From b1f6bde29f1e4a150a762beec8a59c33abd441fd Mon Sep 17 00:00:00 2001
From: "Gustavo \"Guz\" L de Mello" <contact@guz.one>
Date: Fri, 16 May 2025 15:17:56 -0300
Subject: [PATCH] feat(ipub,ast): xml.Unmarshaller implementation for Elements

---
 ipub/ast/ast.go     | 37 +++++++++++++++++++++++++++++++++++++
 ipub/ast/content.go |  4 ++++
 ipub/ast/section.go |  3 +++
 3 files changed, 44 insertions(+)

diff --git a/ipub/ast/ast.go b/ipub/ast/ast.go
index 7939d33..c04ebad 100644
--- a/ipub/ast/ast.go
+++ b/ipub/ast/ast.go
@@ -34,6 +34,8 @@ type Element interface {
 	InsertBefore(self, v1, insertee Element)
 	InsertAfter(self, v1, insertee Element)
 
+	xml.Unmarshaler
+}
 
 type BaseElement struct {
 	next       Element
@@ -178,6 +180,41 @@ func (e *BaseElement) InsertBefore(self, v1, insertee Element) {
 	}
 }
 
+func (e *BaseElement) UnmarshalChildren(self Element, d *xml.Decoder, start xml.StartElement) error {
+	for {
+		token, err := d.Token()
+		if err != nil {
+			return err
+		}
+		if err == io.EOF {
+			return nil
+		}
+
+		switch tt := token.(type) {
+		case xml.StartElement:
+			i := slices.IndexFunc(tt.Attr, func(a xml.Attr) bool {
+				return a.Name.Local == "data-ipub-element"
+			})
+			if i == -1 {
+				return fmt.Errorf("element kind not specified")
+			}
+
+			kind := tt.Attr[i].Value
+			kt, ok := elementKindList[ElementKind(kind)]
+			if !ok {
+				return fmt.Errorf("element kind not found")
+			}
+
+			err := d.DecodeElement(kt, &tt)
+			if err != nil && err != io.EOF {
+				return err
+			}
+
+			e.AppendChild(self, kt)
+		}
+	}
+}
+
 func ensureIsolated(e Element) {
 	if p := e.Parent(); p != nil {
 		p.RemoveChild(p, e)
diff --git a/ipub/ast/content.go b/ipub/ast/content.go
index 4013265..4c3e336 100644
--- a/ipub/ast/content.go
+++ b/ipub/ast/content.go
@@ -15,3 +15,7 @@ func (n *Content) Kind() ElementKind {
 	return KindContent
 }
 
+func (n *Content) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+	return n.UnmarshalChildren(n, d, start)
+}
+
diff --git a/ipub/ast/section.go b/ipub/ast/section.go
index 10d5228..d2223a5 100644
--- a/ipub/ast/section.go
+++ b/ipub/ast/section.go
@@ -18,3 +18,6 @@ func (n *Body) Kind() ElementKind {
 	return KindBody
 }
 
+func (n *Body) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+	return n.UnmarshalChildren(n, d, start)
+}