Vakyartha documentation

1//! GFM-to-Slack `mrkdwn` projection.
2//!
3//! Slack's `mrkdwn` dialect diverges from GFM in exactly the spots that
4//! matter most: bold uses a single `*`, italic uses `_`, links use
5//! `<url|text>`, there is no heading syntax and no table syntax at all.
6//! This module renders a conservative GFM subset into text that actually
7//! looks right when Slack's client parses it.
8
9/// Convert a conservative GFM subset to Slack `mrkdwn`.
10pub fn markdown_to_mrkdwn(markdown: &str) -> String {
11 let mut out = String::with_capacity(markdown.len() + 64);
12 let mut in_fence = false;
13 let mut fence = Vec::new();
14 let mut table = Vec::new();
15 let mut blank_pending = false;
16
17 for line in markdown.lines() {
18 let trimmed = line.trim_start();
19
20 if trimmed.starts_with("```") {
21 flush_table(&mut out, &mut table);
22 if in_fence {
23 out.push_str("```\n");
24 out.push_str(&fence.join("\n"));
25 out.push_str("\n```\n");
26 fence.clear();
27 }
28 in_fence = !in_fence;
29 blank_pending = false;
30 continue;
31 }
32 if in_fence {
33 fence.push(line.to_string());
34 continue;
35 }
36
37 if trimmed.is_empty() {
38 flush_table(&mut out, &mut table);
39 blank_pending = !out.is_empty();
40 continue;
41 }
42
43 if is_spoiler(trimmed) {
44 flush_table(&mut out, &mut table);
45 if blank_pending && !out.is_empty() {
46 out.push('\n');
47 }
48 blank_pending = false;
49 out.push_str(trimmed);
50 out.push('\n');
51 continue;
52 }
53
54 if trimmed.starts_with('|') && trimmed.ends_with('|') && trimmed.len() > 1 {
55 if blank_pending {
56 out.push('\n');
57 }
58 blank_pending = false;
59 table.push(trimmed.to_string());
60 continue;
61 }
62 flush_table(&mut out, &mut table);
63
64 if is_horizontal_rule(trimmed) {
65 if blank_pending {
66 out.push('\n');
67 }
68 blank_pending = false;
69 out.push_str("──────────\n");
70 continue;
71 }
72
73 if let Some(after) = trimmed.strip_prefix('#')
74 && after.starts_with(' ')
75 {
76 let text = after.trim().trim_start_matches('#').trim();
77 if !text.is_empty() {
78 if blank_pending && !out.is_empty() {
79 out.push('\n');
80 }
81 blank_pending = false;
82 out.push('*');
83 out.push_str(&inline_mrkdwn(text));
84 out.push_str("*\n");
85 continue;
86 }
87 }
88
89 if let Some(quote) = trimmed.strip_prefix("> ") {
90 blank_pending = false;
91 out.push_str("> ");
92 out.push_str(&inline_mrkdwn(quote));
93 out.push('\n');
94 continue;
95 }
96
97 let indent = line.len() - trimmed.len();
98 let depth = indent / 2;
99
100 if let Some(rest) = strip_task_item(trimmed) {
101 blank_pending = false;
102 out.push_str(&" ".repeat(depth));
103 out.push_str(bullet_for_depth(depth));
104 out.push(' ');
105 out.push_str(&inline_mrkdwn(&rest));
106 out.push('\n');
107 continue;
108 }
109
110 if let Some(item) = trimmed
111 .strip_prefix("- ")
112 .or_else(|| trimmed.strip_prefix("* "))
113 .or_else(|| trimmed.strip_prefix("+ "))
114 {
115 blank_pending = false;
116 out.push_str(&" ".repeat(depth));
117 out.push_str(bullet_for_depth(depth));
118 out.push(' ');
119 out.push_str(&inline_mrkdwn(item));
120 out.push('\n');
121 continue;
122 }
123
124 if let Some((number, rest)) = split_ordered_item(trimmed) {
125 blank_pending = false;
126 out.push_str(&" ".repeat(depth));
127 out.push_str(&number);
128 out.push_str(". ");
129 out.push_str(&inline_mrkdwn(rest));
130 out.push('\n');
131 continue;
132 }
133
134 if blank_pending && !out.is_empty() {
135 out.push('\n');
136 }
137 blank_pending = false;
138 out.push_str(&inline_mrkdwn(line));
139 out.push('\n');
