ochrepad_core/

transform.rs

//! Text transforms: case conversion, line sorting, and line operations
//! (trim, duplicate, move, join, delete, transpose, insert, reverse, remove
//! empty or duplicate lines) and blank operations (trim, EOL to space, tabs
//! and spaces). Each resolves to one transaction.

use std::cmp::Ordering;
use std::collections::{BTreeSet, HashSet};
use std::ops::Range;

use serde::{Deserialize, Serialize};

use crate::changeset::{Bias, ChangeSet, Edit};
use crate::history::EditKind;
use unicode_segmentation::UnicodeSegmentation;

use crate::position::{ByteOffset, grapheme_width, visual_col_to_byte, visual_col_to_byte_ceil};
use crate::resolve::Resolved;
use crate::selection::{Selection, SelectionSet};
use crate::text::Document;

#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub enum CaseMode {
    Upper,
    Lower,
    /// First letter of each word upper case, the rest lower case.
    Title,
    /// First letter of each word upper case, the rest as it was
    /// (Notepad++'s Proper Case (blend)).
    TitleBlend,
    /// First letter of each sentence upper case, the rest lower case.
    Sentence,
    /// First letter of each sentence upper case, the rest as it was.
    SentenceBlend,
    /// Swap the case of every letter.
    Invert,
    /// Each letter upper or lower case at random (Notepad++'s ranDOm
    /// CasE); the seed decides, so a macro replays it.
    Random {
        seed: u64,
    },
}

#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
pub struct SortOptions {
    pub descending: bool,
    pub case_insensitive: bool,
    /// Compare by the number at the start of each line (integer or
    /// decimal); lines without one sort first.
    pub numeric: bool,
    /// Drop lines equal to the line before them after sorting.
    pub remove_duplicates: bool,
    /// Compare by length in characters (then as text).
    #[serde(default)]
    pub by_length: bool,
}

/// Converts `text` to `mode`. The result may be longer or shorter (`ß` →
/// `SS`).
pub fn convert_case(text: &str, mode: CaseMode) -> String {
    match mode {
        CaseMode::Upper => text.to_uppercase(),
        CaseMode::Lower => text.to_lowercase(),
        CaseMode::Invert => text
            .chars()
            .flat_map(|c| -> Box<dyn Iterator<Item = char>> {
                if c.is_uppercase() {
                    Box::new(c.to_lowercase())
                } else if c.is_lowercase() {
                    Box::new(c.to_uppercase())
                } else {
                    Box::new(std::iter::once(c))
                }
            })
            .collect(),
        CaseMode::Title | CaseMode::TitleBlend => {
            let blend = mode == CaseMode::TitleBlend;
            let mut out = String::with_capacity(text.len());
            let mut in_word = false;
            for c in text.chars() {
                if c.is_alphanumeric() {
                    if !in_word {
                        out.extend(c.to_uppercase());
                    } else if blend {
                        out.push(c);
                    } else {
                        out.extend(c.to_lowercase());
                    }
                    in_word = true;
                } else {
                    out.push(c);
                    // "don't" stays one word.
                    in_word = in_word && (c == '\'' || c == '\u{2019}');
                }
            }
            out
        }
        CaseMode::Sentence | CaseMode::SentenceBlend => {
            // As Notepad++: a sentence starts the text, follows a `.`, `!`
            // or `?` with no letter right after it (the first dot of
            // "e.g." does not end one), and follows a blank line.
            let blend = mode == CaseMode::SentenceBlend;
            let chars: Vec<char> = text.chars().collect();
            let mut out = String::with_capacity(text.len());
            let (mut starts, mut after_break) = (true, false);
            for (i, &c) in chars.iter().enumerate() {
                if c.is_alphabetic() {
                    if starts {
                        out.extend(c.to_uppercase());
                    } else if blend {
                        out.push(c);
                    } else {
                        out.extend(c.to_lowercase());
                    }
                    starts = false;
                    after_break = false;
                    continue;
                }
                out.push(c);
                if c == '\n' {
                    starts |= after_break;
                    after_break = true;
                } else if !c.is_whitespace() {
                    // Not a blank line; and "2.50" has no sentence end.
                    after_break = false;
                    if matches!(c, '.' | '!' | '?') {
                        starts |= !chars.get(i + 1).is_some_and(|n| n.is_alphanumeric());
                    }
                }
            }
            out
        }
        CaseMode::Random { seed } => {
            // xorshift64*, as Randomize Line Order.
            let mut state = seed | 1;
            let mut upper = || {
                state ^= state >> 12;
                state ^= state << 25;
                state ^= state >> 27;
                state.wrapping_mul(0x2545_F491_4F6C_DD1D) >> 63 == 1
            };
            text.chars()
                .flat_map(|c| -> Box<dyn Iterator<Item = char>> {
                    if !c.is_alphabetic() {
                        Box::new(std::iter::once(c))
                    } else if upper() {
                        Box::new(c.to_uppercase())
                    } else {
                        Box::new(c.to_lowercase())
                    }
                })
                .collect()
        }
    }
}

fn line_range(doc: &Document, line: usize) -> Range<ByteOffset> {
    doc.line_start(line)..doc.line_end(line)
}

/// Lines a selection covers. A non-empty selection ending at the very start
/// of a line does not include that line (as in Notepad++).
fn lines_of(doc: &Document, s: &Selection) -> (usize, usize) {
    let first = doc.line_of(s.start());
    let mut last = doc.line_of(s.end());
    if !s.is_empty() && last > first && s.end() == doc.line_start(last) {
        last -= 1;
    }
    (first, last)
}

/// Sorts and merges overlapping or touching ranges.
fn merge(mut ranges: Vec<Range<ByteOffset>>) -> Vec<Range<ByteOffset>> {
    ranges.sort_by_key(|r| (r.start, r.end));
    let mut out: Vec<Range<ByteOffset>> = Vec::with_capacity(ranges.len());
    for r in ranges {
        match out.last_mut() {
            Some(last) if r.start <= last.end => last.end = last.end.max(r.end),
            _ => out.push(r),
        }
    }
    out
}

fn edit_result(changes: ChangeSet, after: SelectionSet, sels: &SelectionSet) -> Resolved {
    if changes.is_empty() {
        Resolved::Selections(sels.clone())
    } else {
        Resolved::Edit {
            changes,
            after,
            kind: EditKind::Other,
        }
    }
}

