feat(markdown): ast supports modifier

1 files changed, 104 insertions, 0 deletions

diff --git a/mardown/ast_modifier.go b/mardown/ast_modifier.go
new file mode 100644
index 0000000..e505aef
--- /dev/null
+++ b/mardown/ast_modifier.go
@@ -0,0 +1,104 @@
+package mardown
+
+import (
+	"errors"
+	"fmt"
+	"html/template"
+)
+
+var (
+	ErrInternalError         = errors.New("internal error")
+	ErrInvalidModifier       = errors.Join(ErrInvalidParagraph, errors.New("invalid modifier organization"))
+	ErrInvalidTypeInModifier = errors.Join(ErrInvalidParagraph, errors.New("invalid type in modifier"))
+)
+
+type modifierTag string
+
+const (
+	boldTag modifierTag = "b"
+	emTag   modifierTag = "em"
+	codeTag modifierTag = "code"
+)
+
+type astModifier struct {
+	symbols string
+	tag     modifierTag
+	content []block
+	parent  *astModifier
+}
+
+func (a *astModifier) Eval() (template.HTML, error) {
+	var content template.HTML
+	for _, c := range a.content {
+		ct, err := c.Eval()
+		if err != nil {
+			return "", err
+		}
+		content += ct
+	}
+	return template.HTML(fmt.Sprintf("<%s>%s</%s>", a.tag, content, a.tag)), nil
+}
+
+func modifier(lxs lexers) (*astModifier, error) {
+	current := lxs.Current().Value
+	mod := modifierDetect(current)
+	modInside := mod
+	if len(mod.content) > 0 {
+		var ok bool
+		modInside, ok = mod.content[0].(*astModifier)
+		if modInside.content != nil && !ok {
+			return nil, ErrInternalError
+		}
+		// getting the last modifier
+		for len(modInside.content) > 0 {
+			modInside, ok = modInside.content[0].(*astModifier)
+			if modInside.content != nil && !ok {
+				return nil, ErrInternalError
+			}
+		}
+	}
+	n := len(modInside.symbols)
+	var s string
+	for lxs.Next() {
+		switch lxs.Current().Type {
+		case lexerLiteral:
+			s += lxs.Current().Value
+		case lexerModifier:
+			if len(lxs.Current().Value) < n {
+				return nil, ErrInvalidModifier
+			}
+			if lxs.Current().Value[:n] != modInside.symbols {
+				return nil, ErrInvalidModifier
+			}
+			modInside.content = append(modInside.content, astLiteral(s))
+			s = ""
+			modInside = modInside.parent
+		default:
+			return nil, ErrInvalidTypeInModifier
+		}
+	}
+	return mod, nil
+}
+
+func modifierDetect(val string) *astModifier {
+	mod := new(astModifier)
+	if len(val) == 1 {
+		mod.symbols = val
+		if val == "`" {
+			mod.tag = codeTag
+		} else {
+			mod.tag = emTag
+		}
+		return mod
+	}
+	if val[:2] == "**" || val[:2] == "__" {
+		mod.symbols = val
+		mod.tag = boldTag
+	} else {
+		mod = modifierDetect(val[:1])
+		next := modifierDetect(val[1:])
+		next.parent = mod
+		mod.content = append(mod.content, next)
+	}
+	return mod
+}