140 }
141 if in_fence {
142 out.push_str("```\n");
143 out.push_str(&fence.join("\n"));
144 out.push_str("\n```\n");
145 }
146 flush_table(&mut out, &mut table);
147 out.trim_end_matches('\n').to_string()
148}
149
150fn is_horizontal_rule(trimmed: &str) -> bool {
151 let compact: String = trimmed.chars().filter(|c| !c.is_whitespace()).collect();
152 compact.len() >= 3
153 && (compact.chars().all(|c| c == '-')
154 || compact.chars().all(|c| c == '*')
155 || compact.chars().all(|c| c == '_'))
156}
157
158fn is_spoiler(trimmed: &str) -> bool {
159 trimmed.starts_with("||") && trimmed.ends_with("||") && trimmed.len() > 4
160}
161
162fn split_ordered_item(trimmed: &str) -> Option<(String, &str)> {
163 let digits_end = trimmed.find(|c: char| !c.is_ascii_digit())?;
164 if digits_end == 0 {
165 return None;
166 }
167 let (number, rest) = trimmed.split_at(digits_end);
168 let rest = rest
169 .strip_prefix(". ")
170 .or_else(|| rest.strip_prefix(") "))?;
171 Some((number.to_string(), rest))
172}
173
174fn bullet_for_depth(depth: usize) -> &'static str {
175 match depth % 3 {
176 0 => "•",
177 1 => "◦",
178 _ => "▪",
179 }
180}
181
182fn strip_task_item(trimmed: &str) -> Option<String> {
183 trimmed
184 .strip_prefix("- [ ] ")
185 .map(|rest| format!("☐ {}", rest))
186 .or_else(|| {
187 trimmed
188 .strip_prefix("- [x] ")
189 .map(|rest| format!("☑ {}", rest))
190 })
191}
192
193fn flush_table(out: &mut String, rows: &mut Vec<String>) {
194 if rows.is_empty() {
195 return;
196 }
197 let parsed: Vec<Vec<String>> = rows
198 .iter()
199 .filter(|row| !is_separator_row(row))
200 .map(|row| {
201 row.trim()
202 .trim_matches('|')
203 .split('|')
204 .map(|cell| cell.trim().to_string())
205 .collect()
206 })
207 .collect();
208
209 if parsed.is_empty() {
210 rows.clear();
211 return;
212 }
213
214 let columns = parsed.iter().map(|row| row.len()).max().unwrap_or(0);
215 let mut widths = vec![0usize; columns];
216 for row in &parsed {
217 for (index, cell) in row.iter().enumerate() {
218 widths[index] = widths[index].max(cell.chars().count());
219 }
220 }
221
222 out.push_str("```\n");
223 for (row_index, row) in parsed.iter().enumerate() {
224 for (index, width) in widths.iter().enumerate() {
225 let cell = row.get(index).map(String::as_str).unwrap_or("");
226 out.push_str(cell);
227 out.push_str(&" ".repeat(width.saturating_sub(cell.chars().count())));
228 if index + 1 < columns {
229 out.push_str(" ");
230 }
231 }
232 out.push('\n');
233 if row_index == 0 {
234 let underline: usize = widths.iter().sum::<usize>() + (columns.saturating_sub(1) * 2);
235 out.push_str(&"─".repeat(underline));
236 out.push('\n');
237 }
238 }
239 out.push_str("```\n");
240 rows.clear();
241}
242
243fn is_separator_row(row: &str) -> bool {
244 row.replace(['|', '-', ' ', ':'], "").is_empty()
245}
246
247/// Slack's mrkdwn has only three literal characters that must be escaped
248/// outside of code spans: `&`, `<`, `>`.
249fn escape_mrkdwn(value: &str) -> String {
250 value
251 .replace('&', "&")
252 .replace('<', "<")
253 .replace('>', ">")
254}
255
256fn inline_mrkdwn(value: &str) -> String {
257 let mut codes = Vec::new();
258 let value = replace_code_spans(value, &mut codes);
259 let mut value = escape_mrkdwn(&value);
260 value = replace_links(&value);
261 value = replace_pairs(&value, "~~", "~", "~");
262 // Slack has no native spoiler syntax; ||spoiler|| passes through as
263 // literal text (best-effort — the line-level handler also passes it
264 // through so the markup is preserved rather than lost).
