Pig Latin

typescript/pig-latin/pig-latin.ts

@@ -0,0 +1,93 @@
+const vowels = ['A', 'E', 'I', 'O', 'U']
+const consonants = [
+  'B',
+  'C',
+  'D',
+  'F',
+  'G',
+  'H',
+  'J',
+  'K',
+  'L',
+  'M',
+  'N',
+  'P',
+  'Q',
+  'R',
+  'S',
+  'T',
+  'V',
+  'W',
+  'X',
+  'Y',
+  'Z',
+]
+
+const startsWiths = ['XR', 'YT', 'AY']
+
+const rule1 = (word: string) =>
+  // If a word begins with a vowel, or starts with `"xr"` or `"yt"`,
+  // add an `"ay"` sound to the end of the word.
+  vowels.concat(startsWiths).some(s => word.toUpperCase().startsWith(s))
+    ? `${word}ay`
+    : word
+
+const rule2RegExp = new RegExp(`^([${consonants.join('')}]+)(.*)`, 'i')
+
+const rule2 = (word: string): string =>
+  // If a word begins with a one or more consonants, first move
+  // those consonants to the end of the word and then add an `"ay"`
+  // sound to the end of the word.
+  word.replace(
+    rule2RegExp,
+    (_, match, rest) => `${rest}${match}${match ? 'ay' : ''}`,
+  )
+
+const rule3RegExp = new RegExp(`^(qu|[${consonants.join('')}]*qu)(.*)`, 'i')
+
+const rule3 = (word: string): string =>
+  // If a word starts with zero or more consonants followed by `"qu"`,
+  // first move those consonants (if any) and the `"qu"` part to the end
+  // of the word, and then add an `"ay"` sound to the end of the word.
+  word.replace(
+    rule3RegExp,
+    (_, match, rest) => `${rest}${match}${match ? 'ay' : ''}`,
+  )
+
+const rule4RegExp = new RegExp(`^([${consonants.join('')}]+)(y.*)`, 'i')
+
+const rule4 = (word: string): string =>
+  // If a word starts with one or more consonants followed by `"y"`,
+  // first move the consonants preceding the `"y"`to the end of the word,
+  // and then add an `"ay"` sound to the end of the word.
+  word.replace(
+    rule4RegExp,
+    (_, match, rest) => `${rest}${match}${match ? 'ay' : ''}`,
+  )
+
+const applyRule =
+  (rule: (word: string) => string) =>
+  ({
+    originalWord,
+    hasChanged,
+  }: {
+    originalWord: string
+    hasChanged: boolean
+  }) => {
+    if (hasChanged) return { originalWord, hasChanged }
+    const word = rule(originalWord)
+    return { originalWord: word, hasChanged: word !== originalWord }
+  }
+
+export const translate = (text: string): string => {
+  return text
+    .split(' ')
+    .filter(Boolean)
+    .map(word => ({ originalWord: word, hasChanged: false }))
+    .map(applyRule(rule1))
+    .map(applyRule(rule3))
+    .map(applyRule(rule4))
+    .map(applyRule(rule2))
+    .map(({ originalWord }) => originalWord)
+    .join(' ')
+}