forked from jaytaylor/html2text
/
html2text.go
218 lines (174 loc) · 4.67 KB
/
html2text.go
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package html2text
import (
"bytes"
"io"
"regexp"
"strings"
"unicode"
"golang.org/x/net/html"
"golang.org/x/net/html/atom"
)
var (
spacingRe = regexp.MustCompile(`[ \r\n\t]+`)
newlineRe = regexp.MustCompile(`\n\n+`)
)
type textifyTraverseCtx struct {
Buf bytes.Buffer
endsWithSpace bool
PreviousNode *html.Node
}
func (ctx *textifyTraverseCtx) setPreviousNode(previous *html.Node) {
ctx.PreviousNode = previous
}
func (ctx *textifyTraverseCtx) Traverse(node *html.Node) error {
defer ctx.setPreviousNode(node)
switch node.Type {
default:
return ctx.TraverseChildren(node)
case html.TextNode:
//data := strings.Trim(spacingRe.ReplaceAllString(node.Data, " "), " ")
data := spacingRe.ReplaceAllString(node.Data, " ")
return ctx.Emit(data)
case html.ElementNode:
switch node.DataAtom {
case atom.Br:
return ctx.Emit("\n")
case atom.Td:
if ctx.PreviousNode.DataAtom != atom.Tr {
ctx.Emit(" ")
}
return ctx.TraverseChildren(node)
case atom.H1, atom.H2, atom.H3:
subCtx := textifyTraverseCtx{}
if err := subCtx.TraverseChildren(node); err != nil {
return err
}
str := subCtx.Buf.String()
dividerLen := 0
for _, line := range strings.Split(str, "\n") {
if lineLen := len([]rune(line)); lineLen-1 > dividerLen {
dividerLen = lineLen - 1
}
}
divider := ""
if node.DataAtom == atom.H1 {
divider = strings.Repeat("*", dividerLen)
} else {
divider = strings.Repeat("-", dividerLen)
}
if node.DataAtom == atom.H3 {
return ctx.Emit("\n\n" + str + "\n" + divider + "\n\n")
}
return ctx.Emit("\n\n" + divider + "\n" + str + "\n" + divider + "\n\n")
case atom.Li:
if err := ctx.Emit("* "); err != nil {
return err
}
if err := ctx.TraverseChildren(node); err != nil {
return err
}
return ctx.Emit("\n")
case atom.A:
child := node.FirstChild
hasSingleChild := child != nil && child == node.LastChild
// If image is the only child, take its alt text as the link text
if hasSingleChild && child.DataAtom == atom.Img {
if altText := getAttrVal(child, "alt"); altText != "" {
ctx.Emit(altText)
}
} else if err := ctx.TraverseChildren(node); err != nil {
return err
}
// If there's a single inner text node, then get its text. We do not
// want to output the link if it matches the inner text. This is
// imperfect - we really want to compare the link to the text that
// was output by TraverseChildren(), but it's not easily available.
innerText := ""
if hasSingleChild && child.Type == html.TextNode {
innerText = node.FirstChild.Data
}
hrefLink := ""
if attrVal := getAttrVal(node, "href"); attrVal != "" {
attrVal = ctx.NormalizeHrefLink(attrVal)
if attrVal != "" && attrVal != innerText {
hrefLink = " ( " + attrVal + " )"
}
}
return ctx.Emit(hrefLink)
case atom.P, atom.Ul, atom.Table:
if err := ctx.Emit("\n\n"); err != nil {
return err
}
if err := ctx.TraverseChildren(node); err != nil {
return err
}
return ctx.Emit("\n\n")
case atom.Tr:
if err := ctx.TraverseChildren(node); err != nil {
return err
}
return ctx.Emit("\n")
case atom.Style, atom.Script, atom.Head:
// Ignore the subtree
return nil
default:
return ctx.TraverseChildren(node)
}
}
}
func (ctx *textifyTraverseCtx) TraverseChildren(node *html.Node) error {
for c := node.FirstChild; c != nil; c = c.NextSibling {
if err := ctx.Traverse(c); err != nil {
return err
}
}
return nil
}
func (ctx *textifyTraverseCtx) Emit(data string) error {
if len(data) == 0 {
return nil
}
runes := []rune(data)
//startsWithSpace := unicode.IsSpace(runes[0])
// if !startsWithSpace && !ctx.endsWithSpace {
// ctx.Buf.WriteByte(' ')
// }
ctx.endsWithSpace = unicode.IsSpace(runes[len(runes)-1])
_, err := ctx.Buf.WriteString(data)
return err
}
func (ctx *textifyTraverseCtx) NormalizeHrefLink(link string) string {
link = strings.TrimSpace(link)
link = strings.TrimPrefix(link, "mailto:")
return link
}
func getAttrVal(node *html.Node, attrName string) string {
for _, attr := range node.Attr {
if attr.Key == attrName {
return attr.Val
}
}
return ""
}
func FromReader(reader io.Reader) (string, error) {
doc, err := html.Parse(reader)
if err != nil {
return "", err
}
ctx := textifyTraverseCtx{
Buf: bytes.Buffer{},
}
if err = ctx.Traverse(doc); err != nil {
return "", err
}
text := strings.TrimSpace(newlineRe.ReplaceAllString(
strings.Replace(ctx.Buf.String(), "\n ", "\n", -1), "\n\n"))
return text, nil
}
func FromString(input string) (string, error) {
text, err := FromReader(strings.NewReader(input))
if err != nil {
return "", err
}
return text, nil
}