feat: support core regex flags (#26)

Author: mdjastrzebski

src/__tests__/builder.test.ts

@@ -0,0 +1,25 @@
+import { buildRegex } from '../builders';
+
+test('"regexBuilder" flags', () => {
+  expect(buildRegex('a').flags).toBe('');
+  expect(buildRegex({}, 'a').flags).toBe('');
+
+  expect(buildRegex({ global: true }, 'a').flags).toBe('g');
+  expect(buildRegex({ global: false }, 'a').flags).toBe('');
+
+  expect(buildRegex({ ignoreCase: true }, 'a').flags).toBe('i');
+  expect(buildRegex({ ignoreCase: false }, 'a').flags).toBe('');
+
+  expect(buildRegex({ multiline: true }, 'a').flags).toBe('m');
+  expect(buildRegex({ multiline: false }, 'a').flags).toBe('');
+
+  expect(buildRegex({ hasIndices: true }, 'a').flags).toBe('d');
+  expect(buildRegex({ hasIndices: false }, 'a').flags).toBe('');
+
+  expect(buildRegex({ sticky: true }, 'a').flags).toBe('y');
+  expect(buildRegex({ sticky: false }, 'a').flags).toBe('');
+
+  expect(
+    buildRegex({ global: true, ignoreCase: true, multiline: false }, 'a').flags
+  ).toBe('gi');
+});

src/builders.ts

@@ -1,15 +1,42 @@
 import type { RegexElement } from './components/types';
 import { encodeSequence } from './encoder/encoder';
+import { isRegexElement } from './utils';
+
+export interface RegexFlags {
+  /** Global search. */
+  global?: boolean;
+  /** Case-insensitive search. */
+  ignoreCase?: boolean;
+  /** Allows ^ and $ to match newline characters. */
+  multiline?: boolean;
+  /** Generate indices for substring matches. */
+  hasIndices?: boolean;
+  /** Perform a "sticky" search that matches starting at the current position in the target string. */
+  sticky?: boolean;
+}
 
 /**
  * Generate RegExp object for elements.
  *
  * @param elements
  * @returns
  */
-export function buildRegex(...elements: Array<RegexElement | string>): RegExp {
-  const pattern = encodeSequence(elements).pattern;
-  return new RegExp(pattern);
+export function buildRegex(...elements: Array<RegexElement | string>): RegExp;
+export function buildRegex(
+  flags: RegexFlags,
+  ...elements: Array<RegexElement | string>
+): RegExp;
+export function buildRegex(
+  first: RegexFlags | RegexElement | string,
+  ...rest: Array<RegexElement | string>
+): RegExp {
+  if (typeof first === 'string' || isRegexElement(first)) {
+    return buildRegex({}, first, ...rest);
+  }
+
+  const pattern = encodeSequence(rest).pattern;
+  const flags = encodeFlags(first);
+  return new RegExp(pattern, flags);
 }
 
 /**
@@ -22,3 +49,24 @@ export function buildPattern(
 ): string {
   return encodeSequence(elements).pattern;
 }
+
+function encodeFlags(flags: RegexFlags): string {
+  let result = '';
+  if (flags.global) {
+    result += 'g';
+  }
+  if (flags.ignoreCase) {
+    result += 'i';
+  }
+  if (flags.multiline) {
+    result += 'm';
+  }
+  if (flags.hasIndices) {
+    result += 'd';
+  }
+  if (flags.sticky) {
+    result += 'y';
+  }
+
+  return result;
+}

src/utils.ts

@@ -1,3 +1,4 @@
+import type { RegexElement } from './components/types';
 import { type EncoderNode, EncoderPrecedence } from './encoder/types';
 
 /**
@@ -29,6 +30,10 @@ export function concatNodes(nodes: EncoderNode[]): EncoderNode {
   };
 }
 
+export function isRegexElement(element: unknown): element is RegexElement {
+  return typeof element === 'object' && element !== null && 'type' in element;
+}
+
 // Source: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_expressions#escaping
 export function escapeText(text: string) {
   return text.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string