From e43a445c3412a584d7bf9bd06a72104391cccfdc Mon Sep 17 00:00:00 2001
From: Steven <stevenlgtm@gmail.com>
Date: Sat, 16 Dec 2023 11:47:29 +0800
Subject: [PATCH] chore: implement escaping character node

---
 plugin/gomark/ast/inline.go                   | 10 +++++
 plugin/gomark/ast/node.go                     |  1 +
 plugin/gomark/parser/escaping_character.go    | 41 +++++++++++++++++++
 .../gomark/parser/escaping_character_test.go  | 30 ++++++++++++++
 plugin/gomark/parser/parser.go                |  1 +
 plugin/gomark/parser/parser_test.go           | 28 +++++++++++++
 plugin/gomark/parser/tokenizer/tokenizer.go   |  3 ++
 plugin/gomark/render/html/html.go             |  7 ++++
 plugin/gomark/render/html/html_test.go        |  4 ++
 plugin/gomark/render/string/string.go         |  7 ++++
 10 files changed, 132 insertions(+)
 create mode 100644 plugin/gomark/parser/escaping_character.go
 create mode 100644 plugin/gomark/parser/escaping_character_test.go

diff --git a/plugin/gomark/ast/inline.go b/plugin/gomark/ast/inline.go
index 8e82c54d..82450fb0 100644
--- a/plugin/gomark/ast/inline.go
+++ b/plugin/gomark/ast/inline.go
@@ -101,3 +101,13 @@ type Strikethrough struct {
 func (*Strikethrough) Type() NodeType {
 	return StrikethroughNode
 }
+
+type EscapingCharacter struct {
+	BaseInline
+
+	Symbol string
+}
+
+func (*EscapingCharacter) Type() NodeType {
+	return EscapingCharacterNode
+}
diff --git a/plugin/gomark/ast/node.go b/plugin/gomark/ast/node.go
index 9e4c5315..6552555e 100644
--- a/plugin/gomark/ast/node.go
+++ b/plugin/gomark/ast/node.go
@@ -23,6 +23,7 @@ const (
 	LinkNode
 	TagNode
 	StrikethroughNode
+	EscapingCharacterNode
 )
 
 type Node interface {
diff --git a/plugin/gomark/parser/escaping_character.go b/plugin/gomark/parser/escaping_character.go
new file mode 100644
index 00000000..8b3f74ed
--- /dev/null
+++ b/plugin/gomark/parser/escaping_character.go
@@ -0,0 +1,41 @@
+package parser
+
+import (
+	"errors"
+
+	"github.com/usememos/memos/plugin/gomark/ast"
+	"github.com/usememos/memos/plugin/gomark/parser/tokenizer"
+)
+
+type EscapingCharacterParser struct{}
+
+func NewEscapingCharacterParser() *EscapingCharacterParser {
+	return &EscapingCharacterParser{}
+}
+
+func (*EscapingCharacterParser) Match(tokens []*tokenizer.Token) (int, bool) {
+	if len(tokens) == 0 {
+		return 0, false
+	}
+	if tokens[0].Type != tokenizer.Backslash {
+		return 0, false
+	}
+	if len(tokens) == 1 {
+		return 0, false
+	}
+	if tokens[1].Type == tokenizer.Newline || tokens[1].Type == tokenizer.Space || tokens[1].Type == tokenizer.Text || tokens[1].Type == tokenizer.Number {
+		return 0, false
+	}
+	return 2, true
+}
+
+func (p *EscapingCharacterParser) Parse(tokens []*tokenizer.Token) (ast.Node, error) {
+	size, ok := p.Match(tokens)
+	if size == 0 || !ok {
+		return nil, errors.New("not matched")
+	}
+
+	return &ast.EscapingCharacter{
+		Symbol: tokens[1].Value,
+	}, nil
+}
diff --git a/plugin/gomark/parser/escaping_character_test.go b/plugin/gomark/parser/escaping_character_test.go
new file mode 100644
index 00000000..da6b2d31
--- /dev/null
+++ b/plugin/gomark/parser/escaping_character_test.go
@@ -0,0 +1,30 @@
+package parser
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/usememos/memos/plugin/gomark/ast"
+	"github.com/usememos/memos/plugin/gomark/parser/tokenizer"
+)
+
+func TestEscapingCharacterParser(t *testing.T) {
+	tests := []struct {
+		text string
+		node ast.Node
+	}{
+		{
+			text: `\# 123`,
+			node: &ast.EscapingCharacter{
+				Symbol: "#",
+			},
+		},
+	}
+
+	for _, test := range tests {
+		tokens := tokenizer.Tokenize(test.text)
+		node, _ := NewEscapingCharacterParser().Parse(tokens)
+		require.Equal(t, StringifyNodes([]ast.Node{test.node}), StringifyNodes([]ast.Node{node}))
+	}
+}
diff --git a/plugin/gomark/parser/parser.go b/plugin/gomark/parser/parser.go
index 545d5a50..9c647f36 100644
--- a/plugin/gomark/parser/parser.go
+++ b/plugin/gomark/parser/parser.go
@@ -71,6 +71,7 @@ func ParseBlockWithParsers(tokens []*tokenizer.Token, blockParsers []BlockParser
 }
 
