/*
Copyright 2015 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package main

// Command docs are in cbtdoc.go.

import (
	"bytes"
	"flag"
	"fmt"
	"go/format"
	"io"
	"log"
	"os"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"text/tabwriter"
	"text/template"
	"time"

	"cloud.google.com/go/bigtable"
	"cloud.google.com/go/bigtable/internal/cbtconfig"
	"golang.org/x/net/context"
	"google.golang.org/api/option"
	"google.golang.org/grpc"
)

var (
	oFlag = flag.String("o", "", "if set, redirect stdout to this file")

	config              *cbtconfig.Config
	client              *bigtable.Client
	adminClient         *bigtable.AdminClient
	instanceAdminClient *bigtable.InstanceAdminClient

	version      = "<unknown version>"
	revision     = "<unknown revision>"
	revisionDate = "<unknown revision date>"
)

func getCredentialOpts(opts []option.ClientOption) []option.ClientOption {
	if ts := config.TokenSource; ts != nil {
		opts = append(opts, option.WithTokenSource(ts))
	}
	if tlsCreds := config.TLSCreds; tlsCreds != nil {
		opts = append(opts, option.WithGRPCDialOption(grpc.WithTransportCredentials(tlsCreds)))
	}
	return opts
}

func getClient() *bigtable.Client {
	if client == nil {
		var opts []option.ClientOption
		if ep := config.DataEndpoint; ep != "" {
			opts = append(opts, option.WithEndpoint(ep))
		}
		opts = getCredentialOpts(opts)
		var err error
		client, err = bigtable.NewClient(context.Background(), config.Project, config.Instance, opts...)
		if err != nil {
			log.Fatalf("Making bigtable.Client: %v", err)
		}
	}
	return client
}

func getAdminClient() *bigtable.AdminClient {
	if adminClient == nil {
		var opts []option.ClientOption
		if ep := config.AdminEndpoint; ep != "" {
			opts = append(opts, option.WithEndpoint(ep))
		}
		opts = getCredentialOpts(opts)
		var err error
		adminClient, err = bigtable.NewAdminClient(context.Background(), config.Project, config.Instance, opts...)
		if err != nil {
			log.Fatalf("Making bigtable.AdminClient: %v", err)
		}
	}
	return adminClient
}

func getInstanceAdminClient() *bigtable.InstanceAdminClient {
	if instanceAdminClient == nil {
		var opts []option.ClientOption
		if ep := config.AdminEndpoint; ep != "" {
			opts = append(opts, option.WithEndpoint(ep))
		}
		opts = getCredentialOpts(opts)
		var err error
		instanceAdminClient, err = bigtable.NewInstanceAdminClient(context.Background(), config.Project, opts...)
		if err != nil {
			log.Fatalf("Making bigtable.InstanceAdminClient: %v", err)
		}
	}
	return instanceAdminClient
}

func main() {
	var err error
	config, err = cbtconfig.Load()
	if err != nil {
		log.Fatal(err)
	}
	config.RegisterFlags()

	flag.Usage = func() { usage(os.Stderr) }
	flag.Parse()
	if flag.NArg() == 0 {
		usage(os.Stderr)
		os.Exit(1)
	}

	if *oFlag != "" {
		f, err := os.Create(*oFlag)
		if err != nil {
			log.Fatal(err)
		}
		defer func() {
			if err := f.Close(); err != nil {
				log.Fatal(err)
			}
		}()
		os.Stdout = f
	}

	ctx := context.Background()
	for _, cmd := range commands {
		if cmd.Name == flag.Arg(0) {
			if err := config.CheckFlags(cmd.Required); err != nil {
				log.Fatal(err)
			}
			cmd.do(ctx, flag.Args()[1:]...)
			return
		}
	}
	log.Fatalf("Unknown command %q", flag.Arg(0))
}

func usage(w io.Writer) {
	fmt.Fprintf(w, "Usage: %s [flags] <command> ...\n", os.Args[0])
	flag.CommandLine.SetOutput(w)
	flag.CommandLine.PrintDefaults()
	fmt.Fprintf(w, "\n%s", cmdSummary)
}

