use super::region::Region;
use super::vertical::stands_upright;
use super::{
    Affine, BezPath, Breakpoint, Burasagari, EPS, FirstBaseline, FontDb, HyphenationOptions, Kinsoku, KinsokuShoriType, LeadingModel, SGlyph,
    hyphen_glyph, is_cjk, no_line_end, no_line_start, points_for, soft_line_start,
};
use crate::justify::is_format_control;

/// Vertical metrics of a line: (ascent, descent, leading, cap height, x height).
#[derive(Clone, Copy, Debug, PartialEq)]
pub(super) struct Metrics {
    pub(super) asc: f64,
    pub(super) desc: f64,
    pub(super) lead: f64,
    pub(super) cap: f64,
    pub(super) xh: f64,
    /// Height of the top of the ideographic em box above the baseline.
    pub(super) top: f64,
}

impl Metrics {
    pub(super) fn of(g: &SGlyph) -> Self {
        let em = g.face.units_per_em() * g.sy;
        Self { asc: g.ascent, desc: g.descent, lead: g.leading, cap: g.cap, xh: g.xh, top: (g.face.ideographic_centre() + 0.5) * em }
    }
    pub(super) fn max(g: &[SGlyph]) -> Option<Self> {
        let mut it = g.iter();
        let first = Self::of(it.next()?);
        Some(it.fold(first, |m, g| m.union(Self::of(g))))
    }
    /// The larger of each of the metrics of `self` and `o`: those of a line holding both.
    pub(super) fn union(self, o: Self) -> Self {
        Self {
            asc: self.asc.max(o.asc),
            desc: self.desc.max(o.desc),
            lead: self.lead.max(o.lead),
            cap: self.cap.max(o.cap),
            xh: self.xh.max(o.xh),
            top: self.top.max(o.top),
        }
    }
    /// Distance from the frame top to the first baseline.
    pub(super) fn first_baseline(&self, fb: FirstBaseline, min: f64) -> f64 {
        let v = match fb {
            FirstBaseline::Ascent => self.asc,
            FirstBaseline::CapHeight => self.cap,
            FirstBaseline::XHeight => self.xh,
            FirstBaseline::Leading => self.lead,
            FirstBaseline::Fixed => 0.0,
        };
        v.max(min)
    }
}

/// Where the next line goes: the region being filled and the previous baseline in it.
#[derive(Clone)]
pub(super) struct Pen<'r> {
    pub(super) regions: Option<&'r [Region]>,
    pub(super) ri: usize,
    pub(super) prev: Option<f64>,
    pub(super) pending: f64,
    pub(super) fb: FirstBaseline,
    pub(super) fb_min: f64,
    /// Further spans at the current baseline (text wrapping on both sides of an object).
    pub(super) queued: Vec<(f64, f64, f64)>,
    /// Leading measured from em box top to em box top: where the next line's em box top goes.
    pub(super) model: LeadingModel,
    pub(super) next_top: Option<f64>,
    /// The narrowest word no line from here down is wide enough for (see [`Pen::place`]).
    pub(super) no_room_for: f64,
    /// Baseline steps still allowed over all the frame's cells and placements (shared by this pen's
    /// copies): see [`MAX_TOTAL_STEPS`].
    pub(super) steps_left: std::rc::Rc<std::cell::Cell<usize>>,
    /// What is left of the every-line composer's search over the frame's paragraphs (shared by
    /// this pen's copies): see [`super::shaped::Budget`].
    pub(super) search: std::rc::Rc<super::shaped::Budget>,
}

/// The largest number of steps layout takes to move a line down a frame cell to find room for it:
/// in a cell taller than this many leads, a step is the cell's height divided by this.
const MAX_STEPS: usize = 100_000;

