Move elements and attributes into html package (#52)

This makes it easier to use dot-imports.

Also updated the readme and examples with new usage, and move the `Classes` helper into the `components` package.

1 files changed, 37 insertions, 0 deletions

diff --git a/components/attributes.go b/components/attributes.go
new file mode 100644
index 0000000..dc7ef9b
--- /dev/null
+++ b/components/attributes.go
@@ -0,0 +1,37 @@
+package components
+
+import (
+	"io"
+	"sort"
+	"strings"
+
+	g "github.com/maragudk/gomponents"
+	"github.com/maragudk/gomponents/html"
+)
+
+// Classes is a map of strings to booleans, which Renders to an attribute with name "class".
+// The attribute value is a sorted, space-separated string of all the map keys,
+// for which the corresponding map value is true.
+type Classes map[string]bool
+
+func (c Classes) Render(w io.Writer) error {
+	var included []string
+	for c, include := range c {
+		if include {
+			included = append(included, c)
+		}
+	}
+	sort.Strings(included)
+	return html.Class(strings.Join(included, " ")).Render(w)
+}
+
+func (c Classes) Type() g.NodeType {
+	return g.AttributeType
+}
+
+// String satisfies fmt.Stringer.
+func (c Classes) String() string {
+	var b strings.Builder
+	_ = c.Render(&b)
+	return b.String()
+}