1use std::{cmp::Ordering, collections::HashMap, ops::Range};
2
3/// Construct a string and a list of offsets within that string using a single
4/// string containing embedded position markers.
5pub fn marked_text_offsets_by(
6 marked_text: &str,
7 markers: Vec<char>,
8) -> (String, HashMap<char, Vec<usize>>) {
9 let mut extracted_markers: HashMap<char, Vec<usize>> = Default::default();
10 let mut unmarked_text = String::new();
11
12 for char in marked_text.chars() {
13 if markers.contains(&char) {
14 let char_offsets = extracted_markers.entry(char).or_insert(Vec::new());
15 char_offsets.push(unmarked_text.len());
16 } else {
17 unmarked_text.push(char);
18 }
19 }
20
21 (unmarked_text, extracted_markers)
22}
23
24/// Construct a string and a list of ranges within that string using a single
25/// string containing embedded range markers, using arbitrary characters as
26/// range markers. By using multiple different range markers, you can construct
27/// ranges that overlap each other.
28///
29/// The returned ranges will be grouped by their range marking characters.
30pub fn marked_text_ranges_by(
31 marked_text: &str,
32 markers: Vec<TextRangeMarker>,
33) -> (String, HashMap<TextRangeMarker, Vec<Range<usize>>>) {
34 let all_markers = markers.iter().flat_map(|m| m.markers()).collect();
35
36 let (unmarked_text, mut marker_offsets) = marked_text_offsets_by(marked_text, all_markers);
37 let range_lookup = markers
38 .into_iter()
39 .map(|marker| {
40 (
41 marker.clone(),
42 match marker {
43 TextRangeMarker::Empty(empty_marker_char) => marker_offsets
44 .remove(&empty_marker_char)
45 .unwrap_or_default()
46 .into_iter()
47 .map(|empty_index| empty_index..empty_index)
48 .collect::<Vec<Range<usize>>>(),
49 TextRangeMarker::Range(start_marker, end_marker) => {
50 let starts = marker_offsets.remove(&start_marker).unwrap_or_default();
51 let ends = marker_offsets.remove(&end_marker).unwrap_or_default();
52 assert_eq!(starts.len(), ends.len(), "marked ranges are unbalanced");
53 starts
54 .into_iter()
55 .zip(ends)
56 .map(|(start, end)| {
57 assert!(end >= start, "marked ranges must be disjoint");
58 start..end
59 })
60 .collect::<Vec<Range<usize>>>()
61 }
62 TextRangeMarker::ReverseRange(start_marker, end_marker) => {
63 let starts = marker_offsets.remove(&start_marker).unwrap_or_default();
64 let ends = marker_offsets.remove(&end_marker).unwrap_or_default();
65 assert_eq!(starts.len(), ends.len(), "marked ranges are unbalanced");
66 starts
67 .into_iter()
68 .zip(ends)
69 .map(|(start, end)| {
70 assert!(end >= start, "marked ranges must be disjoint");
71 end..start
72 })
73 .collect::<Vec<Range<usize>>>()
74 }
75 },
76 )
77 })
78 .collect();
79
80 (unmarked_text, range_lookup)
81}
82
83/// Construct a string and a list of ranges within that string using a single
84/// string containing embedded range markers. The characters used to mark the
85/// ranges are as follows:
86///
87/// 1. To mark a range of text, surround it with the `«` and `»` angle brackets,
88/// which can be typed on a US keyboard with the `alt-|` and `alt-shift-|` keys.
89///
90/// ```text
91/// foo «selected text» bar
92/// ```
93///
94/// 2. To mark a single position in the text, use the `ˇ` caron,
95/// which can be typed on a US keyboard with the `alt-shift-t` key.
96///
97/// ```text
98/// the cursors are hereˇ and hereˇ.
