use clap::{ArgGroup, Parser};
use itertools::Itertools;
use regex::bytes::Regex;
use similar::ChangeTag;
use std::cmp::{max, min, Ordering};
use std::collections::HashSet;
use std::ffi::OsString;
use std::ops::Range;
use std::path::PathBuf;
fn find_unchanged_ranges(
old_bytes: &[u8],
new_bytes: &[u8],
) -> Vec<(Range<usize>, Range<usize>)> {
let diff = similar::TextDiff::configure()
.algorithm(similar::Algorithm::Patience)
.diff_lines(old_bytes, new_bytes);
let mut new_unchanged_ranges = vec![];
let mut old_index = 0;
let mut new_index = 0;
for diff in diff.iter_all_changes() {
match diff.tag() {
ChangeTag::Equal => {
new_unchanged_ranges.push((
old_index..old_index + diff.value().len(),
new_index..new_index + diff.value().len(),
));
old_index += diff.value().len();
new_index += diff.value().len();
}
ChangeTag::Delete => {
old_index += diff.value().len();
}
ChangeTag::Insert => {
new_index += diff.value().len();
}
}
}
new_unchanged_ranges
}
/// Returns a list of all the lines in the input (including trailing newlines),
/// but only if they all match the regex and they are sorted.
fn get_lines<'input>(
input: &'input [u8],
regex: &Regex,
) -> Option<Vec<&'input [u8]>> {
let lines = input.split_inclusive(|x| *x == b'\n').collect_vec();
let mut previous_line = "".as_bytes();
for line in &lines {
if *line < previous_line {
return None;
}
if !regex.is_match(line) {
return None;
}
previous_line = line;
}
Some(lines)
}
fn resolve_conflict(
base_slice: &[u8],
local_slice: &[u8],
other_slice: &[u8],
regex: &Regex,
) -> Option<Vec<u8>> {
let base_lines = get_lines(base_slice, regex)?;
let local_lines = get_lines(local_slice, regex)?;
let other_lines = get_lines(other_slice, regex)?;
let base_lines_set: HashSet<_> = base_lines.iter().copied().collect();
let local_lines_set: HashSet<_> = local_lines.iter().copied().collect();
let other_lines_set: HashSet<_> = other_lines.iter().copied().collect();
let mut result = local_lines_set;
for to_add in other_lines_set.difference(&base_lines_set) {
result.insert(to_add);
}
for to_remove in base_lines_set.difference(&other_lines_set) {
result.remove(to_remove);
}
Some(result.into_iter().sorted().collect_vec().concat())
}
fn resolve(
base_bytes: &[u8],
local_bytes: &[u8],
other_bytes: &[u8],
regex: &Regex,
) -> (Vec<u8>, Vec<u8>, Vec<u8>) {
// Find unchanged ranges between the base and the two sides. We do that by
// initially considering the whole base unchanged. Then we compare each
// side with the base and intersect the unchanged ranges we find with
// what we had before.
let unchanged_ranges = vec![UnchangedRange {
base_range: 0..base_bytes.len(),
offsets: vec![],
}];
let unchanged_ranges = intersect_regions(
unchanged_ranges,
&find_unchanged_ranges(base_bytes, local_bytes),
);
let mut unchanged_ranges = intersect_regions(
unchanged_ranges,
&find_unchanged_ranges(base_bytes, other_bytes),
);
// Add an empty UnchangedRange at the end to make it easier to find change
// ranges. That way there's a changed range before each UnchangedRange.
unchanged_ranges.push(UnchangedRange {
base_range: base_bytes.len()..base_bytes.len(),
offsets: vec![
local_bytes.len().wrapping_sub(base_bytes.len()) as isize,
other_bytes.len().wrapping_sub(base_bytes.len()) as isize,
],
});
let mut new_base_bytes: Vec<u8> = vec![];
let mut new_local_bytes: Vec<u8> = vec![];
let mut new_other_bytes: Vec<u8> = vec![];
let mut previous = UnchangedRange {
base_range: 0..0,
offsets: vec![0, 0],
};
for current in unchanged_ranges {
let base_slice =
&base_bytes[previous.base_range.end..current.base_range.start];
let local_slice = &local_bytes[previous.end(0)..current.start(0)];
let other_slice = &other_bytes[previous.end(1)..current.start(1)];
if let Some(resolution) =
resolve_conflict(base_slice, local_slice, other_slice, regex)
{
new_base_bytes.extend(&resolution);
new_local_bytes.extend(&resolution);
new_other_bytes.extend(&resolution);
} else {
new_base_bytes.extend(base_slice);
new_local_bytes.extend(local_slice);
new_other_bytes.extend(other_slice);
}
new_base_bytes.extend(&base_bytes[current.base_range.clone()]);
new_local_bytes.extend(&local_bytes[current.start(0)..current.end(0)]);
new_other_bytes.extend(&other_bytes[current.start(1)..current.end(1)]);
previous = current;
}
(new_base_bytes, new_local_bytes, new_other_bytes)
}
/// A tool that performs a 3-way merge, resolving conflicts in sorted lists and
/// leaving other conflicts unchanged. This is useful with Mercurial's support
/// for partial merge tools (configured in `[partial-merge-tools]`).
