texttools.go

package texttools

import (
	"crypto/rand"
	"math/big"
	"regexp"
	"strings"

	strip "github.com/grokify/html-strip-tags-go"
	camelcase "github.com/segmentio/go-camelcase"
	snakecase "github.com/segmentio/go-snakecase"
)

// For random str generation
const possibleChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

var (
	reNonAlphabetAndNumbers  = regexp.MustCompile("[^a-zA-Z0-9-]")
	reLinesAndChars          = regexp.MustCompile("[\\s\\r\\n]+")
	reSpaceBeforePunctuation = regexp.MustCompile("\\s+([.,;!?]+)")
	specialCharsReplacer     = strings.NewReplacer(
		"À", "A",
		"Á", "A",
		"Â", "A",
		"Ã", "A",
		"Ä", "A",
		"Å", "A",
		"Æ", "AE",
		"Ç", "C",
		"È", "E",
		"É", "E",
		"Ê", "E",
		"Ë", "E",
		"Ì", "I",
		"Í", "I",
		"Î", "I",
		"Ï", "I",
		"Ð", "Eth",
		"Ñ", "N",
		"Ò", "O",
		"Ó", "O",
		"Ô", "O",
		"Õ", "O",
		"Ö", "O",
		"Ø", "O",
		"Ù", "U",
		"Ú", "U",
		"Û", "U",
		"Ü", "U",
		"Ý", "Y",
		"Þ", "Thorn",
		"ß", "s",
		"à", "a",
		"á", "a",
		"â", "a",
		"ã", "a",
		"ä", "a",
		"å", "a",
		"æ", "ae",
		"ç", "c",
		"è", "e",
		"é", "e",
		"ê", "e",
		"ë", "e",
		"ì", "i",
		"í", "i",
		"î", "i",
		"ï", "i",
		"ð", "eth",
		"ñ", "n",
		"ò", "o",
		"ó", "o",
		"ô", "o",
		"õ", "o",
		"ö", "o",
		"ø", "o",
		"ù", "u",
		"ú", "u",
		"û", "u",
		"ü", "u",
		"ý", "y",
		"þ", "thorn",
		"ÿ", "y",
	)
)

// Shorten tries to create the most sensible (to a human) shortened text.
// If possible, it will try to cut at a non-word char.
// It will strip newlines and carriage returns.
func Shorten(str string, length int, appendStr string) (shorter string) {
	// Replace all line chars with space
	str = reLinesAndChars.ReplaceAllLiteralString(str, " ")

	// Replace all spaces before punctuation chars
	str = reSpaceBeforePunctuation.ReplaceAllString(str, "$1")

	// Trim the string
	str = strings.Trim(str, " ")

	// If the string is shorter than max, then return it
	if len(str) <= length {
		return str
	}

	// Split into "words"
	parts := strings.Split(str, " ")

	// Go through all the parts
	for _, part := range parts {
		// If the part is an empty string, continue to the next part
		if part == "" {
			continue
		}

		// Check if the string gets too long with the next part
		if len(shorter)+len(part)+len(appendStr) < length {
			if len(shorter) > 0 {
				shorter += " "
			}

			shorter += part
		} else {
			// If the length was more than max allowed, stop iterating
			break
		}
	}

	// If we have an empty string (e.g. due to 1 long word), try "substringing"
	if shorter == "" {
		endAt := length - len(appendStr)
		shorter = str[0:endAt]
	}

	// If the appendStr not is empty, remove any typical punctuation
	if len(shorter) > 0 && len(appendStr) > 0 {
		lastChar := shorter[len(shorter)-1 : len(shorter)]
		if lastChar == "." || lastChar == "," || lastChar == ";" {
			shorter = shorter[0 : len(shorter)-1]

		} else if lastChar == "?" || lastChar == "!" {
			appendStr = appendStr[0 : len(appendStr)-1]
		}
	}

	shorter += appendStr

	return
}

// SpecialCharsToStandard replaces all kinds of non-ascii chars with transliterations.
func SpecialCharsToStandard(str string) string {
	return specialCharsReplacer.Replace(str)
}

// UnCase takes a string in any "case" (kebab-case, snake_case, etc.) and creates a "normal" string.
// E.g. my-slug-string -> "My slug string"
func UnCase(str string) string {
	str = strings.Replace(snakecase.Snakecase(str), "_", " ", -1)
	str = strings.ToUpper(str[0:1]) + str[1:]
	return str
}

