aboutsummaryrefslogtreecommitdiff
path: root/helix-core/src/surround.rs
blob: 32161b700a58f2ad9454d41ca79d560f338099db (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
use crate::{search, Selection};
use ropey::RopeSlice;

pub const PAIRS: &[(char, char)] = &[
    ('(', ')'),
    ('[', ']'),
    ('{', '}'),
    ('<', '>'),
    ('«', '»'),
    ('「', '」'),
    ('(', ')'),
];

/// Given any char in [PAIRS], return the open and closing chars. If not found in
/// [PAIRS] return (ch, ch).
///
/// ```
/// use helix_core::surround::get_pair;
///
/// assert_eq!(get_pair('['), ('[', ']'));
/// assert_eq!(get_pair('}'), ('{', '}'));
/// assert_eq!(get_pair('"'), ('"', '"'));
/// ```
pub fn get_pair(ch: char) -> (char, char) {
    PAIRS
        .iter()
        .find(|(open, close)| *open == ch || *close == ch)
        .copied()
        .unwrap_or((ch, ch))
}

/// Find the position of surround pairs of `ch` which can be either a closing
/// or opening pair. `n` will skip n - 1 pairs (eg. n=2 will discard (only)
/// the first pair found and keep looking)
pub fn find_nth_pairs_pos(
    text: RopeSlice,
    ch: char,
    pos: usize,
    n: usize,
) -> Option<(usize, usize)> {
    let (open, close) = get_pair(ch);

    if text.len_chars() < 2 || pos >= text.len_chars() {
        return None;
    }

    if open == close {
        if Some(open) == text.get_char(pos) {
            // Special case: cursor is directly on a matching char.
            match pos {
                0 => Some((pos, search::find_nth_next(text, close, pos + 1, n)?)),
                _ if (pos + 1) == text.len_chars() => {
                    Some((search::find_nth_prev(text, open, pos, n)?, pos))
                }
                // We return no match because there's no way to know which
                // side of the char we should be searching on.
                _ => None,
            }
        } else {
            Some((
                search::find_nth_prev(text, open, pos, n)?,
                search::find_nth_next(text, close, pos, n)?,
            ))
        }
    } else {
        Some((
            find_nth_open_pair(text, open, close, pos, n)?,
            find_nth_close_pair(text, open, close, pos, n)?,
        ))
    }
}

fn find_nth_open_pair(
    text: RopeSlice,
    open: char,
    close: char,
    mut pos: usize,
    n: usize,
) -> Option<usize> {
    let mut chars = text.chars_at(pos + 1);

    // Adjusts pos for the first iteration, and handles the case of the
    // cursor being *on* the close character which will get falsely stepped over
    // if not skipped here
    if chars.prev()? == open {
        return Some(pos);
    }

    for _ in 0..n {
        let mut step_over: usize = 0;

        loop {
            let c = chars.prev()?;
            pos = pos.saturating_sub(1);

            // ignore other surround pairs that are enclosed *within* our search scope
            if c == close {
                step_over += 1;
            } else if c == open {
                if step_over == 0 {
                    break;
                }

                step_over = step_over.saturating_sub(1);
            }
        }
    }

    Some(pos)
}

fn find_nth_close_pair(
    text: RopeSlice,
    open: char,
    close: char,
    mut pos: usize,
    n: usize,
) -> Option<usize> {
    if pos >= text.len_chars() {
        return None;
    }

    let mut chars = text.chars_at(pos);

    if chars.next()? == close {
        return Some(pos);
    }

    for _ in 0..n {
        let mut step_over: usize = 0;

        loop {
            let c = chars.next()?;
            pos += 1;

            if c == open {
                step_over += 1;
            } else if c == close {
                if step_over == 0 {
                    break;
                }

                step_over = step_over.saturating_sub(1);
            }
        }
    }

    Some(pos)
}

/// Find position of surround characters around every cursor. Returns None
/// if any positions overlap. Note that the positions are in a flat Vec.
/// Use get_surround_pos().chunks(2) to get matching pairs of surround positions.
/// `ch` can be either closing or opening pair.
pub fn get_surround_pos(
    text: RopeSlice,
    selection: &Selection,
    ch: char,
    skip: usize,
) -> Option<Vec<usize>> {
    let mut change_pos = Vec::new();

    for range in selection {
        let (open_pos, close_pos) = find_nth_pairs_pos(text, ch, range.head, skip)?;
        if change_pos.contains(&open_pos) || change_pos.contains(&close_pos) {
            return None;
        }
        change_pos.extend_from_slice(&[open_pos, close_pos]);
    }
    Some(change_pos)
}

