porterstemmer.go

package porterstemmer



import (
//	"log"
	"unicode"
)



func isConsonant(s []rune, i int) bool {

	//DEBUG
	//log.Printf("isConsonant: [%+v]", string(s[i]))

	result := true

	switch (  s[i]  ) {
		case 'a', 'e', 'i', 'o', 'u':
			result = false
		case 'y':
			if 0 == i {
				result = true
			} else {
				result = !isConsonant(s, i-1)
			}
		default: 
			result = true
   }

	return result
}



func measure(s []rune) uint {

	// Initialize.
		lenS := len(s)
		result := uint(0)
		i := 0


	// Short Circuit.
		if 0 == lenS {
/////////// RETURN
			return result
		}


	// Ignore (potential) consonant sequence at the beginning of word.
		for isConsonant(s, i) {

			//DEBUG
			//log.Printf("[measure([%s])] Eat Consonant [%d] -> [%s]", string(s), i, string(s[i]))

			i++
			if i >= lenS {
/////////////// RETURN
				return result
			}
		}


	// For each pair of a vowel sequence followed by a consonant sequence, increment result.
		Outer:
		for i < lenS {

			for !isConsonant(s, i) {

				//DEBUG
				//log.Printf("[measure([%s])] VOWEL [%d] -> [%s]", string(s), i, string(s[i]))

				i++
				if i >= lenS {
		/////////// BREAK
					break Outer
				}
			}
			for isConsonant(s, i) {

				//DEBUG
				//log.Printf("[measure([%s])] CONSONANT [%d] -> [%s]", string(s), i, string(s[i]))

				i++
				if i >= lenS {
					result++
		/////////// BREAK
					break Outer
				}
			}
			result++
		}


	// Return
		return result
}



func hasSuffix(s, suffix []rune) bool {

	lenSMinusOne      := len(s)      - 1
	lenSuffixMinusOne := len(suffix) - 1

	if lenSMinusOne <= lenSuffixMinusOne {
		return false
	} else if s[lenSMinusOne] != suffix[lenSuffixMinusOne] { // I suspect checking this first should speed this function up in practice.
/////// RETURN
		return false
	} else {

		for i := 0; i < lenSuffixMinusOne ; i++ {

			if suffix[i] != s[lenSMinusOne-lenSuffixMinusOne+i] {
/////////////// RETURN
				return false
			}

		}

	}


	return true
}



func containsVowel(s []rune) bool {

	lenS := len(s)

	for i := 0 ; i < lenS ; i++ {

		if !isConsonant(s, i) {
/////////// RETURN
			return true
		}

	}

	return false
}



func hasRepeatDoubleConsonantSuffix(s []rune) bool {

	// Initialize.
		lenS := len(s)

		result := false


	// Do it!
		if 2 > lenS {
			result = false
		} else if s[lenS-1] == s[lenS-2] && isConsonant(s, lenS-1) { // Will using isConsonant() cause a problem with "YY"?
			result = true
		} else {
			result = false
		}


	// Return,
		return result
}



func hasConsonantVowelConsonantSuffix(s []rune) bool {

	// Initialize.
		lenS := len(s)

		result := false


	// Do it!
		if 3 > lenS {
			result = false
		} else if isConsonant(s, lenS-3) && !isConsonant(s, lenS-2) && isConsonant(s, lenS-1) {
			result = true
		} else  {
			result = false
		}


	// Return
		return result
}



func step1a(s []rune) []rune {

	// Initialize.
		var result []rune = s

		lenS := len(s)


	// Do it!
		if suffix := []rune("sses") ; hasSuffix(s, suffix) {

			lenTrim := 2

			subSlice := s[:lenS-lenTrim]

			result = subSlice
		} else if suffix := []rune("ies") ; hasSuffix(s, suffix) {
			lenTrim := 2

			subSlice := s[:lenS-lenTrim]

			result = subSlice
		} else if suffix := []rune("ss") ; hasSuffix(s, suffix) {

			result = s
		} else if suffix := []rune("s") ; hasSuffix(s, suffix) {

			lenSuffix := 1

			subSlice := s[:lenS-lenSuffix]

			result = subSlice
		}	


	// Return.
		return result
}



func step1b(s []rune) []rune {

	// Initialize.
		var result []rune = s

		lenS := len(s)


