snapshot of https://github.com/cortezaproject/corteza.git (2024.9.x, 2026-09-18; blobs > 131072B omitted)

server/pkg/str/soundex.go

@@ -0,0 +1,104 @@
+package str
+
+import (
+	"strings"
+)
+
+// ToSoundex takes a word and returns the soundex code for it.
+// https://en.wikipedia.org/wiki/Soundex
+//
+//  1. Retain the first letter of the name and drop all other occurrences of a, e, i, o, u, y, h, w.
+//  2. Replace consonants with digits as follows (after the first letter):
+//     b, f, p, v → 1
+//     c, g, j, k, q, s, x, z → 2
+//     d, t → 3
+//     l → 4
+//     m, n → 5
+//     r → 6
+//  3. If two or more letters with the same number are adjacent in the original name (before step 1),
+//     only retain the first letter; also two letters with the same number separated
+//     by 'h' or 'w' are coded as a single number, whereas such letters separated by a vowel are coded twice.
+//     This rule also applies to the first letter.
+//  4. Iterate the previous step until you have one letter and three numbers.
+//     If you have too few letters in your word that you can't assign three numbers, append with zeros
+//     until there are three numbers. If you have more than 3 letters, just retain the first 3 numbers.
+func ToSoundex(s string) string {
+	var (
+		// soundex code
+		code string
+		// last code
+		lastCode string
+		// last rune
+		lastRune rune
+		// last rune is vowel
+		lastRuneIsVowel bool
+	)
+
+	// retain the first letter of the name and drop all other occurrences of a, e, i, o, u, y, h, w
+	for _, r := range s {
+		if r == 'a' || r == 'e' || r == 'i' || r == 'o' || r == 'u' || r == 'y' || r == 'h' || r == 'w' {
+			continue
+		}
+
+		code = string(r)
+		break
+	}
+
+	// replace consonants with digits as follows (after the first letter)
+	for _, r := range s {
+		if r == 'a' || r == 'e' || r == 'i' || r == 'o' || r == 'u' || r == 'y' || r == 'h' || r == 'w' {
+			lastRuneIsVowel = true
+			continue
+		}
+
+		if lastRuneIsVowel {
+			lastRuneIsVowel = false
+			lastCode = ""
+		}
+
+		switch r {
+		case 'b', 'f', 'p', 'v':
+			lastCode = "1"
+		case 'c', 'g', 'j', 'k', 'q', 's', 'x', 'z':
+			lastCode = "2"
+		case 'd', 't':
+			lastCode = "3"
+		case 'l':
+			lastCode = "4"
+		case 'm', 'n':
+			lastCode = "5"
+		case 'r':
+			lastCode = "6"
+		}
+
+		if lastCode != "" && lastCode != string(lastRune) {
+			code += lastCode
+		}
+
+		lastRune = r
+	}
+
+	// if two or more letters with the same number are adjacent in the original name (before step 1),
+	// only retain the first letter
+	// also two letters with the same number separated by 'h' or 'w' are coded as a single number,
+	// whereas such letters separated by a vowel are coded twice
+	// this rule also applies to the first letter
+	code = strings.ReplaceAll(code, "11", "1")
+	code = strings.ReplaceAll(code, "22", "2")
+	code = strings.ReplaceAll(code, "33", "3")
+	code = strings.ReplaceAll(code, "44", "4")
+	code = strings.ReplaceAll(code, "55", "5")
+	code = strings.ReplaceAll(code, "66", "6")
+
+	// iterate the previous step until you have one letter and three numbers
+	// if you have too few letters in your word that you can't assign three numbers,
+	// append with zeros until there are three numbers
+	// if you have more than 3 letters, just retain the first 3 numbers
+	if len(code) < 4 {
+		code += strings.Repeat("0", 4-len(code))
+	} else {
+		code = code[:4]
+	}
+
+	return code
+}