lib: move package "net/html" to "lib/html"

Putting "html" under "net" package make no sense.
Another reason is to make the package flat under "lib/" directory.

1 files changed, 93 insertions, 0 deletions

diff --git a/lib/html/node_iterator.go b/lib/html/node_iterator.go
new file mode 100644
index 00000000..ca1819d4
--- /dev/null
+++ b/lib/html/node_iterator.go
@@ -0,0 +1,93 @@
+// Copyright 2020, Shulhan <ms@kilabit.info>. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package html
+
+import (
+	"io"
+	"strings"
+
+	"golang.org/x/net/html"
+)
+
+// NodeIterator simplify iterating each node from top to bottom.
+type NodeIterator struct {
+	current  *Node
+	previous *Node
+	next     *html.Node
+	hasNext  bool
+}
+
+// Parse returns the NodeIterator to iterate through HTML tree.
+func Parse(r io.Reader) (iter *NodeIterator, err error) {
+	node, err := html.Parse(r)
+	if err != nil {
+		return nil, err
+	}
+	iter = &NodeIterator{
+		current:  NewNode(node),
+		previous: NewNode(nil),
+	}
+	return iter, nil
+}
+
+// Next return the first child or the next sibling of current node.
+// If no more node in the tree, it will return nil.
+func (iter *NodeIterator) Next() *Node {
+	if iter.hasNext {
+		iter.current.Node = iter.next
+		iter.next = nil
+		iter.hasNext = false
+		return iter.current
+	}
+	if iter.current.Node == nil {
+		return nil
+	}
+
+	for {
+		switch {
+		case iter.current.FirstChild != nil &&
+			iter.current.FirstChild != iter.previous.Node &&
+			iter.current.LastChild != iter.previous.Node:
+			iter.current.Node = iter.current.FirstChild
+		case iter.current.NextSibling != nil:
+			iter.current.Node = iter.current.NextSibling
+		default:
+			iter.previous.Node = iter.current.Node
+			iter.current.Node = iter.current.Parent
+		}
+		if iter.current.Node == nil {
+			return nil
+		}
+
+		// Skip empty text node.
+		if iter.current.Type != html.TextNode {
+			break
+		}
+		text := strings.TrimSpace(iter.current.Data)
+		if len(text) != 0 {
+			break
+		}
+	}
+	return iter.current
+}
+
+// SetNext set the node for iteration to Node "el" only if its not nil.
+func (iter *NodeIterator) SetNext(el *Node) {
+	if el == nil {
+		return
+	}
+	iter.hasNext = true
+	iter.next = el.Node
+}
+
+// SetNextNode set the next iteration node to html.Node "el" only if its not
+// nil.
+func (iter *NodeIterator) SetNextNode(el *html.Node) {
+	if el == nil {
+		return
+	}
+	iter.hasNext = true
+	iter.next = el
+}