go_goutils/stringsx/funcs.go

package stringsx

import (
	`strings`
	`unicode`
)

/*
Indent takes string s and indents it with string `indent` `level` times.

If indent is an empty string, [DefIndentStr] will be used.

If ws is true, lines consisting of only whitespace will be indented as well.
(To then trim any extraneous trailing space, you may want to use [TrimSpaceRight]
or [TrimLines].)

If empty is true, lines with no content will be replaced with lines that purely
consist of (indent * level) (otherwise they will be left as empty lines).

This function can also be used to prefix lines with arbitrary strings as well.
e.g:

	Indent("foo\nbar\nbaz\n", "# ", 1, false, false)

would yield:

	# foo
	# bar
	# baz
	<empty line>

thus allowing you to "comment out" multiple lines at once.
*/
func Indent(s, indent string, level uint, ws, empty bool) (indented string) {

	var i string
	var nl string
	var endsNewline bool
	var sb strings.Builder
	var lineStripped string

	if indent == "" {
		indent = DefIndentStr
	}

	// This condition functionally won't do anything, so just return the input as-is.
	if level == 0 {
		indented = s
		return
	}

	i = strings.Repeat(indent, int(level))

	// This condition functionally won't do anything, so just return the input as-is.
	if s == "" {
		if empty {
			indented = i
		}
		return
	}

	for line := range strings.Lines(s) {
		lineStripped = strings.TrimSpace(line)
		nl = getNewLine(line)
		endsNewline = nl != ""
		// fmt.Printf("%#v => %#v\n", line, lineStripped)
		if lineStripped == "" {
			// fmt.Printf("WS/EMPTY LINE (%#v) (ws %v, empty %v): \n", s, ws, empty)
			if line != (lineStripped + nl) {
				// whitespace-only line
				if ws {
					sb.WriteString(i)
				}
			} else {
				// empty line
				if empty {
					sb.WriteString(i)
				}
			}
			sb.WriteString(line)
			continue
		}
		// non-empty/non-whitespace-only line.
		sb.WriteString(i + line)
	}

	// If it ends with a trailing newline and nothing after, strings.Lines() will skip the last (empty) line.
	if endsNewline && empty {
		nl = getNewLine(s)
		sb.WriteString(i)
	}

	indented = sb.String()

	return
}

/*
Redact provides a "masked" version of string s (e.g. `my_terrible_password` -> `my****************rd`).

maskStr is the character or sequence of characters
to repeat for every masked character of s.
If an empty string, the default [DefMaskStr] will be used.
(maskStr does not need to be a single character.
It is recommended to use a multi-char mask to help obfuscate a string's length.)

leading specifies the number of leading characters of s to leave *unmasked*.
If 0, no leading characters will be unmasked.

trailing specifies the number of trailing characters of s to leave *unmasked*.
if 0, no trailing characters will be unmasked.

newlines, if true, will preserve newline characters - otherwise
they will be treated as regular characters.

As a safety precaution, if:

	len(s) <= (leading + trailing)

then the entire string will be *masked* and no unmasking will be performed.
*/
func Redact(s, maskStr string, leading, trailing uint, newlines bool) (redacted string) {

	var nl string
	var numMasked int
	var sb strings.Builder
	var endIdx int = int(leading)

	// This condition functionally won't do anything, so just return the input as-is.
	if s == "" {
		return
	}

	if maskStr == "" {
		maskStr = DefMaskStr
	}

	if newlines {
		for line := range strings.Lines(s) {
			nl = getNewLine(line)
			sb.WriteString(
				Redact(
					strings.TrimSuffix(line, nl), maskStr, leading, trailing, false,
				),
			)
			sb.WriteString(nl)
		}
	} else {
		if len(s) <= int(leading+trailing) {
			redacted = strings.Repeat(maskStr, len(s))
			return
		}

		if leading == 0 && trailing == 0 {
			redacted = strings.Repeat(maskStr, len(s))
			return
		}

		numMasked = len(s) - int(leading+trailing)
		endIdx = endIdx + numMasked

		if leading > 0 {
			sb.WriteString(s[:int(leading)])
		}

		sb.WriteString(strings.Repeat(maskStr, numMasked))

		if trailing > 0 {
			sb.WriteString(s[endIdx:])
		}
	}

	redacted = sb.String()

	return
}

/*
TrimLines is like [strings.TrimSpace] but operates on *each line* of s.
It is *NIX-newline (`\n`) vs. Windows-newline (`\r\n`) agnostic.
The first encountered linebreak (`\n` vs. `\r\n`) are assumed to be
the canonical linebreak for the rest of s.

left, if true, performs a [TrimSpaceLeft] on each line (retaining the newline).

right, if true, performs a [TrimSpaceRight] on each line (retaining the newline).
*/
func TrimLines(s string, left, right bool) (trimmed string) {

	var sl string
	var nl string
	var sb strings.Builder

	// These conditions functionally won't do anything, so just return the input as-is.
	if s == "" {
		return
	}
	if !left && !right {
		trimmed = s
		return
	}

	for line := range strings.Lines(s) {
		nl = getNewLine(line)
		sl = strings.TrimSuffix(line, nl)
		if left && right {
			sl = strings.TrimSpace(sl)
		} else if left {
			sl = TrimSpaceLeft(sl)
		} else if right {
			sl = TrimSpaceRight(sl)
		}
		sb.WriteString(sl + nl)
	}

	trimmed = sb.String()

	return
}

// TrimSpaceLeft is like [strings.TrimSpace] but only removes leading whitespace from string s.
func TrimSpaceLeft(s string) (trimmed string) {

	trimmed = strings.TrimLeftFunc(s, unicode.IsSpace)

	return
}

/*
TrimSpaceRight is like [strings.TrimSpace] but only removes trailing whitespace from string s.
*/
func TrimSpaceRight(s string) (trimmed string) {

	trimmed = strings.TrimRightFunc(s, unicode.IsSpace)

	return
}

// getNewLine is too unpredictable to be used outside of this package so it isn't exported.
func getNewLine(s string) (nl string) {

	if strings.HasSuffix(s, "\r\n") {
		nl = "\r\n"
	} else if strings.HasSuffix(s, "\n") {
		nl = "\n"
	}

	return
}