141 lines
3 KiB
Go
141 lines
3 KiB
Go
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package cli
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import (
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"bufio"
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"errors"
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"fmt"
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"io"
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"os"
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"os/signal"
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"strings"
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)
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// Ui is an interface for interacting with the terminal, or "interface"
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// of a CLI. This abstraction doesn't have to be used, but helps provide
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// a simple, layerable way to manage user interactions.
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type Ui interface {
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// Ask asks the user for input using the given query. The response is
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// returned as the given string, or an error.
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Ask(string) (string, error)
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// Output is called for normal standard output.
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Output(string)
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// Info is called for information related to the previous output.
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// In general this may be the exact same as Output, but this gives
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// Ui implementors some flexibility with output formats.
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Info(string)
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// Error is used for any error messages that might appear on standard
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// error.
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Error(string)
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}
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// BasicUi is an implementation of Ui that just outputs to the given
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// writer. This UI is not threadsafe by default, but you can wrap it
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// in a ConcurrentUi to make it safe.
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type BasicUi struct {
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Reader io.Reader
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Writer io.Writer
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ErrorWriter io.Writer
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}
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func (u *BasicUi) Ask(query string) (string, error) {
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if _, err := fmt.Fprint(u.Writer, query+" "); err != nil {
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return "", err
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}
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// Register for interrupts so that we can catch it and immediately
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// return...
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sigCh := make(chan os.Signal, 1)
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signal.Notify(sigCh, os.Interrupt)
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defer signal.Stop(sigCh)
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// Ask for input in a go-routine so that we can ignore it.
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errCh := make(chan error, 1)
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lineCh := make(chan string, 1)
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go func() {
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r := bufio.NewReader(u.Reader)
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line, err := r.ReadString('\n')
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if err != nil {
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errCh <- err
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return
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}
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lineCh <- strings.TrimRight(line, "\r\n")
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}()
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select {
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case err := <-errCh:
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return "", err
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case line := <-lineCh:
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return line, nil
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case <-sigCh:
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// Print a newline so that any further output starts properly
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// on a new line.
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fmt.Fprintln(u.Writer)
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return "", errors.New("interrupted")
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}
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}
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func (u *BasicUi) Error(message string) {
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w := u.Writer
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if u.ErrorWriter != nil {
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w = u.ErrorWriter
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}
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fmt.Fprint(w, message)
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fmt.Fprint(w, "\n")
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}
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func (u *BasicUi) Info(message string) {
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u.Output(message)
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}
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func (u *BasicUi) Output(message string) {
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fmt.Fprint(u.Writer, message)
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fmt.Fprint(u.Writer, "\n")
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}
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// PrefixedUi is an implementation of Ui that prefixes messages.
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type PrefixedUi struct {
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AskPrefix string
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OutputPrefix string
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InfoPrefix string
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ErrorPrefix string
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Ui Ui
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}
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func (u *PrefixedUi) Ask(query string) (string, error) {
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if query != "" {
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query = fmt.Sprintf("%s%s", u.AskPrefix, query)
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}
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return u.Ui.Ask(query)
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}
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func (u *PrefixedUi) Error(message string) {
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if message != "" {
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message = fmt.Sprintf("%s%s", u.ErrorPrefix, message)
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}
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u.Ui.Error(message)
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}
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func (u *PrefixedUi) Info(message string) {
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if message != "" {
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message = fmt.Sprintf("%s%s", u.InfoPrefix, message)
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}
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u.Ui.Info(message)
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}
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func (u *PrefixedUi) Output(message string) {
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if message != "" {
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message = fmt.Sprintf("%s%s", u.OutputPrefix, message)
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}
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u.Ui.Output(message)
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}
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