feat: implement code block parser (#1727)

plugin/gomark/parser/code_block.go

@@ -0,0 +1,52 @@
+package parser
+
+import "github.com/usememos/memos/plugin/gomark/parser/tokenizer"
+
+type CodeBlockParser struct {
+	Language string
+	Content  string
+}
+
+func NewCodeBlockParser() *CodeBlockParser {
+	return &CodeBlockParser{}
+}
+
+func (*CodeBlockParser) Match(tokens []*tokenizer.Token) *CodeBlockParser {
+	if len(tokens) < 9 {
+		return nil
+	}
+
+	if tokens[0].Type != tokenizer.Backtick || tokens[1].Type != tokenizer.Backtick || tokens[2].Type != tokenizer.Backtick {
+		return nil
+	}
+	if tokens[3].Type != tokenizer.Newline && tokens[4].Type != tokenizer.Newline {
+		return nil
+	}
+	cursor, language := 4, ""
+	if tokens[3].Type != tokenizer.Newline {
+		language = tokens[3].Value
+		cursor = 5
+	}
+
+	content, matched := "", false
+	for ; cursor < len(tokens)-3; cursor++ {
+		if tokens[cursor].Type == tokenizer.Newline && tokens[cursor+1].Type == tokenizer.Backtick && tokens[cursor+2].Type == tokenizer.Backtick && tokens[cursor+3].Type == tokenizer.Backtick {
+			if cursor+3 == len(tokens)-1 {
+				matched = true
+				break
+			} else if tokens[cursor+4].Type == tokenizer.Newline {
+				matched = true
+				break
+			}
+		}
+		content += tokens[cursor].Value
+	}
+	if !matched {
+		return nil
+	}
+
+	return &CodeBlockParser{
+		Language: language,
+		Content:  content,
+	}
+}