// Slug will convert a string to a slug.
// It will also do  transliteration of non-ascii chars.
func Slug(str string) string {
	return KebabCase(SpecialCharsToStandard(str))
}

// SnakeCase will convert a string to snake_case
func SnakeCase(str string) string {
	return snakecase.Snakecase(str)
}

// KebabCase will convert a string to kebab-case
func KebabCase(str string) string {
	return strings.Replace(snakecase.Snakecase(str), "_", "-", -1)
}

// CamelCase will convert a string to camelCase
func CamelCase(str string) string {
	return camelcase.Camelcase(str)
}

// PascalCase will convert a string to PascalCase.
// This is the same as camelCase, but with the first letter capitalized.
func PascalCase(str string) string {
	out := camelcase.Camelcase(str)
	if len(out) > 0 {
		out = strings.ToUpper(out[0:1]) + out[1:]
	}
	return out
}

// StringInSlice will check if a string is in a slice and return true if it is.
func StringInSlice(searchStr string, strs []string) bool {
	for _, str := range strs {
		if searchStr == str {
			return true
		}
	}
	return false
}

// HTMLToText converts HTML to standard text.
func HTMLToText(html string) (text string) {
	text = strings.Replace(html, "\r\n", " ", -1)
	text = strip.StripTags(text)
	text = strings.Trim(text, " ")
	return
}

// TextSanitizer converts HTML to standard text, but also replaces some special chars and escapings.
func SanitizeText(txt string) (newTxt string) {
	newTxt = HTMLToText(txt)
	newTxt = strings.Replace(newTxt, "½", "1/2", -1)
	newTxt = strings.Replace(newTxt, "\\\\", "\\", -1)
	newTxt = strings.Replace(newTxt, "\\'", "'", -1)
	newTxt = strings.Replace(newTxt, `\"`, `"`, -1)
	return
}

// CP1258ToUTF8 converts a CP1258 byte array to a UTF-8 string.
func CP1258ToUTF8(txt []byte) (utf8Txt string) {
	for _, chr := range txt {
		if r := cp1258[chr]; len(string(r)) > 0 {
			utf8Txt += string(r)
		} else {
			utf8Txt += string(chr)
		}
	}
	return
}

// RandomString creates a secure pseudorandom string using the crypto rand package.
func RandomString(n int) (str string) {
	// Note: Counter-intuitively, the max here means < max
	max := big.NewInt(int64(len(possibleChars)))
	b := make([]byte, n)

	for i := 0; i < n; i++ {
		idx, _ := rand.Int(rand.Reader, max)
		b[i] = possibleChars[idx.Int64()]
	}

