/*
Copyright 2022 The Kubernetes Authors.

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 printers

import (
	"io"
	"os"
	"runtime"
	"strings"

	"github.com/moby/term"
)

// terminalEscaper replaces ANSI escape sequences and other terminal special
// characters to avoid terminal escape character attacks (issue #101695).
var terminalEscaper = strings.NewReplacer("\x1b", "^[", "\r", "\\r")

// WriteEscaped replaces unsafe terminal characters with replacement strings
// and writes them to the given writer.
func WriteEscaped(writer io.Writer, output string) error {
	_, err := terminalEscaper.WriteString(writer, output)
	return err
}

// EscapeTerminal escapes terminal special characters in a human readable (but
// non-reversible) format.
func EscapeTerminal(in string) string {
	return terminalEscaper.Replace(in)
}

// IsTerminal returns whether the passed object is a terminal or not.
func IsTerminal(i interface{}) bool {
	_, terminal := term.GetFdInfo(i)
	return terminal
}

// AllowsColorOutput returns true if the specified writer is a terminal and
// the process environment indicates color output is supported and desired.
func AllowsColorOutput(w io.Writer) bool {
	if !IsTerminal(w) {
		return false
	}

	// https://en.wikipedia.org/wiki/Computer_terminal#Dumb_terminals.
	if os.Getenv("TERM") == "dumb" {
		return false
	}

	// https://no-color.org/
	if _, nocolor := os.LookupEnv("NO_COLOR"); nocolor {
		return false
	}

	// On Windows WT_SESSION is set by the modern terminal component.
	// Older terminals have poor support for UTF-8, VT escape codes, etc.
	if runtime.GOOS == "windows" && os.Getenv("WT_SESSION") == "" {
		return false
	}

	return true
}