/// The most baseline steps one frame's layout takes in all, over every cell: a cell may take
/// [`MAX_STEPS`], but rows and columns of tall, narrow-shaped cells would multiply that.
pub(super) const MAX_TOTAL_STEPS: usize = 10_000_000;

impl Pen<'_> {
    /// Baseline and horizontal span for a line with estimated metrics `est` and indents that starts
    /// with a word `word` wide; `None` = the frame is full (overflow).
    /// In a frame that isn't a rectangle, lines too short for the word are left empty and it moves
    /// down to the first one wide enough. Only when no line is does it go on the first line with
    /// room for any text, and get broken there.
    /// The `bool` is true for a further span at the previous line's baseline.
    pub(super) fn place(&mut self, est: Metrics, ind_l: f64, ind_r: f64, word: f64) -> Option<(f64, f64, f64, bool)> {
        if word > 0.0 && word < self.no_room_for {
            let mut pen = self.clone();
            if let Some(placed) = pen.place_at_least(est, ind_l, ind_r, word) {
                *self = pen;
                return Some(placed);
            }
            // Lines further down are no wider for this word: don't search for it, or a wider one, again.
            self.no_room_for = word;
        }
        self.place_at_least(est, ind_l, ind_r, 0.0)
    }

    /// [`Pen::place`], skipping lines of a non-rectangular frame narrower than `min`.
    fn place_at_least(&mut self, est: Metrics, ind_l: f64, ind_r: f64, min: f64) -> Option<(f64, f64, f64, bool)> {
        let Some(regions) = self.regions else {
            let b = self.prev.map_or(0.0, |b| self.next_baseline(b, est));
            return Some((b, f64::NEG_INFINITY, f64::INFINITY, false));
        };
        // A further span was measured across the height of the line set before it on its baseline.
        // This line gets the part of it that is free across its own height: a taller line can
        // reach a wrap object the line before it stayed clear of. A span with no such part is
        // left empty, and so is a part the line's height made narrower than `min`.
        while !self.queued.is_empty() {
            let (b, x0, x1) = self.queued.remove(0);
            let Some(r) = regions.get(self.ri) else { return Some((b, x0, x1, true)) };
            let mut free = r.spans(b - est.asc, b + est.desc).into_iter().filter_map(|(s, e)| {
                let (s, e) = (s.max(x0), e.min(x1));
                let room = e - s - ind_l - ind_r;
                let narrowed = s > x0 + EPS || e < x1 - EPS;
                (room > est.asc.max(1.0) && (!narrowed || room + EPS >= min)).then_some((s, e))
            });
            let Some((s, e)) = free.next() else { continue };
            // An object inside the span splits it: the parts after the first stay queued.
            let rest: Vec<_> = free.map(|(s, e)| (b, s, e)).collect();
            self.queued.splice(0..0, rest);
            return Some((b, s, e, true));
        }
        loop {
            let r = regions.get(self.ri)?;
            let mut baseline = match self.prev {
                None if self.model == LeadingModel::EmBoxTop => r.top() + r.shift + est.top.max(self.fb_min),
                None => r.top() + r.shift + est.first_baseline(self.fb, self.fb_min),
                Some(b) => self.next_baseline(b, est) + r.gap,
            };
            // The baseline moves down the cell a lead at a time, or a `MAX_STEPS`th of the cell's
            // height when that is more, in at most `MAX_STEPS` steps.
            let step = est.lead.max(1.0).max(r.cell.height() / MAX_STEPS as f64);
            for _ in 0..=MAX_STEPS {
                let left = self.steps_left.get();
                if left == 0 {
                    // Out of steps: the frame is full as far as this text goes.
                    return None;
                }
                self.steps_left.set(left - 1);
                // A baseline a step no longer moves (past a gutter of 1e300, say) won't reach a line.
                if baseline + est.desc > r.bottom() + 0.01 || baseline + step <= baseline || baseline.is_nan() {
                    break;
                }
                // A rectangle's lines are all as wide: none below has more room for the word
                // (until wrap shapes can narrow the first baseline: they stay bounded).
                let constant = (r.rect || r.polys.is_empty()) && r.wraps.is_empty();
                let min = if constant { 0.0 } else { min };
                let fits = |&(a, b): &(f64, f64)| {
                    let room = b - a - ind_l - ind_r;
                    room > est.asc.max(1.0) && room + EPS >= min
                };
                if r.wraps.is_empty() {
                    match r.span(baseline - est.asc, baseline + est.desc) {
                        Some(s) if fits(&s) => return Some((baseline, s.0, s.1, false)),
                        // Too narrow here is too narrow all the way down the cell: next cell.
                        Some(_) if constant => break,
                        _ => baseline += step,
                    }
                } else {
                    // Wrap objects can split a line: fill every span, left to right.
                    let mut spans: Vec<(f64, f64)> = r.spans(baseline - est.asc, baseline + est.desc).into_iter().filter(fits).collect();
                    if spans.is_empty() {
                        baseline += step;
                        continue;
                    }
                    let (a, b) = spans.remove(0);
                    self.queued = spans.into_iter().map(|(a, b)| (baseline, a, b)).collect();
                    return Some((baseline, a, b, false));
                }
            }
            // Next row/column.
            self.ri += 1;
            self.prev = None;
            self.pending = 0.0;
            self.queued.clear();
        }
    }
    pub(super) fn bottom(&self) -> f64 {
        self.regions.and_then(|r| r.get(self.ri)).map_or(f64::INFINITY, |r| r.bottom())
    }
    /// The baseline of the line after the one at `prev`, for a line of metrics `est`.
    fn next_baseline(&self, prev: f64, est: Metrics) -> f64 {
        match (self.model, self.next_top) {
            (LeadingModel::EmBoxTop, Some(top)) => top + est.top + self.pending,
            _ => prev + est.lead + self.pending,
        }
    }
    /// A line was set at `baseline` with metrics `m`: where the next one goes from.
    pub(super) fn settled(&mut self, baseline: f64, m: Metrics) {
        self.prev = Some(baseline);
        self.next_top = Some(baseline - m.top + m.lead);
    }
}