	return string(b)
}

// cp1258 codepage chars
var cp1258 = [256]rune{
	0x0000, //NULL
	0x0001, //START OF HEADING
	0x0002, //START OF TEXT
	0x0003, //END OF TEXT
	0x0004, //END OF TRANSMISSION
	0x0005, //ENQUIRY
	0x0006, //ACKNOWLEDGE
	0x0007, //BELL
	0x0008, //BACKSPACE
	0x0009, //HORIZONTAL TABULATION
	0x000A, //LINE FEED
	0x000B, //VERTICAL TABULATION
	0x000C, //FORM FEED
	0x000D, //CARRIAGE RETURN
	0x000E, //SHIFT OUT
	0x000F, //SHIFT IN
	0x0010, //DATA LINK ESCAPE
	0x0011, //DEVICE CONTROL ONE
	0x0012, //DEVICE CONTROL TWO
	0x0013, //DEVICE CONTROL THREE
	0x0014, //DEVICE CONTROL FOUR
	0x0015, //NEGATIVE ACKNOWLEDGE
	0x0016, //SYNCHRONOUS IDLE
	0x0017, //END OF TRANSMISSION BLOCK
	0x0018, //CANCEL
	0x0019, //END OF MEDIUM
	0x001A, //SUBSTITUTE
	0x001B, //ESCAPE
	0x001C, //FILE SEPARATOR
	0x001D, //GROUP SEPARATOR
	0x001E, //RECORD SEPARATOR
	0x001F, //UNIT SEPARATOR
	0x0020, //SPACE
	0x0021, //EXCLAMATION MARK
	0x0022, //QUOTATION MARK
	0x0023, //NUMBER SIGN
	0x0024, //DOLLAR SIGN
	0x0025, //PERCENT SIGN
	0x0026, //AMPERSAND
	0x0027, //APOSTROPHE
	0x0028, //LEFT PARENTHESIS
	0x0029, //RIGHT PARENTHESIS
	0x002A, //ASTERISK
	0x002B, //PLUS SIGN
	0x002C, //COMMA
	0x002D, //HYPHEN-MINUS
	0x002E, //FULL STOP
	0x002F, //SOLIDUS
	0x0030, //DIGIT ZERO
	0x0031, //DIGIT ONE
	0x0032, //DIGIT TWO
	0x0033, //DIGIT THREE
	0x0034, //DIGIT FOUR
	0x0035, //DIGIT FIVE
	0x0036, //DIGIT SIX
	0x0037, //DIGIT SEVEN
	0x0038, //DIGIT EIGHT
	0x0039, //DIGIT NINE
	0x003A, //COLON
	0x003B, //SEMICOLON
	0x003C, //LESS-THAN SIGN
	0x003D, //EQUALS SIGN
	0x003E, //GREATER-THAN SIGN
	0x003F, //QUESTION MARK
	0x0040, //COMMERCIAL AT
	0x0041, //LATIN CAPITAL LETTER A
	0x0042, //LATIN CAPITAL LETTER B
	0x0043, //LATIN CAPITAL LETTER C
	0x0044, //LATIN CAPITAL LETTER D
	0x0045, //LATIN CAPITAL LETTER E
	0x0046, //LATIN CAPITAL LETTER F
	0x0047, //LATIN CAPITAL LETTER G
	0x0048, //LATIN CAPITAL LETTER H
	0x0049, //LATIN CAPITAL LETTER I
	0x004A, //LATIN CAPITAL LETTER J
	0x004B, //LATIN CAPITAL LETTER K
	0x004C, //LATIN CAPITAL LETTER L
	0x004D, //LATIN CAPITAL LETTER M
	0x004E, //LATIN CAPITAL LETTER N
	0x004F, //LATIN CAPITAL LETTER O
	0x0050, //LATIN CAPITAL LETTER P
	0x0051, //LATIN CAPITAL LETTER Q
	0x0052, //LATIN CAPITAL LETTER R
	0x0053, //LATIN CAPITAL LETTER S
	0x0054, //LATIN CAPITAL LETTER T
	0x0055, //LATIN CAPITAL LETTER U
	0x0056, //LATIN CAPITAL LETTER V
	0x0057, //LATIN CAPITAL LETTER W
	0x0058, //LATIN CAPITAL LETTER X
	0x0059, //LATIN CAPITAL LETTER Y
	0x005A, //LATIN CAPITAL LETTER Z
	0x005B, //LEFT SQUARE BRACKET
	0x005C, //REVERSE SOLIDUS
	0x005D, //RIGHT SQUARE BRACKET
	0x005E, //CIRCUMFLEX ACCENT
	0x005F, //LOW LINE
	0x0060, //GRAVE ACCENT
	0x0061, //LATIN SMALL LETTER A
	0x0062, //LATIN SMALL LETTER B
	0x0063, //LATIN SMALL LETTER C
