feat: add original message formatting helpers with tests

formatting.go

@@ -0,0 +1,396 @@
+package botapi
+
+import (
+	"html"
+	"slices"
+	"strconv"
+	"strings"
+	"unicode"
+	"unicode/utf16"
+)
+
+var mdMap = map[MessageEntityType]string{
+	EntityBold:   "*",
+	EntityItalic: "_",
+	EntityCode:   "`",
+	EntityPre:    "```",
+}
+
+var mdV2Map = map[MessageEntityType]string{
+	EntityBold:                 "*",
+	EntityItalic:               "_",
+	EntityCode:                 "`",
+	EntityPre:                  "```",
+	EntityUnderline:            "__",
+	EntityStrikethrough:        "~",
+	EntitySpoiler:              "||",
+	EntityBlockquote:           ">",
+	EntityExpandableBlockquote: "**>",
+}
+
+var htmlMap = map[MessageEntityType]string{
+	EntityBold:                 "b",
+	EntityItalic:               "i",
+	EntityCode:                 "code",
+	EntityPre:                  "pre",
+	EntityUnderline:            "u",
+	EntityStrikethrough:        "s",
+	EntitySpoiler:              "span class=\"tg-spoiler\"",
+	EntityBlockquote:           "blockquote",
+	EntityExpandableBlockquote: "blockquote expandable",
+}
+
+// TextAndEntities gets message or caption text and entities
+func (m *Message) TextAndEntities() (string, []MessageEntity) {
+	if m.Text != "" {
+		return m.Text, m.Entities
+	}
+
+	return m.Caption, m.CaptionEntities
+}
+
+// OriginalMD gets the original markdown formatting of a message text.
+func (m *Message) OriginalMD() string {
+	return getOrigMsgMD(utf16.Encode([]rune(m.Text)), m.Entities)
+}
+
+// OriginalMDV2 gets the original markdownV2 formatting of a message text.
+func (m *Message) OriginalMDV2() string {
+	return getOrigMsgMDV2(utf16.Encode([]rune(m.Text)), m.Entities)
+}
+
+// OriginalHTML gets the original HTML formatting of a message text.
+func (m *Message) OriginalHTML() string {
+	return getOrigMsgHTML(utf16.Encode([]rune(m.Text)), m.Entities)
+}
+
+// OriginalCaptionMD gets the original markdown formatting of a message caption.
+func (m *Message) OriginalCaptionMD() string {
+	return getOrigMsgMD(utf16.Encode([]rune(m.Caption)), m.CaptionEntities)
+}
+
+// OriginalCaptionMDV2 gets the original markdownV2 formatting of a message caption.
+func (m *Message) OriginalCaptionMDV2() string {
+	return getOrigMsgMDV2(utf16.Encode([]rune(m.Caption)), m.CaptionEntities)
+}
+
+// OriginalCaptionHTML gets the original HTML formatting of a message caption.
+func (m *Message) OriginalCaptionHTML() string {
+	return getOrigMsgHTML(utf16.Encode([]rune(m.Caption)), m.CaptionEntities)
+}
+
+// OriginalTextMD gets the original markdown formatting of a message text or caption.
+func (m *Message) OriginalTextMD() string {
+	text, ents := m.TextAndEntities()
+	return getOrigMsgMD(utf16.Encode([]rune(text)), ents)
+}
+
+// OriginalTextMDV2 gets the original markdownV2 formatting of a message text or caption.
+func (m *Message) OriginalTextMDV2() string {
+	text, ents := m.TextAndEntities()
+	return getOrigMsgMDV2(utf16.Encode([]rune(text)), ents)
+}
+
+// OriginalTextHTML gets the original HTML formatting of a message text caption.
+func (m *Message) OriginalTextHTML() string {
+	text, ents := m.TextAndEntities()
+	return getOrigMsgHTML(utf16.Encode([]rune(text)), ents)
+}
+
+// Does not support nesting. only look at upper entities.