/// Maps every selection through `changes` (anchor and head both `Before`,
/// so insertions at a caret land after it).
fn map_before(sels: &SelectionSet, changes: &ChangeSet) -> SelectionSet {
    sels.map(|s| Selection {
        anchor: changes.map_position(s.anchor, Bias::Before),
        head: changes.map_position(s.head, Bias::Before),
        goal: None,
    })
}

/// Converts each selection, or the caret's line for an empty selection.
pub(crate) fn case(doc: &Document, sels: &SelectionSet, mode: CaseMode) -> Resolved {
    let targets = sels
        .ranges()
        .iter()
        .map(|s| {
            if s.is_empty() {
                line_range(doc, doc.line_of(s.head))
            } else {
                s.range()
            }
        })
        .collect();
    let pieces: Vec<(Range<ByteOffset>, String, String)> = merge(targets)
        .into_iter()
        .map(|r| {
            let old = doc.slice(r.clone());
            let new = convert_case(&old, mode);
            (r, old, new)
        })
        .collect();
    let changes = ChangeSet::new(
        doc.len(),
        pieces
            .iter()
            .filter(|(_, old, new)| old != new)
            .map(|(r, _, new)| Edit::new(r.start, r.end, new.as_str()))
            .collect(),
    );
    // Range ends map to the ends of the converted text, so selections cover
    // it even when its length changed; a caret inside keeps its char index.
    let remap = |pos: ByteOffset| {
        let Some((r, old, new)) = pieces.iter().find(|(r, ..)| r.start <= pos && pos <= r.end)
        else {
            return changes.map_position(pos, Bias::Before);
        };
        let new_start = changes.map_position(r.start, Bias::Before);
        if pos == r.end {
            return ByteOffset(new_start.0 + new.len());
        }
        let chars = old[..pos.0 - r.start.0].chars().count();
        let off = new.char_indices().nth(chars).map_or(new.len(), |(i, _)| i);
        ByteOffset(new_start.0 + off)
    };
    let after = sels
        .map(|s| Selection::new(remap(s.anchor), remap(s.head)))
        .with_rect(sels.rect().cloned());
    edit_result(changes, after, sels)
}

/// The number at the start of `s` (after leading whitespace).
fn leading_number(s: &str) -> Option<f64> {
    let t = s.trim_start();
    let b = t.as_bytes();
    let mut i = 0;
    if i < b.len() && (b[i] == b'-' || b[i] == b'+') {
        i += 1;
    }
    let digits_start = i;
    while i < b.len() && b[i].is_ascii_digit() {
        i += 1;
    }
    let mut digits = i - digits_start;
    if i < b.len() && b[i] == b'.' {
        let frac_start = i + 1;
        let mut j = frac_start;
        while j < b.len() && b[j].is_ascii_digit() {
            j += 1;
        }
        if j > frac_start {
            digits += j - frac_start;
            i = j;
        }
    }
    if digits == 0 {
        return None;
    }
    t[..i].parse().ok()
}

/// Sorts the selected lines, the rectangle's lines keyed by the text inside
/// it, or the whole document when nothing is selected.
pub(crate) fn sort(
    doc: &Document,
    sels: &SelectionSet,
    o: SortOptions,
    tab_width: usize,
) -> Resolved {
    reorder(doc, sels, tab_width, o.case_insensitive, |lines, keys| {
        let compare = |a: usize, b: usize| -> Ordering {
            let ord = if o.numeric {
                match (leading_number(&keys[a]), leading_number(&keys[b])) {
                    (Some(x), Some(y)) => x.total_cmp(&y),
                    (None, Some(_)) => Ordering::Less,
                    (Some(_), None) => Ordering::Greater,
                    (None, None) => keys[a].cmp(&keys[b]),
                }
            } else if o.by_length {
                let len = |i: usize| keys[i].chars().count();
                len(a).cmp(&len(b)).then_with(|| keys[a].cmp(&keys[b]))
            } else {
                keys[a].cmp(&keys[b])
            };
            if o.descending { ord.reverse() } else { ord }
        };
        let mut order: Vec<usize> = (0..lines.len()).collect();
        order.sort_by(|&a, &b| compare(a, b)); // stable
        if o.remove_duplicates {
            let same = |a: &str, b: &str| {
                if o.case_insensitive {
                    a.to_lowercase() == b.to_lowercase()
                } else {
                    a == b
                }
            };
            order.dedup_by(|b, a| same(&lines[*a], &lines[*b]));
        }
        order
    })
}

/// Puts the lines Sort Lines would sort in a random order, from `seed`
/// (Randomize Line Order).
pub(crate) fn shuffle(
    doc: &Document,
    sels: &SelectionSet,
    seed: u64,
    tab_width: usize,
) -> Resolved {
    reorder(doc, sels, tab_width, false, |lines, _| {
        // xorshift64*, then Fisher-Yates.
        let mut state = seed | 1;
        let mut next = || {
            state ^= state >> 12;
            state ^= state << 25;
            state ^= state >> 27;
            state.wrapping_mul(0x2545_F491_4F6C_DD1D)
        };
        let mut order: Vec<usize> = (0..lines.len()).collect();
        for i in (1..order.len()).rev() {
            let j = (next() % (i as u64 + 1)) as usize;
            order.swap(i, j);
        }
        order
    })
}

