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https://salsa.debian.org/mdosch/feed-to-muc.git
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535 lines
13 KiB
Go
535 lines
13 KiB
Go
package html2text
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import (
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"bytes"
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"io"
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"regexp"
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"strings"
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"unicode"
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"github.com/olekukonko/tablewriter"
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"github.com/ssor/bom"
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"golang.org/x/net/html"
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"golang.org/x/net/html/atom"
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)
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// Options provide toggles and overrides to control specific rendering behaviors.
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type Options struct {
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PrettyTables bool // Turns on pretty ASCII rendering for table elements.
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PrettyTablesOptions *PrettyTablesOptions // Configures pretty ASCII rendering for table elements.
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OmitLinks bool // Turns on omitting links
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}
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// PrettyTablesOptions overrides tablewriter behaviors
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type PrettyTablesOptions struct {
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AutoFormatHeader bool
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AutoWrapText bool
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ReflowDuringAutoWrap bool
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ColWidth int
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ColumnSeparator string
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RowSeparator string
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CenterSeparator string
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HeaderAlignment int
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FooterAlignment int
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Alignment int
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ColumnAlignment []int
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NewLine string
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HeaderLine bool
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RowLine bool
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AutoMergeCells bool
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Borders tablewriter.Border
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}
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// NewPrettyTablesOptions creates PrettyTablesOptions with default settings
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func NewPrettyTablesOptions() *PrettyTablesOptions {
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return &PrettyTablesOptions{
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AutoFormatHeader: true,
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AutoWrapText: true,
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ReflowDuringAutoWrap: true,
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ColWidth: tablewriter.MAX_ROW_WIDTH,
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ColumnSeparator: tablewriter.COLUMN,
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RowSeparator: tablewriter.ROW,
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CenterSeparator: tablewriter.CENTER,
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HeaderAlignment: tablewriter.ALIGN_DEFAULT,
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FooterAlignment: tablewriter.ALIGN_DEFAULT,
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Alignment: tablewriter.ALIGN_DEFAULT,
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ColumnAlignment: []int{},
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NewLine: tablewriter.NEWLINE,
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HeaderLine: true,
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RowLine: false,
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AutoMergeCells: false,
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Borders: tablewriter.Border{Left: true, Right: true, Bottom: true, Top: true},
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}
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}
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// FromHTMLNode renders text output from a pre-parsed HTML document.
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func FromHTMLNode(doc *html.Node, o ...Options) (string, error) {
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var options Options
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if len(o) > 0 {
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options = o[0]
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}
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ctx := textifyTraverseContext{
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buf: bytes.Buffer{},
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options: options,
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}
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if err := ctx.traverse(doc); err != nil {
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return "", err
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}
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text := strings.TrimSpace(newlineRe.ReplaceAllString(
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strings.Replace(ctx.buf.String(), "\n ", "\n", -1), "\n\n"),
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)
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return text, nil
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}
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// FromReader renders text output after parsing HTML for the specified
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// io.Reader.
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func FromReader(reader io.Reader, options ...Options) (string, error) {
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newReader, err := bom.NewReaderWithoutBom(reader)
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if err != nil {
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return "", err
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}
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doc, err := html.Parse(newReader)
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if err != nil {
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return "", err
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}
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return FromHTMLNode(doc, options...)
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}
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// FromString parses HTML from the input string, then renders the text form.
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func FromString(input string, options ...Options) (string, error) {
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bs := bom.CleanBom([]byte(input))
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text, err := FromReader(bytes.NewReader(bs), options...)
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if err != nil {
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return "", err
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}
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return text, nil
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}
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var (
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spacingRe = regexp.MustCompile(`[ \r\n\t]+`)
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newlineRe = regexp.MustCompile(`\n\n+`)
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)
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// traverseTableCtx holds text-related context.
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type textifyTraverseContext struct {
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buf bytes.Buffer
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prefix string
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tableCtx tableTraverseContext
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options Options
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endsWithSpace bool
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justClosedDiv bool
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blockquoteLevel int
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lineLength int
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isPre bool
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}
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// tableTraverseContext holds table ASCII-form related context.
