feat: Support highlight syntax (#31)

* support callout

* fix eslint

* support hightlight syntax

* fix eslint

src/nodes/highlight.ts

@@ -0,0 +1,13 @@
+import { NodeKind } from './node-kind'
+import { Node } from './node'
+import { Delimited } from './delimited'
+
+export class Highlight extends Delimited implements Node {
+  readonly children: Node[] = []
+  readonly kind = NodeKind.Highlight
+
+  constructor (children: Node[]) {
+    super('==', '==')
+    this.children = children
+  }
+}

src/nodes/node-kind.ts

@@ -24,6 +24,7 @@ export const enum NodeKind {
   Math = 1 << 21,
   BlockquoteItem = 1 << 22,
   CalloutItem = 1 << 23,
+  Highlight = 1 << 24,
 
   // combinations
   All = -1,
@@ -33,7 +34,7 @@ export const enum NodeKind {
   Code = InlineCode | BlockCode,
   Link = InlineLink | ReferenceLink,
   Image = InlineImage | ReferenceImage,
-  Style = Strong | Emphasis | Strikethrough,
+  Style = Strong | Emphasis | Strikethrough | Highlight,
   Inline = NaturualConstructs | InlineCode | Link | Style | HTMLTag | InlineImage | ReferenceImage | Math,
   Block = ~Inline,
 }

src/parser/parse.ts

@@ -9,6 +9,7 @@ import { SquareQuoted } from '../nodes/square-quoted'
 import { Emphasis, EmphasisDelimiter } from '../nodes/empasis'
 import { Quoted } from '../nodes/quoted'
 import { Strong, StrongDelimiter } from '../nodes/strong'
+import { Highlight } from '../nodes/highlight'
 import { Strikethrough } from '../nodes/strikethrough'
 import { Document } from '../nodes/document'
 import { compactTree } from '../transformers/compact'
@@ -178,7 +179,7 @@ export function parse (str: string, options :NormalizedPadMarkdownOptions): Docu
       i++
     }
 
-    // Strong, Emphasis, Strikethrough
+    // Strong, Emphasis, Strikethrough, highlight
     else if (state === State.Emphasis && c === emphasisDelimiter && c === '_' && isWordBoundary(str[i + 1])) {
       resolve(new Emphasis(popNodes(), emphasisDelimiter))
       i++
@@ -195,6 +196,10 @@ export function parse (str: string, options :NormalizedPadMarkdownOptions): Docu
       resolve(new Strikethrough(popNodes()))
       i += 2
     }
+    else if (state === State.Highlight && c2 === '==') {
+      resolve(new Highlight(popNodes()))
+      i += 2
+    }
 
     // ListItems
     else if (state === State.UnorderedListItem && c === '\n') {
@@ -278,6 +283,9 @@ export function parse (str: string, options :NormalizedPadMarkdownOptions): Docu
       strongDelimiter = c2
       i += 2
       push(State.Strong)
+    } else if (c2 === '==' && allow(NodeKind.Highlight)) {
+      i += 2
+      push(State.Highlight)
     } else if (c === '*' && allow(NodeKind.Emphasis)) {
       emphasisDelimiter = c
       i++
@@ -354,6 +362,9 @@ export function parse (str: string, options :NormalizedPadMarkdownOptions): Docu
       case State.Strong:
         resolve(...[...strongDelimiter].map(c => Punctuation.create(c)), ...popNodes())
         break
+      case State.Highlight:
+        resolve(Punctuation.create('='), Punctuation.create('='), ...popNodes())
+        break
       case State.InlineCode:
         resolve(
           ...[...inlineCodeDelimiter].map(c => Punctuation.create(c)),

src/parser/state.ts

@@ -20,6 +20,7 @@ export enum State {
   UnorderedListItem,  // *<space>
   BlockquoteItem,     // >
   CalloutItem,        // [!
+  Highlight,          // ==
 
   // natural language syntax
   Quoted,             // " in natural language

test/parser/parse.spec.ts

@@ -475,6 +475,79 @@ describe('parse()', () => {
     })
   })
 
+  describe('Highlight', () => {
+    it('should allow highlight', () => {
+      const doc = parse('==123==', options)
+      expect(doc.children).toHaveLength(1)
+
+      const highlight = doc.children[0]
+      expect(highlight).toMatchObject({
+        kind: NodeKind.Highlight
+      })
+
+      expect(highlight.children).toHaveLength(1)
+      const number = highlight.children[0]
+      expect(number).toMatchObject({
+        kind: NodeKind.AlphabetNumeric,
+        text: '123'
+      })
+
+      expect(highlight.toMarkdown()).toEqual('==123==')
+    })
+
+    it('should expand Highlight when EOF found', () => {
+      const doc = parse('==123', options)
+      expect(doc.children).toHaveLength(3)
+
+      const [p1, p2, a1] = doc.children
+      expect(p1).toMatchObject({
+        kind: NodeKind.Punctuation,
+        char: '='
+      })
+      expect(p2).toMatchObject({
+        kind: NodeKind.Punctuation,
+        char: '='
+      })
+      expect(a1).toMatchObject({
+        kind: NodeKind.AlphabetNumeric,
+        text: '123'
+      })
+    })
+
+    it('should expand repeatedly Highlight when NL found', () => {
+      const doc = parse('==foo\n==bar==', options)
+      expect(doc.children).toHaveLength(5)
+
+      const [p1, p2, a1, blank, highlight] = doc.children
+      expect(p1).toMatchObject({
+        kind: NodeKind.Punctuation,
+        char: '='
+      })
+      expect(p2).toMatchObject({
+        kind: NodeKind.Punctuation,
+        char: '='
+      })
+      expect(a1).toMatchObject({
+        kind: NodeKind.AlphabetNumeric,
+        text: 'foo'
+      })
+      expect(blank).toMatchObject({
+        kind: NodeKind.Blank,
+        char: '\n'
+      })
+      expect(highlight).toMatchObject({
+        kind: NodeKind.Highlight
+      })
+
+      expect(highlight.children).toHaveLength(1)
+      const alphabet = highlight.children[0]
+      expect(alphabet).toMatchObject({
+        kind: NodeKind.AlphabetNumeric,
+        text: 'bar'
+      })
+    })
+  })
+
   describe('BlockCode', () => {
     it('should parse block code', () => {
       const doc = parse('```\ncode\n```', options)