/// Rewrites the lines Sort Lines works on (the selected lines, a
/// rectangle's lines keyed by the text inside it, or the whole document)
/// in the order `order` gives from the lines and their keys.
fn reorder(
    doc: &Document,
    sels: &SelectionSet,
    tab_width: usize,
    case_insensitive: bool,
    order: impl FnOnce(&[String], &[String]) -> Vec<usize>,
) -> Resolved {
    let rect = sels.rect().cloned();
    let any_selected = sels.ranges().iter().any(|s| !s.is_empty());
    let (first, mut last) = if let Some(r) = &rect {
        (r.top(), r.bottom())
    } else if any_selected {
        let spans: Vec<_> = sels.ranges().iter().map(|s| lines_of(doc, s)).collect();
        let first = spans.iter().map(|s| s.0).min().unwrap_or(0);
        let last = spans.iter().map(|s| s.1).max().unwrap_or(0);
        (first, last)
    } else {
        (0, doc.line_count() - 1)
    };
    // A trailing newline's empty last line is not a line to sort.
    if last > first && last + 1 == doc.line_count() && doc.line_text(last).is_empty() {
        last -= 1;
    }
    if last <= first {
        return Resolved::Selections(sels.clone());
    }
    let lines: Vec<String> = (first..=last).map(|l| doc.line_text(l)).collect();
    let keys: Vec<String> = (first..=last)
        .zip(&lines)
        .map(|(line, text)| {
            let key = match &rect {
                Some(r) => {
                    let start = doc.line_start(line).0;
                    let right = visual_col_to_byte(doc, line, r.right(), tab_width).0 - start;
                    let left = (visual_col_to_byte_ceil(doc, line, r.left(), tab_width).0 - start)
                        .min(right);
                    text[left..right].to_owned()
                }
                None => text.clone(),
            };
            if case_insensitive {
                key.to_lowercase()
            } else {
                key
            }
        })
        .collect();
    let order = order(&lines, &keys);
    let new: Vec<&str> = order.iter().map(|&i| lines[i].as_str()).collect();
    let new = new.join("\n");
    let start = doc.line_start(first);
    let end = doc.line_end(last);
    let changes = ChangeSet::new(doc.len(), vec![Edit::new(start, end, new.as_str())]);
    let after = if any_selected || rect.is_some() {
        SelectionSet::single(Selection::new(start, ByteOffset(start.0 + new.len())))
    } else {
        SelectionSet::caret(start)
    };
    edit_result(changes, after, sels)
}

/// The lines touched by non-empty selections, or every line if none.
fn selected_lines(doc: &Document, sels: &SelectionSet) -> BTreeSet<usize> {
    let selected: BTreeSet<usize> = sels
        .ranges()
        .iter()
        .filter(|s| !s.is_empty())
        .flat_map(|s| {
            let (a, b) = lines_of(doc, s);
            a..=b
        })
        .collect();
    if selected.is_empty() {
        (0..doc.line_count()).collect()
    } else {
        selected
    }
}

/// Removes spaces and tabs at the ends of the selected lines (all lines
/// when nothing is selected).
pub(crate) fn trim_trailing(doc: &Document, sels: &SelectionSet) -> Resolved {
    let edits = selected_lines(doc, sels)
        .into_iter()
        .filter_map(|line| {
            let text = doc.line_text(line);
            let keep = text.trim_end_matches([' ', '\t']).len();
            (keep < text.len()).then(|| {
                let start = doc.line_start(line).0;
                Edit::new(ByteOffset(start + keep), doc.line_end(line), "")
            })
        })
        .collect();
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_before(sels, &changes);
    edit_result(changes, after, sels)
}

/// Duplicates the caret's line below itself, or a selection right after it.
/// The carets and selections stay on the originals.
pub(crate) fn duplicate(doc: &Document, sels: &SelectionSet) -> Resolved {
    let mut lines = BTreeSet::new();
    let mut edits = Vec::new();
    for s in sels.ranges() {
        if s.is_empty() {
            lines.insert(doc.line_of(s.head));
        } else {
            edits.push(Edit::new(s.end(), s.end(), doc.slice(s.range())));
        }
    }
    for line in lines {
        let end = doc.line_end(line);
        edits.push(Edit::new(end, end, format!("\n{}", doc.line_text(line))));
    }
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_before(sels, &changes);
    edit_result(changes, after, sels)
}

/// Moves the block of lines covered by the selections up or down one line;
/// the selections move with it.
pub(crate) fn move_lines(doc: &Document, sels: &SelectionSet, up: bool) -> Resolved {
    let spans: Vec<_> = sels.ranges().iter().map(|s| lines_of(doc, s)).collect();
    let first = spans.iter().map(|s| s.0).min().unwrap_or(0);
    let last = spans.iter().map(|s| s.1).max().unwrap_or(0);
    let block = doc.slice(doc.line_start(first)..doc.line_end(last));
    let (edit, shift): (Edit, isize) = if up {
        if first == 0 {
            return Resolved::Selections(sels.clone());
        }
        let prev = doc.line_text(first - 1);
        (
            Edit::new(
                doc.line_start(first - 1),
                doc.line_end(last),
                format!("{block}\n{prev}"),
            ),
            -(prev.len() as isize + 1),
        )
    } else {
        if last + 1 >= doc.line_count() {
            return Resolved::Selections(sels.clone());
        }
        let next = doc.line_text(last + 1);
        (
            Edit::new(
                doc.line_start(first),
                doc.line_end(last + 1),
                format!("{next}\n{block}"),
            ),
            next.len() as isize + 1,
        )
    };
    let changes = ChangeSet::new(doc.len(), vec![edit]);
    // Every selection endpoint lies in the moved block (or at the start of
    // the line after it), so all of them shift by the same amount. Moving
    // down past the last line, "the start of the line after the block" no
    // longer exists (the block now ends the document): clamp to the end.
    let new_len = changes.new_len().0 as isize;
    let shift_pos = |p: ByteOffset| ByteOffset((p.0 as isize + shift).clamp(0, new_len) as usize);
    let after = sels.map(|s| Selection::new(shift_pos(s.anchor), shift_pos(s.head)));
    edit_result(changes, after, sels)
}