var cmdSummary string // generated in init, below

func init() {
	var buf bytes.Buffer
	tw := tabwriter.NewWriter(&buf, 10, 8, 4, '\t', 0)
	for _, cmd := range commands {
		fmt.Fprintf(tw, "cbt %s\t%s\n", cmd.Name, cmd.Desc)
	}
	tw.Flush()
	buf.WriteString(configHelp)
	cmdSummary = buf.String()
}

var configHelp = `
For convenience, values of the -project, -instance, -creds,
-admin-endpoint and -data-endpoint flags may be specified in
` + cbtconfig.Filename() + ` in this format:
	project = my-project-123
	instance = my-instance
	creds = path-to-account-key.json
	admin-endpoint = hostname:port
	data-endpoint = hostname:port
All values are optional, and all will be overridden by flags.

cbt ` + version + ` ` + revision + ` ` + revisionDate + `
`

var commands = []struct {
	Name, Desc string
	do         func(context.Context, ...string)
	Usage      string
	Required   cbtconfig.RequiredFlags
}{
	{
		Name:     "count",
		Desc:     "Count rows in a table",
		do:       doCount,
		Usage:    "cbt count <table>",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name:     "createfamily",
		Desc:     "Create a column family",
		do:       doCreateFamily,
		Usage:    "cbt createfamily <table> <family>",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name: "createtable",
		Desc: "Create a table",
		do:   doCreateTable,
		Usage: "cbt createtable <table> [initial_splits...]\n" +
			"  initial_splits=row		A row key to be used to initially split the table " +
			"into multiple tablets. Can be repeated to create multiple splits.",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name:     "deletecolumn",
		Desc:     "Delete all cells in a column",
		do:       doDeleteColumn,
		Usage:    "cbt deletecolumn <table> <row> <family> <column>",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name:     "deletefamily",
		Desc:     "Delete a column family",
		do:       doDeleteFamily,
		Usage:    "cbt deletefamily <table> <family>",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name:     "deleterow",
		Desc:     "Delete a row",
		do:       doDeleteRow,
		Usage:    "cbt deleterow <table> <row>",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name:     "deletetable",
		Desc:     "Delete a table",
		do:       doDeleteTable,
		Usage:    "cbt deletetable <table>",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name:     "doc",
		Desc:     "Print godoc-suitable documentation for cbt",
		do:       doDoc,
		Usage:    "cbt doc",
		Required: cbtconfig.NoneRequired,
	},
	{
		Name:     "help",
		Desc:     "Print help text",
		do:       doHelp,
		Usage:    "cbt help [command]",
		Required: cbtconfig.NoneRequired,
	},
	{
		Name:     "listinstances",
		Desc:     "List instances in a project",
		do:       doListInstances,
		Usage:    "cbt listinstances",
		Required: cbtconfig.ProjectRequired,
	},
	{
		Name:     "lookup",
		Desc:     "Read from a single row",
		do:       doLookup,
		Usage:    "cbt lookup <table> <row>",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name: "ls",
		Desc: "List tables and column families",
		do:   doLS,
		Usage: "cbt ls			List tables\n" +
			"cbt ls <table>		List column families in <table>",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name:     "mddoc",
		Desc:     "Print documentation for cbt in Markdown format",
		do:       doMDDoc,
		Usage:    "cbt mddoc",
		Required: cbtconfig.NoneRequired,
	},
	{
		Name: "read",
		Desc: "Read rows",
		do:   doRead,
		Usage: "cbt read <table> [start=<row>] [end=<row>] [prefix=<prefix>]" +
			" [regex=<regex>] [count=<n>]\n" +
			"  start=<row>		Start reading at this row\n" +
			"  end=<row>		Stop reading before this row\n" +
			"  prefix=<prefix>	Read rows with this prefix\n" +
			"  regex=<regex> 	Read rows with keys matching this regex\n" +
			"  count=<n>		Read only this many rows\n",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name: "set",
		Desc: "Set value of a cell",
		do:   doSet,
		Usage: "cbt set <table> <row> family:column=val[@ts] ...\n" +
			"  family:column=val[@ts] may be repeated to set multiple cells.\n" +
			"\n" +
			"  ts is an optional integer timestamp.\n" +
			"  If it cannot be parsed, the `@ts` part will be\n" +
			"  interpreted as part of the value.",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name: "setgcpolicy",
		Desc: "Set the GC policy for a column family",
		do:   doSetGCPolicy,
		Usage: "cbt setgcpolicy <table> <family> ( maxage=<d> | maxversions=<n> )\n" +
			"\n" +
			`  maxage=<d>		Maximum timestamp age to preserve (e.g. "1h", "4d")` + "\n" +
			"  maxversions=<n>	Maximum number of versions to preserve",
		Required: cbtconfig.ProjectAndInstanceRequired,
	},
	{
		Name:     "version",
		Desc:     "Print the current cbt version",
		do:       doVersion,
		Usage:    "cbt version",
		Required: cbtconfig.NoneRequired,
	},
}