265 // GFM bold (** or __) -> Slack bold (*); GFM italic (* or _) -> Slack
266 // italic (_). Bold must be swapped before italic so a leftover single
267 // `*`/`_` is read as the italic marker, not a stray bold delimiter.
268 value = replace_pairs(&value, "**", "\u{1}", "\u{1}");
269 value = replace_pairs(&value, "__", "\u{1}", "\u{1}");
270 value = replace_spaced_pairs(&value, "*", "_", "_");
271 value = replace_spaced_pairs(&value, "_", "_", "_");
272 value = value.replace('\u{1}', "*");
273 for (index, code) in codes.iter().enumerate() {
274 value = value.replace(
275 &format!("\u{0}{index}\u{0}"),
276 &format!("`{}`", code.replace('`', "'")),
277 );
278 }
279 value
280}
281
282fn replace_code_spans(value: &str, sink: &mut Vec<String>) -> String {
283 let mut out = String::new();
284 let mut rest = value;
285 while let Some((before, after)) = rest.split_once('`') {
286 match after.split_once('`') {
287 Some((content, tail)) => {
288 sink.push(content.to_string());
289 out.push_str(before);
290 out.push_str(&format!("\u{0}{}\u{0}", sink.len() - 1));
291 rest = tail;
292 }
293 None => {
294 out.push_str(before);
295 out.push('`');
296 rest = after;
297 }
298 }
299 }
300 out.push_str(rest);
301 out
302}
303
304fn replace_links(value: &str) -> String {
305 let mut out = String::new();
306 let mut rest = value;
307 while let Some(open) = rest.find('[') {
308 let Some(relative_text_end) = rest[open..].find("](") else {
309 break;
310 };
311 let text_end = open + relative_text_end;
312 let Some(relative_url_end) = rest[text_end..].find(')') else {
313 break;
314 };
315 let url_end = text_end + relative_url_end;
316 let url = &rest[text_end + 2..url_end];
317 if url.contains(['"', '<', '>', ' ']) {
318 out.push_str(&rest[..open + 1]);
319 rest = &rest[open + 1..];
320 continue;
321 }
322 out.push_str(&rest[..open]);
323 out.push('<');
324 out.push_str(url);
325 out.push('|');
326 out.push_str(&rest[open + 1..text_end]);
327 out.push('>');
328 rest = &rest[url_end + 1..];
329 }
330 out.push_str(rest);
331 out
332}
333
334fn replace_pairs(value: &str, marker: &str, open: &str, close: &str) -> String {
335 let mut out = String::new();
336 let mut rest = value;
337 loop {
338 match rest.split_once(marker) {
339 Some((before, after)) => match after.split_once(marker) {
340 Some((inner, tail)) if !inner.is_empty() => {
341 out.push_str(before);
342 out.push_str(open);
343 out.push_str(inner);
344 out.push_str(close);
345 rest = tail;
346 }
347 _ => {
348 out.push_str(before);
349 out.push_str(marker);
350 rest = after;
351 }
352 },
353 None => {
354 out.push_str(rest);
355 return out;
356 }
357 }
358 }
359}
360
361fn replace_spaced_pairs(value: &str, marker: &str, open: &str, close: &str) -> String {
362 let mut out = String::new();
363 let mut rest = value;
364 loop {
365 match rest.split_once(marker) {
366 Some((before, after)) => {
367 let opens = after.chars().next().is_some_and(|c| !c.is_whitespace());
368 let boundary = before.is_empty()
369 || before.chars().last().is_some_and(|c| !c.is_alphanumeric());
370 match after.split_once(marker) {
371 Some((inner, tail)) if opens && boundary && !inner.trim().is_empty() => {
372 out.push_str(before);
373 out.push_str(open);
374 out.push_str(inner.trim_end_matches(marker));
375 out.push_str(close);
376 rest = tail;
377 }
378 _ => {
379 out.push_str(before);
380 out.push_str(marker);
381 rest = after;
382 }
383 }
384 }
385 None => {
386 out.push_str(rest);
387 return out;
