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

use std::fmt::Write;

#[derive(Clone, Default)]
pub struct Buffer {
    pub buffer: Vec<char>,
    pub buffer_pos: usize,
}

impl Buffer {
    pub fn new() -> Self {
        Self { ..Self::default() }
    }

    pub fn insert(&mut self, c: char) {
        self.buffer.insert(self.buffer_pos, c);
        self.move_forward();
    }

    pub fn insert_str(&mut self, s: &str) {
        s.chars().for_each(|c| self.insert(c));
    }

    pub fn set_buffer_pos(&mut self, pos: usize) {
        self.buffer_pos = pos;
    }

    pub fn remove_current_char(&mut self) -> Option<char> {
        if !self.is_empty() && self.buffer_pos < self.buffer.len() {
            let character = self.buffer.remove(self.buffer_pos);
            Some(character)
        } else {
            None
        }
    }

    pub fn next_char(&self) -> Option<&char> {
        self.buffer.get(self.buffer_pos + 1)
    }

    pub fn current_char(&self) -> Option<&char> {
        self.buffer.get(self.buffer_pos)
    }

    pub fn previous_char(&self) -> Option<&char> {
        if self.buffer_pos > 0 {
            self.buffer.get(self.buffer_pos - 1)
        } else {
            None
        }
    }

    pub fn move_forward(&mut self) {
        self.buffer_pos += 1;
    }

    pub fn move_backward(&mut self) {
        if self.buffer_pos != 0 {
            self.buffer_pos -= 1;
        }
    }

    pub fn clear(&mut self) {
        self.buffer.clear();
        self.buffer_pos = 0;
    }

    pub fn len(&self) -> usize {
        self.buffer.len()
    }

    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    pub fn is_at_string_line_start(&self) -> bool {
        self.is_empty()
            || self.buffer[..self.buffer_pos]
                .rsplitn(2, |d| d == &'\n')
                .next()
                .unwrap_or_default()
                .iter()
                .all(|c| c.is_whitespace())
    }

    pub fn is_at_start(&self) -> bool {
        self.buffer_pos == 0
    }

    pub fn is_at_end(&self) -> bool {
        self.buffer_pos == self.buffer.len()
    }

    pub fn goto_start(&mut self) {
        self.buffer_pos = 0;
    }

    pub fn goto_end(&mut self) {
        self.buffer_pos = self.buffer.len();
    }

    pub fn _push_str(&mut self, str: &str) {
        self.buffer.extend(str.chars());
        self.buffer_pos = self.buffer.len();
    }

    pub fn get(&self, idx: usize) -> Option<&char> {
        self.buffer.get(idx)
    }

    pub fn _last(&self) -> Option<&char> {
        self.buffer.last()
    }

    pub fn iter(&self) -> impl Iterator<Item = &char> {
        self.buffer.iter()
    }

    pub fn take(&mut self) -> Vec<char> {
        let buffer = std::mem::take(&mut self.buffer);
        self.clear();
        self.goto_start();
        buffer
    }
}

impl std::fmt::Display for Buffer {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        for c in self.buffer.iter() {
            f.write_char(*c)?;
        }
        Ok(())
    }
}

impl From<&str> for Buffer {
    fn from(string: &str) -> Self {
        Self {
            buffer: string.chars().collect(),
            buffer_pos: 0,
        }
    }
}
impl From<String> for Buffer {
    fn from(string: String) -> Self {
        Self {
            buffer: string.chars().collect(),
            buffer_pos: 0,
        }
    }
}
impl From<Vec<char>> for Buffer {
    fn from(buffer: Vec<char>) -> Self {
        Self {
            buffer,
            buffer_pos: 0,
        }
    }
}
impl FromIterator<char> for Buffer {
    fn from_iter<I: IntoIterator<Item = char>>(iter: I) -> Buffer {
        let mut buffer = Buffer::new();
        for c in iter {
            buffer.buffer.push(c);
        }
        buffer
    }
}