func doCount(ctx context.Context, args ...string) {
	if len(args) != 1 {
		log.Fatal("usage: cbt count <table>")
	}
	tbl := getClient().Open(args[0])

	n := 0
	err := tbl.ReadRows(ctx, bigtable.InfiniteRange(""), func(_ bigtable.Row) bool {
		n++
		return true
	}, bigtable.RowFilter(bigtable.StripValueFilter()))
	if err != nil {
		log.Fatalf("Reading rows: %v", err)
	}
	fmt.Println(n)
}

func doCreateFamily(ctx context.Context, args ...string) {
	if len(args) != 2 {
		log.Fatal("usage: cbt createfamily <table> <family>")
	}
	err := getAdminClient().CreateColumnFamily(ctx, args[0], args[1])
	if err != nil {
		log.Fatalf("Creating column family: %v", err)
	}
}

func doCreateTable(ctx context.Context, args ...string) {
	if len(args) < 1 {
		log.Fatal("usage: cbt createtable <table> [initial_splits...]")
	}
	var err error
	if len(args) > 1 {
		splits := args[1:]
		err = getAdminClient().CreatePresplitTable(ctx, args[0], splits)
	} else {
		err = getAdminClient().CreateTable(ctx, args[0])
	}
	if err != nil {
		log.Fatalf("Creating table: %v", err)
	}
}

func doDeleteColumn(ctx context.Context, args ...string) {
	if len(args) != 4 {
		log.Fatal("usage: cbt deletecolumn <table> <row> <family> <column>")
	}
	tbl := getClient().Open(args[0])
	mut := bigtable.NewMutation()
	mut.DeleteCellsInColumn(args[2], args[3])
	if err := tbl.Apply(ctx, args[1], mut); err != nil {
		log.Fatalf("Deleting cells in column: %v", err)
	}
}

func doDeleteFamily(ctx context.Context, args ...string) {
	if len(args) != 2 {
		log.Fatal("usage: cbt deletefamily <table> <family>")
	}
	err := getAdminClient().DeleteColumnFamily(ctx, args[0], args[1])
	if err != nil {
		log.Fatalf("Deleting column family: %v", err)
	}
}

func doDeleteRow(ctx context.Context, args ...string) {
	if len(args) != 2 {
		log.Fatal("usage: cbt deleterow <table> <row>")
	}
	tbl := getClient().Open(args[0])
	mut := bigtable.NewMutation()
	mut.DeleteRow()
	if err := tbl.Apply(ctx, args[1], mut); err != nil {
		log.Fatalf("Deleting row: %v", err)
	}
}

func doDeleteTable(ctx context.Context, args ...string) {
	if len(args) != 1 {
		log.Fatalf("Can't do `cbt deletetable %s`", args)
	}
	err := getAdminClient().DeleteTable(ctx, args[0])
	if err != nil {
		log.Fatalf("Deleting table: %v", err)
	}
}

