Repair the TypeScript for distance functions

lib/natural/distance/index.d.ts

@@ -40,10 +40,7 @@ declare interface DamerauLevenshteinDistanceOptions {
   /** @default 1 */
   transposition_cost?: number
   /** @default false */
-  search?: boolean
-  /** @default false */
   restricted?: boolean
-  damerau?: boolean
 }
 
 declare interface SubstringDistanceResult {
@@ -66,23 +63,23 @@ export function LevenshteinDistance (
  * Valid edit operations are:
  *  - transposition, insertion, deletion, and substitution
  */
-export function DamerauLevenshteinDistance (
+export function LevenshteinDistanceSearch (
   source: string,
   target: string,
-  options: DamerauLevenshteinDistanceOptions & { search: true }
+  options?: DamerauLevenshteinDistanceOptions
 ): SubstringDistanceResult
 
 export function DamerauLevenshteinDistance (
   source: string,
   target: string,
-  options?: DamerauLevenshteinDistanceOptions & { search?: false }
+  options?: DamerauLevenshteinDistanceOptions
 ): number
 
-export function DamerauLevenshteinDistance (
+export function DamerauLevenshteinDistanceSearch (
   source: string,
   target: string,
-  options: DamerauLevenshteinDistanceOptions & { search: boolean }
-): number | SubstringDistanceResult
+  options?: DamerauLevenshteinDistanceOptions
+): SubstringDistanceResult
 
 export function DiceCoefficient (str1: string, str2: string): number
 

ts_spec/damerau_levenshtein_spec.ts

@@ -0,0 +1,53 @@
+'use strict'
+
+import { DamerauLevenshteinDistance, DamerauLevenshteinDistanceSearch } from 'lib/natural'
+
+describe('DamerauLevenshtein', function () {
+  describe('default', function () {
+    it('should be 0 when given equal strings', function () {
+      expect(DamerauLevenshteinDistance('test', 'test')).toBe(0)
+    })
+
+    it('should calculate 1 for adjacent transposition', function () {
+      expect(DamerauLevenshteinDistance('za', 'az')).toBe(1)
+      expect(DamerauLevenshteinDistance('Tomato', 'oTmato')).toBe(1)
+    })
+
+    it('should handle custom transposition_cost', function () {
+      expect(DamerauLevenshteinDistance('za', 'az', { transposition_cost: 0 })).toBe(0)
+    })
+
+    it('should calculate 2 when there are 2 transpositions', function () {
+      expect(DamerauLevenshteinDistance('tomato', 'otmaot')).toBe(2)
+    })
+
+    it('should calculate 2 for 1 transposition and 1 insertion', function () {
+      expect(DamerauLevenshteinDistance('CA', 'ABC')).toBe(2)
+      expect(DamerauLevenshteinDistance('a cat', 'a abct')).toBe(2)
+    })
+  })
+
+  describe('options.restricted = true', function () {
+    const restricted = { restricted: true }
+    it('should calculate 0 for equal strings', function () {
+      expect(DamerauLevenshteinDistance('identity', 'identity', restricted)).toBe(0)
+    })
+    it('should calculate 1 for an adjacent transposition', function () {
+      expect(DamerauLevenshteinDistance('za', 'az', restricted)).toBe(1)
+    })
+    it('should not count transposition more than 1 char away', function () {
+      expect(DamerauLevenshteinDistance('CA', 'ABC', restricted)).toBe(3)
+    })
+  })
+
+  it('should combine search with Damerau', function () {
+    const source = 'The RainCoat BookStore'
+    const target = 'All the best books are here at the Rain Coats Book Store'
+    const result = DamerauLevenshteinDistanceSearch(source, target)
+    expect(result).toEqual({
+      substring: 'the Rain Coats Book Store',
+      distance: 4,
+      offset: 31
+    })
+  })
+})