("files deleted")
			err := restic.ParallelRemove(ctx, repo, removeSnIDs, restic.WriteableSnapshotFile, func(id restic.ID, err error) error {
				if err != nil {
					printer.E("unable to remove %v/%v from the repository\n", restic.SnapshotFile, id)
					failedSnIDs.Insert(id)
				} else {
					printer.VV("removed %v/%v\n", restic.SnapshotFile, id)
				}
				return nil
			}, bar)
			bar.Done()
			if err != nil {
				return err
			}
		} else {
			printer.P("Would have removed the following snapshots:\n%v\n\n", removeSnIDs)
		}
	}

	if gopts.JSON && len(jsonGroups) > 0 {
		err = printJSONForget(globalOptions.stdout, jsonGroups)
		if err != nil {
			return err
		}
	}

	if len(failedSnIDs) > 0 {
		return ErrFailedToRemoveOneOrMoreSnapshots
	}

	if len(removeSnIDs) > 0 && opts.Prune {
		if opts.DryRun {
			printer.P("%d snapshots would be removed, running prune dry run\n", len(removeSnIDs))
		} else {
			printer.P("%d snapshots have been removed, running prune\n", len(removeSnIDs))
		}
		pruneOptions.DryRun = opts.DryRun
		return runPruneWithRepo(ctx, pruneOptions, repo, removeSnIDs, printer)
	}

	return nil
}

// ForgetGroup helps to print what is forgotten in JSON.
type ForgetGroup struct {
	Tags    []string     `json:"tags"`
	Host    string       `json:"host"`
	Paths   []string     `json:"paths"`
	Keep    []Snapshot   `json:"keep"`
	Remove  []Snapshot   `json:"remove"`
	Reasons []KeepReason `json:"reasons"`
}

func asJSONSnapshots(list restic.Snapshots) []Snapshot {
	var resultList []Snapshot
	for _, sn := range list {
		k := Snapshot{
			Snapshot: sn,
			ID:       sn.ID(),
			ShortID:  sn.ID().Str(),
		}
		resultList = append(resultList, k)
	}
	return resultList
}

// KeepReason helps to print KeepReasons as JSON with Snapshots with their ID included.
type KeepReason struct {
	Snapshot Snapshot `json:"snapshot"`
	Matches  []string `json:"matches"`
}

func asJSONKeeps(list []restic.KeepReason) []KeepReason {
	var resultList []KeepReason
	for _, keep := range list {
		k := KeepReason{
			Snapshot: Snapshot{
				Snapshot: keep.Snapshot,
				ID:       keep.Snapshot.ID(),
				ShortID:  keep.Snapshot.ID().Str(),
			},
			Matches: keep.Matches,
		}
		resultList = append(resultList, k)
	}
	return resultList
}

func printJSONForget(stdout io.Writer, forgets []*ForgetGroup) error {
	return json.NewEncoder(stdout).Encode(forgets)
}