/// Joins the selected lines (or the caret's line with the next) into one,
/// replacing each line break and the whitespace around it with one space.
pub(crate) fn join(doc: &Document, sels: &SelectionSet) -> Resolved {
    let last_line = doc.line_count() - 1;
    let mut breaks = BTreeSet::new();
    for s in sels.ranges() {
        let (a, b) = lines_of(doc, s);
        let b = if a == b { (a + 1).min(last_line) } else { b };
        breaks.extend(a..b);
    }
    let edits = breaks
        .into_iter()
        .map(|line| {
            let text = doc.line_text(line);
            let next = doc.line_text(line + 1);
            let kept = text.trim_end_matches([' ', '\t']);
            let rest = next.trim_start_matches([' ', '\t']);
            let start = ByteOffset(doc.line_start(line).0 + kept.len());
            let end = ByteOffset(doc.line_start(line + 1).0 + (next.len() - rest.len()));
            let sep = if kept.is_empty() || rest.is_empty() {
                ""
            } else {
                " "
            };
            Edit::new(start, end, sep)
        })
        .collect();
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_before(sels, &changes);
    edit_result(changes, after, sels)
}

/// The lines the selections touch (a selection ending at a line start does
/// not take that line), or the carets' lines.
/// Splits each touched line wider than `width` columns at the blanks
/// between its words (Split Lines): each run of blanks where it breaks
/// becomes a line break and the line's indentation, so the new lines line
/// up with it. A word wider than the width stays whole on its own line,
/// and blanks at the end of the line stay.
pub(crate) fn split_lines(
    doc: &Document,
    sels: &SelectionSet,
    width: usize,
    tab_width: usize,
) -> Resolved {
    let mut edits = Vec::new();
    for line in touched_lines(doc, sels) {
        let text = doc.line_text(line);
        let start = doc.line_start(line).0;
        let lead = text.len() - text.trim_start_matches([' ', '\t']).len();
        let indent = &text[..lead];
        for blanks in split_points(&text, width.max(1), tab_width) {
            edits.push(Edit::new(
                ByteOffset(start + blanks.start),
                ByteOffset(start + blanks.end),
                format!("\n{indent}"),
            ));
        }
    }
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_selections_around(sels, &changes);
    edit_result(changes, after, sels)
}

/// The runs of blanks (byte ranges) at which `text`, one line, breaks so
/// that its pieces fit `width` columns where they can.
fn split_points(text: &str, width: usize, tab_width: usize) -> Vec<Range<usize>> {
    let cols = |s: &str, from: usize| {
        s.graphemes(true)
            .fold(from, |col, g| col + grapheme_width(g, col, tab_width))
            - from
    };
    let blank_end = |at: usize| text.len() - text[at..].trim_start_matches([' ', '\t']).len();
    let lead = blank_end(0);
    let indent = cols(&text[..lead], 0);
    let mut breaks = Vec::new();
    // The column the next character goes at, and whether a word is on the
    // piece being filled already.
    let (mut col, mut filled) = (indent, false);
    let mut at = lead;
    while at < text.len() {
        let word = blank_end(at);
        if word == text.len() {
            break;
        }
        let end = text[word..]
            .find([' ', '\t'])
            .map_or(text.len(), |i| word + i);
        let blanks = cols(&text[at..word], col);
        let word_cols = cols(&text[word..end], col + blanks);
        if filled && col + blanks + word_cols > width {
            breaks.push(at..word);
            col = indent + cols(&text[word..end], indent);
        } else {
            col += blanks + word_cols;
        }
        filled = true;
        at = end;
    }
    breaks
}

fn touched_lines(doc: &Document, sels: &SelectionSet) -> BTreeSet<usize> {
    sels.ranges()
        .iter()
        .flat_map(|s| {
            let (a, b) = lines_of(doc, s);
            a..=b
        })
        .collect()
}

/// Whether Tab should indent lines rather than insert: some selection spans
/// more than one line.
pub(crate) fn spans_lines(doc: &Document, sels: &SelectionSet) -> bool {
    sels.ranges().iter().any(|s| {
        let (a, b) = lines_of(doc, s);
        !s.is_empty() && a != b
    })
}

/// Maps selections through an edit that inserts or removes at line starts,
/// keeping a selection that starts at a line start covering what was
/// inserted there.
fn map_selections_around(sels: &SelectionSet, changes: &ChangeSet) -> SelectionSet {
    sels.map(|s| {
        let (start_bias, end_bias) = (Bias::Before, Bias::After);
        let map = |p: ByteOffset, bias| changes.map_position(p, bias);
        if s.is_empty() {
            Selection::caret(map(s.head, Bias::After))
        } else if s.anchor <= s.head {
            Selection::new(map(s.anchor, start_bias), map(s.head, end_bias))
        } else {
            Selection::new(map(s.anchor, end_bias), map(s.head, start_bias))
        }
    })
}

/// Indents each touched line (except empty ones) by `unit`.
pub(crate) fn indent(doc: &Document, sels: &SelectionSet, unit: &str) -> Resolved {
    let edits = touched_lines(doc, sels)
        .into_iter()
        .filter(|&l| doc.line_start(l) < doc.line_end(l))
        .map(|l| Edit::new(doc.line_start(l), doc.line_start(l), unit))
        .collect();
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_selections_around(sels, &changes);
    edit_result(changes, after, sels)
}

/// Removes one level of indentation from each touched line: a leading tab,
/// or up to `width` leading spaces.
pub(crate) fn unindent(doc: &Document, sels: &SelectionSet, width: usize) -> Resolved {
    let edits = touched_lines(doc, sels)
        .into_iter()
        .filter_map(|l| {
            let text = doc.line_text(l);
            let n = if text.starts_with('\t') {
                1
            } else {
                text.bytes()
                    .take(width.max(1))
                    .take_while(|&b| b == b' ')
                    .count()
            };
            let start = doc.line_start(l);
            (n > 0).then(|| Edit::new(start, ByteOffset(start.0 + n), ""))
        })
        .collect();
    let changes = ChangeSet::new(doc.len(), edits);
    let after = sels.map(|s| Selection {
        anchor: changes.map_position(s.anchor, Bias::Before),
        head: changes.map_position(s.head, Bias::Before),
        goal: None,
    });
    edit_result(changes, after, sels)
}