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type tableTraverseContext struct {
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header []string
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body [][]string
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footer []string
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tmpRow int
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isInFooter bool
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}
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func (tableCtx *tableTraverseContext) init() {
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tableCtx.body = [][]string{}
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tableCtx.header = []string{}
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tableCtx.footer = []string{}
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tableCtx.isInFooter = false
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tableCtx.tmpRow = 0
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}
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func (ctx *textifyTraverseContext) handleElement(node *html.Node) error {
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ctx.justClosedDiv = false
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switch node.DataAtom {
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case atom.Br:
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return ctx.emit("\n")
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case atom.H1, atom.H2, atom.H3:
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subCtx := textifyTraverseContext{}
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if err := subCtx.traverseChildren(node); err != nil {
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return err
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}
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str := subCtx.buf.String()
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dividerLen := 0
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for _, line := range strings.Split(str, "\n") {
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if lineLen := len([]rune(line)); lineLen-1 > dividerLen {
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dividerLen = lineLen - 1
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}
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}
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var divider string
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if node.DataAtom == atom.H1 {
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divider = strings.Repeat("*", dividerLen)
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} else {
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divider = strings.Repeat("-", dividerLen)
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}
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if node.DataAtom == atom.H3 {
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return ctx.emit("\n\n" + str + "\n" + divider + "\n\n")
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}
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return ctx.emit("\n\n" + divider + "\n" + str + "\n" + divider + "\n\n")
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case atom.Blockquote:
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ctx.blockquoteLevel++
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ctx.prefix = strings.Repeat(">", ctx.blockquoteLevel) + " "
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if err := ctx.emit("\n"); err != nil {
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return err
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}
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if ctx.blockquoteLevel == 1 {
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if err := ctx.emit("\n"); err != nil {
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return err
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}
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}
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if err := ctx.traverseChildren(node); err != nil {
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return err
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}
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ctx.blockquoteLevel--
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ctx.prefix = strings.Repeat(">", ctx.blockquoteLevel)
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if ctx.blockquoteLevel > 0 {
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ctx.prefix += " "
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}
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return ctx.emit("\n\n")
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case atom.Div:
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if ctx.lineLength > 0 {
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if err := ctx.emit("\n"); err != nil {
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return err
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}
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}
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if err := ctx.traverseChildren(node); err != nil {
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return err
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}
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var err error
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if !ctx.justClosedDiv {
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err = ctx.emit("\n")
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}
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ctx.justClosedDiv = true
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return err
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case atom.Li:
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if err := ctx.emit("* "); err != nil {
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return err
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}
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if err := ctx.traverseChildren(node); err != nil {
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return err
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}
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return ctx.emit("\n")
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case atom.B, atom.Strong:
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subCtx := textifyTraverseContext{}
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subCtx.endsWithSpace = true
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if err := subCtx.traverseChildren(node); err != nil {
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return err
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}
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str := subCtx.buf.String()
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return ctx.emit("*" + str + "*")
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case atom.A:
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linkText := ""
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// For simple link element content with single text node only, peek at the link text.
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if node.FirstChild != nil && node.FirstChild.NextSibling == nil && node.FirstChild.Type == html.TextNode {
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linkText = node.FirstChild.Data
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}
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// If image is the only child, take its alt text as the link text.
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if img := node.FirstChild; img != nil && node.LastChild == img && img.DataAtom == atom.Img {
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if altText := getAttrVal(img, "alt"); altText != "" {
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if err := ctx.emit(altText); err != nil {
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return err
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}
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}
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} else if err := ctx.traverseChildren(node); err != nil {
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return err
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}
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hrefLink := ""
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if attrVal := getAttrVal(node, "href"); attrVal != "" {
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attrVal = ctx.normalizeHrefLink(attrVal)
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// Don't print link href if it matches link element content or if the link is empty.
