feat(markdown): simple lexer

1 files changed, 72 insertions, 0 deletions

diff --git a/mardown/lexer.go b/mardown/lexer.go
new file mode 100644
index 0000000..a7b364d
--- /dev/null
+++ b/mardown/lexer.go
@@ -0,0 +1,72 @@
+package mardown
+
+import "fmt"
+
+type lexerType string
+
+const (
+	lexerBreak lexerType = "break"
+
+	lexerModifier lexerType = "modifier"
+	lexerCode     lexerType = "code"
+	lexerHeader   lexerType = "header"
+	lexerQuote    lexerType = "quote"
+
+	lexerLiteral lexerType = "literal"
+)
+
+type lexer struct {
+	Type  lexerType
+	Value string
+}
+
+func (l *lexer) String() string {
+	return fmt.Sprintf("%s(%s)", l.Type, l.Value)
+}
+
+type lexers struct {
+	current int
+	lexers  []lexer
+}
+
+func (l *lexers) Next() lexer {
+	l.current++
+	return l.lexers[l.current]
+}
+
+func (l *lexers) Finished() bool {
+	return l.current+1 >= len(l.lexers)
+}
+
+func lex(s string) *lexers {
+	lxs := &lexers{current: -1}
+	var lexs []lexer
+	var currentType lexerType
+	var previous string
+	fn := func(c rune, t lexerType) {
+		if currentType != t && len(previous) > 0 {
+			lexs = append(lexs, lexer{Type: currentType, Value: previous})
+			previous = ""
+		}
+		currentType = t
+		previous += string(c)
+	}
+	for _, c := range []rune(s) {
+		switch c {
+		case '*', '_':
+			fn(c, lexerModifier)
+		case '`':
+			fn(c, lexerCode)
+		case '\n':
+			fn(c, lexerBreak)
+		case '#':
+			fn(c, lexerHeader)
+		case '>':
+			fn(c, lexerQuote)
+		default:
+			fn(c, lexerLiteral)
+		}
+	}
+	lxs.lexers = lexs
+	return lxs
+}