#[derive(Parser, Debug)]
#[clap(version, about, long_about = None)]
#[clap(group(ArgGroup::new("match").required(true).args(&["pattern", "python-imports"])))]
struct Args {
/// Path to the file's content in the "local" side
local: OsString,
/// Path to the file's content in the base
base: OsString,
/// Path to the file's content in the "other" side
other: OsString,
/// Regular expression to use
#[clap(long, short)]
pattern: Option<String>,
/// Use built-in regular expression for Python imports
#[clap(long)]
python_imports: bool,
}
fn get_regex(args: &Args) -> Regex {
let pattern = if args.python_imports {
r"import \w+(\.\w+)*( +#.*)?\n|from (\w+(\.\w+)* import \w+( as \w+)?(, \w+( as \w+)?)*( +#.*)?)"
} else if let Some(pattern) = &args.pattern {
pattern
} else {
".*"
};
let pattern = format!(r"{}\r?\n?", pattern);
regex::bytes::Regex::new(&pattern).unwrap()
}
fn main() {
let args: Args = Args::parse();
let base_path = PathBuf::from(&args.base);
let local_path = PathBuf::from(&args.local);
let other_path = PathBuf::from(&args.other);
let base_bytes = std::fs::read(&base_path).unwrap();
let local_bytes = std::fs::read(&local_path).unwrap();
let other_bytes = std::fs::read(&other_path).unwrap();
let regex = get_regex(&args);
let (new_base_bytes, new_local_bytes, new_other_bytes) =
resolve(&base_bytes, &local_bytes, &other_bytes, ®ex);
// Write out the result if anything changed
if new_base_bytes != base_bytes {
std::fs::write(&base_path, new_base_bytes).unwrap();
}
if new_local_bytes != local_bytes {
std::fs::write(&local_path, new_local_bytes).unwrap();
}
if new_other_bytes != other_bytes {
std::fs::write(&other_path, new_other_bytes).unwrap();
}
}
fn checked_add(base: usize, offset: isize) -> usize {
if offset < 0 {
base.checked_sub(offset.checked_abs().unwrap() as usize)
.unwrap()
} else {
base.checked_add(offset as usize).unwrap()
}
}
// The remainder of the file is copied from
// https://github.com/martinvonz/jj/blob/main/lib/src/diff.rs
#[derive(Clone, PartialEq, Eq, Debug)]
struct UnchangedRange {
base_range: Range<usize>,
offsets: Vec<isize>,
}
impl UnchangedRange {
fn start(&self, side: usize) -> usize {
checked_add(self.base_range.start, self.offsets[side])
}
fn end(&self, side: usize) -> usize {
checked_add(self.base_range.end, self.offsets[side])
}
}
impl PartialOrd for UnchangedRange {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl Ord for UnchangedRange {
fn cmp(&self, other: &Self) -> Ordering {
self.base_range
.start
.cmp(&other.base_range.start)
.then_with(|| self.base_range.end.cmp(&other.base_range.end))
}
}
/// Takes the current regions and intersects it with the new unchanged ranges
/// from a 2-way diff. The result is a map of unchanged regions with one more
/// offset in the map's values.
fn intersect_regions(
current_ranges: Vec<UnchangedRange>,
new_unchanged_ranges: &[(Range<usize>, Range<usize>)],
) -> Vec<UnchangedRange> {
let mut result = vec![];
let mut current_ranges_iter = current_ranges.into_iter().peekable();
for (new_base_range, other_range) in new_unchanged_ranges.iter() {
assert_eq!(new_base_range.len(), other_range.len());
while let Some(UnchangedRange {
base_range,
offsets,
}) = current_ranges_iter.peek()
{
// No need to look further if we're past the new range.
if base_range.start >= new_base_range.end {
break;
}
// Discard any current unchanged regions that don't match between
// the base and the new input.
if base_range.end <= new_base_range.start {
current_ranges_iter.next();
continue;
}
let new_start = max(base_range.start, new_base_range.start);
let new_end = min(base_range.end, new_base_range.end);
let mut new_offsets = offsets.clone();
new_offsets
.push(other_range.start.wrapping_sub(new_base_range.start)
as isize);
result.push(UnchangedRange {
base_range: new_start..new_end,
offsets: new_offsets,
});
if base_range.end >= new_base_range.end {
// Break without consuming the item; there may be other new
// ranges that overlap with it.
break;
}
current_ranges_iter.next();
}
}
result
}