125 lines
2.5 KiB
Go
125 lines
2.5 KiB
Go
package main
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// Handler to make management of subcommands easier.
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import (
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"flag"
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"fmt"
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"os"
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)
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type (
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Command struct {
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Use string // command name (used for matching)
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Short string // a short description to display
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Long string // a long help text
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Example string // an example string
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Run func(*Command, []string) // the command to run
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flagSet *flag.FlagSet // internal flagset with all flags
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commands []*Command // the list of subcommands
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}
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)
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// This function adds a new sub command.
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func (c *Command) AddCommand(cmds ...*Command) {
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res := c.commands
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for _, cmd := range cmds {
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res = append(res, cmd)
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}
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c.commands = res
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}
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// Evaluate the arguments and call either the subcommand or parse it as flags.
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func (c *Command) eval(args []string) error {
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var name string = ""
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var rest []string = []string{}
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if len(args) > 0 {
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name = args[0]
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}
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if len(args) > 1 {
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rest = args[1:]
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}
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if name == "help" {
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c.Help(rest)
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return nil
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}
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for _, cmd := range c.commands {
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if cmd.Use == name {
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return cmd.eval(rest)
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}
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}
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if err := c.Flags().Parse(args); err != nil {
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return err
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}
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if c.Run != nil {
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c.Run(c, rest)
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} else {
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c.Help(rest)
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}
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return nil
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}
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// Execute the command. It will fetch os.Args[1:] itself.
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func (c *Command) Execute() error {
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return c.eval(os.Args[1:])
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}
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// Return the flagset currently in use.
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func (c *Command) Flags() *flag.FlagSet {
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if c.flagSet == nil {
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c.flagSet = flag.NewFlagSet(c.Use, flag.ContinueOnError)
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}
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return c.flagSet
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}
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// Print the help for the current command or a subcommand.
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func (c *Command) Help(args []string) {
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if len(args) > 0 {
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for _, cmd := range c.commands {
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if args[0] == cmd.Use {
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cmd.Help([]string{})
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return
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}
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}
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}
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if c.Long != "" {
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fmt.Println(c.Long, "\n")
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}
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c.Usage()
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}
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// Print the usage information.
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func (c *Command) Usage() {
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usage := ""
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if c.Use != "" {
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usage = usage + " " + c.Use
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}
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if len(c.commands) > 0 {
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usage = usage + " command"
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}
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if c.flagSet != nil {
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usage = usage + " [flags]"
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}
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fmt.Printf("Usage: %s%s\n", os.Args[0], usage)
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if len(c.commands) > 0 {
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fmt.Printf("\nwhere command is one of:\n")
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for _, cmd := range c.commands {
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fmt.Printf("\t%s\t\t%s\n", cmd.Use, cmd.Short)
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}
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}
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if c.flagSet != nil {
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fmt.Printf("\nwhere flags is any of:\n")
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c.Flags().SetOutput(os.Stdout)
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c.Flags().PrintDefaults()
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}
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if c.Example != "" {
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fmt.Println("\nexample:")
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fmt.Printf("\t%s\n", c.Example)
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}
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}
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