rpn_cli/
undo.rs

1use crate::value::Value;
2use std::fmt::{Display, Formatter};
3
4#[derive(Debug, PartialEq)]
5pub struct Undo {
6    remove: usize,
7    insert: Vec<Value>,
8    tokens: Vec<String>,
9}
10
11impl Undo {
12    pub fn new(remove: usize, insert: Vec<Value>, tokens: Vec<String>) -> Self {
13        Self { remove, insert, tokens }
14    }
15
16    pub fn is_empty(&self) -> bool {
17        self.remove == 0 && self.insert.is_empty()
18    }
19
20    pub fn merge(&mut self, remove: usize, mut insert: Vec<Value>, token: Option<&str>) {
21        if let Some(start) = insert.len().checked_sub(self.remove) {
22            insert.drain(start..);
23            insert.append(&mut self.insert);
24            self.remove = remove;
25            self.insert = insert;
26        } else if let Some(delta) = self.remove.checked_sub(insert.len()) {
27            self.remove = remove + delta;
28        }
29        if let Some(token) = token {
30            self.tokens.push(String::from(token));
31        }
32    }
33
34    pub fn clear(&mut self) {
35        self.remove = 0;
36        self.insert.clear();
37        self.tokens.clear();
38    }
39
40    pub fn apply_to(&mut self, stack: &mut Vec<Value>) -> Self {
41        let start = stack.len().checked_sub(self.remove).unwrap_or(0);
42        let remove = self.insert.len();
43        let insert = stack.drain(start..).collect();
44        let tokens = self.tokens.drain(..).collect();
45        stack.append(&mut self.insert);
46        self.remove = 0;
47        Self::new(remove, insert, tokens)
48    }
49}
50
51impl Default for Undo {
52    fn default() -> Self {
53        Self::new(0, Vec::new(), Vec::new())
54    }
55}
56
57impl Display for Undo {
58    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
59        let tokens = self.tokens.join(" ");
60        write!(f, "{}", tokens)?;
61        Ok(())
62    }
63}
64
65#[cfg(test)]
66pub mod tests {
67    use crate::engine::tests::create_values;
68    use crate::undo::Undo;
69    use pretty_assertions::assert_eq;
70
71    #[test]
72    fn test_values_are_merged_with_underflow() {
73        let mut undo = create_undo(1, vec!["2", "3"], vec![]);
74        undo.merge(1, create_values(vec!["1", "5"]), None);
75        assert_eq!(undo.remove, 1);
76        assert_eq!(undo.insert, create_values(vec!["1", "2", "3"]));
77    }
78
79    #[test]
80    fn test_values_are_merged_with_overflow() {
81        let mut undo = create_undo(3, vec!["2", "3"], vec![]);
82        undo.merge(1, create_values(vec!["1", "5"]), None);
83        assert_eq!(undo.remove, 2);
84        assert_eq!(undo.insert, create_values(vec!["2", "3"]));
85    }
86
87    #[test]
88    fn test_changes_are_applied_with_underflow() {
89        let mut stack = create_values(vec!["1", "2", "3"]);
90        let mut undo = create_undo(2, vec!["4", "5"], vec![]);
91        undo.apply_to(&mut stack);
92        assert_eq!(stack, create_values(vec!["1", "4", "5"]));
93    }
94
95    #[test]
96    fn test_changes_are_applied_with_overflow() {
97        let mut stack = create_values(vec!["1", "2", "3"]);
98        let mut undo = create_undo(4, vec!["4", "5"], vec![]);
99        undo.apply_to(&mut stack);
100        assert_eq!(stack, create_values(vec!["4", "5"]));
101    }
102
103    pub fn create_undo(remove: usize, insert: Vec<&str>, tokens: Vec<&str>) -> Undo {
104        let insert = create_values(insert);
105        let tokens = tokens.iter().map(|x| x.to_string()).collect();
106        Undo::new(remove, insert, tokens)
107    }
108}
rpn_cli/undo.rs

rpn_cli/
undo.rs