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if !ctx.options.OmitLinks && attrVal != "" && linkText != attrVal {
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hrefLink = "( " + attrVal + " )"
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}
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}
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return ctx.emit(hrefLink)
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case atom.P, atom.Ul:
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return ctx.paragraphHandler(node)
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case atom.Table, atom.Tfoot, atom.Th, atom.Tr, atom.Td:
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if ctx.options.PrettyTables {
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return ctx.handleTableElement(node)
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} else if node.DataAtom == atom.Table {
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return ctx.paragraphHandler(node)
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}
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return ctx.traverseChildren(node)
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case atom.Pre:
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ctx.isPre = true
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err := ctx.traverseChildren(node)
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ctx.isPre = false
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return err
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case atom.Style, atom.Script, atom.Head:
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// Ignore the subtree.
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return nil
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default:
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return ctx.traverseChildren(node)
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}
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}
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// paragraphHandler renders node children surrounded by double newlines.
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func (ctx *textifyTraverseContext) paragraphHandler(node *html.Node) error {
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if err := ctx.emit("\n\n"); err != nil {
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return err
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}
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if err := ctx.traverseChildren(node); err != nil {
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return err
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}
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return ctx.emit("\n\n")
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}
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// handleTableElement is only to be invoked when options.PrettyTables is active.
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func (ctx *textifyTraverseContext) handleTableElement(node *html.Node) error {
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if !ctx.options.PrettyTables {
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panic("handleTableElement invoked when PrettyTables not active")
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}
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switch node.DataAtom {
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case atom.Table:
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if err := ctx.emit("\n\n"); err != nil {
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return err
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}
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// Re-intialize all table context.
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ctx.tableCtx.init()
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// Browse children, enriching context with table data.
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if err := ctx.traverseChildren(node); err != nil {
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return err
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}
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buf := &bytes.Buffer{}
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table := tablewriter.NewWriter(buf)
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if ctx.options.PrettyTablesOptions != nil {
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options := ctx.options.PrettyTablesOptions
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table.SetAutoFormatHeaders(options.AutoFormatHeader)
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table.SetAutoWrapText(options.AutoWrapText)
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table.SetReflowDuringAutoWrap(options.ReflowDuringAutoWrap)
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table.SetColWidth(options.ColWidth)
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table.SetColumnSeparator(options.ColumnSeparator)
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table.SetRowSeparator(options.RowSeparator)
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table.SetCenterSeparator(options.CenterSeparator)
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table.SetHeaderAlignment(options.HeaderAlignment)
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table.SetFooterAlignment(options.FooterAlignment)
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table.SetAlignment(options.Alignment)
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table.SetColumnAlignment(options.ColumnAlignment)
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table.SetNewLine(options.NewLine)
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table.SetHeaderLine(options.HeaderLine)
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table.SetRowLine(options.RowLine)
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table.SetAutoMergeCells(options.AutoMergeCells)
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table.SetBorders(options.Borders)
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}
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table.SetHeader(ctx.tableCtx.header)
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table.SetFooter(ctx.tableCtx.footer)
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table.AppendBulk(ctx.tableCtx.body)
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// Render the table using ASCII.