/// Advance of a tab at pen position `x`: up to the next stop after it (explicit stops first, then
/// every ½ inch), and the leader of that stop (default stops have none). Right, centre and decimal
/// stops align the text that follows (`rest`, up to the next tab) on the stop.
pub(super) fn tab_advance<'t>(tabs: &'t [vectorcraft_doc::TabStop], origin: f64, x: f64, rest: &[SGlyph]) -> (f64, &'t str) {
    use vectorcraft_doc::TabAlign;
    let rel = x - origin;
    let seg: Vec<&SGlyph> = rest.iter().take_while(|g| g.ch != '\t' && g.ch != '\u{2028}').collect();
    let width: f64 = seg.iter().map(|g| g.adv).sum();
    let target = |pos: f64, align: TabAlign, on: char| match align {
        TabAlign::Left => pos,
        TabAlign::Right => pos - width,
        TabAlign::Center => pos - width / 2.0,
        TabAlign::Decimal => pos - seg.iter().take_while(|g| g.ch != on).map(|g| g.adv).sum::<f64>(),
    };
    let explicit = tabs.iter().find_map(|t| {
        let at = target(t.position, t.align, t.align_on);
        (at > rel + 1e-6).then_some((at, t.leader.as_str()))
    });
    let (at, leader) = explicit.unwrap_or_else(|| {
        let last = tabs.iter().map(|t| t.position).fold(0.0, f64::max).max(0.0);
        let base = rel.max(last);
        (((base / vectorcraft_doc::text::DEFAULT_TAB_INTERVAL).floor() + 1.0) * vectorcraft_doc::text::DEFAULT_TAB_INTERVAL, "")
    });
    ((at - rel).max(0.0), leader)
}

/// The width of glyphs `from..to` of `sg` set on a line whose content starts `x_start` from the
/// tab origin: tabs of the text take what [`tab_advance`] gives them, not the width of their
/// glyph. The tab of a list marker (length 0) keeps its own width.
pub(super) fn set_width(sg: &[SGlyph], from: usize, to: usize, tabs: &[vectorcraft_doc::TabStop], x_start: f64) -> f64 {
    let mut x = x_start;
    for (j, g) in sg.iter().enumerate().take(to).skip(from) {
        x += if g.ch == '\t' && g.len > 0 { tab_advance(tabs, 0.0, x, sg.get(j + 1..to).unwrap_or_default()).0 } else { g.adv };
    }
    x - x_start
}

/// Most copies of a leader drawn in one tab: a tiny type size and a far stop must not make
/// millions of outlines.
const MAX_LEADER_COPIES: f64 = 4096.0;

