1 files changed, 132 insertions, 0 deletions
diff --git a/markdown/lexer.go b/markdown/lexer.go
new file mode 100644
index 0000000..a02ec54
--- /dev/null
+++ b/markdown/lexer.go
@@ -0,0 +1,132 @@
+package markdown
+
+import "fmt"
+
+type lexerType string
+
+const (
+	lexerBreak lexerType = "break"
+
+	lexerModifier lexerType = "modifier"
+
+	lexerCode lexerType = "code"
+
+	lexerHeader lexerType = "header"
+	lexerQuote  lexerType = "quote"
+	lexerList   lexerType = "list"
+
+	lexerExternal lexerType = "external"
+
+	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() bool {
+	l.current++
+	return !l.Finished()
+}
+
+func (l *lexers) Current() lexer {
+	return l.lexers[l.current]
+}
+
+func (l *lexers) Finished() bool {
+	return l.current >= len(l.lexers)
+}
+
+func (l *lexers) Before() bool {
+	l.current--
+	return l.current >= 0 && !l.Finished()
+}
+
+func (l *lexers) String() string {
+	s := "Lexers["
+	for _, l := range l.lexers {
+		s += l.String() + " "
+	}
+	return s + "]"
+}
+
+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)
+	}
+	newLine := true
+	literalNext := false
+	runes := []rune(s)
+	for i, c := range runes {
+		if literalNext {
+			fn(c, lexerLiteral)
+			literalNext = false
+			continue
+		}
+		if c == '\\' {
+			literalNext = true
+			continue
+		}
+		switch c {
+		case '*', '_':
+			if c == '*' && newLine && i < len(runes)-1 && runes[i+1] == ' ' {
+				fn(c, lexerList)
+			} else {
+				if (currentType != lexerModifier && len(previous) > 0) ||
+					(len(previous) > 0 && []rune(previous)[0] != c) ||
+					len(previous) >= 3 {
+					lexs = append(lexs, lexer{Type: currentType, Value: previous})
+					previous = ""
+				}
+				currentType = lexerModifier
+				previous += string(c)
+			}
+			newLine = false
+		case '`':
+			newLine = false
+			fn(c, lexerCode)
+		case '\n':
+			newLine = true
+			fn(c, lexerBreak)
+		case '#':
+			newLine = false
+			fn(c, lexerHeader)
+		case '>':
+			newLine = false
+			fn(c, lexerQuote)
+		case '[', ']', '(', ')', '!':
+			newLine = false
+			fn(c, lexerExternal)
+		case '-', '1', '2', '3', '4', '5', '6', '7', '8', '9', '.':
+			newLine = false
+			fn(c, lexerList)
+		default:
+			newLine = false
+			fn(c, lexerLiteral)
+		}
+	}
+	if len(previous) > 0 {
+		lexs = append(lexs, lexer{Type: currentType, Value: previous})
+	}
+	lxs.lexers = lexs
+	return lxs
+}