388 }
389 }
390 }
391}
392
393#[cfg(test)]
394mod tests {
395 use super::*;
396
397 #[test]
398 fn converts_bold_and_italic_conventions() {
399 let out = markdown_to_mrkdwn("**bold** and *italic* and _also italic_");
400 assert!(out.contains("*bold*"));
401 assert!(out.contains("_italic_"));
402 assert!(out.contains("_also italic_"));
403 }
404
405 #[test]
406 fn converts_links_to_angle_pipe_form() {
407 let out = markdown_to_mrkdwn("[site](https://example.com)");
408 assert_eq!(out, "<https://example.com|site>");
409 }
410
411 #[test]
412 fn headings_become_bold_lines() {
413 let out = markdown_to_mrkdwn("# Title\n\nbody");
414 assert!(out.starts_with("*Title*"));
415 }
416
417 #[test]
418 fn renders_bullets_and_ordered_items() {
419 let out = markdown_to_mrkdwn("- one\n- two\n1. first\n2. second");
420 assert!(out.contains("• one"));
421 assert!(out.contains("• two"));
422 assert!(out.contains("1. first"));
423 assert!(out.contains("2. second"));
424 }
425
426 #[test]
427 fn renders_table_as_aligned_code_block() {
428 let out = markdown_to_mrkdwn("| A | B |\n| - | - |\n| 1 | 22 |");
429 assert!(out.contains("```"));
430 assert!(out.contains("A"));
431 assert!(out.contains("22"));
432 }
433
434 #[test]
435 fn strikethrough_and_code_spans_convert() {
436 let out = markdown_to_mrkdwn("~~gone~~ and `code`");
437 assert!(out.contains("~gone~"));
438 assert!(out.contains("`code`"));
439 }
440
441 #[test]
442 fn escapes_ampersand_and_angle_brackets_outside_code() {
443 let out = markdown_to_mrkdwn("A & B < C > D");
444 assert!(out.contains("&"));
445 assert!(out.contains("<"));
446 assert!(out.contains(">"));
447 }
448}
449

1//! GFM-to-Slack `mrkdwn` projection.
2//!
3//! Slack's `mrkdwn` dialect diverges from GFM in exactly the spots that
4//! matter most: bold uses a single `*`, italic uses `_`, links use
5//! `<url|text>`, there is no heading syntax and no table syntax at all.
6//! This module renders a conservative GFM subset into text that actually
7//! looks right when Slack's client parses it.
8
9/// Convert a conservative GFM subset to Slack `mrkdwn`.
10pub fn markdown_to_mrkdwn(markdown: &str) -> String {
11 let mut out = String::with_capacity(markdown.len() + 64);
12 let mut in_fence = false;
13 let mut fence = Vec::new();
14 let mut table = Vec::new();
15 let mut blank_pending = false;
16
17 for line in markdown.lines() {
18 let trimmed = line.trim_start();
19
20 if trimmed.starts_with("```") {
21 flush_table(&mut out, &mut table);
22 if in_fence {
23 out.push_str("```\n");
24 out.push_str(&fence.join("\n"));
25 out.push_str("\n```\n");
26 fence.clear();
27 }
28 in_fence = !in_fence;
29 blank_pending = false;
30 continue;
31 }
32 if in_fence {
33 fence.push(line.to_string());
34 continue;
35 }
36
37 if trimmed.is_empty() {
38 flush_table(&mut out, &mut table);
39 blank_pending = !out.is_empty();
40 continue;
41 }
42
43 if is_spoiler(trimmed) {
44 flush_table(&mut out, &mut table);
45 if blank_pending && !out.is_empty() {
46 out.push('\n');
47 }
48 blank_pending = false;
49 out.push_str(trimmed);
50 out.push('\n');
51 continue;
52 }
53
54 if trimmed.starts_with('|') && trimmed.ends_with('|') && trimmed.len() > 1 {
55 if blank_pending {
56 out.push('\n');
57 }
58 blank_pending = false;
59 table.push(trimmed.to_string());
60 continue;
61 }
62 flush_table(&mut out, &mut table);
63
64 if is_horizontal_rule(trimmed) {
65 if blank_pending {
66 out.push('\n');
67 }
68 blank_pending = false;