+func getOrigMsgMD(utf16Data []uint16, ents []MessageEntity) string {
+	out := strings.Builder{}
+	prev := 0
+
+	for _, ent := range getUpperEntities(ents) {
+		newPrev := ent.Offset + ent.Length
+		prevText := string(utf16.Decode(utf16Data[prev:ent.Offset]))
+
+		text := utf16.Decode(utf16Data[ent.Offset:newPrev])
+		pre, cleanCntnt, post := splitEdgeWhitespace(string(text), ent)
+		cleanCntntRune := []rune(cleanCntnt)
+
+		switch ent.Type {
+		case EntityBold, EntityItalic, EntityCode:
+			out.WriteString(prevText + pre + mdMap[ent.Type] + escapeContainedMDV1(cleanCntntRune, []rune(mdMap[ent.Type])) + mdMap[ent.Type] + post)
+		case EntityPre:
+			if ent.Language == "" {
+				out.WriteString(prevText + pre + mdMap[ent.Type] +
+					escapeContainedMDV1(cleanCntntRune, []rune(mdMap[ent.Type])) + mdMap[ent.Type] + post)
+			} else {
+				out.WriteString(prevText + pre + mdMap[ent.Type] +
+					ent.Language + "\n" + escapeContainedMDV1(cleanCntntRune, []rune(mdMap[ent.Type])) + mdMap[ent.Type] + post)
+			}
+		case EntityTextMention:
+			out.WriteString(prevText + pre + "[" + escapeContainedMDV1(cleanCntntRune, []rune("[]()")) + "](tg://user?id=" +
+				strconv.FormatInt(ent.User.ID, 10) + ")" + post)
+		case EntityTextLink:
+			out.WriteString(prevText + pre + "[" + escapeContainedMDV1(cleanCntntRune, []rune("[]()")) + "](" + ent.URL + ")" + post)
+		default:
+			continue
+		}
+
+		prev = newPrev
+	}
+
+	out.WriteString(string(utf16.Decode(utf16Data[prev:])))
+
+	return out.String()
+}
+
+func getOrigMsgHTML(utf16Data []uint16, ents []MessageEntity) string {
+	if len(ents) == 0 {
+		return html.EscapeString(string(utf16.Decode(utf16Data)))
+	}
+
+	bd := strings.Builder{}
+	prev := 0
+
+	for _, e := range getUpperEntities(ents) {
+		data, end := fillNestedHTML(utf16Data, e, prev, getChildEntities(e, ents))
+		bd.WriteString(data)
+
+		prev = end
+	}
+
+	bd.WriteString(html.EscapeString(string(utf16.Decode(utf16Data[prev:]))))
+
+	return bd.String()
+}
+
+func getOrigMsgMDV2(utf16Data []uint16, ents []MessageEntity) (origMsg string) {
+	if len(ents) == 0 {
+		return string(utf16.Decode(utf16Data))
+	}
+
+	bd := strings.Builder{}
+	prev := 0
+
+	for _, e := range getUpperEntities(ents) {
+		data, end := fillNestedMarkdownV2(utf16Data, e, prev, getChildEntities(e, ents))
+		bd.WriteString(data)
+
+		prev = end
+	}
+
+	bd.WriteString(string(utf16.Decode(utf16Data[prev:])))
+
+	return bd.String()
+}
+
+func fillNestedHTML(data []uint16, ent MessageEntity, start int, entities []MessageEntity) (finalHTML string, entEnd int) {
+	entEnd = ent.Offset + ent.Length
+	if len(entities) == 0 || entEnd < entities[0].Offset {
+		// no nesting; just return straight away and move to next.