/// Bytes of leading spaces and tabs.
fn indent_len(text: &str) -> usize {
    text.len() - text.trim_start_matches([' ', '\t']).len()
}

/// What a line comment command does.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub(crate) enum CommentOp {
    /// Comment the lines, or uncomment them if they all are.
    Toggle,
    /// Comment the lines, even those that already are.
    Add,
    /// Uncomment the lines that are.
    Remove,
}

/// Comments the touched lines with `marker` at their common indent, or
/// uncomments them (`op`; `Toggle` uncomments if every non-blank one is
/// commented).
pub(crate) fn line_comment(
    doc: &Document,
    sels: &SelectionSet,
    marker: &str,
    op: CommentOp,
) -> Resolved {
    let lines: Vec<(usize, String)> = touched_lines(doc, sels)
        .into_iter()
        .map(|l| (l, doc.line_text(l)))
        .filter(|(_, t)| !t.trim().is_empty())
        .collect();
    if lines.is_empty() {
        return Resolved::Selections(sels.clone());
    }
    let commented = |t: &str| t[indent_len(t)..].starts_with(marker);
    let remove = match op {
        CommentOp::Toggle => lines.iter().all(|(_, t)| commented(t)),
        CommentOp::Add => false,
        CommentOp::Remove => true,
    };
    let edits = if remove {
        lines
            .iter()
            .filter(|(_, t)| commented(t))
            .map(|(l, t)| {
                let at = doc.line_start(*l).0 + indent_len(t);
                let rest = &t[indent_len(t) + marker.len()..];
                let len = marker.len() + usize::from(rest.starts_with(' '));
                Edit::new(ByteOffset(at), ByteOffset(at + len), "")
            })
            .collect()
    } else {
        let col = lines.iter().map(|(_, t)| indent_len(t)).min().unwrap_or(0);
        lines
            .iter()
            .map(|(l, _)| {
                let at = ByteOffset(doc.line_start(*l).0 + col);
                Edit::new(at, at, format!("{marker} "))
            })
            .collect()
    };
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_selections_around(sels, &changes);
    edit_result(changes, after, sels)
}

/// Wraps each selection (a caret: its line's text) in `open` … `close`, or
/// unwraps it if it already is wrapped.
pub(crate) fn toggle_block_comment(
    doc: &Document,
    sels: &SelectionSet,
    open: &str,
    close: &str,
) -> Resolved {
    let mut edits = Vec::new();
    for s in sels.ranges() {
        let range = if s.is_empty() {
            let line = doc.line_of(s.head);
            let text = doc.line_text(line);
            let start = doc.line_start(line).0;
            ByteOffset(start + indent_len(&text))..ByteOffset(start + text.trim_end().len())
        } else {
            s.range()
        };
        if range.start >= range.end {
            continue;
        }
        let text = doc.slice(range.clone());
        let lead = text.len() - text.trim_start().len();
        let inner = text.trim();
        if in_block_comment(&text, open, close) {
            // Unwrap, with one space inside each marker if there is one.
            let start = range.start.0 + lead;
            let end = start + inner.len();
            let body = &inner[open.len()..inner.len() - close.len()];
            let a = open.len() + usize::from(body.starts_with(' '));
            let b = close.len() + usize::from(body.len() > 1 && body.ends_with(' '));
            edits.push(Edit::new(ByteOffset(start), ByteOffset(start + a), ""));
            edits.push(Edit::new(ByteOffset(end - b), ByteOffset(end), ""));
        } else {
            edits.push(Edit::new(range.start, range.start, format!("{open} ")));
            edits.push(Edit::new(range.end, range.end, format!(" {close}")));
        }
    }
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_selections_around(sels, &changes);
    edit_result(changes, after, sels)
}

/// Whether `text`, blanks aside, is one block comment.
fn in_block_comment(text: &str, open: &str, close: &str) -> bool {
    let inner = text.trim();
    // The first close after the open is the one at the end: "/* a */ b
    // /* c */" is two comments, not one.
    inner.len() >= open.len() + close.len()
        && inner.starts_with(open)
        && inner[open.len()..].find(close) == Some(inner.len() - open.len() - close.len())
}

/// Line comments with the line marker, or a block comment around the lines'
/// text for a language with only block comments.
pub(crate) fn comment_lines(
    doc: &Document,
    sels: &SelectionSet,
    syntax: &crate::buffer::CommentSyntax,
    op: CommentOp,
) -> Option<Resolved> {
    if let Some(marker) = &syntax.line {
        return Some(line_comment(doc, sels, marker, op));
    }
    let (open, close) = syntax.block.as_ref()?;
    // Each run of touched lines is one block: from its first non-blank
    // line's text to its last one's end.
    let text_start = |l: usize| ByteOffset(doc.line_start(l).0 + indent_len(&doc.line_text(l)));
    let span = |a: usize, b: usize| Selection::new(text_start(a), doc.line_end(b));
    let is_comment = |s: &Selection| in_block_comment(&doc.slice(s.range()), open, close);
    let mut runs: Vec<(usize, usize)> = Vec::new();
    for l in touched_lines(doc, sels) {
        match runs.last_mut() {
            Some((_, end)) if *end + 1 == l => *end = l,
            _ => runs.push((l, l)),
        }
    }
    // What to toggle: a run's block, or its lines that are comments each.
    let mut targets = Vec::new();
    for (a, b) in runs {
        let filled: Vec<usize> = (a..=b)
            .filter(|&l| !doc.line_text(l).trim().is_empty())
            .collect();
        let (Some(&first), Some(&last)) = (filled.first(), filled.last()) else {
            continue;
        };
        let whole = span(first, last);
        let each: Vec<Selection> = filled.iter().map(|&l| span(l, l)).collect();
        let one = is_comment(&whole);
        let every = each.iter().all(&is_comment);
        match op {
            CommentOp::Add if !one && !every => targets.push(whole),
            CommentOp::Add => {}
            _ if one => targets.push(whole),
            CommentOp::Remove => targets.extend(each.into_iter().filter(&is_comment)),
            CommentOp::Toggle if every => targets.extend(each),
            CommentOp::Toggle => targets.push(whole),
        }
    }
    if targets.is_empty() {
        return Some(Resolved::Selections(sels.clone()));
    }
    // Each target is wrapped if it is not a comment and unwrapped if it is.
    let targets = SelectionSet::new(targets, 0);
    match toggle_block_comment(doc, &targets, open, close) {
        Resolved::Edit { changes, kind, .. } => {
            let after = map_selections_around(sels, &changes);
            Some(Resolved::Edit {
                changes,
                after,
                kind,
            })
        }
        other => Some(other),
    }
}