69 out.push_str("──────────\n");
70 continue;
71 }
72
73 if let Some(after) = trimmed.strip_prefix('#')
74 && after.starts_with(' ')
75 {
76 let text = after.trim().trim_start_matches('#').trim();
77 if !text.is_empty() {
78 if blank_pending && !out.is_empty() {
79 out.push('\n');
80 }
81 blank_pending = false;
82 out.push('*');
83 out.push_str(&inline_mrkdwn(text));
84 out.push_str("*\n");
85 continue;
86 }
87 }
88
89 if let Some(quote) = trimmed.strip_prefix("> ") {
90 blank_pending = false;
91 out.push_str("> ");
92 out.push_str(&inline_mrkdwn(quote));
93 out.push('\n');
94 continue;
95 }
96
97 let indent = line.len() - trimmed.len();
98 let depth = indent / 2;
99
100 if let Some(rest) = strip_task_item(trimmed) {
101 blank_pending = false;
102 out.push_str(&" ".repeat(depth));
103 out.push_str(bullet_for_depth(depth));
104 out.push(' ');
105 out.push_str(&inline_mrkdwn(&rest));
106 out.push('\n');
107 continue;
108 }
109
110 if let Some(item) = trimmed
111 .strip_prefix("- ")
112 .or_else(|| trimmed.strip_prefix("* "))
113 .or_else(|| trimmed.strip_prefix("+ "))
114 {
115 blank_pending = false;
116 out.push_str(&" ".repeat(depth));
117 out.push_str(bullet_for_depth(depth));
118 out.push(' ');
119 out.push_str(&inline_mrkdwn(item));
120 out.push('\n');
121 continue;
122 }
123
124 if let Some((number, rest)) = split_ordered_item(trimmed) {
125 blank_pending = false;
126 out.push_str(&" ".repeat(depth));
127 out.push_str(&number);
128 out.push_str(". ");
129 out.push_str(&inline_mrkdwn(rest));
130 out.push('\n');
131 continue;
132 }
133
134 if blank_pending && !out.is_empty() {
135 out.push('\n');
136 }
137 blank_pending = false;
138 out.push_str(&inline_mrkdwn(line));
139 out.push('\n');
140 }
141 if in_fence {
142 out.push_str("```\n");
143 out.push_str(&fence.join("\n"));
144 out.push_str("\n```\n");
145 }
146 flush_table(&mut out, &mut table);
147 out.trim_end_matches('\n').to_string()
148}
149
150fn is_horizontal_rule(trimmed: &str) -> bool {
151 let compact: String = trimmed.chars().filter(|c| !c.is_whitespace()).collect();
152 compact.len() >= 3
153 && (compact.chars().all(|c| c == '-')
154 || compact.chars().all(|c| c == '*')
155 || compact.chars().all(|c| c == '_'))
156}
157
158fn is_spoiler(trimmed: &str) -> bool {
159 trimmed.starts_with("||") && trimmed.ends_with("||") && trimmed.len() > 4
160}
161
162fn split_ordered_item(trimmed: &str) -> Option<(String, &str)> {
163 let digits_end = trimmed.find(|c: char| !c.is_ascii_digit())?;
164 if digits_end == 0 {
165 return None;
166 }
167 let (number, rest) = trimmed.split_at(digits_end);
168 let rest = rest
169 .strip_prefix(". ")
170 .or_else(|| rest.strip_prefix(") "))?;
171 Some((number.to_string(), rest))
172}
173
174fn bullet_for_depth(depth: usize) -> &'static str {
175 match depth % 3 {
176 0 => "•",
177 1 => "◦",
178 _ => "▪",
179 }
180}
181
182fn strip_task_item(trimmed: &str) -> Option<String> {
183 trimmed
184 .strip_prefix("- [ ] ")
185 .map(|rest| format!("☐ {}", rest))
186 .or_else(|| {
187 trimmed
188 .strip_prefix("- [x] ")
189 .map(|rest| format!("☑ {}", rest))
190 })
191}
192
193fn flush_table(out: &mut String, rows: &mut Vec<String>) {
194 if rows.is_empty() {
195 return;
196 }
197 let parsed: Vec<Vec<String>> = rows
198 .iter()
199 .filter(|row| !is_separator_row(row))
200 .map(|row| {
201 row.trim()
202 .trim_matches('|')
203 .split('|')
204 .map(|cell| cell.trim().to_string())
205 .collect()
206 })
207 .collect();
208
