106 lines
2.5 KiB
Go
106 lines
2.5 KiB
Go
package mailer
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import (
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"regexp"
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"strings"
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"github.com/pocketbase/pocketbase/tools/list"
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"golang.org/x/net/html"
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)
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var whitespaceRegex = regexp.MustCompile(`\s+`)
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// Very rudimentary auto HTML to Text mail body converter.
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//
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// Caveats:
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// - This method doesn't check for correctness of the HTML document.
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// - Links will be converted to "[text](url)" format.
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// - List items (<li>) are prefixed with "- ".
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// - Indentation is stripped (both tabs and spaces).
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// - Trailing spaces are preserved.
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// - Multiple consequence newlines are collapsed as one unless multiple <br> tags are used.
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func html2Text(htmlDocument string) (string, error) {
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var builder strings.Builder
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doc, err := html.Parse(strings.NewReader(htmlDocument))
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if err != nil {
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return "", err
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}
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tagsToSkip := []string{
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"style", "script", "iframe", "applet", "object", "svg", "img",
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"button", "form", "textarea", "input", "select", "option", "template",
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}
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inlineTags := []string{
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"a", "span", "small", "strike", "strong",
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"sub", "sup", "em", "b", "u", "i",
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}
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var canAddNewLine bool
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// see https://pkg.go.dev/golang.org/x/net/html#Parse
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var f func(*html.Node)
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f = func(n *html.Node) {
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// start link wrapping for producing "[text](link)" formatted string
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isLink := n.Type == html.ElementNode && n.Data == "a"
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if isLink {
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builder.WriteString("[")
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}
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switch n.Type {
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case html.TextNode:
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txt := whitespaceRegex.ReplaceAllString(n.Data, " ")
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// the prev node has new line so it is safe to trim the indentation
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if !canAddNewLine {
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txt = strings.TrimLeft(txt, " ")
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}
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if txt != "" {
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builder.WriteString(txt)
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canAddNewLine = true
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}
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case html.ElementNode:
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if n.Data == "br" {
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// always write new lines when <br> tag is used
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builder.WriteString("\r\n")
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canAddNewLine = false
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} else if canAddNewLine && !list.ExistInSlice(n.Data, inlineTags) {
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builder.WriteString("\r\n")
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canAddNewLine = false
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}
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// prefix list items with dash
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if n.Data == "li" {
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builder.WriteString("- ")
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}
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}
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for c := n.FirstChild; c != nil; c = c.NextSibling {
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if c.Type != html.ElementNode || !list.ExistInSlice(c.Data, tagsToSkip) {
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f(c)
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}
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}
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// end link wrapping
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if isLink {
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builder.WriteString("]")
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for _, a := range n.Attr {
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if a.Key == "href" {
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if a.Val != "" {
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builder.WriteString("(")
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builder.WriteString(a.Val)
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builder.WriteString(")")
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}
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break
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}
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}
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}
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}
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f(doc)
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return strings.TrimSpace(builder.String()), nil
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}
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