Some work

helpers/levenshtein.go

@@ -0,0 +1,99 @@
+/*
+Copyright © Brian Buller <brian@bullercodeworks.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+*/
+package helpers
+
+import "unicode/utf8"
+
+const levMinLngthThreshold = 32
+
+func ComputeLevDistance(a, b string) int {
+	if len(a) == 0 {
+		return utf8.RuneCountInString(b)
+	}
+	if len(b) == 0 {
+		return utf8.RuneCountInString(a)
+	}
+
+	if a == b {
+		return 0
+	}
+	s1 := []rune(a)
+	s2 := []rune(b)
+
+	if len(s1) > len(s2) {
+		s1, s2 = s2, s1
+	}
+
+	s1, s2 = trimLongestCommonSuffix(s1, s2)
+	s1, s2 = trimLongestCommonPrefix(s1, s2)
+
+	lenS1 := len(s1)
+	lenS2 := len(s2)
+
+	// Init the row
+	var x []uint16
+	if lenS1+1 > levMinLngthThreshold {
+		x = make([]uint16, lenS1+1)
+	} else {
+		x = make([]uint16, levMinLngthThreshold)
+		x = x[:lenS1+1]
+	}
+
+	for i := 1; i < len(x); i++ {
+		x[i] = uint16(i)
+	}
+
+	_ = x[lenS1]
+	y := x[1:]
+	y = y[:lenS1]
+	for i := 0; i < lenS2; i++ {
+		prev := uint16(i + 1)
+		for j := 0; j < lenS1; j++ {
+			current := x[j]
+			if s2[i] != s1[j] {
+				current = min(x[j], prev, y[j]) + 1
+			}
+			x[j] = prev
+			prev = current
+		}
+		x[lenS1] = prev
+	}
+	return int(x[lenS1])
+}
+
+func trimLongestCommonSuffix(a, b []rune) ([]rune, []rune) {
+	m := min(len(a), len(b))
+	a2 := a[len(a)-m:]
+	b2 := b[len(b)-m:]
+	i := len(a2)
+	b2 = b2[:i]
+	for ; i > 0 && a2[i-1] == b2[i-1]; i-- {
+	}
+	return a[:len(a)-len(a2)+i], b[:len(b)-len(b2)+i]
+}
+
+func trimLongestCommonPrefix(a, b []rune) ([]rune, []rune) {
+	var i int
+	for m := min(len(a), len(b)); i < m && a[i] == b[i]; i++ {
+	}
+	return a[i:], b[i:]
+}