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use std::fmt;
use std::io::Write;
use termcolor::{Ansi, Color, ColorSpec, NoColor, WriteColor};
#[derive(Debug, Eq, PartialEq)]
pub enum Change<T> {
Add(usize, T),
Remove(usize, T),
Keep(usize, usize, T),
}
pub fn diff<'a, T>(a: &'a [T], b: &'a [T]) -> Vec<Change<&'a T>>
where
T: PartialEq,
{
if a.is_empty() && b.is_empty() {
return vec![];
}
let mut diff = vec![];
for (prev_x, prev_y, x, y) in backtrack(&a, &b) {
if x == prev_x {
diff.push(Change::Add(prev_y + 1, &b[prev_y]));
} else if y == prev_y {
diff.push(Change::Remove(prev_x + 1, &a[prev_x]));
} else {
diff.push(Change::Keep(prev_x + 1, prev_y + 1, &a[prev_x]));
}
}
diff.reverse();
diff
}
fn shortest_edit<T>(a: &[T], b: &[T]) -> Vec<Vec<usize>>
where
T: PartialEq,
{
let max = a.len() + b.len();
let mut v = vec![0; 2 * max + 1];
let mut trace = vec![];
for d in 0..=max {
trace.push(v.clone());
for k in (0..=(2 * d)).step_by(2) {
let mut x = if k == 0 || (k != 2 * d && v[max - d + k - 1] < v[max - d + k + 1]) {
v[max - d + k + 1]
} else {
v[max - d + k - 1] + 1
};
let mut y = x + d - k;
while x < a.len() && y < b.len() && a[x] == b[y] {
x += 1;
y += 1;
}
v[max - d + k] = x;
if x >= a.len() && y >= b.len() {
return trace;
}
}
}
panic!("finished without hitting end?");
}
fn backtrack<T>(a: &[T], b: &[T]) -> Vec<(usize, usize, usize, usize)>
where
T: PartialEq,
{
let mut result = vec![];
let mut x = a.len();
let mut y = b.len();
let max = x + y;
for (d, v) in shortest_edit(a, b).iter().enumerate().rev() {
let k = x + d - y;
let prev_k = if k == 0 || (k != 2 * d && v[max - d + k - 1] < v[max - d + k + 1]) {
k + 1
} else {
k - 1
};
let prev_x = v[max - d + prev_k];
let prev_y = (prev_x + d).saturating_sub(prev_k);
while x > prev_x && y > prev_y {
result.push((x - 1, y - 1, x, y));
x -= 1;
y -= 1;
}
if d > 0 {
result.push((prev_x, prev_y, x, y));
}
x = prev_x;
y = prev_y;
}
return result;
}
pub fn colored_diff<'a, T>(a: &'a [T], b: &'a [T]) -> String
where
T: PartialEq + fmt::Display,
{
let changes = diff(a, b);
render_colored_changes(&changes)
}
pub fn render_colored_changes<T: fmt::Display>(changes: &[Change<T>]) -> String {
let mut red = ColorSpec::new();
red.set_fg(Some(Color::Red));
let mut green = ColorSpec::new();
green.set_fg(Some(Color::Green));
let mut dim = ColorSpec::new();
dim.set_dimmed(true);
let mut v = Vec::new();
let mut result: Box<dyn WriteColor> = if crate::is_ci() {
Box::new(NoColor::new(&mut v))
} else {
Box::new(Ansi::new(&mut v))
};
for change in changes {
let (nums, sign, color, text) = match change {
Change::Add(i, s) => (format!(" {:<4} ", i), '+', &green, s),
Change::Remove(i, s) => (format!("{:<4} ", i), '-', &red, s),
Change::Keep(x, y, s) => (format!("{:<4}{:<4} ", x, y), ' ', &dim, s),
};
result.set_color(&dim).unwrap();
write!(result, "{}", nums).unwrap();
let mut bold = color.clone();
bold.set_bold(true);
result.set_color(&bold).unwrap();
write!(result, "{}", sign).unwrap();
result.reset().unwrap();
result.set_color(&color).unwrap();
write!(result, "{}", text).unwrap();
result.reset().unwrap();
writeln!(result).unwrap();
}
drop(result);
String::from_utf8(v).unwrap()
}
#[cfg(test)]
pub fn compare(a: &str, b: &str) {
let a: Vec<_> = a.chars().collect();
let b: Vec<_> = b.chars().collect();
let changes = diff(&a, &b);
let mut result = vec![];
for change in changes {
match change {
Change::Add(_, s) => result.push(*s),
Change::Remove(_, _s) => {}
Change::Keep(_, _, s) => result.push(*s),
}
}
assert_eq!(b, result);
}
#[test]
fn basic_tests() {
compare("", "");
compare("A", "");
compare("", "B");
compare("ABCABBA", "CBABAC");
}