// Frontend: Functions for terminal output

// Copyright (C) 2021  Simon Ruderich
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package frontend

import (
	"fmt"
	"regexp"
)

type Color int

const (
	_ Color = iota
	ColorRed
	ColorGreen
	ColorCyan
	ColorMagenta
)

func ColorString(isTTY bool, color Color, x string) string {
	if !isTTY {
		return x
	}

	var code string
	switch color {
	case ColorRed:
		code = "31"
	case ColorGreen:
		code = "32"
	case ColorMagenta:
		code = "35"
	case ColorCyan:
		code = "36"
	default:
		panic(fmt.Sprintf("invalid color %v", color))
	}
	// TODO: check terminal support
	return "\033[" + code + "m" + x + "\033[0m"
}

var escapeRegexp = regexp.MustCompile(`[\x00-\x08\x0B-\x1F\x7F]`)

// EscapeControlCharacters escapes all ASCII control characters (except
// newline and tab) by replacing them with their hex value. If the output is
// to a TTY then the escaped characters are colored.
//
// This function must be used when displaying any input from remote hosts to
// prevent terminal escape code injections.
func EscapeControlCharacters(isTTY bool, x string) string {
	return escapeRegexp.ReplaceAllStringFunc(x, func(x string) string {
		if len(x) != 1 {
			panic("invalid escapeRegexp")
		}
		if x == "\r" {
			x = "\\r" // occurs often and more readable than \x0D
		} else {
			x = fmt.Sprintf("\\x%02X", x[0])
		}
		return ColorString(isTTY, ColorMagenta, x)
	})
}