From c439489797962e38870a019d5fb66c36bfff0c55 Mon Sep 17 00:00:00 2001
From: Maciej Jastrzebski <mdjastrzebski@gmail.com>
Date: Mon, 25 Dec 2023 21:27:55 +0100
Subject: [PATCH] feat: base anchors

---
 src/components/__tests__/anchors.test.tsx | 20 +++++++++++++++++++
 src/components/anchors.ts                 | 19 ++++++++++++++++++
 src/components/types.ts                   | 24 ++++++++++++++---------
 src/encoder/encoder.ts                    |  6 ++++++
 4 files changed, 60 insertions(+), 9 deletions(-)
 create mode 100644 src/components/__tests__/anchors.test.tsx
 create mode 100644 src/components/anchors.ts

diff --git a/src/components/__tests__/anchors.test.tsx b/src/components/__tests__/anchors.test.tsx
new file mode 100644
index 0000000..bfc7a8e
--- /dev/null
+++ b/src/components/__tests__/anchors.test.tsx
@@ -0,0 +1,20 @@
+import { endOfString, startOfString } from '../anchors';
+import { oneOrMore } from '../quantifiers';
+
+test('`startOfString` basic cases', () => {
+  expect([startOfString]).toHavePattern('^');
+  expect([startOfString, 'a', 'b']).toHavePattern('^ab');
+});
+
+test('`startOfString` regex tests', () => {
+  expect([startOfString, oneOrMore('a')]).toMatchGroups('a aa aaa', ['a']);
+});
+
+test('`endOfString` basic cases', () => {
+  expect([endOfString]).toHavePattern('$');
+  expect(['a', 'b', endOfString]).toHavePattern('ab$');
+});
+
+test('`endOfString` regex tests', () => {
+  expect([oneOrMore('a'), endOfString]).toMatchGroups('a aa aaa', ['aaa']);
+});
diff --git a/src/components/anchors.ts b/src/components/anchors.ts
new file mode 100644
index 0000000..78e537c
--- /dev/null
+++ b/src/components/anchors.ts
@@ -0,0 +1,19 @@
+import { type EncoderNode, EncoderPrecedence } from '../encoder/types';
+import type { Anchor } from './types';
+
+export const startOfString: Anchor = {
+  type: 'anchor',
+  symbol: '^',
+};
+
+export const endOfString: Anchor = {
+  type: 'anchor',
+  symbol: '$',
+};
+
+export function encodeAnchor(anchor: Anchor): EncoderNode {
+  return {
+    precedence: EncoderPrecedence.Sequence,
+    pattern: anchor.symbol,
+  };
+}
diff --git a/src/components/types.ts b/src/components/types.ts
index ff61c68..7c5e36d 100644
--- a/src/components/types.ts
+++ b/src/components/types.ts
@@ -1,19 +1,13 @@
 export type RegexElement =
   | string
-  | Capture
   | CharacterClass
+  | Anchor
   | ChoiceOf
-  | Quantifier;
+  | Quantifier
+  | Capture;
 
 export type Quantifier = One | OneOrMore | Optionally | ZeroOrMore | Repeat;
 
-export type CharacterClass = {
-  type: 'characterClass';
-  characters: string[];
-  ranges: CharacterRange[];
-  isInverted: boolean;
-};
-
 /**
  * Character range from start to end (inclusive).
  */
@@ -23,6 +17,18 @@ export type CharacterRange = {
 };
 
 // Components
+export type CharacterClass = {
+  type: 'characterClass';
+  characters: string[];
+  ranges: CharacterRange[];
+  isInverted: boolean;
+};
+
+export type Anchor = {
+  type: 'anchor';
+  symbol: string;
+};
+
 export type ChoiceOf = {
   type: 'choiceOf';
   children: RegexElement[][];
diff --git a/src/encoder/encoder.ts b/src/encoder/encoder.ts
index bd6c8ec..b588235 100644
--- a/src/encoder/encoder.ts
+++ b/src/encoder/encoder.ts
@@ -1,4 +1,5 @@
 import type { RegexElement } from '../components/types';
+import { encodeAnchor } from '../components/anchors';
 import { encodeCapture } from '../components/capture';
 import { encodeCharacterClass } from '../components/character-class';
 import { encodeChoiceOf } from '../components/choice-of';
@@ -10,6 +11,7 @@ import {
 } from '../components/quantifiers';
 import { encodeRepeat } from '../components/repeat';
 import { escapeText } from '../utils/text';
+
 import { type EncoderNode, EncoderPrecedence } from './types';
 import { concatNodes } from './utils';
 
@@ -26,6 +28,10 @@ export function encodeElement(element: RegexElement): EncoderNode {
     return encodeCharacterClass(element);
   }
 
+  if (element.type === 'anchor') {
+    return encodeAnchor(element);
+  }
+
   if (element.type === 'choiceOf') {
     return encodeChoiceOf(element, encodeSequence);
   }