test: fixed Test_markdownToTelegramMarkdownV2
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Aleksandr Bortnikov
parent
1000daa9e2
commit
167887361c
2 changed files with 188 additions and 155 deletions
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@ -1,163 +1,196 @@
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package telegram
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import (
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"regexp"
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"strings"
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)
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// markdownToTelegramMarkdownV2 takes a standardized markdown string and
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// strictly escapes or transforms it to fit Telegram's MarkdownV2 requirements.
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// https://core.telegram.org/bots/api#formatting-options
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// mdV2SpecialChars are all characters that must be escaped in Telegram MarkdownV2
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var mdV2SpecialChars = map[rune]bool{
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'*': true,
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'_': true,
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'[': true,
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']': true,
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'(': true,
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')': true,
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'~': true,
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'`': true,
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'>': true,
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'#': true,
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'+': true,
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'-': true,
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'=': true,
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'|': true,
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'{': true,
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'}': true,
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'.': true,
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'!': true,
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'\\': true,
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}
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// entityPattern describes one Telegram MarkdownV2 inline entity type.
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type entityPattern struct {
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re *regexp.Regexp
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open string
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close string
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}
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// allEntityPatterns lists every recognised entity in priority order
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// (longer / more-specific delimiters first so they win over shorter ones).
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// Each entry's regex is anchored to find the first occurrence in a string.
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var allEntityPatterns = []entityPattern{
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// fenced code block — content is completely verbatim
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{re: regexp.MustCompile("(?s)```(?:[\\w]*\\n)?[\\s\\S]*?```"), open: "```", close: "```"},
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// inline code — content is completely verbatim
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{re: regexp.MustCompile("`(?:[^`\\\n]|\\\\.)*`"), open: "`", close: "`"},
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// expandable block-quote opener **>…
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{re: regexp.MustCompile(`(?m)\*\*>(?:[^\n]*)`), open: "**>", close: ""},
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// block-quote line >…
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{re: regexp.MustCompile(`(?m)>(?:[^\n]*)`), open: ">", close: ""},
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// custom emoji / timestamp  — must come before plain link
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{re: regexp.MustCompile(`!\[[^\]]*\]\([^)]*\)`), open: "!", close: ""},
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// inline URL / user mention […](…)
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{re: regexp.MustCompile(`\[[^\]]*\]\([^)]*\)`), open: "[", close: ""},
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// spoiler ||…|| — before single | so it wins
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{re: regexp.MustCompile(`\|\|(?:[^|\\\n]|\\.)*\|\|`), open: "||", close: "||"},
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// underline __…__ — before single _ so it wins
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{re: regexp.MustCompile(`__(?:[^_\\\n]|\\.)*__`), open: "__", close: "__"},
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// bold *…*
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{re: regexp.MustCompile(`\*(?:[^*\\\n]|\\.)*\*`), open: "*", close: "*"},
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// italic _…_
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{re: regexp.MustCompile(`_(?:[^_\\\n]|\\.)*_`), open: "_", close: "_"},
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// strikethrough ~…~
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{re: regexp.MustCompile(`~(?:[^~\\\n]|\\.)*~`), open: "~", close: "~"},
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}
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// verbatimEntities are entity types whose inner content must never be
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// touched (code blocks, URLs, quotes, custom emoji).
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// Their content is passed through completely unchanged.
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var verbatimEntities = map[string]bool{
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"```": true,
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"`": true,
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"**>": true,
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">": true,
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"!": true,
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"[": true,
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}
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// markdownToTelegramMarkdownV2 converts a Markdown string into a string safe
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// for sending with Telegram's MarkdownV2 parse mode.
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//
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// Rules:
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// - Markdown headings (# … ######) are converted to *bold*.
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// - **bold** Markdown syntax is converted to *bold*.
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// - Recognised Telegram MarkdownV2 entity spans are preserved; their inner
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// content is processed recursively so that nested valid entities are kept
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// intact while stray special characters are escaped.
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// - All plain-text segments have their MarkdownV2 special characters escaped.
