refactor: split files

src/additional/truncate.test.ts

@@ -0,0 +1,47 @@
+import { type Truncate, truncate } from './truncate.js'
+
+namespace TruncateTests {
+  type test1 = Expect<Equal<Truncate<'Hello, world', 9>, 'Hello,...'>>
+  type test2 = Expect<Equal<Truncate<'Hello, world', 12>, 'Hello, world'>>
+  type test3 = Expect<Equal<Truncate<'Hello, world', 2>, '...'>>
+  type test4 = Expect<Equal<Truncate<'Hello, world', 9, '[...]'>, 'Hell[...]'>>
+  type test5 = Expect<Equal<Truncate<'Hello, world', -1>, '...'>>
+  type test6 = Expect<Equal<Truncate<'Hello, world', 0, '[...]'>, '[...]'>>
+}
+
+describe('truncate', () => {
+  test('truncate small sentence does nothing', () => {
+    const expected = 'Hello' as const
+    const result = truncate('Hello', 9)
+    expect(result).toEqual(expected)
+    type test = Expect<Equal<typeof result, typeof expected>>
+  })
+
+  test('truncate big sentence truncate', () => {
+    const expected = 'Hello ...' as const
+    const result = truncate('Hello world', 9)
+    expect(result).toEqual(expected)
+    type test = Expect<Equal<typeof result, typeof expected>>
+  })
+
+  test('truncate with negative integer does truncate', () => {
+    const expected = '...' as const
+    const result = truncate('Hello world', -1)
+    expect(result).toEqual(expected)
+    type test = Expect<Equal<typeof result, typeof expected>>
+  })
+
+  test('truncate big sentence with specified omission', () => {
+    const expected = 'Hello[...]' as const
+    const result = truncate('Hello world', 10, '[...]')
+    expect(result).toEqual(expected)
+    type test = Expect<Equal<typeof result, typeof expected>>
+  })
+
+  test('truncate small sentence with specified omission', () => {
+    const expected = 'Hello' as const
+    const result = truncate('Hello', 10, '[...]')
+    expect(result).toEqual(expected)
+    type test = Expect<Equal<typeof result, typeof expected>>
+  })
+})

src/additional/truncate.ts

@@ -0,0 +1,39 @@
+import type { Math } from '../internal/math.js'
+import { join, type Join } from '../native/join.js'
+import { type Length } from '../native/length.js'
+import { type Slice } from '../native/slice.js'
+
+// STRING FUNCTIONS
+
+/**
+ * Truncate a string if it's longer than the given maximum length.
+ * The last characters of the truncated string are replaced with the omission string which defaults to "...".
+ */
+export type Truncate<
+  T extends string,
+  Size extends number,
+  Omission extends string = '...',
+> = Math.IsNegative<Size> extends true
+  ? Omission
+  : Math.Subtract<Length<T>, Size> extends 0
+  ? T
+  : Join<[Slice<T, 0, Math.Subtract<Size, Length<Omission>>>, Omission]>
+
+/**
+ * A strongly typed function to truncate a string if it's longer than the given maximum string length.
+ * The last characters of the truncated string are replaced with the omission string which defaults to "...".
+ * @param sentence the sentence to extract the words from.
+ * @param length the maximum length of the string.
+ * @param omission the string to append to the end of the truncated string.
+ * @returns the truncated string
+ * @example truncate('Hello, World', 8) // 'Hello...'
+ */
+export function truncate<
+  T extends string,
+  S extends number,
+  P extends string = '...',
+>(sentence: T, length: S, omission = '...' as P): Truncate<T, S, P> {
+  if (length < 0) return omission as Truncate<T, S, P>
+  if (sentence.length <= length) return sentence as Truncate<T, S, P>
+  return join([sentence.slice(0, length - omission.length), omission])
+}