/// The lines a removing line operation looks at: the rectangle's lines, the
/// lines touched by non-empty selections, or every line. A trailing
/// newline's empty last line is not a line here (as in `sort`).
fn target_lines(doc: &Document, sels: &SelectionSet) -> Vec<usize> {
    let mut lines: Vec<usize> = match sels.rect() {
        Some(r) => (r.top()..=r.bottom()).collect(),
        None => selected_lines(doc, sels).into_iter().collect(),
    };
    let last = doc.line_count() - 1;
    if last > 0 && lines.last() == Some(&last) && doc.line_text(last).is_empty() {
        lines.pop();
    }
    lines
}

/// Deletes whole lines (sorted, distinct) with their line breaks. A run of
/// lines that ends the document takes the line break before it instead, so
/// no empty line is left behind.
/// Deletes `lines` (sorted) with their line breaks; the last line takes
/// the break before it.
pub(crate) fn remove_lines(doc: &Document, sels: &SelectionSet, lines: &[usize]) -> Resolved {
    let last = doc.line_count() - 1;
    let mut edits = Vec::new();
    let mut i = 0;
    while i < lines.len() {
        let first = lines[i];
        while i + 1 < lines.len() && lines[i + 1] == lines[i] + 1 {
            i += 1;
        }
        let end = lines[i];
        i += 1;
        let range = if end < last {
            doc.line_start(first)..doc.line_start(end + 1)
        } else if first > 0 {
            doc.line_end(first - 1)..doc.len()
        } else {
            ByteOffset(0)..doc.len()
        };
        if range.start < range.end {
            edits.push(Edit::new(range.start, range.end, ""));
        }
    }
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_before(sels, &changes);
    edit_result(changes, after, sels)
}

/// Removes the empty lines among the target lines; with
/// `include_whitespace`, also lines of only spaces and tabs.
pub(crate) fn remove_empty(
    doc: &Document,
    sels: &SelectionSet,
    include_whitespace: bool,
) -> Resolved {
    let lines: Vec<usize> = target_lines(doc, sels)
        .into_iter()
        .filter(|&line| {
            let text = doc.line_text(line);
            if include_whitespace {
                text.trim_matches([' ', '\t']).is_empty()
            } else {
                text.is_empty()
            }
        })
        .collect();
    remove_lines(doc, sels, &lines)
}

/// Removes target lines equal to an earlier target line, keeping the first
/// of each and the order; with `consecutive_only`, only lines equal to the
/// line right before them.
pub(crate) fn remove_duplicates(
    doc: &Document,
    sels: &SelectionSet,
    consecutive_only: bool,
) -> Resolved {
    let mut seen = HashSet::new();
    let mut prev: Option<(usize, String)> = None;
    let mut lines = Vec::new();
    for line in target_lines(doc, sels) {
        let text = doc.line_text(line);
        let duplicate = if consecutive_only {
            prev.as_ref()
                .is_some_and(|(l, t)| l + 1 == line && *t == text)
        } else {
            !seen.insert(text.clone())
        };
        if duplicate {
            lines.push(line);
        }
        prev = Some((line, text));
    }
    remove_lines(doc, sels, &lines)
}

/// Deletes the lines the selections touch (the caret's line for a caret),
/// with their line breaks: Notepad++'s Line Delete (Ctrl+Shift+L).
pub(crate) fn delete_lines(doc: &Document, sels: &SelectionSet) -> Resolved {
    let lines: Vec<usize> = touched_lines(doc, sels).into_iter().collect();
    remove_lines(doc, sels, &lines)
}

/// Swaps each caret's line with the line above it (Ctrl+T). The caret goes
/// to the start of its line, which now holds the text from above, as in
/// Notepad++. A line next to one already swapped is left alone.
pub(crate) fn transpose(doc: &Document, sels: &SelectionSet) -> Resolved {
    let lines: BTreeSet<usize> = sels.ranges().iter().map(|s| doc.line_of(s.head)).collect();
    let mut edits = Vec::new();
    let mut swapped = BTreeSet::new();
    for line in lines {
        if line == 0 || swapped.contains(&(line - 1)) {
            continue;
        }
        let above = doc.line_text(line - 1);
        let this = doc.line_text(line);
        edits.push(Edit::new(
            doc.line_start(line - 1),
            doc.line_end(line),
            format!("{this}\n{above}"),
        ));
        swapped.insert(line);
    }
    let changes = ChangeSet::new(doc.len(), edits);
    // A swap keeps the length of what it replaces, so positions outside the
    // swaps stay; inside one, a position follows its text to its new line.
    let follow = |pos: ByteOffset| {
        for &line in &swapped {
            let (above, this) = (doc.line_start(line - 1), doc.line_start(line));
            let this_len = doc.line_end(line).0 - this.0;
            if above <= pos && pos < this {
                return ByteOffset(pos.0 + this_len + 1);
            }
            if this <= pos && pos <= doc.line_end(line) {
                return ByteOffset(above.0 + pos.0 - this.0);
            }
        }
        pos
    };
    let after = sels.map(|s| {
        let line = doc.line_of(s.head);
        if swapped.contains(&line) {
            let this_len = doc.line_end(line).0 - doc.line_start(line).0;
            Selection::caret(ByteOffset(doc.line_start(line - 1).0 + this_len + 1))
        } else {
            Selection::new(follow(s.anchor), follow(s.head))
        }
    });
    edit_result(changes, after, sels)
}