// to break circular dependencies
var (
	doDocFn   func(ctx context.Context, args ...string)
	doHelpFn  func(ctx context.Context, args ...string)
	doMDDocFn func(ctx context.Context, args ...string)
)

func init() {
	doDocFn = doDocReal
	doHelpFn = doHelpReal
	doMDDocFn = doMDDocReal
}

func doDoc(ctx context.Context, args ...string)   { doDocFn(ctx, args...) }
func doHelp(ctx context.Context, args ...string)  { doHelpFn(ctx, args...) }
func doMDDoc(ctx context.Context, args ...string) { doMDDocFn(ctx, args...) }

func docFlags() []*flag.Flag {
	// Only include specific flags, in a specific order.
	var flags []*flag.Flag
	for _, name := range []string{"project", "instance", "creds"} {
		f := flag.Lookup(name)
		if f == nil {
			log.Fatalf("Flag not linked: -%s", name)
		}
		flags = append(flags, f)
	}
	return flags
}

func doDocReal(ctx context.Context, args ...string) {
	data := map[string]interface{}{
		"Commands": commands,
		"Flags":    docFlags(),
	}
	var buf bytes.Buffer
	if err := docTemplate.Execute(&buf, data); err != nil {
		log.Fatalf("Bad doc template: %v", err)
	}
	out, err := format.Source(buf.Bytes())
	if err != nil {
		log.Fatalf("Bad doc output: %v", err)
	}
	os.Stdout.Write(out)
}

func indentLines(s, ind string) string {
	ss := strings.Split(s, "\n")
	for i, p := range ss {
		ss[i] = ind + p
	}
	return strings.Join(ss, "\n")
}

var docTemplate = template.Must(template.New("doc").Funcs(template.FuncMap{
	"indent": indentLines,
}).
	Parse(`
// Copyright 2016 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// DO NOT EDIT. THIS IS AUTOMATICALLY GENERATED.
// Run "go generate" to regenerate.
//go:generate go run cbt.go -o cbtdoc.go doc

/*
Cbt is a tool for doing basic interactions with Cloud Bigtable. To learn how to
install the cbt tool, see the
[cbt overview](https://cloud.google.com/bigtable/docs/go/cbt-overview).

Usage:

	cbt [options] command [arguments]

The commands are:
{{range .Commands}}
	{{printf "%-25s %s" .Name .Desc}}{{end}}

Use "cbt help <command>" for more information about a command.

The options are:
{{range .Flags}}
	-{{.Name}} string
		{{.Usage}}{{end}}

{{range .Commands}}
{{.Desc}}

Usage:
{{indent .Usage "\t"}}



{{end}}
*/
package main
`))

func doHelpReal(ctx context.Context, args ...string) {
	if len(args) == 0 {
		usage(os.Stdout)
		return
	}
	for _, cmd := range commands {
		if cmd.Name == args[0] {
			fmt.Println(cmd.Usage)
			return
		}
	}
	log.Fatalf("Don't know command %q", args[0])
}

func doListInstances(ctx context.Context, args ...string) {
	if len(args) != 0 {
		log.Fatalf("usage: cbt listinstances")
	}
	is, err := getInstanceAdminClient().Instances(ctx)
	if err != nil {
		log.Fatalf("Getting list of instances: %v", err)
	}
	tw := tabwriter.NewWriter(os.Stdout, 10, 8, 4, '\t', 0)
	fmt.Fprintf(tw, "Instance Name\tInfo\n")
	fmt.Fprintf(tw, "-------------\t----\n")
	for _, i := range is {
		fmt.Fprintf(tw, "%s\t%s\n", i.Name, i.DisplayName)
	}
	tw.Flush()
}

func doLookup(ctx context.Context, args ...string) {
	if len(args) != 2 {
		log.Fatalf("usage: cbt lookup <table> <row>")
	}
	table, row := args[0], args[1]
	tbl := getClient().Open(table)
	r, err := tbl.ReadRow(ctx, row)
	if err != nil {
		log.Fatalf("Reading row: %v", err)
	}
	printRow(r)
}

func printRow(r bigtable.Row) {
	fmt.Println(strings.Repeat("-", 40))
	fmt.Println(r.Key())

	var fams []string
	for fam := range r {
		fams = append(fams, fam)
	}
	sort.Strings(fams)
	for _, fam := range fams {
		ris := r[fam]
		sort.Sort(byColumn(ris))
		for _, ri := range ris {
			ts := time.Unix(0, int64(ri.Timestamp)*1e3)
			fmt.Printf("  %-40s @ %s\n", ri.Column, ts.Format("2006/01/02-15:04:05.000000"))
			fmt.Printf("    %q\n", ri.Value)
		}
	}
}

