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

//! Functions that compute a new char index.

use ropey::Rope;
use std::cmp::min;

pub fn right(text: &Rope, char_idx: usize) -> usize {
    let len_chars = text.len_chars();
    min(
        if len_chars > 0 { len_chars } else { 0 },
        char_idx + 1
    )
}

pub fn left(char_idx: usize) -> usize {
    if char_idx > 0 {
        char_idx - 1
    } else {
        0
    }
}

pub fn down(text: &Rope, char_idx: usize) -> usize {
    vertical(text, char_idx, 1)
}

pub fn up(text: &Rope, char_idx: usize) -> usize {
    vertical(text, char_idx, -1)
}

fn vertical(text: &Rope, char_idx: usize, lines: isize) -> usize {
    // > If char_idx is one-past-the-end, then one-past-the-end line index is returned.
    // Circumvent this behavior by clipping to the last valid line index.
    let line_idx = min(text.len_lines() - 1, text.char_to_line(char_idx));
    if lines < 0 && line_idx > 0 || lines > 0 && line_idx < text.len_lines() - 1 {
        let x = char_idx - text.line_to_char(line_idx);
        let next_line_idx = if lines > 0 {
            line_idx + lines as usize
        } else {
            line_idx - lines.abs() as usize
        };
        let line_len = text.line(next_line_idx).len_chars();

        text.line_to_char(next_line_idx) +
        if x <= line_len {
            x
        } else if line_len > 0 {
            line_len - 1
        } else {
            0
        }
    } else {
        char_idx
    }
}

pub fn line_start(text: &Rope, char_idx: usize) -> usize {
    let line_idx = text.char_to_line(char_idx);
    text.line_to_char(line_idx)
}

pub fn line_end(text: &Rope, char_idx: usize) -> usize {
    let line_idx = text.char_to_line(char_idx);
    text.line_to_char(line_idx) + if line_idx < text.len_lines() {
        let line_len = text.line(line_idx).len_chars();
        if line_len > 0 {
            line_len - 1
        } else {
            0
        }
    } else {
        0
    }
}

#[cfg(test)]
mod tests {
    use ropey::Rope;

    const TEXT: &str = concat!(
        "1st\n",
        "2nd line\n",
        "3rd line"
    );

    #[test]
    fn right() {{
        let text = Rope::from_str(TEXT);
        let len_chars = text.len_chars();
        assert_eq!(1,             super::right(&text, 0));
        assert_eq!(len_chars - 1, super::right(&text, len_chars - 2));
        assert_eq!(len_chars,     super::right(&text, len_chars - 1));
        assert_eq!(len_chars,     super::right(&text, len_chars));
    } {
        let text = Rope::from_str("");
        assert_eq!(0, super::right(&text, 0));
    }}

    #[test]
    fn left() {
        assert_eq!(0, super::left(0));
        assert_eq!(0, super::left(1));
        assert_eq!(1, super::left(2));
    }

    #[test]
    fn down() {{
        let text = Rope::from_str(TEXT);
        assert_eq!(text.line_to_char(1),     super::down(&text, text.line_to_char(0)));
        assert_eq!(text.line_to_char(2),     super::down(&text, text.line_to_char(1)));
        assert_eq!(text.line_to_char(2),     super::down(&text, text.line_to_char(2)));
        assert_eq!(text.line_to_char(2) + 3, super::down(&text, text.line_to_char(1) + 3));
        assert_eq!(text.len_chars(),         super::down(&text, text.line_to_char(2) - 1));
    } {
        let text = Rope::from_str("");
        assert_eq!(0, super::down(&text, 0));
    }}

    #[test]
    fn up() {{
        let text = Rope::from_str(TEXT);
        assert_eq!(text.line_to_char(1), super::up(&text, text.line_to_char(2)));
        assert_eq!(text.line_to_char(0), super::up(&text, text.line_to_char(1)));
        assert_eq!(text.line_to_char(0), super::up(&text, text.line_to_char(0)));
        assert_eq!(text.line_to_char(0) + 3, super::up(&text, text.line_to_char(1) + 3));
        assert_eq!(text.line_to_char(1) - 1, super::up(&text, text.line_to_char(2) - 2));
    } {
        let text = Rope::from_str("");
        assert_eq!(0, super::up(&text, 0));
    }}

    #[test]
    fn line_start() {{
        let text = Rope::from_str(TEXT);
        assert_eq!(text.line_to_char(1), super::line_start(&text, 12));
        assert_eq!(text.line_to_char(1), super::line_start(&text, text.line_to_char(1)));
    } {
        let text = Rope::from_str("");
        assert_eq!(0, super::line_start(&text, 0));
    }}

    #[test]
    fn line_end() {{
        let text = Rope::from_str(TEXT);
        assert_eq!(text.line_to_char(2) - 1, super::line_end(&text, 12));
        assert_eq!(text.line_to_char(2) - 1, super::line_end(&text, text.line_to_char(2) - 1));
    } {
        let text = Rope::from_str("");
        assert_eq!(0, super::line_end(&text, 0));
    }}
}