/// Inserts a line above (or below) each caret's line, or above a
/// selection's first line (below its last), indented like that line; the
/// carets go to the new lines.
pub(crate) fn insert_line(doc: &Document, sels: &SelectionSet, above: bool) -> Resolved {
    let line_for = |s: &Selection| {
        let (first, last) = lines_of(doc, s);
        if above { first } else { last }
    };
    let lines: BTreeSet<usize> = sels.ranges().iter().map(line_for).collect();
    // (line, where the text goes in, the caret's offset from there)
    let mut spots = Vec::new();
    let mut edits = Vec::new();
    for line in lines {
        let text = doc.line_text(line);
        let indent = &text[..indent_len(&text)];
        if above {
            let at = doc.line_start(line);
            edits.push(Edit::new(at, at, format!("{indent}\n")));
            spots.push((line, at, indent.len()));
        } else {
            let at = doc.line_end(line);
            edits.push(Edit::new(at, at, format!("\n{indent}")));
            spots.push((line, at, indent.len() + 1));
        }
    }
    let changes = ChangeSet::new(doc.len(), edits);
    let primary_line = line_for(sels.primary());
    let primary = spots
        .iter()
        .position(|(line, ..)| *line == primary_line)
        .unwrap_or(0);
    let carets = spots
        .iter()
        .map(|&(_, at, offset)| {
            Selection::caret(ByteOffset(
                changes.map_position(at, Bias::Before).0 + offset,
            ))
        })
        .collect();
    edit_result(changes, SelectionSet::new(carets, primary), sels)
}

/// Reverses the order of the selected lines (from the first to the last),
/// the rectangle's lines, or every line when nothing is selected.
pub(crate) fn reverse(doc: &Document, sels: &SelectionSet) -> Resolved {
    let rect = sels.rect().cloned();
    let any_selected = sels.ranges().iter().any(|s| !s.is_empty());
    let (first, mut last) = if let Some(r) = &rect {
        (r.top(), r.bottom())
    } else if any_selected {
        let spans: Vec<_> = sels.ranges().iter().map(|s| lines_of(doc, s)).collect();
        let first = spans.iter().map(|s| s.0).min().unwrap_or(0);
        let last = spans.iter().map(|s| s.1).max().unwrap_or(0);
        (first, last)
    } else {
        (0, doc.line_count() - 1)
    };
    // A trailing newline's empty last line is not a line to move.
    if last > first && last + 1 == doc.line_count() && doc.line_text(last).is_empty() {
        last -= 1;
    }
    if last <= first {
        return Resolved::Selections(sels.clone());
    }
    let mut lines: Vec<String> = (first..=last).map(|l| doc.line_text(l)).collect();
    lines.reverse();
    let new = lines.join("\n");
    let (start, end) = (doc.line_start(first), doc.line_end(last));
    if doc.slice(start..end) == new {
        return Resolved::Selections(sels.clone());
    }
    let changes = ChangeSet::new(doc.len(), vec![Edit::new(start, end, new.as_str())]);
    let after = if any_selected || rect.is_some() {
        SelectionSet::single(Selection::new(start, ByteOffset(start.0 + new.len())))
    } else {
        SelectionSet::caret(start)
    };
    edit_result(changes, after, sels)
}

/// Removes leading spaces and tabs (and with `trailing`, trailing ones too)
/// from the selected lines, or from every line when nothing is selected.
pub(crate) fn trim_lines(doc: &Document, sels: &SelectionSet, trailing: bool) -> Resolved {
    let mut edits = Vec::new();
    for line in selected_lines(doc, sels) {
        let text = doc.line_text(line);
        let start = doc.line_start(line).0;
        let lead = indent_len(&text);
        // A blank line is all lead; nothing is left to trim at its end.
        let keep_end = if trailing {
            text.trim_end_matches([' ', '\t']).len().max(lead)
        } else {
            text.len()
        };
        if lead > 0 {
            edits.push(Edit::new(ByteOffset(start), ByteOffset(start + lead), ""));
        }
        if keep_end < text.len() {
            edits.push(Edit::new(
                ByteOffset(start + keep_end),
                ByteOffset(start + text.len()),
                "",
            ));
        }
    }
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_before(sels, &changes);
    edit_result(changes, after, sels)
}

/// Replaces each line break between the target lines with a space, joining
/// each run of them into one line (Notepad++'s EOL to Space). Unlike Join
/// Lines, the spaces and tabs around the breaks stay.
pub(crate) fn eol_to_space(doc: &Document, sels: &SelectionSet) -> Resolved {
    let lines = target_lines(doc, sels);
    let edits = lines
        .windows(2)
        .filter(|w| w[1] == w[0] + 1)
        .map(|w| Edit::new(doc.line_end(w[0]), doc.line_start(w[1]), " "))
        .collect();
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_before(sels, &changes);
    edit_result(changes, after, sels)
}

/// Replaces every tab on the selected lines (every line when nothing is
/// selected) with the spaces that reach the same tab stop.
pub(crate) fn tabs_to_spaces(doc: &Document, sels: &SelectionSet, tab_width: usize) -> Resolved {
    let width = tab_width.max(1);
    let mut edits = Vec::new();
    for line in selected_lines(doc, sels) {
        let text = doc.line_text(line);
        if !text.contains('\t') {
            continue;
        }
        let start = doc.line_start(line).0;
        let mut col = 0;
        for (i, g) in text.grapheme_indices(true) {
            let w = grapheme_width(g, col, width);
            if g == "\t" {
                edits.push(Edit::new(
                    ByteOffset(start + i),
                    ByteOffset(start + i + 1),
                    " ".repeat(w),
                ));
            }
            col += w;
        }
    }
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_before(sels, &changes);
    edit_result(changes, after, sels)
}