	// Do it!
		if suffix := []rune("eed") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if  0 < m {
				lenTrim := 1

				result = s[:lenS-lenTrim]
			}
		} else if suffix := []rune("ed") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			if containsVowel(subSlice) {

				if suffix2 := []rune("at") ; hasSuffix(subSlice, suffix2) {
					lenTrim := -1

					result = s[:lenS-lenSuffix-lenTrim]
				} else if suffix2 := []rune("bl") ; hasSuffix(subSlice, suffix2) {
					lenTrim := -1

					result = s[:lenS-lenSuffix-lenTrim]
				} else if suffix2 := []rune("iz") ; hasSuffix(subSlice, suffix2) {
					lenTrim := -1

					result = s[:lenS-lenSuffix-lenTrim]
				} else if c := subSlice[len(subSlice)-1] ; 'l' != c && 's' != c && 'z' != c && hasRepeatDoubleConsonantSuffix(subSlice) {
					lenTrim := 1

					lenSubSlice := len(subSlice)

					result = subSlice[:lenSubSlice-lenTrim]
				} else if c := subSlice[len(subSlice)-1] ; 1 == measure(subSlice) && hasConsonantVowelConsonantSuffix(subSlice) && 'w' != c && 'x' != c && 'y' != c {
					lenTrim := -1

					result = s[:lenS-lenSuffix-lenTrim]

					result[len(result)-1] = 'e'
				} else {
					result = subSlice
				}

			}
		} else if suffix := []rune("ing") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			if containsVowel(subSlice) {

				if suffix2 := []rune("at") ; hasSuffix(subSlice, suffix2) {
					lenTrim := -1

					result = s[:lenS-lenSuffix-lenTrim]

					result[len(result)-1] = 'e'
				} else if suffix2 := []rune("bl") ; hasSuffix(subSlice, suffix2) {
					lenTrim := -1

					result = s[:lenS-lenSuffix-lenTrim]

					result[len(result)-1] = 'e'
				} else if suffix2 := []rune("iz") ; hasSuffix(subSlice, suffix2) {
					lenTrim := -1

					result = s[:lenS-lenSuffix-lenTrim]

					result[len(result)-1] = 'e'
				} else if c := subSlice[len(subSlice)-1] ; 'l' != c && 's' != c && 'z' != c && hasRepeatDoubleConsonantSuffix(subSlice) {
					lenTrim := 1

					lenSubSlice := len(subSlice)

					result = subSlice[:lenSubSlice-lenTrim]
				} else if c := subSlice[len(subSlice)-1] ; 1 == measure(subSlice) && hasConsonantVowelConsonantSuffix(subSlice) && 'w' != c && 'x' != c && 'y' != c {
					lenTrim := -1

					result = s[:lenS-lenSuffix-lenTrim]

					result[len(result)-1] = 'e'
				} else {
					result = subSlice
				}

			}
		}


	// Return.
		return result
}



func step1c(s []rune) []rune {

	// Initialize.
		lenS := len(s)

		result := s


	// Do it!
		if 2 > lenS {
/////////// RETURN
			return result
		}

		if 'y' == s[lenS-1] && containsVowel(s[:lenS-1])  {

			result[lenS-1] = 'i';

		} else if 'Y' == s[lenS-1] && containsVowel(s[:lenS-1])  {

			result[lenS-1] = 'I';

		}


	// Return.
		return result
}



func step2(s []rune) []rune {

	// Initialize.
		lenS := len(s)

		result := s


	// Do it!
		if suffix := []rune("ational") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result[lenS-5] = 'e'
				result = result[:lenS-4]
			}
		} else if suffix := []rune("tional") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result = result[:lenS-2]
			}
		} else if suffix := []rune("enci") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result[lenS-1] = 'e'
			}
		} else if suffix := []rune("anci") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result[lenS-1] = 'e'
			}
		} else if suffix := []rune("izer") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result = s[:lenS-1]
			}
		} else if suffix := []rune("bli") ; hasSuffix(s, suffix) { // --DEPARTURE--
//		} else if suffix := []rune("abli") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result[lenS-1] = 'e'
			}
		} else if suffix := []rune("alli") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result = s[:lenS-2]
			}
		} else if suffix := []rune("entli") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result = s[:lenS-2]
			}
		} else if suffix := []rune("eli") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result = s[:lenS-2]
			}
		} else if suffix := []rune("ousli") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result = s[:lenS-2]
			}
		} else if suffix := []rune("ization") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result[lenS-5] = 'e'

				result = s[:lenS-4]
			}
		} else if suffix := []rune("ation") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result[lenS-3] = 'e'

				result = s[:lenS-2]
			}
		} else if suffix := []rune("ator") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result[lenS-2] = 'e'

				result = s[:lenS-1]
			}
		} else if suffix := []rune("alism") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result = s[:lenS-3]
			}
		} else if suffix := []rune("iveness") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result = s[:lenS-4]
			}
		} else if suffix := []rune("fulness") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result = s[:lenS-4]
			}
		} else if suffix := []rune("ousness") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result = s[:lenS-4]
			}
		} else if suffix := []rune("aliti") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result = s[:lenS-3]
			}
		} else if suffix := []rune("iviti") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result[lenS-3] = 'e'

