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exer5.7.go
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exer5.7.go
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package main
import (
"fmt"
"io"
"os"
"log"
"strings"
"golang.org/x/net/html"
)
var depth int
type PrettyPrinter struct{
w io.Writer
err error
}
func NewPrettyPrinter() PrettyPrinter{
return PrettyPrinter{}
}
func (pp PrettyPrinter) Pretty(w io.Writer, n *html.Node) error {
pp.w = w
pp.err = nil
pp.forEachNode(n, pp.start, pp.end)
return pp.Err()
}
func (pp PrettyPrinter) Err() error {
return pp.err
}
func (pp PrettyPrinter) forEachNode(n *html.Node, pre, post func (n *html.Node)) {
if pre != nil {
pre(n)
}
if pp.Err() != nil {
return
}
for c := n.FirstChild; c != nil; c = c.NextSibling {
pp.forEachNode(c, pre, post)
}
if post != nil {
post(n)
}
if pp.Err() != nil {
return
}
}
func (pp PrettyPrinter) printf(format string, args ...interface{}){
_, err := fmt.Fprintf(pp.w, format, args...)
pp.err = err
}
func (pp PrettyPrinter) startElement(n *html.Node) {
end := ">"
if n.FirstChild == nil {
end = "/>"
}
attrs := make([]string, 0, len(n.Attr))
for _, a := range n.Attr {
attrs = append(attrs, fmt.Sprintf(`%s="%s"`, a.Key, a.Val))
}
attrStr := ""
if len(n.Attr) > 0 {
attrStr = " " + strings.Join(attrs, " ")
}
name := n.Data
pp.printf("%*s<%s%s%s\n", depth*2, "", name, attrStr, end)
depth++
}
func (pp PrettyPrinter) endElement(n *html.Node){
depth--
if n.FirstChild == nil {
return
}
pp.printf("%*s%s\n", depth*2, "", n.Data)
}
func (pp PrettyPrinter) startText(n *html.Node){
text := strings.TrimSpace(n.Data)
if len(text) == 0 {
return
}
pp.printf("%*s%s\n", depth*2, "", n.Data)
}
func (pp PrettyPrinter) startComment(n *html.Node){
pp.printf("<!--%s-->\n", n.Data)
}
func (pp PrettyPrinter) start(n *html.Node){
switch n.Type {
case html.ElementNode:
pp.startElement(n)
case html.TextNode:
pp.startText(n)
case html.CommentNode:
pp.startComment(n)
}
}
func (pp PrettyPrinter) end(n *html.Node){
if n.Type == html.ElementNode {
pp.endElement(n)
}
}
func main(){
doc, err := html.Parse(os.Stdin)
if err != nil {
log.Fatal(err)
}
pp := NewPrettyPrinter()
pp.Pretty(os.Stdout, doc)
}