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table.Render()
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if err := ctx.emit(buf.String()); err != nil {
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return err
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}
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return ctx.emit("\n\n")
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case atom.Tfoot:
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ctx.tableCtx.isInFooter = true
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if err := ctx.traverseChildren(node); err != nil {
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return err
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}
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ctx.tableCtx.isInFooter = false
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case atom.Tr:
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ctx.tableCtx.body = append(ctx.tableCtx.body, []string{})
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if err := ctx.traverseChildren(node); err != nil {
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return err
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}
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ctx.tableCtx.tmpRow++
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case atom.Th:
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res, err := ctx.renderEachChild(node)
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if err != nil {
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return err
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}
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ctx.tableCtx.header = append(ctx.tableCtx.header, res)
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case atom.Td:
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res, err := ctx.renderEachChild(node)
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if err != nil {
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return err
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}
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if ctx.tableCtx.isInFooter {
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ctx.tableCtx.footer = append(ctx.tableCtx.footer, res)
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} else {
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ctx.tableCtx.body[ctx.tableCtx.tmpRow] = append(ctx.tableCtx.body[ctx.tableCtx.tmpRow], res)
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}
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}
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return nil
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}
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func (ctx *textifyTraverseContext) traverse(node *html.Node) error {
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switch node.Type {
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default:
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return ctx.traverseChildren(node)
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case html.TextNode:
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var data string
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if ctx.isPre {
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data = node.Data
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} else {
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data = strings.TrimSpace(spacingRe.ReplaceAllString(node.Data, " "))
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}
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return ctx.emit(data)
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case html.ElementNode:
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return ctx.handleElement(node)
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}
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}
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func (ctx *textifyTraverseContext) traverseChildren(node *html.Node) error {
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for c := node.FirstChild; c != nil; c = c.NextSibling {
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if err := ctx.traverse(c); err != nil {
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return err
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}
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}
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return nil
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}
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func (ctx *textifyTraverseContext) emit(data string) error {
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if data == "" {
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return nil
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}
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var (
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lines = ctx.breakLongLines(data)
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err error
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)
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for _, line := range lines {
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runes := []rune(line)
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startsWithSpace := unicode.IsSpace(runes[0])
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if !startsWithSpace && !ctx.endsWithSpace && !strings.HasPrefix(data, ".") {
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if err = ctx.buf.WriteByte(' '); err != nil {
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return err
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}
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ctx.lineLength++
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}
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ctx.endsWithSpace = unicode.IsSpace(runes[len(runes)-1])
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for _, c := range line {
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if _, err = ctx.buf.WriteString(string(c)); err != nil {
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return err
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}
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ctx.lineLength++
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if c == '\n' {
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ctx.lineLength = 0
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if ctx.prefix != "" {
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if _, err = ctx.buf.WriteString(ctx.prefix); err != nil {
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return err
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}
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}
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}
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}
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}
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return nil
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}
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const maxLineLen = 74
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func (ctx *textifyTraverseContext) breakLongLines(data string) []string {
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// Only break lines when in blockquotes.
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if ctx.blockquoteLevel == 0 {
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return []string{data}
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}
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var (
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ret = []string{}
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runes = []rune(data)
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l = len(runes)
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existing = ctx.lineLength
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)
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if existing >= maxLineLen {
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ret = append(ret, "\n")
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existing = 0
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}
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for l+existing > maxLineLen {
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i := maxLineLen - existing
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for i >= 0 && !unicode.IsSpace(runes[i]) {
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i--
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}
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if i == -1 {
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// No spaces, so go the other way.
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i = maxLineLen - existing
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for i < l && !unicode.IsSpace(runes[i]) {
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i++
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}
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}
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ret = append(ret, string(runes[:i])+"\n")
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for i < l && unicode.IsSpace(runes[i]) {
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i++
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}
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runes = runes[i:]
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l = len(runes)
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existing = 0
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}
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if len(runes) > 0 {
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ret = append(ret, string(runes))
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}
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return ret
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}
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func (ctx *textifyTraverseContext) normalizeHrefLink(link string) string {
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link = strings.TrimSpace(link)
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link = strings.TrimPrefix(link, "mailto:")
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return link
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}
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// renderEachChild visits each direct child of a node and collects the sequence of
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// textuual representaitons separated by a single newline.
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func (ctx *textifyTraverseContext) renderEachChild(node *html.Node) (string, error) {
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buf := &bytes.Buffer{}
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for c := node.FirstChild; c != nil; c = c.NextSibling {
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s, err := FromHTMLNode(c, ctx.options)
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if err != nil {
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return "", err
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}
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if _, err = buf.WriteString(s); err != nil {
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return "", err
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}
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if c.NextSibling != nil {
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if err = buf.WriteByte('\n'); err != nil {
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return "", err
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}
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}
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}
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return buf.String(), nil
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}
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func getAttrVal(node *html.Node, attrName string) string {
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for _, attr := range node.Attr {
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if attr.Key == attrName {
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return attr.Val
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}
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}
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return ""
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}
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