				result = result[:lenS-2]
			}
		} else if suffix := []rune("biliti") ; hasSuffix(s, suffix) {
			if 0 < measure(s[:lenS-len(suffix)]) {
				result[lenS-5] = 'l'
				result[lenS-4] = 'e'

				result = result[:lenS-3]
			}
		} else if suffix := []rune("logi") ; hasSuffix(s, suffix) { // --DEPARTURE--
			if 0 < measure(s[:lenS-len(suffix)]) {
				lenTrim := 1

				result = s[:lenS-lenTrim]
			}
		}


	// Return.
		return result
}



func step3(s []rune) []rune {

	// Initialize.
		lenS := len(s)
		result := s


	// Do it!
		if suffix := []rune("icate") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			if 0 < measure(s[:lenS-lenSuffix]) {
				result = result[:lenS-3]
			}
		} else if suffix := []rune("ative") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 0 < m {
				result = subSlice
			}
		} else if suffix := []rune("alize") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			if 0 < measure(s[:lenS-lenSuffix]) {
				result = result[:lenS-3]
			}
		} else if suffix := []rune("iciti") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			if 0 < measure(s[:lenS-lenSuffix]) {
				result = result[:lenS-3]
			}
		} else if suffix := []rune("ical") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			if 0 < measure(s[:lenS-lenSuffix]) {
				result = result[:lenS-2]
			}
		} else if suffix := []rune("ful") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 0 < m {
				result = subSlice
			}
		} else if suffix := []rune("ness") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 0 < m {
				result = subSlice
			}
		}


	// Return.
		return result
}



func step4(s []rune) []rune {

	// Initialize.
		lenS := len(s)
		result := s


	// Do it!
		if suffix := []rune("al") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = result[:lenS-lenSuffix]
			}
		} else if suffix := []rune("ance") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = result[:lenS-lenSuffix]
			}
		} else if suffix := []rune("ence") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = result[:lenS-lenSuffix]
			}
		} else if suffix := []rune("er") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ic") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("able") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ible") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ant") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ement") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ment") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ent") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ion") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			c := subSlice[len(subSlice)-1]

			if 1 < m && ('s' == c || 't' == c) {
				result = subSlice
			}
		} else if suffix := []rune("ou") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ism") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ate") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("iti") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ous") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ive") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		} else if suffix := []rune("ize") ; hasSuffix(s, suffix) {
			lenSuffix := len(suffix)

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		}


	// Return.
		return result
}



func step5a(s []rune) []rune {

	// Initialize.
		lenS := len(s)
		result := s
		if lenS < 2 {
			return result
		}


	// Do it!
		if 'e' == s[lenS-1] {
			lenSuffix := 1

			subSlice := s[:lenS-lenSuffix]
			if len(subSlice) == 0 {
				return result
			}
			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			} else if 1 == m {
					if c := subSlice[len(subSlice)-1] ; !( hasConsonantVowelConsonantSuffix(subSlice) && 'w' != c && 'x' != c && 'y' != c)  {
					result = subSlice
				}
			}
		}


	// Return.
		return result
}



func step5b(s []rune) []rune {

	// Initialize.
		lenS := len(s)
		result := s


	// Do it!
		if 2 < lenS && 'l' == s[lenS-2] && 'l' == s[lenS-1] {

			lenSuffix := 1

			subSlice := s[:lenS-lenSuffix]

			m := measure(subSlice)

			if 1 < m {
				result = subSlice
			}
		}


	// Return.
		return result
}
 



func StemString(s string) string {

	// Convert string to []rune
		runeArr := []rune(s)

	// Stem.
		runeArr = Stem(runeArr)

	// Convert []rune to string
		str := string(runeArr)

	// Return.
		return str
}

func Stem(s []rune) []rune {

	// Initialize.
		lenS := len(s)


	// Short circuit.
		if 0 == lenS {
/////////// RETURN
			return s
		}


	// Make all runes lowercase.
		for i := 0 ; i < lenS ; i++ {
			s[i] = unicode.ToLower(s[i])
		}


	// Stem
		result := StemWithoutLowerCasing(s)


	// Return.
		return result
}

func StemWithoutLowerCasing(s []rune) []rune {

	// Initialize.
		lenS := len(s)


	// Words that are of length 2 or less is already stemmed.
	// Don't do anything.
		if 2 >= lenS {
/////////// RETURN
			return s
		}


	// Stem
		s = step1a(s)
		s = step1b(s)
		s = step1c(s)
		s = step2(s)
		s = step3(s)
		s = step4(s)
		s = step5a(s)
		s = step5b(s)


	// Return.
		return s
}