From 3f4b361fad1b5e1088fb7f9c26dc04af480e2067 Mon Sep 17 00:00:00 2001
From: Steven <stevenlgtm@gmail.com>
Date: Mon, 15 Jan 2024 22:30:06 +0800
Subject: [PATCH] feat: implement highlight parser

---
 plugin/gomark/ast/ast.go                    |  1 +
 plugin/gomark/ast/inline.go                 | 14 +++++
 plugin/gomark/parser/highlight.go           | 58 +++++++++++++++++++++
 plugin/gomark/parser/highlight_test.go      | 41 +++++++++++++++
 plugin/gomark/parser/parser.go              |  1 +
 plugin/gomark/parser/tokenizer/tokenizer.go |  3 ++
 6 files changed, 118 insertions(+)
 create mode 100644 plugin/gomark/parser/highlight.go
 create mode 100644 plugin/gomark/parser/highlight_test.go

diff --git a/plugin/gomark/ast/ast.go b/plugin/gomark/ast/ast.go
index 9bf2fba7..fdcdd9ae 100644
--- a/plugin/gomark/ast/ast.go
+++ b/plugin/gomark/ast/ast.go
@@ -28,6 +28,7 @@ const (
 	StrikethroughNode
 	EscapingCharacterNode
 	MathNode
+	HighlightNode
 )
 
 type Node interface {
diff --git a/plugin/gomark/ast/inline.go b/plugin/gomark/ast/inline.go
index 075c6b6d..0631c747 100644
--- a/plugin/gomark/ast/inline.go
+++ b/plugin/gomark/ast/inline.go
@@ -191,3 +191,17 @@ func (*Math) Type() NodeType {
 func (n *Math) Restore() string {
 	return fmt.Sprintf("$%s$", n.Content)
 }
+
+type Highlight struct {
+	BaseInline
+
+	Content string
+}
+
+func (*Highlight) Type() NodeType {
+	return HighlightNode
+}
+
+func (n *Highlight) Restore() string {
+	return fmt.Sprintf("==%s==", n.Content)
+}
diff --git a/plugin/gomark/parser/highlight.go b/plugin/gomark/parser/highlight.go
new file mode 100644
index 00000000..37bebbf5
--- /dev/null
+++ b/plugin/gomark/parser/highlight.go
@@ -0,0 +1,58 @@
+package parser
+
+import (
+	"errors"
+
+	"github.com/usememos/memos/plugin/gomark/ast"
+	"github.com/usememos/memos/plugin/gomark/parser/tokenizer"
+)
+
+type HighlightParser struct{}
+
+func NewHighlightParser() InlineParser {
+	return &HighlightParser{}
+}
+
+func (*HighlightParser) Match(tokens []*tokenizer.Token) (int, bool) {
+	if len(tokens) < 5 {
+		return 0, false
+	}
+
+	prefixTokens := tokens[:2]
+	if prefixTokens[0].Type != prefixTokens[1].Type {
+		return 0, false
+	}
+	prefixTokenType := prefixTokens[0].Type
+	if prefixTokenType != tokenizer.EqualSign {
+		return 0, false
+	}
+
+	cursor, matched := 2, false
+	for ; cursor < len(tokens)-1; cursor++ {
+		token, nextToken := tokens[cursor], tokens[cursor+1]
+		if token.Type == tokenizer.Newline || nextToken.Type == tokenizer.Newline {
+			return 0, false
+		}
+		if token.Type == prefixTokenType && nextToken.Type == prefixTokenType {
+			matched = true
+			break
+		}
+	}
+	if !matched {
+		return 0, false
+	}
+
+	return cursor + 2, true
+}
+
+func (p *HighlightParser) Parse(tokens []*tokenizer.Token) (ast.Node, error) {
+	size, ok := p.Match(tokens)
+	if size == 0 || !ok {
+		return nil, errors.New("not matched")
+	}
+
+	contentTokens := tokens[2 : size-2]
+	return &ast.Highlight{
+		Content: tokenizer.Stringify(contentTokens),
+	}, nil
+}
diff --git a/plugin/gomark/parser/highlight_test.go b/plugin/gomark/parser/highlight_test.go
new file mode 100644
index 00000000..346b6844
--- /dev/null
+++ b/plugin/gomark/parser/highlight_test.go
@@ -0,0 +1,41 @@
+package parser
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/usememos/memos/plugin/gomark/ast"
+	"github.com/usememos/memos/plugin/gomark/parser/tokenizer"
+	"github.com/usememos/memos/plugin/gomark/restore"
+)
+
+func TestHighlightParser(t *testing.T) {
+	tests := []struct {
+		text string
+		bold ast.Node
+	}{
+		{
+			text: "==Hello world!",
+			bold: nil,
+		},
+		{
+			text: "==Hello==",
+			bold: &ast.Highlight{
+				Content: "Hello",
+			},
+		},
+		{
+			text: "==Hello world==",
+			bold: &ast.Highlight{
+				Content: "Hello world",
+			},
+		},
+	}
+
+	for _, test := range tests {
+		tokens := tokenizer.Tokenize(test.text)
+		node, _ := NewHighlightParser().Parse(tokens)
+		require.Equal(t, restore.Restore([]ast.Node{test.bold}), restore.Restore([]ast.Node{node}))
+	}
+}
diff --git a/plugin/gomark/parser/parser.go b/plugin/gomark/parser/parser.go
index bf67a46f..4f1de8a7 100644
--- a/plugin/gomark/parser/parser.go
+++ b/plugin/gomark/parser/parser.go
@@ -80,6 +80,7 @@ var defaultInlineParsers = []InlineParser{
 	NewAutoLinkParser(),
 	NewBoldParser(),
 	NewItalicParser(),
+	NewHighlightParser(),
 	NewCodeParser(),
 	NewMathParser(),
 	NewTagParser(),
diff --git a/plugin/gomark/parser/tokenizer/tokenizer.go b/plugin/gomark/parser/tokenizer/tokenizer.go
index 8322a23a..56435554 100644
--- a/plugin/gomark/parser/tokenizer/tokenizer.go
+++ b/plugin/gomark/parser/tokenizer/tokenizer.go
@@ -19,6 +19,7 @@ const (
 	LessThan           TokenType = "<"
 	GreaterThan        TokenType = ">"
 	DollarSign         TokenType = "$"
+	EqualSign          TokenType = "="
 	Backslash          TokenType = "\\"
 	Newline            TokenType = "\n"
 	Space              TokenType = " "
@@ -77,6 +78,8 @@ func Tokenize(text string) []*Token {
 			tokens = append(tokens, NewToken(Dot, "."))
 		case '$':
 			tokens = append(tokens, NewToken(DollarSign, "$"))
+		case '=':
+			tokens = append(tokens, NewToken(EqualSign, "="))
 		case '\\':
 			tokens = append(tokens, NewToken(Backslash, `\`))
 		case '\n':