 var defaultInlineParsers = []InlineParser{
+	NewEscapingCharacterParser(),
 	NewBoldItalicParser(),
 	NewImageParser(),
 	NewLinkParser(),
diff --git a/plugin/gomark/parser/parser_test.go b/plugin/gomark/parser/parser_test.go
index 602d09bc..b1c489e5 100644
--- a/plugin/gomark/parser/parser_test.go
+++ b/plugin/gomark/parser/parser_test.go
@@ -26,6 +26,34 @@ func TestParser(t *testing.T) {
 				},
 			},
 		},
+		{
+			text: "# Hello world!",
+			nodes: []ast.Node{
+				&ast.Heading{
+					Level: 1,
+					Children: []ast.Node{
+						&ast.Text{
+							Content: "Hello world!",
+						},
+					},
+				},
+			},
+		},
+		{
+			text: "\\# Hello world!",
+			nodes: []ast.Node{
+				&ast.Paragraph{
+					Children: []ast.Node{
+						&ast.EscapingCharacter{
+							Symbol: "#",
+						},
+						&ast.Text{
+							Content: " Hello world!",
+						},
+					},
+				},
+			},
+		},
 		{
 			text: "**Hello** world!",
 			nodes: []ast.Node{
diff --git a/plugin/gomark/parser/tokenizer/tokenizer.go b/plugin/gomark/parser/tokenizer/tokenizer.go
index e138ba82..de217037 100644
--- a/plugin/gomark/parser/tokenizer/tokenizer.go
+++ b/plugin/gomark/parser/tokenizer/tokenizer.go
@@ -17,6 +17,7 @@ const (
 	PlusSign           TokenType = "+"
 	Dot                TokenType = "."
 	GreaterThan        TokenType = ">"
+	Backslash          TokenType = "\\"
 	Newline            TokenType = "\n"
 	Space              TokenType = " "
 )
@@ -70,6 +71,8 @@ func Tokenize(text string) []*Token {
 			tokens = append(tokens, NewToken(PlusSign, "+"))
 		case '.':
 			tokens = append(tokens, NewToken(Dot, "."))
+		case '\\':
+			tokens = append(tokens, NewToken(Backslash, `\`))
 		case '\n':
 			tokens = append(tokens, NewToken(Newline, "\n"))
 		case ' ':
diff --git a/plugin/gomark/render/html/html.go b/plugin/gomark/render/html/html.go
index 47979ac6..7757aca4 100644
--- a/plugin/gomark/render/html/html.go
+++ b/plugin/gomark/render/html/html.go
@@ -59,6 +59,8 @@ func (r *HTMLRender) RenderNode(node ast.Node) {
 		r.renderTag(n)
 	case *ast.Strikethrough:
 		r.renderStrikethrough(n)
+	case *ast.EscapingCharacter:
+		r.renderEscapingCharacter(n)
 	case *ast.Text:
 		r.renderText(n)
 	default:
@@ -199,3 +201,8 @@ func (r *HTMLRender) renderStrikethrough(node *ast.Strikethrough) {
 	r.output.WriteString(node.Content)
 	r.output.WriteString(`</del>`)
 }
+
+func (r *HTMLRender) renderEscapingCharacter(node *ast.EscapingCharacter) {
+	r.output.WriteString("\\")
+	r.output.WriteString(node.Symbol)
+}
diff --git a/plugin/gomark/render/html/html_test.go b/plugin/gomark/render/html/html_test.go
index fb6499a5..1a76b66f 100644
--- a/plugin/gomark/render/html/html_test.go
+++ b/plugin/gomark/render/html/html_test.go
@@ -42,6 +42,10 @@ func TestHTMLRender(t *testing.T) {
 			text:     "#article #memo",
 			expected: `<p><span>#article</span> <span>#memo</span></p>`,
 		},
+		{
+			text:     "#article \\#memo",
+			expected: `<p><span>#article</span> \#memo</p>`,
+		},
 		{
 			text:     "* Hello\n* world!",
 			expected: `<ul><li>Hello</li><li>world!</li></ul>`,
diff --git a/plugin/gomark/render/string/string.go b/plugin/gomark/render/string/string.go
index f8a5dab0..51cfbbce 100644
--- a/plugin/gomark/render/string/string.go
+++ b/plugin/gomark/render/string/string.go
@@ -59,6 +59,8 @@ func (r *StringRender) RenderNode(node ast.Node) {
 		r.renderTag(n)
 	case *ast.Strikethrough:
 		r.renderStrikethrough(n)
+	case *ast.EscapingCharacter:
+		r.renderEscapingCharacter(n)
 	case *ast.Text:
 		r.renderText(n)
 	default:
@@ -157,3 +159,8 @@ func (r *StringRender) renderTag(node *ast.Tag) {
 func (r *StringRender) renderStrikethrough(node *ast.Strikethrough) {
 	r.output.WriteString(node.Content)
 }
+
+func (r *StringRender) renderEscapingCharacter(node *ast.EscapingCharacter) {
+	r.output.WriteString("\\")
+	r.output.WriteString(node.Symbol)
+}