feat: common patterns infrastructure (hex color)

package.json

@@ -15,6 +15,18 @@
     "!**/__mocks__",
     "!**/.*"
   ],
+  "exports": {
+    ".": {
+      "require": "./lib/commonjs/index",
+      "import": "./lib/module/index",
+      "types": "./lib/typescript/src/index.d.ts"
+    },
+    "./patterns": {
+      "require": "./lib/commonjs/patterns/index",
+      "import": "./lib/module/patterns/index",
+      "types": "./lib/typescript/src/patterns/index.d.ts"
+    }
+  },
   "scripts": {
     "test": "jest",
     "typecheck": "tsc --noEmit",

src/patterns/__tests__/hex-color.test.ts

@@ -0,0 +1,22 @@
+import { hexColorFinder, hexColorValidator } from '..';
+
+test('hexColorValidator', () => {
+  expect(hexColorValidator).toMatchString('#ffffff');
+  expect(hexColorValidator).toMatchString('#000');
+
+  expect(hexColorValidator).not.toMatchString('#000 ');
+  expect(hexColorValidator).not.toMatchString(' #000');
+  expect(hexColorValidator).not.toMatchString('#0');
+  expect(hexColorValidator).not.toMatchString('#11');
+  expect(hexColorValidator).not.toMatchString('#4444');
+  expect(hexColorValidator).not.toMatchString('#55555');
+  expect(hexColorValidator).not.toMatchString('#7777777');
+});
+
+test('hexColorFinder', () => {
+  expect(hexColorFinder).toMatchAllGroups('The color is #ffffff', [['#ffffff']]);
+  expect(hexColorFinder).toMatchAllGroups('The colors are #1, #22, #333, #4444, #55555, #666666', [
+    ['#333'],
+    ['#666666'],
+  ]);
+});

src/patterns/hex-color.ts

@@ -0,0 +1,38 @@
+import { buildRegExp } from '../builders';
+import { endOfString, startOfString, wordBoundary } from '../constructs/anchors';
+import { charClass, charRange, digit } from '../constructs/character-class';
+import { choiceOf } from '../constructs/choice-of';
+import { repeat } from '../constructs/repeat';
+
+const hexDigit = charClass(digit, charRange('a', 'f'));
+
+/** Find hex color strings in a text. */
+export const hexColorFinder = buildRegExp(
+  [
+    '#',
+    choiceOf(
+      repeat(hexDigit, 6), // #rrggbb
+      repeat(hexDigit, 3), // #rgb
+    ),
+    wordBoundary,
+  ],
+  { ignoreCase: true, global: true },
+);
+
+/**
+ * Check that given text is a valid hex color.
+ *
+ * Allows both 3 and 6 digit hex colors.
+ * */
+export const hexColorValidator = buildRegExp(
+  [
+    startOfString, // Match whole string
+    '#',
+    choiceOf(
+      repeat(hexDigit, 6), // #rrggbb
+      repeat(hexDigit, 3), // #rgb
+    ),
+    endOfString,
+  ],
+  { ignoreCase: true },
+);

src/patterns/index.ts

@@ -0,0 +1 @@
+export { hexColorFinder, hexColorValidator } from './hex-color';