/// The tabs (and spaces) for `n` spaces starting at visual column `col`,
/// keeping every column: each stretch of two or more spaces that reaches a
/// tab stop becomes a tab. `None` when nothing would change.
fn spaces_as_tabs(col: usize, n: usize, width: usize) -> Option<String> {
    let end = col + n;
    let mut out = String::new();
    let mut c = col;
    let mut changed = false;
    while c < end {
        let stop = (c / width + 1) * width;
        if stop > end {
            out.push_str(&" ".repeat(end - c));
            break;
        }
        if stop - c >= 2 {
            out.push('\t');
            changed = true;
        } else {
            out.push(' ');
        }
        c = stop;
    }
    changed.then_some(out)
}

/// Replaces spaces with tabs on the selected lines (every line when nothing
/// is selected) wherever that keeps every column: Notepad++'s Space to TAB
/// (All). Leading whitespace becomes tabs and then spaces narrower than a
/// tab, as Convert Indentation does; after it, each run of two or more
/// spaces reaching a tab stop becomes a tab.
pub(crate) fn spaces_to_tabs(doc: &Document, sels: &SelectionSet, tab_width: usize) -> Resolved {
    let width = tab_width.max(1);
    let mut edits = Vec::new();
    for line in selected_lines(doc, sels) {
        let text = doc.line_text(line);
        if !text.contains(' ') {
            continue;
        }
        let start = doc.line_start(line).0;
        let lead = indent_len(&text);
        let mut col = 0;
        for b in text[..lead].bytes() {
            col = if b == b'\t' {
                col + width - col % width
            } else {
                col + 1
            };
        }
        let indent = format!("{}{}", "\t".repeat(col / width), " ".repeat(col % width));
        if indent != text[..lead] {
            edits.push(Edit::new(
                ByteOffset(start),
                ByteOffset(start + lead),
                indent,
            ));
        }
        // Runs of spaces after the indentation: (byte, column) of the first.
        let mut run: Option<(usize, usize)> = None;
        let flush = |run: &mut Option<(usize, usize)>, col: usize, edits: &mut Vec<Edit>| {
            if let Some((byte, from)) = run.take()
                && let Some(tabs) = spaces_as_tabs(from, col - from, width)
            {
                edits.push(Edit::new(
                    ByteOffset(start + byte),
                    ByteOffset(start + byte + col - from),
                    tabs,
                ));
            }
        };
        for (i, g) in text[lead..].grapheme_indices(true) {
            if g == " " {
                run.get_or_insert((lead + i, col));
            } else {
                flush(&mut run, col, &mut edits);
            }
            col += grapheme_width(g, col, width);
        }
        flush(&mut run, col, &mut edits);
    }
    let changes = ChangeSet::new(doc.len(), edits);
    let after = map_before(sels, &changes);
    edit_result(changes, after, sels)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn case_modes() {
        let s = "hello WORLD, don't straße";
        assert_eq!(
            convert_case(s, CaseMode::Upper),
            "HELLO WORLD, DON'T STRASSE"
        );
        assert_eq!(
            convert_case(s, CaseMode::Lower),
            "hello world, don't straße"
        );
        assert_eq!(
            convert_case(s, CaseMode::Title),
            "Hello World, Don't Straße"
        );
        assert_eq!(
            convert_case(s, CaseMode::Invert),
            "HELLO world, DON'T STRASSE"
        );
        assert_eq!(
            convert_case("hello WORLD, mcDonald", CaseMode::TitleBlend),
            "Hello WORLD, McDonald"
        );
    }

    #[test]
    fn sentence_case_starts_after_an_end_mark_or_a_blank_line() {
        let s = "HELLO there. e.g. THIS one! and? yes\nno\n\nNEW para";
        // As in Notepad++, only the first dot of "e.g." is inside a
        // sentence.
        assert_eq!(
            convert_case(s, CaseMode::Sentence),
            "Hello there. E.g. This one! And? Yes\nno\n\nNew para"
        );
        assert_eq!(
            convert_case(s, CaseMode::SentenceBlend),
            "HELLO there. E.g. THIS one! And? Yes\nno\n\nNEW para"
        );
        assert_eq!(convert_case("", CaseMode::Sentence), "");
        assert_eq!(
            convert_case("3 apples. ok", CaseMode::Sentence),
            "3 Apples. Ok"
        );
        // A decimal point ends no sentence; a line of blanks is blank.
        assert_eq!(
            convert_case("it costs 2.50 DOLLARS", CaseMode::Sentence),
            "It costs 2.50 dollars"
        );
        assert_eq!(convert_case("a\n  \nb", CaseMode::Sentence), "A\n  \nB");
    }

    #[test]
    fn random_case_changes_only_letters_and_follows_the_seed() {
        let s = "abcdefghijklmnop 123 straße!";
        let a = convert_case(s, CaseMode::Random { seed: 7 });
        assert_eq!(a, convert_case(s, CaseMode::Random { seed: 7 }));
        assert_ne!(a, convert_case(s, CaseMode::Random { seed: 8 }));
        assert_eq!(a.to_lowercase().replace("ss", "ß"), s);
        assert!(a.chars().any(char::is_uppercase) && a.chars().any(char::is_lowercase));
    }

    #[test]
    fn spaces_become_tabs_only_where_columns_stay() {
        assert_eq!(spaces_as_tabs(1, 3, 4), Some("\t".to_owned()));
        assert_eq!(
            spaces_as_tabs(3, 1, 4),
            None,
            "one space before a stop stays"
        );
        assert_eq!(spaces_as_tabs(2, 8, 4), Some("\t\t  ".to_owned()));
        assert_eq!(spaces_as_tabs(0, 3, 4), None);
    }

    #[test]
    fn numbers_at_line_starts() {
        assert_eq!(leading_number("  42 apples"), Some(42.0));
        assert_eq!(leading_number("-3.5x"), Some(-3.5));
        assert_eq!(leading_number("7."), Some(7.0));
        assert_eq!(leading_number("x1"), None);
        assert_eq!(leading_number("-"), None);
    }
}