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cleanup.go
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cleanup.go
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package ebook
// Copyright 2022 Hal Canary
// Use of this program is governed by the file LICENSE.
import (
"net/url"
"regexp"
"strings"
"github.com/HalCanary/facility/dom"
)
type Node = dom.Node
// Clean up a HTML fragment.
func Cleanup(node *Node) *Node {
node = cleanupStyle(node)
cleanupTables(node)
cleanupCenter(node)
cleanupDoubled(node)
return node
}
var whiteSpaceOnly = regexp.MustCompile("^\\pZ*$")
var spaceOnly = regexp.MustCompile("^\\pZs*$")
var semiRegexp = regexp.MustCompile("\\s*;\\s*")
func styler(v string) string {
var result []string
for _, term := range semiRegexp.Split(v, -1) {
switch term {
case "background-attachment: initial",
"background-clip: initial",
"background-image: initial",
"background-origin: initial",
"background-position: initial",
"background-repeat: initial",
"background-size: initial",
"break-before: page",
"margin-bottom: 0in",
"background: transparent",
"font-family: Arial",
"font-family: Segoe UI",
"font-family: Segoe UI, sans-serif",
"font-family: Segoe UI, serif",
"font-style: normal",
"font-variant: normal",
"font-weight: normal",
"margin-bottom: 0",
"page-break-before: always",
"text-decoration: none",
"":
// do nothing
case "font-family: Courier New, monospace":
result = append(result, "font-family:monospace")
default:
result = append(result, term)
}
}
return strings.Join(result, ";")
}
func cleanupCenter(node *Node) {
if node != nil && node.Type == dom.ElementNode {
if node.Data == "center" {
node.Data = "div"
if i := getNodeAttributeIndex(node, "class"); i >= 0 {
node.Attr[i].Val = node.Attr[i].Val + " mid"
} else {
dom.AddAttribute(node, "class", "mid")
}
}
if node.Data == "big" {
node.Data = "span"
dom.AddAttribute(node, "style", "font-size:larger")
}
c := node.FirstChild
for c != nil {
next := c.NextSibling
cleanupCenter(c)
c = next
}
}
}
func cleanupDoubled(node *Node) {
if node.Type == dom.ElementNode {
data := node.Data
for c := node.FirstChild; c != nil; {
next := c.NextSibling
cleanupDoubled(c)
if data == "ul" && c.Type == dom.ElementNode && c.Data == data {
dom.Remove(c)
for c2 := c.FirstChild; c2 != nil; {
n2 := c2.NextSibling
c.RemoveChild(c2)
node.InsertBefore(c2, next)
c2 = n2
}
}
c = next
}
}
}
func cleanupTables(node *Node) {
if node != nil && node.Type == dom.ElementNode {
if i := getNodeAttributeIndex(node, "border"); i >= 0 {
v := node.Attr[i].Val
if v != "1" && v != "" {
if v == "none" {
node.Attr[i].Val = ""
} else {
node.Attr[i].Val = "1"
}
}
}
c := node.FirstChild
for c != nil {
next := c.NextSibling
cleanupTables(c)
c = next
}
if node.FirstChild == nil {
switch node.Data {
case "tbody", "dd", "dl":
dom.Remove(node)
}
}
}
}
func resolve(oldUrl string, ref *url.URL) string {
if u, _ := url.Parse(oldUrl); u != nil {
return ref.ResolveReference(u).String()
}
return oldUrl
}
// Resolve all links in the tree, relative to `ref`.
func ResolveLinks(node *Node, ref *url.URL) *Node {
if node != nil && node.Type == dom.ElementNode {
if attr := getNodeAttribute(node, "href"); attr != nil {
attr.Val = resolve(attr.Val, ref)
}
if attr := getNodeAttribute(node, "src"); attr != nil {
attr.Val = resolve(attr.Val, ref)
}
for c := node.FirstChild; c != nil; c = c.NextSibling {
ResolveLinks(c, ref)
}
}
return node
}
func cleanupStyle(node *Node) *Node {
if node != nil {
switch node.Type {
case dom.TextNode:
if node.Data != "" && whiteSpaceOnly.MatchString(node.Data) {
if !spaceOnly.MatchString(node.Data) {
node.Data = "\n"
}
}
case dom.ElementNode:
if node.Data == "p" {
if isWhitespaceOnly(node) {
dom.Remove(node)
return nil
}
if i := getNodeAttributeIndex(node, "align"); i >= 0 {
switch node.Attr[i].Val {
case "left":
node.Attr = append(node.Attr[:i], node.Attr[i+1:]...)
}
}
}
if i := getNodeAttributeIndex(node, "style"); i >= 0 {
v := styler(node.Attr[i].Val)
if v == "" {
node.Attr = append(node.Attr[:i], node.Attr[i+1:]...)
} else {
node.Attr[i].Val = v
}
}
child := node.FirstChild
for child != nil {
next := child.NextSibling
cleanupStyle(child)
child = next
}
if node.Data == "span" && len(node.Attr) == 0 {
if parent := node.Parent; parent != nil {
nextSibling := node.NextSibling
child := node.FirstChild
for child != nil {
next := child.NextSibling
node.RemoveChild(child)
parent.InsertBefore(child, nextSibling)
child = next
}
parent.RemoveChild(node)
}
}
if node.Data == "img" {
if i := getNodeAttributeIndex(node, "src"); i >= 0 {
if node.Attr[i].Val == "" {
node.Attr[i].Val = "data:null;,"
}
} else {
node.Attr = append(node.Attr, dom.Attribute{Key: "src", Val: "data:null;,"})
}
}
if node.Data == "script" {
dom.Remove(node)
return nil
}
if node.Data == "noscript" {
node.Data = "span"
}
}
}
return node
}
func countChildren(node *Node) int {
var count int = 0
if node != nil {
for child := node.FirstChild; child != nil; child = child.NextSibling {
count++
}
}
return count
}
func getNodeAttributeIndex(node *Node, key string) int {
if node != nil {
for idx, attr := range node.Attr {
if attr.Namespace == "" && attr.Key == key {
return idx
}
}
}
return -1
}
func getNodeAttribute(node *Node, key string) *dom.Attribute {
if node != nil {
for idx, attr := range node.Attr {
if attr.Namespace == "" && attr.Key == key {
return &node.Attr[idx]
}
}
}
return nil
}
func isWhitespaceOnly(node *Node) bool {
if node != nil {
switch node.Type {
case dom.TextNode:
return whiteSpaceOnly.MatchString(node.Data)
case dom.ElementNode:
for child := node.FirstChild; child != nil; child = child.NextSibling {
if !isWhitespaceOnly(child) {
return false
}
}
}
}
return true
}