209 if parsed.is_empty() {
210 rows.clear();
211 return;
212 }
213
214 let columns = parsed.iter().map(|row| row.len()).max().unwrap_or(0);
215 let mut widths = vec![0usize; columns];
216 for row in &parsed {
217 for (index, cell) in row.iter().enumerate() {
218 widths[index] = widths[index].max(cell.chars().count());
219 }
220 }
221
222 out.push_str("```\n");
223 for (row_index, row) in parsed.iter().enumerate() {
224 for (index, width) in widths.iter().enumerate() {
225 let cell = row.get(index).map(String::as_str).unwrap_or("");
226 out.push_str(cell);
227 out.push_str(&" ".repeat(width.saturating_sub(cell.chars().count())));
228 if index + 1 < columns {
229 out.push_str(" ");
230 }
231 }
232 out.push('\n');
233 if row_index == 0 {
234 let underline: usize = widths.iter().sum::<usize>() + (columns.saturating_sub(1) * 2);
235 out.push_str(&"─".repeat(underline));
236 out.push('\n');
237 }
238 }
239 out.push_str("```\n");
240 rows.clear();
241}
242
243fn is_separator_row(row: &str) -> bool {
244 row.replace(['|', '-', ' ', ':'], "").is_empty()
245}
246
247/// Slack's mrkdwn has only three literal characters that must be escaped
248/// outside of code spans: `&`, `<`, `>`.
249fn escape_mrkdwn(value: &str) -> String {
250 value
251 .replace('&', "&")
252 .replace('<', "<")
253 .replace('>', ">")
254}
255
256fn inline_mrkdwn(value: &str) -> String {
257 let mut codes = Vec::new();
258 let value = replace_code_spans(value, &mut codes);
259 let mut value = escape_mrkdwn(&value);
260 value = replace_links(&value);
261 value = replace_pairs(&value, "~~", "~", "~");
262 // Slack has no native spoiler syntax; ||spoiler|| passes through as
263 // literal text (best-effort — the line-level handler also passes it
264 // through so the markup is preserved rather than lost).
265 // GFM bold (** or __) -> Slack bold (*); GFM italic (* or _) -> Slack
266 // italic (_). Bold must be swapped before italic so a leftover single
267 // `*`/`_` is read as the italic marker, not a stray bold delimiter.
268 value = replace_pairs(&value, "**", "\u{1}", "\u{1}");
269 value = replace_pairs(&value, "__", "\u{1}", "\u{1}");
270 value = replace_spaced_pairs(&value, "*", "_", "_");
271 value = replace_spaced_pairs(&value, "_", "_", "_");
272 value = value.replace('\u{1}', "*");
273 for (index, code) in codes.iter().enumerate() {
274 value = value.replace(
275 &format!("\u{0}{index}\u{0}"),
276 &format!("`{}`", code.replace('`', "'")),
277 );
278 }
279 value
280}
281
282fn replace_code_spans(value: &str, sink: &mut Vec<String>) -> String {
283 let mut out = String::new();
284 let mut rest = value;
285 while let Some((before, after)) = rest.split_once('`') {
286 match after.split_once('`') {
287 Some((content, tail)) => {
288 sink.push(content.to_string());
289 out.push_str(before);
290 out.push_str(&format!("\u{0}{}\u{0}", sink.len() - 1));
291 rest = tail;
292 }
293 None => {
294 out.push_str(before);
295 out.push('`');
296 rest = after;
297 }
298 }
299 }
300 out.push_str(rest);
301 out
302}
303
304fn replace_links(value: &str) -> String {
305 let mut out = String::new();
306 let mut rest = value;
307 while let Some(open) = rest.find('[') {
308 let Some(relative_text_end) = rest[open..].find("](") else {
309 break;
310 };
311 let text_end = open + relative_text_end;
312 let Some(relative_url_end) = rest[text_end..].find(')') else {
313 break;
314 };
315 let url_end = text_end + relative_url_end;
316 let url = &rest[text_end + 2..url_end];