/// The outline of a tab leader: `leader`'s characters, in the font and size of tab `g`, repeated
/// across the tab's gap `from..to` on baseline `y`. Copies sit on a grid of the leader's width
/// from `origin` (where tab stops are measured from), so the leaders of lines above one another
/// line up; only whole copies are drawn. Characters the font lacks draw nothing.
pub(super) fn leader_outline(db: &FontDb, g: &SGlyph, leader: &str, origin: f64, from: f64, to: f64, y: f64) -> BezPath {
    let mut out = BezPath::new();
    let glyphs: Vec<(u32, f64)> = leader
        .chars()
        .filter(|c| !c.is_control())
        .map(|c| {
            let gid = g.face.glyph_for(c);
            (gid, g.face.advance(gid) * g.sx)
        })
        .collect();
    let width: f64 = glyphs.iter().map(|(_, a)| a).sum();
    if !(width > EPS && width.is_finite() && from.is_finite() && to.is_finite()) {
        return out;
    }
    let first = ((from - origin) / width - EPS).ceil();
    let copies = (((to - origin) / width + EPS).floor() - first).clamp(0.0, MAX_LEADER_COPIES) as usize;
    let local = Affine::translate((0.0, -g.bshift)) * Affine::rotate(-g.rotation.to_radians()) * Affine::scale_non_uniform(g.sx, g.sy);
    for k in 0..copies {
        let mut pen = origin + (first + k as f64) * width;
        for &(gid, adv) in &glyphs {
            if gid != 0 {
                let m = Affine::translate((pen, y)) * local;
                out.extend(db.outline(&g.face, gid).elements().iter().map(|el| m * *el));
            }
            pen += adv;
        }
    }
    out
}

/// Width of the word starting at glyph `i`: its advances up to the first place a line may break
/// (spaces left out, the hyphen of a soft hyphen in), the least room a line needs not to break
/// inside it. As in [`break_line`], kinsoku keeps a character that may not end a line with the one
/// after it, a No Break run (its spaces inside it included) is one word up to a forced line break,
/// and a cluster is never split. A soft hyphen just before a forced line break adds no hyphen. A list marker at `i` (glyphs of length 0) counts whole, with the word after it. A word
/// that ends where a line may end is measured as the line is set: without the spaces at its end,
/// and with its last glyph as narrow as `line_end` sets it; one that ends at a soft hyphen or past
/// the measured glyphs is not.
pub(super) fn word_width(g: &[SGlyph], i: usize, line_end: &[f64], kinsoku: Kinsoku) -> f64 {
    /// Glyphs measured at most: a word wrapped over many lines is measured again from each line's
    /// start, and one this long is broken inside whatever cell it meets.
    const MAX_GLYPHS: usize = 1024;
    let rest = g.get(i..).unwrap_or_default();
    let marker = rest.iter().take_while(|gl| gl.len == 0).count();
    let mut w: f64 = rest.iter().take(marker).map(|gl| gl.adv).sum();
    let start = i + marker;
    let mut end = start;
    // The spaces at the end of what is measured so far (inside a No Break run), and the end of its
    // last glyph that is not a space.
    let (mut trailing, mut ink) = (0.0, start);
    let set = |w: f64, trailing: f64, ink: usize| w - trailing - line_end_credit(g, line_end, ink);
    while let Some(gl) = g.get(end).filter(|_| end - start < MAX_GLYPHS) {
        // A forced line break ends the line, inside a No Break run too, as in [`break_line`].
        if gl.ch == '\u{2028}' {
            return set(w, trailing, ink);
        }
        if gl.is_space() && (end == start || !splits_no_break(g, end)) {
            return set(w, trailing, ink);
        }
        let forced_next = g.get(end + 1).is_some_and(|n| n.ch == '\u{2028}');
        if gl.is_soft_hyphen() && !forced_next && kinsoku_allows(g, end, kinsoku) && !splits_no_break(g, end + 1) {
            return w + hyphen_glyph(gl).adv;
        }
        w += gl.adv;
        end += 1;
        if gl.is_space() {
            trailing += gl.adv;
        } else {
            (trailing, ink) = (0.0, end);
        }
        let cluster_ends = g.get(end).is_none_or(|next| next.byte != gl.byte);
        if gl.break_after() && cluster_ends && kinsoku_allows(g, end - 1, kinsoku) && !splits_no_break(g, end) {
            return set(w, trailing, ink);
        }
    }
    if end >= g.len() { set(w, trailing, ink) } else { w }
}