	0x0064, //LATIN SMALL LETTER D
	0x0065, //LATIN SMALL LETTER E
	0x0066, //LATIN SMALL LETTER F
	0x0067, //LATIN SMALL LETTER G
	0x0068, //LATIN SMALL LETTER H
	0x0069, //LATIN SMALL LETTER I
	0x006A, //LATIN SMALL LETTER J
	0x006B, //LATIN SMALL LETTER K
	0x006C, //LATIN SMALL LETTER L
	0x006D, //LATIN SMALL LETTER M
	0x006E, //LATIN SMALL LETTER N
	0x006F, //LATIN SMALL LETTER O
	0x0070, //LATIN SMALL LETTER P
	0x0071, //LATIN SMALL LETTER Q
	0x0072, //LATIN SMALL LETTER R
	0x0073, //LATIN SMALL LETTER S
	0x0074, //LATIN SMALL LETTER T
	0x0075, //LATIN SMALL LETTER U
	0x0076, //LATIN SMALL LETTER V
	0x0077, //LATIN SMALL LETTER W
	0x0078, //LATIN SMALL LETTER X
	0x0079, //LATIN SMALL LETTER Y
	0x007A, //LATIN SMALL LETTER Z
	0x007B, //LEFT CURLY BRACKET
	0x007C, //VERTICAL LINE
	0x007D, //RIGHT CURLY BRACKET
	0x007E, //TILDE
	0x007F, //DELETE
	0x20AC, //EURO SIGN
	0xFFFD, //UNDEFINED
	0x201A, //SINGLE LOW-9 QUOTATION MARK
	0x0192, //LATIN SMALL LETTER F WITH HOOK
	0x201E, //DOUBLE LOW-9 QUOTATION MARK
	0x2026, //HORIZONTAL ELLIPSIS
	0x2020, //DAGGER
	0x2021, //DOUBLE DAGGER
	0x02C6, //MODIFIER LETTER CIRCUMFLEX ACCENT
	0x2030, //PER MILLE SIGN
	0xFFFD, //UNDEFINED
	0x2039, //SINGLE LEFT-POINTING ANGLE QUOTATION MARK
	0x0152, //LATIN CAPITAL LIGATURE OE
	0xFFFD, //UNDEFINED
	0xFFFD, //UNDEFINED
	0xFFFD, //UNDEFINED
	0xFFFD, //UNDEFINED
	0x2018, //LEFT SINGLE QUOTATION MARK
	0x2019, //RIGHT SINGLE QUOTATION MARK
	0x201C, //LEFT DOUBLE QUOTATION MARK
	0x201D, //RIGHT DOUBLE QUOTATION MARK
	0x2022, //BULLET
	0x2013, //EN DASH
	0x2014, //EM DASH
	0x02DC, //SMALL TILDE
	0x2122, //TRADE MARK SIGN
	0xFFFD, //UNDEFINED
	0x203A, //SINGLE RIGHT-POINTING ANGLE QUOTATION MARK
	0x0153, //LATIN SMALL LIGATURE OE
	0xFFFD, //UNDEFINED
	0xFFFD, //UNDEFINED
	0x0178, //LATIN CAPITAL LETTER Y WITH DIAERESIS
	0x00A0, //NO-BREAK SPACE
	0x00A1, //INVERTED EXCLAMATION MARK
	0x00A2, //CENT SIGN
	0x00A3, //POUND SIGN
	0x00A4, //CURRENCY SIGN
	0x00A5, //YEN SIGN
	0x00A6, //BROKEN BAR
	0x00A7, //SECTION SIGN
	0x00A8, //DIAERESIS
	0x00A9, //COPYRIGHT SIGN
	0x00AA, //FEMININE ORDINAL INDICATOR
	0x00AB, //LEFT-POINTING DOUBLE ANGLE QUOTATION MARK
	0x00AC, //NOT SIGN
	0x00AD, //SOFT HYPHEN
	0x00AE, //REGISTERED SIGN
	0x00AF, //MACRON
	0x00B0, //DEGREE SIGN
	0x00B1, //PLUS-MINUS SIGN
	0x00B2, //SUPERSCRIPT TWO
	0x00B3, //SUPERSCRIPT THREE
	0x00B4, //ACUTE ACCENT
	0x00B5, //MICRO SIGN
	0x00B6, //PILCROW SIGN
	0x00B7, //MIDDLE DOT
	0x00B8, //CEDILLA
	0x00B9, //SUPERSCRIPT ONE
	0x00BA, //MASCULINE ORDINAL INDICATOR
	0x00BB, //RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK
	0x00BC, //VULGAR FRACTION ONE QUARTER
	0x00BD, //VULGAR FRACTION ONE HALF
	0x00BE, //VULGAR FRACTION THREE QUARTERS
	0x00BF, //INVERTED QUESTION MARK
