102 lines
2.4 KiB
Go
102 lines
2.4 KiB
Go
package main
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import (
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"fmt"
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"strings"
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)
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type Flags struct {
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NoCache bool
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Verbose bool
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}
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// Command definition for CLI subcommands.
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type Command struct {
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Label string
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Handler func([]string, Flags, State) error
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Usage string
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Description string
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}
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// Represents a CLI invocation.
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// Must be initialized with commands via AddCommand before running
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// with Run.
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type CLI struct {
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// Commands in enumeration order.
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OrderedCommands []string
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// Command metadata entries.
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Commands map[string]Command
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Metadata map[string]string
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}
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// Registers a command.
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// This specifies a label that is used to route the user input to
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// the right command, a handler that is called when the label is used,
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// and usage/description details that get included in autogenerated help messaging.
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func (c CLI) AddCommand(label string, handler func([]string, Flags, State) error, usage string, description string) CLI {
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if c.Commands == nil {
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c.Commands = map[string]Command{}
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c.OrderedCommands = []string{}
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}
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c.OrderedCommands = append(c.OrderedCommands, label)
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c.Commands[label] = Command{Label: label, Handler: handler, Usage: usage, Description: description}
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return c
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}
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// Executes one of the registered commands if any match the provided
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// user arguments.
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func (c CLI) Run(args []string, currentState State) error {
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if len(args) == 0 {
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c.Help()
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return nil
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}
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command := args[0]
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if command == "help" {
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c.Help()
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return nil
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}
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flags := collectFlags(args)
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return c.Commands[command].Handler(args, flags, currentState)
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}
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// Prints autogenerated help documentation specifying command usage
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// and descriptions based on registered commands (see: AddCommand).
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func (c CLI) Help() {
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usageStrings := []string{}
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for _, commandLabel := range c.OrderedCommands {
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command := c.Commands[commandLabel]
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usageStrings = append(usageStrings, fmt.Sprintf("\033[1m%-30s\033[0m%s", command.Usage, command.Description))
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}
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helpString := fmt.Sprintf(`v: A simple version manager. (v%s)
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---
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%s`, c.Metadata["Version"], strings.Join(usageStrings, "\n"))
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fmt.Println(helpString)
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}
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// Traverses input arguments and extracts flags of
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// the form --<flag-label>.
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func collectFlags(args []string) Flags {
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collected := Flags{}
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for _, arg := range args {
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if !strings.HasPrefix(arg, "--") {
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continue
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}
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if arg == "--verbose" {
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collected.Verbose = true
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} else if arg == "--no-cache" {
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collected.NoCache = true
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}
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}
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return collected
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}
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