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//
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// Reference: https://core.telegram.org/bots/api#formatting-options
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func markdownToTelegramMarkdownV2(text string) string {
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// replace Heading to bolding
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text = reHeading.ReplaceAllString(text, "*$1*")
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// 1. Convert Markdown headings → *escaped heading text*
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text = reHeading.ReplaceAllStringFunc(text, func(match string) string {
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sub := reHeading.FindStringSubmatch(match)
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if len(sub) < 2 {
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return match
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}
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// The heading content is fresh plain text — escape everything
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// including * so the resulting *…* bold span stays valid.
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return "*" + escapeMarkdownV2(sub[1]) + "*"
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})
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// 2. Convert **bold** → *bold*
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text = reBoldStar.ReplaceAllString(text, "*$1*")
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var result strings.Builder
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runes := []rune(text)
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length := len(runes)
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// List of characters that must be escaped in standard text contexts
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needsNormalEscape := func(r rune) bool {
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switch r {
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case '_', '*', '[', ']', '(', ')', '~', '`', '>', '#', '+', '-', '=', '|', '{', '}', '.', '!':
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return true
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}
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return false
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// 3. Recursively escape the full string.
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return processText(text)
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}
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i := 0
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for i < length {
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// 1. Check for Pre-formatted Code Block (```...```)
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if i+2 < length && runes[i] == '`' && runes[i+1] == '`' && runes[i+2] == '`' {
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result.WriteString("```")
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i += 3
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// Find closing ```
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for i < length {
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if i+2 < length && runes[i] == '`' && runes[i+1] == '`' && runes[i+2] == '`' {
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result.WriteString("```")
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i += 3
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break
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}
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// Inside code blocks, escape `\` and `\`
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if runes[i] == '\\' || runes[i] == '`' {
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result.WriteRune('\\')
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}
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result.WriteRune(runes[i])
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i++
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// processText walks `text`, finds the leftmost / longest matching entity,
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// escapes the gap before it, processes the entity (recursing into its inner
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// content when appropriate), then continues with the remainder.
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func processText(text string) string {
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if text == "" {
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return ""
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}
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// Find the leftmost match among all entity patterns.
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bestStart := -1
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bestEnd := -1
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var bestPat *entityPattern
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for i := range allEntityPatterns {
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p := &allEntityPatterns[i]
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loc := p.re.FindStringIndex(text)
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if loc == nil {
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continue
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}
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// 2. Check for Inline Code (`...`)
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if runes[i] == '`' {
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result.WriteRune('`')
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i++
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for i < length {
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if runes[i] == '`' {
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result.WriteRune('`')
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i++
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break
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if bestStart == -1 || loc[0] < bestStart ||
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(loc[0] == bestStart && (loc[1]-loc[0]) > (bestEnd-bestStart)) {
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bestStart = loc[0]
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bestEnd = loc[1]
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bestPat = p
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}
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if runes[i] == '\\' || runes[i] == '`' {
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result.WriteRune('\\')
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}
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result.WriteRune(runes[i])
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i++
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}
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continue
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}
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// 3. Link or Custom Emoji definition: URL part (...)
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// We detect this by checking if the previous non-space character closed a bracket ']',
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// and we are currently on '('. To keep logic linear, we handle it as we traverse.
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// NOTE: A true deep-parser would link `[` to `](...)`. For safety, whenever we see `(`,
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// if it looks like a URL part, we escape it via URL rules. Let's do a basic lookbehind.
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if i != 0 && runes[i] == '(' && i > 0 && runes[i-1] == ']' {
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result.WriteRune('(')
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i++
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for i < length {
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if runes[i] == ')' {
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// Unescaped closing bracket ends the URL
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result.WriteRune(')')
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i++
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break
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}
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// In URL part, escape `\` and `)`
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if runes[i] == '\\' || runes[i] == ')' {
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result.WriteRune('\\')
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}
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result.WriteRune(runes[i])
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i++
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}
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continue
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if bestPat == nil {
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// No entity found — escape everything.