	0x00C0, //LATIN CAPITAL LETTER A WITH GRAVE
	0x00C1, //LATIN CAPITAL LETTER A WITH ACUTE
	0x00C2, //LATIN CAPITAL LETTER A WITH CIRCUMFLEX
	0x0102, //LATIN CAPITAL LETTER A WITH BREVE
	0x00C4, //LATIN CAPITAL LETTER A WITH DIAERESIS
	0x00C5, //LATIN CAPITAL LETTER A WITH RING ABOVE
	0x00C6, //LATIN CAPITAL LETTER AE
	0x00C7, //LATIN CAPITAL LETTER C WITH CEDILLA
	0x00C8, //LATIN CAPITAL LETTER E WITH GRAVE
	0x00C9, //LATIN CAPITAL LETTER E WITH ACUTE
	0x00CA, //LATIN CAPITAL LETTER E WITH CIRCUMFLEX
	0x00CB, //LATIN CAPITAL LETTER E WITH DIAERESIS
	0x0300, //COMBINING GRAVE ACCENT
	0x00CD, //LATIN CAPITAL LETTER I WITH ACUTE
	0x00CE, //LATIN CAPITAL LETTER I WITH CIRCUMFLEX
	0x00CF, //LATIN CAPITAL LETTER I WITH DIAERESIS
	0x0110, //LATIN CAPITAL LETTER D WITH STROKE
	0x00D1, //LATIN CAPITAL LETTER N WITH TILDE
	0x0309, //COMBINING HOOK ABOVE
	0x00D3, //LATIN CAPITAL LETTER O WITH ACUTE
	0x00D4, //LATIN CAPITAL LETTER O WITH CIRCUMFLEX
	0x01A0, //LATIN CAPITAL LETTER O WITH HORN
	0x00D6, //LATIN CAPITAL LETTER O WITH DIAERESIS
	0x00D7, //MULTIPLICATION SIGN
	0x00D8, //LATIN CAPITAL LETTER O WITH STROKE
	0x00D9, //LATIN CAPITAL LETTER U WITH GRAVE
	0x00DA, //LATIN CAPITAL LETTER U WITH ACUTE
	0x00DB, //LATIN CAPITAL LETTER U WITH CIRCUMFLEX
	0x00DC, //LATIN CAPITAL LETTER U WITH DIAERESIS
	0x01AF, //LATIN CAPITAL LETTER U WITH HORN
	0x0303, //COMBINING TILDE
	0x00DF, //LATIN SMALL LETTER SHARP S
	0x00E0, //LATIN SMALL LETTER A WITH GRAVE
	0x00E1, //LATIN SMALL LETTER A WITH ACUTE
	0x00E2, //LATIN SMALL LETTER A WITH CIRCUMFLEX
	0x0103, //LATIN SMALL LETTER A WITH BREVE
	0x00E4, //LATIN SMALL LETTER A WITH DIAERESIS
	0x00E5, //LATIN SMALL LETTER A WITH RING ABOVE
	0x00E6, //LATIN SMALL LETTER AE
	0x00E7, //LATIN SMALL LETTER C WITH CEDILLA
	0x00E8, //LATIN SMALL LETTER E WITH GRAVE
	0x00E9, //LATIN SMALL LETTER E WITH ACUTE
	0x00EA, //LATIN SMALL LETTER E WITH CIRCUMFLEX
	0x00EB, //LATIN SMALL LETTER E WITH DIAERESIS
	0x0301, //COMBINING ACUTE ACCENT
	0x00ED, //LATIN SMALL LETTER I WITH ACUTE
	0x00EE, //LATIN SMALL LETTER I WITH CIRCUMFLEX
	0x00EF, //LATIN SMALL LETTER I WITH DIAERESIS
	0x0111, //LATIN SMALL LETTER D WITH STROKE
	0x00F1, //LATIN SMALL LETTER N WITH TILDE
	0x0323, //COMBINING DOT BELOW
	0x00F3, //LATIN SMALL LETTER O WITH ACUTE
	0x00F4, //LATIN SMALL LETTER O WITH CIRCUMFLEX
	0x01A1, //LATIN SMALL LETTER O WITH HORN
	0x00F6, //LATIN SMALL LETTER O WITH DIAERESIS
	0x00F7, //DIVISION SIGN
	0x00F8, //LATIN SMALL LETTER O WITH STROKE
	0x00F9, //LATIN SMALL LETTER U WITH GRAVE
	0x00FA, //LATIN SMALL LETTER U WITH ACUTE
	0x00FB, //LATIN SMALL LETTER U WITH CIRCUMFLEX
	0x00FC, //LATIN SMALL LETTER U WITH DIAERESIS
	0x01B0, //LATIN SMALL LETTER U WITH HORN
	0x20AB, //DONG SIGN
	0x00FF, //LATIN SMALL LETTER Y WITH DIAERESIS
}