+		return writeFinalHTML(data, ent, start, html.EscapeString(string(utf16.Decode(data[ent.Offset:entEnd])))), entEnd
+	}
+
+	subPrev := ent.Offset
+	subEnd := ent.Offset
+	bd := strings.Builder{}
+
+	for _, e := range getUpperEntities(entities) {
+		if e.Offset < subEnd || e == ent {
+			continue
+		}
+
+		if e.Offset >= entEnd {
+			break
+		}
+
+		out, end := fillNestedHTML(data, e, subPrev, getChildEntities(e, entities))
+		bd.WriteString(out)
+
+		subPrev = end
+	}
+
+	bd.WriteString(html.EscapeString(string(utf16.Decode(data[subPrev:entEnd]))))
+
+	return writeFinalHTML(data, ent, start, bd.String()), entEnd
+}
+
+func fillNestedMarkdownV2(
+	data []uint16,
+	ent MessageEntity,
+	start int,
+	entities []MessageEntity,
+) (finalMD string, entEnd int) {
+	entEnd = ent.Offset + ent.Length
+	if len(entities) == 0 || entEnd < entities[0].Offset {
+		// no nesting; just return straight away and move to next.
+		return writeFinalMarkdownV2(data, ent, start, string(utf16.Decode(data[ent.Offset:entEnd]))), entEnd
+	}
+
+	subPrev := ent.Offset
+	subEnd := ent.Offset
+	bd := strings.Builder{}
+
+	for _, e := range getUpperEntities(entities) {
+		if e.Offset < subEnd || e == ent {
+			continue
+		}
+
+		if e.Offset >= entEnd {
+			break
+		}
+
+		out, end := fillNestedMarkdownV2(data, e, subPrev, getChildEntities(e, entities))
+		bd.WriteString(out)
+
+		subPrev = end
+	}
+
+	bd.WriteString(string(utf16.Decode(data[subPrev:entEnd])))
+
+	return writeFinalMarkdownV2(data, ent, start, bd.String()), entEnd
+}
+
+func writeFinalHTML(data []uint16, ent MessageEntity, start int, cntnt string) string {
+	prevText := html.EscapeString(string(utf16.Decode(data[start:ent.Offset])))
+	switch ent.Type {
+	case EntityBold, EntityItalic, EntityCode, EntityUnderline, EntityStrikethrough, EntitySpoiler:
+		return prevText + "<" + htmlMap[ent.Type] + ">" + cntnt + "</" + closeHTMLTag(htmlMap[ent.Type]) + ">"
+	case EntityPre:
+		if ent.Language == "" {
+			return prevText + "<pre>" + cntnt + "</pre>"
+		}
+
+		return prevText + `<pre><code class="` + ent.Language + `">` + cntnt + "</code></pre>"
+	case EntityCustomEmoji:
+		return prevText + `<tg-emoji emoji-id="` + ent.CustomEmojiID + `">` + cntnt + "</tg-emoji>"
+	case EntityDateTime:
+		if ent.DateTimeFormat != "" {
+			return prevText + `<tg-time unix="` + strconv.Itoa(ent.UnixTime) + `" format="` + ent.DateTimeFormat + `">` + cntnt + "</tg-time>"
+		}
+
+		return prevText + `<tg-time unix="` + strconv.Itoa(ent.UnixTime) + `">` + cntnt + "</tg-time>"
+	case EntityTextMention:
+		return prevText + `<a href="tg://user?id=` + strconv.FormatInt(ent.User.ID, 10) + `">` + cntnt + "</a>"
+	case EntityTextLink:
+		return prevText + `<a href="` + ent.URL + `">` + cntnt + "</a>"
+	case EntityBlockquote:
+		return prevText + `<blockquote>` + cntnt + "</blockquote>"
+	case EntityExpandableBlockquote:
+		return prevText + `<blockquote expandable>` + cntnt + "</blockquote>"
+	default:
+		return prevText + cntnt
+	}
+}
+
+// closeHTMLTag makes sure to generate the correct HTML closing tag for a given opening tag.