type byColumn []bigtable.ReadItem

func (b byColumn) Len() int           { return len(b) }
func (b byColumn) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
func (b byColumn) Less(i, j int) bool { return b[i].Column < b[j].Column }

type byFamilyName []bigtable.FamilyInfo

func (b byFamilyName) Len() int           { return len(b) }
func (b byFamilyName) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
func (b byFamilyName) Less(i, j int) bool { return b[i].Name < b[j].Name }

func doLS(ctx context.Context, args ...string) {
	switch len(args) {
	default:
		log.Fatalf("Can't do `cbt ls %s`", args)
	case 0:
		tables, err := getAdminClient().Tables(ctx)
		if err != nil {
			log.Fatalf("Getting list of tables: %v", err)
		}
		sort.Strings(tables)
		for _, table := range tables {
			fmt.Println(table)
		}
	case 1:
		table := args[0]
		ti, err := getAdminClient().TableInfo(ctx, table)
		if err != nil {
			log.Fatalf("Getting table info: %v", err)
		}
		sort.Sort(byFamilyName(ti.FamilyInfos))
		tw := tabwriter.NewWriter(os.Stdout, 10, 8, 4, '\t', 0)
		fmt.Fprintf(tw, "Family Name\tGC Policy\n")
		fmt.Fprintf(tw, "-----------\t---------\n")
		for _, fam := range ti.FamilyInfos {
			fmt.Fprintf(tw, "%s\t%s\n", fam.Name, fam.GCPolicy)
		}
		tw.Flush()
	}
}

func doMDDocReal(ctx context.Context, args ...string) {
	data := map[string]interface{}{
		"Commands": commands,
		"Flags":    docFlags(),
	}
	var buf bytes.Buffer
	if err := mddocTemplate.Execute(&buf, data); err != nil {
		log.Fatalf("Bad mddoc template: %v", err)
	}
	io.Copy(os.Stdout, &buf)
}

var mddocTemplate = template.Must(template.New("mddoc").Funcs(template.FuncMap{
	"indent": indentLines,
}).
	Parse(`
Cbt is a tool for doing basic interactions with Cloud Bigtable.

Usage:

	cbt [options] command [arguments]

The commands are:
{{range .Commands}}
	{{printf "%-25s %s" .Name .Desc}}{{end}}

Use "cbt help <command>" for more information about a command.

The options are:
{{range .Flags}}
	-{{.Name}} string
		{{.Usage}}{{end}}

{{range .Commands}}
## {{.Desc}}

{{indent .Usage "\t"}}



{{end}}
`))

func doRead(ctx context.Context, args ...string) {
	if len(args) < 1 {
		log.Fatalf("usage: cbt read <table> [args ...]")
	}
	tbl := getClient().Open(args[0])

	parsed := make(map[string]string)
	for _, arg := range args[1:] {
		i := strings.Index(arg, "=")
		if i < 0 {
			log.Fatalf("Bad arg %q", arg)
		}
		key, val := arg[:i], arg[i+1:]
		switch key {
		default:
			log.Fatalf("Unknown arg key %q", key)
		case "limit":
			// Be nicer; we used to support this, but renamed it to "end".
			log.Fatalf("Unknown arg key %q; did you mean %q?", key, "end")
		case "start", "end", "prefix", "count", "regex":
			parsed[key] = val
		}
	}
	if (parsed["start"] != "" || parsed["end"] != "") && parsed["prefix"] != "" {
		log.Fatal(`"start"/"end" may not be mixed with "prefix"`)
	}

	var rr bigtable.RowRange
	if start, end := parsed["start"], parsed["end"]; end != "" {
		rr = bigtable.NewRange(start, end)
	} else if start != "" {
		rr = bigtable.InfiniteRange(start)
	}
	if prefix := parsed["prefix"]; prefix != "" {
		rr = bigtable.PrefixRange(prefix)
	}

	var opts []bigtable.ReadOption
	if count := parsed["count"]; count != "" {
		n, err := strconv.ParseInt(count, 0, 64)
		if err != nil {
			log.Fatalf("Bad count %q: %v", count, err)
		}
		opts = append(opts, bigtable.LimitRows(n))
	}
	if regex := parsed["regex"]; regex != "" {
		opts = append(opts, bigtable.RowFilter(bigtable.RowKeyFilter(regex)))
	}

