enbas/internal/utilities/html.go

package utilities

import (
	"io"
	"strconv"
	"strings"

	"golang.org/x/net/html"
)

const (
	htmlNoList int = iota
	htmlOrderedList
	htmlUnorderedList
)

func ConvertHTMLToText(text string) string {
	var builder strings.Builder

	htmlList := htmlNoList
	orderedListNumber := 1

	token := html.NewTokenizer(strings.NewReader(text))

	for {
		tt := token.Next()
		switch tt {
		case html.ErrorToken:
			return builder.String()
		case html.TextToken:
			text := token.Token().Data
			builder.WriteString(text)
		case html.StartTagToken, html.EndTagToken:
			tag := token.Token().String()
			htmlList, orderedListNumber = processTagToken(&builder, tag, htmlList, orderedListNumber)
		}
	}
}

func processTagToken(writer io.StringWriter, tag string, htmlList, orderedListNumber int) (int, int) {
	switch tag {
	case "<br>", "<p>", "</p>", "</li>":
		_, _ = writer.WriteString("\n")
	case "<ul>":
		htmlList = htmlUnorderedList
		_, _ = writer.WriteString("\n")
	case "<ol>":
		htmlList = htmlOrderedList
		_, _ = writer.WriteString("\n")
	case "</ul>":
		htmlList = htmlNoList
	case "</ol>":
		htmlList = htmlNoList
		orderedListNumber = 1
	case "<li>":
		switch htmlList {
		case htmlUnorderedList:
			_, _ = writer.WriteString("• ")
		case htmlOrderedList:
			_, _ = writer.WriteString(strconv.Itoa(orderedListNumber) + ". ")
			orderedListNumber++
		}
	}

	return htmlList, orderedListNumber
}