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// Copyright 2024 the u-root Authors. All rights reserved
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package cli provides a bare bones CLI with commands.
//
// cli supports standard Go flags.
package cli
import (
"flag"
"fmt"
"io"
"os"
"slices"
"strings"
"text/tabwriter"
)
// Command is a CLI command.
type Command struct {
// Name or Aliases are used to match argv[1] and select this command.
Name string
Aliases []string
// Short is a one-line description for the command.
Short string
// Run is called if argv[1] matches the command. Flags are parsed before Run is called.
Run func(args []string)
flags *flag.FlagSet
}
// Flags returns a modifiable flag set for this command.
//
// If argv[1] matches this command, these flags will be parsed.
func (c *Command) Flags() *flag.FlagSet {
if c.flags == nil {
c.flags = flag.NewFlagSet(c.Name, flag.ContinueOnError)
}
return c.flags
}
// An App is composed of many commands.
type App []Command
// Help returns the app's help string.
func (a App) Help() string {
var s strings.Builder
w := tabwriter.NewWriter(&s, 1, 2, 4, ' ', 0)
fmt.Fprintf(w, "Commands:\n\n")
for _, cmd := range a {
fmt.Fprintf(w, "\t%s\t%s\n", cmd.Name, cmd.Short)
}
w.Flush()
return s.String()
}
func (a App) commandFor(args []string) *Command {
if len(args) == 0 {
return nil
}
for _, cmd := range a {
if args[0] == cmd.Name || slices.Contains(cmd.Aliases, args[0]) {
return &cmd
}
}
return nil
}
func (a App) run(errW io.Writer, args []string) int {
if len(args) == 0 {
fmt.Fprintf(errW, "No program name provided\n")
return 1
}
cmd := a.commandFor(args[1:])
if cmd == nil {
fmt.Fprintf(errW, "%s", a.Help())
return 1
}
cmd.Flags().SetOutput(errW)
if err := cmd.Flags().Parse(args[2:]); err != nil {
cmd.Flags().Output()
return 1
}
cmd.Run(cmd.Flags().Args())
return 0
}
// Run runs the app. Expects program name as the first arg, and an optional command name next.
func (a App) Run(args []string) {
os.Exit(a.run(os.Stderr, args))
}
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