317 if url.contains(['"', '<', '>', ' ']) {
318 out.push_str(&rest[..open + 1]);
319 rest = &rest[open + 1..];
320 continue;
321 }
322 out.push_str(&rest[..open]);
323 out.push('<');
324 out.push_str(url);
325 out.push('|');
326 out.push_str(&rest[open + 1..text_end]);
327 out.push('>');
328 rest = &rest[url_end + 1..];
329 }
330 out.push_str(rest);
331 out
332}
333
334fn replace_pairs(value: &str, marker: &str, open: &str, close: &str) -> String {
335 let mut out = String::new();
336 let mut rest = value;
337 loop {
338 match rest.split_once(marker) {
339 Some((before, after)) => match after.split_once(marker) {
340 Some((inner, tail)) if !inner.is_empty() => {
341 out.push_str(before);
342 out.push_str(open);
343 out.push_str(inner);
344 out.push_str(close);
345 rest = tail;
346 }
347 _ => {
348 out.push_str(before);
349 out.push_str(marker);
350 rest = after;
351 }
352 },
353 None => {
354 out.push_str(rest);
355 return out;
356 }
357 }
358 }
359}
360
361fn replace_spaced_pairs(value: &str, marker: &str, open: &str, close: &str) -> String {
362 let mut out = String::new();
363 let mut rest = value;
364 loop {
365 match rest.split_once(marker) {
366 Some((before, after)) => {
367 let opens = after.chars().next().is_some_and(|c| !c.is_whitespace());
368 let boundary = before.is_empty()
369 || before.chars().last().is_some_and(|c| !c.is_alphanumeric());
370 match after.split_once(marker) {
371 Some((inner, tail)) if opens && boundary && !inner.trim().is_empty() => {
372 out.push_str(before);
373 out.push_str(open);
374 out.push_str(inner.trim_end_matches(marker));
375 out.push_str(close);
376 rest = tail;
377 }
378 _ => {
379 out.push_str(before);
380 out.push_str(marker);
381 rest = after;
382 }
383 }
384 }
385 None => {
386 out.push_str(rest);
387 return out;
388 }
389 }
390 }
391}
392
393#[cfg(test)]
394mod tests {
395 use super::*;
396
397 #[test]
398 fn converts_bold_and_italic_conventions() {
399 let out = markdown_to_mrkdwn("**bold** and *italic* and _also italic_");
400 assert!(out.contains("*bold*"));
401 assert!(out.contains("_italic_"));
402 assert!(out.contains("_also italic_"));
403 }
404
405 #[test]
406 fn converts_links_to_angle_pipe_form() {
407 let out = markdown_to_mrkdwn("[site](https://example.com)");
408 assert_eq!(out, "<https://example.com|site>");
409 }
410
411 #[test]
412 fn headings_become_bold_lines() {
413 let out = markdown_to_mrkdwn("# Title\n\nbody");
414 assert!(out.starts_with("*Title*"));
415 }
416
417 #[test]
418 fn renders_bullets_and_ordered_items() {
419 let out = markdown_to_mrkdwn("- one\n- two\n1. first\n2. second");
420 assert!(out.contains("• one"));
421 assert!(out.contains("• two"));
422 assert!(out.contains("1. first"));
423 assert!(out.contains("2. second"));
424 }
425
426 #[test]
427 fn renders_table_as_aligned_code_block() {
428 let out = markdown_to_mrkdwn("| A | B |\n| - | - |\n| 1 | 22 |");
429 assert!(out.contains("```"));
430 assert!(out.contains("A"));
431 assert!(out.contains("22"));
432 }
433
434 #[test]
435 fn strikethrough_and_code_spans_convert() {
436 let out = markdown_to_mrkdwn("~~gone~~ and `code`");
437 assert!(out.contains("~gone~"));
438 assert!(out.contains("`code`"));
439 }
440
441 #[test]
442 fn escapes_ampersand_and_angle_brackets_outside_code() {
443 let out = markdown_to_mrkdwn("A & B < C > D");
444 assert!(out.contains("&"));
445 assert!(out.contains("<"));
446 assert!(out.contains(">"));
447 }
448}
449

Indexing the workspace…