+func closeHTMLTag(s string) string {
+	if !strings.HasPrefix(s, "span") {
+		return s
+	}
+
+	return "span"
+}
+
+func writeFinalMarkdownV2(data []uint16, ent MessageEntity, start int, cntnt string) string {
+	prevText := string(utf16.Decode(data[start:ent.Offset]))
+	pre, cleanCntnt, post := splitEdgeWhitespace(cntnt, ent)
+
+	switch ent.Type {
+	case EntityBold, EntityItalic, EntityCode, EntityUnderline, EntityStrikethrough, EntitySpoiler:
+		return prevText + pre + mdV2Map[ent.Type] + cleanCntnt + mdV2Map[ent.Type] + post
+	case EntityPre:
+		if ent.Language == "" {
+			return prevText + pre + "```\n" + cleanCntnt + "```" + post
+		}
+
+		return prevText + pre + "```" + ent.Language + "\n" + cleanCntnt + "```" + post
+	case EntityCustomEmoji:
+		return prevText + pre + "![" + cleanCntnt + "](tg://emoji?id=" + ent.CustomEmojiID + ")" + post
+	case EntityDateTime:
+		if ent.DateTimeFormat != "" {
+			return prevText + pre + "![" + cleanCntnt + "](tg://time?unix=" +
+				strconv.Itoa(ent.UnixTime) + "&format=" + ent.DateTimeFormat + ")" + post
+		}
+
+		return prevText + pre + "![" + cleanCntnt + "](tg://time?unix=" + strconv.Itoa(ent.UnixTime) + ")" + post
+	case EntityTextMention:
+		return prevText + pre + "[" + cleanCntnt + "](tg://user?id=" + strconv.FormatInt(ent.User.ID, 10) + ")" + post
+	case EntityTextLink:
+		return prevText + pre + "[" + cleanCntnt + "](" + ent.URL + ")" + post
+	case EntityBlockquote:
+		return prevText + pre + ">" + strings.Join(strings.Split(cleanCntnt, "\n"), "\n>") + post
+	case EntityExpandableBlockquote:
+		return prevText + pre + "**>" + strings.Join(strings.Split(cleanCntnt, "\n"), "\n>") + "||" + post
+	default:
+		return prevText + cntnt
+	}
+}
+
+func getUpperEntities(ents []MessageEntity) []MessageEntity {
+	prev := 0
+	uppers := make([]MessageEntity, 0, len(ents))
+
+	for _, e := range ents {
+		if e.Offset < prev {
+			continue
+		}
+
+		uppers = append(uppers, e)
+		prev = e.Offset + e.Length
+	}
+
+	return uppers
+}
+
+func getChildEntities(ent MessageEntity, ents []MessageEntity) []MessageEntity {
+	end := ent.Offset + ent.Length
+	children := make([]MessageEntity, 0, len(ents))
+
+	for _, e := range ents {
+		if e.Offset < ent.Offset || e == ent {
+			continue
+		}
+
+		if e.Offset >= end {
+			break
+		}
+
+		children = append(children, e)
+	}
+
+	return children
+}
+
+func splitEdgeWhitespace(text string, ent MessageEntity) (pre, cntnt, post string) {
+	keepNewLines := ent.Type == EntityPre
+
+	bd := strings.Builder{}
+	rText := []rune(text)
+
+	for i := 0; i < len(rText) && unicode.IsSpace(rText[i]) && (!keepNewLines || rText[i] != '\n'); i++ {
+		bd.WriteRune(rText[i])
+	}
+
+	pre = bd.String()
+
+	text = strings.TrimPrefix(text, pre)
+
+	bd.Reset()
+
+	for i := len(rText) - 1; i >= 0 && unicode.IsSpace(rText[i]); i-- {
+		bd.WriteRune(rText[i])
+	}
+
+	post = bd.String()
+
+	return pre, strings.TrimSuffix(text, post), post
+}
+
+func escapeContainedMDV1(data, mdType []rune) string {
+	out := strings.Builder{}
+
+	for _, x := range data {
+		if slices.Contains(mdType, x) {
+			out.WriteRune('\\')
+		}
+
+		out.WriteRune(x)
+	}
+
+	return out.String()
+}