#[cfg(test)]
mod test {
    use super::*;
    use crate::Range;

    use ropey::Rope;
    use smallvec::SmallVec;

    #[test]
    fn test_find_nth_pairs_pos() {
        let doc = Rope::from("some (text) here");
        let slice = doc.slice(..);

        // cursor on [t]ext
        assert_eq!(find_nth_pairs_pos(slice, '(', 6, 1), Some((5, 10)));
        assert_eq!(find_nth_pairs_pos(slice, ')', 6, 1), Some((5, 10)));
        // cursor on so[m]e
        assert_eq!(find_nth_pairs_pos(slice, '(', 2, 1), None);
        // cursor on bracket itself
        assert_eq!(find_nth_pairs_pos(slice, '(', 5, 1), Some((5, 10)));
        assert_eq!(find_nth_pairs_pos(slice, '(', 10, 1), Some((5, 10)));
    }

    #[test]
    fn test_find_nth_pairs_pos_skip() {
        let doc = Rope::from("(so (many (good) text) here)");
        let slice = doc.slice(..);

        // cursor on go[o]d
        assert_eq!(find_nth_pairs_pos(slice, '(', 13, 1), Some((10, 15)));
        assert_eq!(find_nth_pairs_pos(slice, '(', 13, 2), Some((4, 21)));
        assert_eq!(find_nth_pairs_pos(slice, '(', 13, 3), Some((0, 27)));
    }

    #[test]
    fn test_find_nth_pairs_pos_same() {
        let doc = Rope::from("'so 'many 'good' text' here'");
        let slice = doc.slice(..);

        // cursor on go[o]d
        assert_eq!(find_nth_pairs_pos(slice, '\'', 13, 1), Some((10, 15)));
        assert_eq!(find_nth_pairs_pos(slice, '\'', 13, 2), Some((4, 21)));
        assert_eq!(find_nth_pairs_pos(slice, '\'', 13, 3), Some((0, 27)));
        // cursor on the quotes
        assert_eq!(find_nth_pairs_pos(slice, '\'', 10, 1), None);
        // this is the best we can do since opening and closing pairs are same
        assert_eq!(find_nth_pairs_pos(slice, '\'', 0, 1), Some((0, 4)));
        assert_eq!(find_nth_pairs_pos(slice, '\'', 27, 1), Some((21, 27)));
    }

    #[test]
    fn test_find_nth_pairs_pos_step() {
        let doc = Rope::from("((so)((many) good (text))(here))");
        let slice = doc.slice(..);

        // cursor on go[o]d
        assert_eq!(find_nth_pairs_pos(slice, '(', 15, 1), Some((5, 24)));
        assert_eq!(find_nth_pairs_pos(slice, '(', 15, 2), Some((0, 31)));
    }

    #[test]
    fn test_find_nth_pairs_pos_mixed() {
        let doc = Rope::from("(so [many {good} text] here)");
        let slice = doc.slice(..);

        // cursor on go[o]d
        assert_eq!(find_nth_pairs_pos(slice, '{', 13, 1), Some((10, 15)));
        assert_eq!(find_nth_pairs_pos(slice, '[', 13, 1), Some((4, 21)));
        assert_eq!(find_nth_pairs_pos(slice, '(', 13, 1), Some((0, 27)));
    }

    #[test]
    fn test_get_surround_pos() {
        let doc = Rope::from("(some) (chars)\n(newline)");
        let slice = doc.slice(..);
        let selection = Selection::new(
            SmallVec::from_slice(&[Range::point(2), Range::point(9), Range::point(20)]),
            0,
        );

        // cursor on s[o]me, c[h]ars, newl[i]ne
        assert_eq!(
            get_surround_pos(slice, &selection, '(', 1)
                .unwrap()
                .as_slice(),
            &[0, 5, 7, 13, 15, 23]
        );
    }

    #[test]
    fn test_get_surround_pos_bail() {
        let doc = Rope::from("[some]\n(chars)xx\n(newline)");
        let slice = doc.slice(..);

        let selection =
            Selection::new(SmallVec::from_slice(&[Range::point(2), Range::point(9)]), 0);

        // cursor on s[o]me, c[h]ars
        assert_eq!(
            get_surround_pos(slice, &selection, '(', 1),
            None // different surround chars
        );

        let selection = Selection::new(
            SmallVec::from_slice(&[Range::point(14), Range::point(24)]),
            0,
        );
        // cursor on [x]x, newli[n]e
        assert_eq!(
            get_surround_pos(slice, &selection, '(', 1),
            None // overlapping surround chars
        );
    }
}