	// TODO(dsymonds): Support filters.
	err := tbl.ReadRows(ctx, rr, func(r bigtable.Row) bool {
		printRow(r)
		return true
	}, opts...)
	if err != nil {
		log.Fatalf("Reading rows: %v", err)
	}
}

var setArg = regexp.MustCompile(`([^:]+):([^=]*)=(.*)`)

func doSet(ctx context.Context, args ...string) {
	if len(args) < 3 {
		log.Fatalf("usage: cbt set <table> <row> family:[column]=val[@ts] ...")
	}
	tbl := getClient().Open(args[0])
	row := args[1]
	mut := bigtable.NewMutation()
	for _, arg := range args[2:] {
		m := setArg.FindStringSubmatch(arg)
		if m == nil {
			log.Fatalf("Bad set arg %q", arg)
		}
		val := m[3]
		ts := bigtable.Now()
		if i := strings.LastIndex(val, "@"); i >= 0 {
			// Try parsing a timestamp.
			n, err := strconv.ParseInt(val[i+1:], 0, 64)
			if err == nil {
				val = val[:i]
				ts = bigtable.Timestamp(n)
			}
		}
		mut.Set(m[1], m[2], ts, []byte(val))
	}
	if err := tbl.Apply(ctx, row, mut); err != nil {
		log.Fatalf("Applying mutation: %v", err)
	}
}

func doSetGCPolicy(ctx context.Context, args ...string) {
	if len(args) < 3 {
		log.Fatalf("usage: cbt setgcpolicy <table> <family> ( maxage=<d> | maxversions=<n> )")
	}
	table := args[0]
	fam := args[1]

	var pol bigtable.GCPolicy
	switch p := args[2]; {
	case strings.HasPrefix(p, "maxage="):
		d, err := parseDuration(p[7:])
		if err != nil {
			log.Fatal(err)
		}
		pol = bigtable.MaxAgePolicy(d)
	case strings.HasPrefix(p, "maxversions="):
		n, err := strconv.ParseUint(p[12:], 10, 16)
		if err != nil {
			log.Fatal(err)
		}
		pol = bigtable.MaxVersionsPolicy(int(n))
	default:
		log.Fatalf("Bad GC policy %q", p)
	}
	if err := getAdminClient().SetGCPolicy(ctx, table, fam, pol); err != nil {
		log.Fatalf("Setting GC policy: %v", err)
	}
}

// parseDuration parses a duration string.
// It is similar to Go's time.ParseDuration, except with a different set of supported units,
// and only simple formats supported.
func parseDuration(s string) (time.Duration, error) {
	// [0-9]+[a-z]+

	// Split [0-9]+ from [a-z]+.
	i := 0
	for ; i < len(s); i++ {
		c := s[i]
		if c < '0' || c > '9' {
			break
		}
	}
	ds, u := s[:i], s[i:]
	if ds == "" || u == "" {
		return 0, fmt.Errorf("invalid duration %q", s)
	}
	// Parse them.
	d, err := strconv.ParseUint(ds, 10, 32)
	if err != nil {
		return 0, fmt.Errorf("invalid duration %q: %v", s, err)
	}
	unit, ok := unitMap[u]
	if !ok {
		return 0, fmt.Errorf("unknown unit %q in duration %q", u, s)
	}
	if d > uint64((1<<63-1)/unit) {
		// overflow
		return 0, fmt.Errorf("invalid duration %q overflows", s)
	}
	return time.Duration(d) * unit, nil
}

var unitMap = map[string]time.Duration{
	"ms": time.Millisecond,
	"s":  time.Second,
	"m":  time.Minute,
	"h":  time.Hour,
	"d":  24 * time.Hour,
}

func doVersion(ctx context.Context, args ...string) {
	fmt.Printf("%s %s %s\n", version, revision, revisionDate)
}