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return escapeMarkdownV2(text)
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}
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// 4. Handle blockquotes starts
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if i != 0 && runes[i] == '>' && (i == 0 || runes[i-1] == '\n') {
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result.WriteRune('>')
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var b strings.Builder
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// Plain text before the entity.
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if bestStart > 0 {
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b.WriteString(escapeMarkdownV2(text[:bestStart]))
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}
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// The matched entity span.
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matched := text[bestStart:bestEnd]
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if verbatimEntities[bestPat.open] {
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// Code blocks, URLs, quotes: pass through completely untouched.
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b.WriteString(matched)
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} else {
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// Inline formatting (bold, italic, underline, strikethrough, spoiler):
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// keep the delimiters and recursively process the inner content so that
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// nested entities survive but stray specials get escaped.
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openLen := len(bestPat.open)
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closeLen := len(bestPat.close)
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inner := matched[openLen : len(matched)-closeLen]
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b.WriteString(bestPat.open)
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b.WriteString(processText(inner))
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b.WriteString(bestPat.close)
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}
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// Continue with the remainder of the string.
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b.WriteString(processText(text[bestEnd:]))
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return b.String()
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}
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// escapeMarkdownV2 escapes every MarkdownV2 special character in a plain-text
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// segment (i.e. a segment that is not part of any recognised entity).
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// Already-escaped sequences (backslash + char) are forwarded verbatim to avoid
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// double-escaping.
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func escapeMarkdownV2(s string) string {
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var b strings.Builder
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b.Grow(len(s) + 8)
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runes := []rune(s)
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for i := 0; i < len(runes); i++ {
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ch := runes[i]
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// Forward an existing escape sequence verbatim.
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if ch == '\\' && i+1 < len(runes) {
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b.WriteRune(ch)
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b.WriteRune(runes[i+1])
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i++
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continue
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}
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// 5. Handle expandable block quotation starts
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if i+3 < length && runes[i] == '>' && runes[i-1] == '*' && runes[i-2] == '*' && (i == 0 || runes[i-3] == '\n') {
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result.WriteRune(runes[i])
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i++
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continue
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if mdV2SpecialChars[ch] {
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b.WriteByte('\\')
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}
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// 6. Handle standard Markdown Entities Boundaries
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// If they are part of valid markdown boundaries, we write them as-is.
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// We trust the syntax rules: * _ ~ || [ ]
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// (Assuming the text is a valid markdown, we don't escape these if formatting is intended)
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// Note on Ambiguity (__ vs _):
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// Telegram parses `__` from left to right greedily.
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if i+1 < length && runes[i] == '_' && runes[i+1] == '_' {
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result.WriteString("__")
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i += 2
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continue
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b.WriteRune(ch)
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}
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if i+1 < length && runes[i] == '|' && runes[i+1] == '|' {
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result.WriteString("||")
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i += 2
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continue
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}
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// Standard single-char boundaries
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if runes[i] == '*' || runes[i] == '_' || runes[i] == '[' || runes[i] == ']' {
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result.WriteRune(runes[i])
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i++
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continue
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}
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// Custom emoji boundary check `![`
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if i+1 < length && runes[i] == '!' && runes[i+1] == '[' {
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result.WriteString("![")
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i += 2
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continue
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}
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// 7. Handle plain text characters
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// Escape remaining special characters if they aren't forming intended valid markup
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if needsNormalEscape(runes[i]) {
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// Check if it's already escaped; if an escape character exists, consume it legitimately
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if runes[i] == '\\' && i+1 < length && needsNormalEscape(runes[i+1]) {
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// Keep the backslash and the escaped char as is, avoiding double escaping
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result.WriteRune('\\')
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result.WriteRune(runes[i+1])
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i += 2
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continue
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}
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// Auto-escape the character
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result.WriteRune('\\')
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}
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result.WriteRune(runes[i])
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i++
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}
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return result.String()
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return b.String()
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}
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@ -48,8 +48,8 @@ func Test_markdownToTelegramMarkdownV2(t *testing.T) {
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},
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{
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name: "",
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input: "~10",
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expected: "\\~10",
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input: "*Last update: ~10 24h*",
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expected: "*Last update: \\~10 24h*",
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},
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}
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