Slightly redesigned types

hatmill.go

@@ -1,4 +1,4 @@
-package main
+package hatmill
 
 import "fmt"
 import "io"
@@ -8,34 +8,15 @@ import "strings"
 // Html is either Element or Text
 type Html interface {
 	io.WriterTo
-  // isHtml is a non-functional marker to differentiate Html from interface{}
+
+	// isHtml is a no-op method to prevent external Html implementations, because
+	// Go doesn't have sum types.
 	isHtml()
 }
 
-func Reader() io.Reader {
-  // TODO in-order traversal of HTML tree to spit out bytes
-  return nil
-}
-
-func String() string {
-  panic("this could be trivially implemented with a Reader and a bytes.Buffer")
-}
-
-type Attrib struct {
-  Key string
-  Value string
-}
-
-type element struct {
-  tagName string
-  attribs []Attrib
-  empty bool
-  children []Html
-}
-
-// writeTo attempts to write the strings in ss to w, incrementing n by the
+// writeStringsTo attempts to write the strings in ss to w, incrementing n by the
 // number of bytes written.
-func writeTo(w io.Writer, n *int64, ss ...string) error {
+func writeStringsTo(w io.Writer, n *int64, ss ...string) error {
 	for _, s := range ss {
 		nCurr, err := io.WriteString(w, s)
 		*n += int64(nCurr)
@@ -46,25 +27,37 @@ func writeTo(w io.Writer, n *int64, ss ...string) error {
 	return nil
 }
 
+type Attrib struct {
+	Key   string
+	Value string
+}
+
 func (a Attrib) WriteTo(w io.Writer) (n int64, err error) {
-  err = writeTo(w, &n, a.Key)
+	err = writeStringsTo(w, &n, a.Key)
 	if err != nil {
 		return
 	}
 	if a.Value != "" {
-    err = writeTo(w, &n, "='", a.Value, "'")
+		err = writeStringsTo(w, &n, "='", a.Value, "'")
 	}
 	return
 }
 
-func (e *element) WriteTo(w io.Writer) (n int64, err error) {
-  err = writeTo(w, &n, "<", e.tagName)
+type EmptyElement struct {
+	TagName string
+	Attribs []Attrib
+}
+
+func (EmptyElement) isHtml() {}
+
+func (e EmptyElement) WriteTo(w io.Writer) (n int64, err error) {
+	err = writeStringsTo(w, &n, "<", e.TagName)
 	if err != nil {
 		return
 	}
 
-  for _, attrib := range e.attribs {
-    err = writeTo(w, &n, " ")
+	for _, attrib := range e.Attribs {
+		err = writeStringsTo(w, &n, " ")
 		if err != nil {
 			return
 		}
@@ -77,13 +70,24 @@ func (e *element) WriteTo(w io.Writer) (n int64, err error) {
 		}
 	}
 
-  err = writeTo(w, &n, ">")
+	err = writeStringsTo(w, &n, ">")
+	return
+}
+
+type ParentElement struct {
+	EmptyElement
+	Children []Html
+}
+
+func (e *ParentElement) isHtml() {}
+
+func (e *ParentElement) WriteTo(w io.Writer) (n int64, err error) {
+	n, err = e.EmptyElement.WriteTo(w)
 	if err != nil {
 		return
 	}
 
-  if !e.empty {
-    for _, child := range e.children {
+	for _, child := range e.Children {
 		var nCurr int64
 		nCurr, err = child.WriteTo(w)
 		n += int64(nCurr)
@@ -92,67 +96,48 @@ func (e *element) WriteTo(w io.Writer) (n int64, err error) {
 		}
 	}
 
-    err = writeTo(w, &n, "</", e.tagName, ">")
-  }
+	err = writeStringsTo(w, &n, "</", e.TagName, ">")
 	return
 }
 
-func (*element) isHtml() {}
+type Text string
 
-func emptyElement(tagName string, attribs []Attrib) Html {
-  return &element{
-    tagName: tagName,
-    attribs: attribs,
-    empty: true,
-  }
-}
+func (Text) isHtml() {}
 
-func elementFunc(tagName string, attribs []Attrib) func(...Html) Html {
-  return func(children ...Html) Html {
-    return &element{
-      tagName: tagName,
-      attribs: attribs,
-      children: children,
-      empty: false,
-    }
-  }
-}
-
-type text string
-
-func Text(s string) Html {
-  return text(s)
-}
-
-func (text) isHtml() {}
-
-func (t text) WriteTo(w io.Writer) (n int64, err error) {
-  err = writeTo(w, &n, string(t))
+func (t Text) WriteTo(w io.Writer) (n int64, err error) {
+	err = writeStringsTo(w, &n, string(t))
 	return
 }
 
-type rText struct {
+type RText struct {
 	io.Reader
 }
 
-func RText(r io.Reader) Html {
-  return rText{Reader: r}
-}
+func (RText) isHtml() {}
 
-func (rText) isHtml() {}
-
-func (rt rText) WriteTo(w io.Writer) (n int64, err error) {
+func (rt RText) WriteTo(w io.Writer) (n int64, err error) {
 	return io.Copy(w, rt.Reader)
 }
 
 // Html5 functions
 
-func Div(attribs ...Attrib) func(children ...Html) Html {
-  return elementFunc("div", attribs)
+func Div(attribs ...Attrib) func(children ...Html) *ParentElement {
+	return func(children ...Html) *ParentElement {
+		return &ParentElement{
+			EmptyElement: EmptyElement{
+				TagName: "div",
+				Attribs: attribs,
+			},
+			Children: children,
+		}
+	}
 }
 
-func Img(attribs ...Attrib) Html {
-  return emptyElement("img", attribs)
+func Img(attribs ...Attrib) EmptyElement {
+	return EmptyElement{
+		TagName: "img",
+		Attribs: attribs,
+	}
 }
 
 func Id(id string) Attrib {
@@ -163,21 +148,37 @@ func Id(id string) Attrib {
 }
 
 func Disabled() Attrib {
-  return Attrib {
+	return Attrib{
 		Key: "disabled",
 	}
 }
 
-func main() {
+// WriteDocument writes an HTML5 doctype declaration, followed by root.
+// root should probably be an <html> element.
+func WriteDocument(w io.Writer, root *ParentElement) (n int64, err error) {
+	err = writeStringsTo(w, &n, "<!DOCTYPE html>")
+	if err != nil {
+		return
+	}
+
+	var nroot int64
+	nroot, err = root.WriteTo(w)
+	n += nroot
+	return
+}
+
+func Main() {
 	var page = Div(Disabled(), Id("container"))(
 		Img(Id("profile-photo")),
 		Text("hello"),
 		Img(Disabled()),
-    RText(strings.NewReader("goodbye!")),
+		RText{strings.NewReader("goodbye!")},
 	)
 
-  n, err := page.WriteTo(os.Stdout)
+	n, err := WriteDocument(os.Stdout, page)
 	fmt.Println()
 	fmt.Println(n)
+	if err != nil {
 		fmt.Println(err)
+	}
 }