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/*
* output.go - Functions for handling command line formatting and output.
*
* Copyright 2017 Google Inc.
* Author: Joe Richey (joerichey@google.com)
*
* 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 cmd
import (
"bytes"
"fmt"
"io"
"io/ioutil"
"log"
"os"
"strings"
"unicode/utf8"
"github.com/google/fscrypt/util"
"golang.org/x/crypto/ssh/terminal"
)
var (
// TabWidth is the number of spaces used to display a tab.
TabWidth = 8
// LineLength is the maximum length of any output. If not set, the width
// of the terminal be detected and assigned to LineLength.
LineLength int
// FallbackLineLength is the LineLength used if detection fails. By
// default we fall back to punch cards.
FallbackLineLength = 80
// MaxLineLength is the maximum allowed detected value of LineLength.
MaxLineLength = 120
// Output is the io.Writer all commands should use for their normal
// output (errors should just return the appropriate error). If not set,
// it is automatically set based on the provided flags.
Output io.Writer
// HelpFlag writes help to Stdout
HelpFlag = &BoolFlag{
Name: "help",
Usage: "Prints this 🧗help text for commands and subcommands",
}
// VerboseFlag indicates that all logging output should be printed.
VerboseFlag = &BoolFlag{
Name: "verbose",
Usage: "Prints additional debug messages.",
}
// QuietFlag indicates that no normal output should be printed.
QuietFlag = &BoolFlag{
Name: "quiet",
Usage: `Prints nothing except for errors and uses any default
option instead of prompting the user.`,
}
// ForceFlag indicates that the operation should proceed if possible.
ForceFlag = &BoolFlag{
Name: "force",
Usage: `Print no confirmation prompts or warnings and
automatically proceed with the requested action.`,
}
)
// Suffixes for questions with a yes or no default
const (
defaultYesSuffix = "[Y/n]"
defaultNoSuffix = "[y/N]"
)
// We use the width of the terminal unless we cannot get the width.
func init() {
if LineLength > 0 {
return
}
width, _, err := terminal.GetSize(int(os.Stdout.Fd()))
if err != nil {
LineLength = FallbackLineLength
} else {
LineLength = util.MinInt(width, MaxLineLength)
}
}
// Takes an input string text, and wraps the text so that each line begins with
// numTabs tabs and ends with a newline (except the last line), and each line
// has length less than lineLength. If the text contains a word which is too
// long, that word gets its own line.
func wrapText(text string, numTabs int) string {
// We use a buffer to format the wrapped text so we get O(n) runtime
var buffer bytes.Buffer
spaceLeft := 0
maxTextLen := LineLength - numTabs*TabWidth
delimiter := strings.Repeat("\t", numTabs)
for i, word := range strings.Fields(text) {
wordLen := utf8.RuneCountInString(word)
if wordLen >= spaceLeft {
// If no room left, write the word on the next line.
buffer.WriteString("\n")
buffer.WriteString(delimiter)
buffer.WriteString(word)
spaceLeft = maxTextLen - wordLen
} else {
// Write word on this line
buffer.WriteByte(' ')
buffer.WriteString(word)
spaceLeft -= 1 + wordLen
}
}
return buffer.String()
}
// Configures the Output and log output io.Writers. Called before running
// commands but after processing flags.
func setupOutput() {
if VerboseFlag.Value {
log.SetOutput(os.Stdout)
} else {
log.SetOutput(ioutil.Discard)
}
if Output != nil {
return
}
if QuietFlag.Value {
Output = ioutil.Discard
} else {
Output = os.Stdout
}
}
// AskQuestion asks the user a yes or no question. Returning a boolean on a
// successful answer and an error if there was not a response from the user.
// Returns the defaultChoice on empty input (or in quiet mode).
func AskQuestion(question string, defaultChoice bool) (bool, error) {
// If in quiet mode, we just use the default.
if QuietFlag.Value {
return defaultChoice, nil
}
// Loop until failure or valid input.
for {
if defaultChoice {
fmt.Fprintf(Output, "%s %s ", question, defaultYesSuffix)
} else {
fmt.Fprintf(Output, "%s %s ", question, defaultNoSuffix)
}
input, err := util.ReadLine()
if err != nil {
return false, err
}
switch strings.ToLower(input) {
case "y", "yes":
return true, nil
case "n", "no":
return false, nil
case "":
return defaultChoice, nil
}
}
}
// AskConfirmation asks the user for confirmation before performing a specific
// action. An error is returned if the user declines or IO fails.
func AskConfirmation(question, warning string, defaultChoice bool) error {
// All confirmations are "yes" if we are forcing.
if ForceFlag.Value {
return nil
}
// Defaults of "no" require forcing.
if QuietFlag.Value {
if defaultChoice {
return nil
}
return ErrMustForce
}
if warning != "" {
fmt.Fprintln(Output, wrapText("WARNING: "+warning, 0))
}
confirmed, err := AskQuestion(question, defaultChoice)
if err != nil {
return err
}
if !confirmed {
return ErrCanceled
}
return nil
}
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