99/// ```
100///
101/// 3. To mark a range whose direction is meaningful (like a selection),
102/// put a caron character beside one of its bounds, on the inside:
103///
104/// ```text
105/// one «ˇreversed» selection and one «forwardˇ» selection
106/// ```
107pub fn marked_text_ranges(
108 marked_text: &str,
109 ranges_are_directed: bool,
110) -> (String, Vec<Range<usize>>) {
111 let mut unmarked_text = String::with_capacity(marked_text.len());
112 let mut ranges = Vec::new();
113 let mut prev_marked_ix = 0;
114 let mut current_range_start = None;
115 let mut current_range_cursor = None;
116
117 for (marked_ix, marker) in marked_text.match_indices(&['«', '»', 'ˇ']) {
118 unmarked_text.push_str(&marked_text[prev_marked_ix..marked_ix]);
119 let unmarked_len = unmarked_text.len();
120 let len = marker.len();
121 prev_marked_ix = marked_ix + len;
122
123 match marker {
124 "ˇ" => {
125 if current_range_start.is_some() {
126 if current_range_cursor.is_some() {
127 panic!("duplicate point marker 'ˇ' at index {marked_ix}");
128 } else {
129 current_range_cursor = Some(unmarked_len);
130 }
131 } else {
132 ranges.push(unmarked_len..unmarked_len);
133 }
134 }
135 "«" => {
136 if current_range_start.is_some() {
137 panic!("unexpected range start marker '«' at index {marked_ix}");
138 }
139 current_range_start = Some(unmarked_len);
140 }
141 "»" => {
142 let current_range_start = if let Some(start) = current_range_start.take() {
143 start
144 } else {
145 panic!("unexpected range end marker '»' at index {marked_ix}");
146 };
147
148 let mut reversed = false;
149 if let Some(current_range_cursor) = current_range_cursor.take() {
150 if current_range_cursor == current_range_start {
151 reversed = true;
152 } else if current_range_cursor != unmarked_len {
153 panic!("unexpected 'ˇ' marker in the middle of a range");
154 }
155 } else if ranges_are_directed {
156 panic!("missing 'ˇ' marker to indicate range direction");
157 }
158
159 ranges.push(if reversed {
160 unmarked_len..current_range_start
161 } else {
162 current_range_start..unmarked_len
163 });
164 }
165 _ => unreachable!(),
166 }
167 }
168
169 unmarked_text.push_str(&marked_text[prev_marked_ix..]);
170 (unmarked_text, ranges)
171}
172
173pub fn marked_text_offsets(marked_text: &str) -> (String, Vec<usize>) {
174 let (text, ranges) = marked_text_ranges(marked_text, false);
175 (
176 text,
177 ranges
178 .into_iter()
179 .map(|range| {
180 assert_eq!(range.start, range.end);
181 range.start
182 })
183 .collect(),
184 )
185}
186
187pub fn generate_marked_text(
188 unmarked_text: &str,
189 ranges: &[Range<usize>],
190 indicate_cursors: bool,
191) -> String {
192 let mut marked_text = unmarked_text.to_string();
193 for range in ranges.iter().rev() {
194 if indicate_cursors {
195 match range.start.cmp(&range.end) {
196 Ordering::Less => {
197 marked_text.insert_str(range.end, "ˇ»");
198 marked_text.insert(range.start, '«');
199 }
200 Ordering::Equal => {
201 marked_text.insert(range.start, 'ˇ');
202 }
203 Ordering::Greater => {
204 marked_text.insert(range.start, '»');
205 marked_text.insert_str(range.end, "«ˇ");
206 }
207 }
208 } else {
209 marked_text.insert(range.end, '»');
210 marked_text.insert(range.start, '«');
211 }
212 }
213 marked_text
214}
215
216#[derive(Clone, Eq, PartialEq, Hash)]
217pub enum TextRangeMarker {
218 Empty(char),
219 Range(char, char),
220 ReverseRange(char, char),
221}
222
223impl TextRangeMarker {
224 fn markers(&self) -> Vec<char> {
225 match self {
226 Self::Empty(m) => vec![*m],
227 Self::Range(l, r) => vec![*l, *r],
228 Self::ReverseRange(l, r) => vec![*l, *r],
229 }
230 }
231}
232
233impl From<char> for TextRangeMarker {
234 fn from(marker: char) -> Self {
235 Self::Empty(marker)
236 }
237}
238
239impl From<(char, char)> for TextRangeMarker {
240 fn from((left_marker, right_marker): (char, char)) -> Self {
241 Self::Range(left_marker, right_marker)
242 }
243}
244
245#[cfg(test)]
246mod tests {
247 use super::{generate_marked_text, marked_text_ranges};
248
249 #[test]
250 fn test_marked_text() {
251 let (text, ranges) = marked_text_ranges("one «ˇtwo» «threeˇ» «ˇfour» fiveˇ six", true);
252
253 assert_eq!(text, "one two three four five six");
254 assert_eq!(ranges.len(), 4);
255 assert_eq!(ranges[0], 7..4);
256 assert_eq!(ranges[1], 8..13);
257 assert_eq!(ranges[2], 18..14);
258 assert_eq!(ranges[3], 23..23);
259
260 assert_eq!(
261 generate_marked_text(&text, &ranges, true),
262 "one «ˇtwo» «threeˇ» «ˇfour» fiveˇ six"
263 );
264 }
265}