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/*
* format.go - Functions for handling output formatting.
*
* 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 (
"bufio"
"bytes"
"fmt"
"io"
"os"
"strings"
"text/template"
"unicode/utf8"
"github.com/google/fscrypt/util"
"golang.org/x/crypto/ssh/terminal"
)
// Suffixes for questions with a yes or no default
const (
defaultYesSuffix = "[Y/n]"
defaultNoSuffix = "[y/N]"
)
// Variables which control how output is formmatted and where it goes.
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
// DefaultLineLength is the LineLength we use if we cannot detect the
// terminal width. By default we fall back to punch cards.
DefaultLineLength = 80
// 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
)
// We use the width of the terminal unless we cannot get the width.
func init() {
if LineLength == 0 {
var err error
LineLength, _, err = terminal.GetSize(int(os.Stdout.Fd()))
if err != nil {
LineLength = DefaultLineLength
}
}
}
// MaxSubcommandLength returns the length of the longest subcommand (where the
// length of the command is Name + Title). Return 0 if there aren't subcommands.
func (c *Command) MaxNameLength() (max int) {
for _, s := range c.SubCommands {
max = util.MaxInt(max, len(s.Name))
}
return
}
// WrapText wraps an input string so that each line begins with numTabs tabs
// (except the first line) 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. The first line's calculated length
// is startSpaces less (to account for strange offsets on the first line).
func WrapText(startSpaces, numTabs int, text string) string {
// We use a buffer to format the wrapped text so we get O(n) runtime
var buffer bytes.Buffer
spaceLeft := 0
maxTextLen := LineLength - startSpaces
delimiter := strings.Repeat("\t", numTabs)
for i, word := range strings.Fields(text) {
wordLen := utf8.RuneCountInString(word)
if i == 0 {
buffer.WriteString(word)
spaceLeft = maxTextLen - wordLen
} else 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()
}
// Add words to this map if pluralization does not just involve adding an s.
var plurals = map[string]string{
"policy": "policies",
}
// Pluralize returns the correct pluralization of a work along with the
// specified count. This means Pluralize(1, "policy") = "1 policy" but
// Pluralize(2, "policy") = "2 policies".
func Pluralize(count int, word string) string {
if count == 1 {
return fmt.Sprintf("%d %s", count, word)
}
if plural, ok := plurals[word]; ok {
return fmt.Sprintf("%d %s", count, plural)
}
return fmt.Sprintf("%d %ss", count, word)
}
// ReadLine returns a line of input from standard input. An empty string is
// returned if the user didn't insert anything, we're in quiet mode or on error.
// This function should be the only way user input is acquired from an
// application (except for passwords).
func ReadLine() (string, error) {
if QuietFlag.Value {
return "", nil
}
scanner := bufio.NewScanner(os.Stdin)
scanner.Scan()
return scanner.Text(), scanner.Err()
}
// 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) {
// 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 := 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
}
if warning != "" {
fmt.Fprintln(Output, "WARNING: "+warning)
}
confirmed, err := AskQuestion(question, defaultChoice)
if err != nil {
return err
}
if !confirmed {
// To override a "false" default, use ForceFlag.
if QuietFlag.Value {
return ErrMustForce
}
return ErrCanceled
}
return nil
}
// ExecuteTemplate creates an anonymous template from the text, and runs it with
// the provided Context and writer. Panics if text cannot be executed.
func ExecuteTemplate(w io.Writer, text string, ctx *Context) {
tmpl := template.Must(template.New("").Funcs(template.FuncMap{
"WrapText": WrapText,
"LineLength": func() int { return LineLength },
"add": func(nums ...int) (sum int) {
for _, num := range nums {
sum += num
}
return
},
}).Parse(text))
if err := tmpl.Execute(w, ctx); err != nil {
panic(err)
}
}
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