/// Greedy break: returns (end glyph index, hyphenated) for a line starting at `i` of `width`.
/// With burasagari, a comma or full stop that doesn't fit ends the line, hanging outside it.
/// `hyphenate` holds the paragraph's Hyphenation options and the Hyphenation Zone in force when
/// the line may hyphenate a word; a line whose text before the overflowing word already ends
/// within the zone breaks before that word. A tab is as wide as it is set: up to its next stop
/// (`tabs`), with the line's content starting `x_start` from the tab origin. Where kinsoku alone
/// keeps the line from breaking before the character that overflows, `kinsoku_type` decides
/// whether the line pushes characters in ([`push_in`]) or out; `hanging` is true when Optical
/// Margin Alignment or Roman Hanging Punctuation is on, and `vertical` in vertical type.
/// `line_end[k]` is how much narrower a line ending with glyph `k` is set (Mojikumi); a cluster
/// that fits only that narrower stays on the line when the line may end after it (empty: none).
#[allow(clippy::too_many_arguments)]
pub(super) fn break_line(
    text: &str,
    g: &[SGlyph],
    i: usize,
    width: f64,
    tabs: &[vectorcraft_doc::TabStop],
    x_start: f64,
    hyphenate: Option<(&HyphenationOptions, f64)>,
    burasagari: Burasagari,
    kinsoku: Kinsoku,
    kinsoku_type: KinsokuShoriType,
    hanging: bool,
    vertical: bool,
    line_end: &[f64],
) -> (usize, bool) {
    if !width.is_finite() {
        if let Some(pos) = g[i..].iter().position(|gl| gl.ch == '\u{2028}') {
            return (i + pos + 1, false);
        }
        return (g.len(), false);
    }
    let mut x = 0.0;
    let mut last_break: Option<(usize, bool)> = None;
    // A list marker (length 0) is a cluster of its own; the line holds it and at least the first
    // cluster after it.
    let first = i + g.get(i..).unwrap_or_default().iter().take_while(|h| h.len == 0).count();
    let mut j = i;
    while j < g.len() {
        let gl = &g[j];
        let mut cluster_end = j + 1;
        while g.get(cluster_end).is_some_and(|next| next.byte == gl.byte && (next.len == 0) == (gl.len == 0)) {
            cluster_end += 1;
        }
        // No Break: the marked characters stay on one line, including across a space inside the run;
        // Bunri-Kinshi keeps an inseparable pair, or a chain of them, on one line too.
        if gl.ch != '\u{2028}' {
            while let Some(n) = g.get(cluster_end) {
                if !splits_no_break(g, cluster_end) || n.ch == '\u{2028}' {
                    break;
                }
                let b = n.byte;
                cluster_end += 1;
                while g.get(cluster_end).is_some_and(|next| next.byte == b) {
                    cluster_end += 1;
                }
            }
        }
        // A list marker's glyphs, its tab included, keep their own widths.
        let cluster_width: f64 = if gl.ch == '\t' && gl.len > 0 {
            tab_advance(tabs, 0.0, x_start + x, g.get(cluster_end..).unwrap_or_default()).0
        } else {
            g[j..cluster_end].iter().map(|glyph| glyph.adv).sum()
        };
        if gl.ch == '\u{2028}' {
            return (cluster_end, false);
        }
        // Measured as the line is set when it ends with this cluster: only the cluster's last glyph
        // is narrowed, and only where the line may end.
        let end_credit =
            Some(line_end_credit(g, line_end, cluster_end)).filter(|&c| c > 0.0 && may_end_after(g, cluster_end, kinsoku)).unwrap_or(0.0);
        if j > first && !gl.is_space() && x + cluster_width - end_credit > width + EPS {
            // It ends the line with the spaces after it.
            if burasagari != Burasagari::None && hangs(gl) && kinsoku_allows(g, cluster_end - 1, kinsoku) {
                let mut end = cluster_end;
                while g.get(end).is_some_and(SGlyph::is_space) {
                    end += 1;
                }
                return (end, false);
            }
            let pushed_out = last_break.map(|b| b.0);
            if let Some(end) = push_in(g, i, j, cluster_end, x + cluster_width, width, pushed_out, kinsoku, kinsoku_type, hanging, vertical, line_end)
            {
                return (end, false);
            }
            break;
        }
        x += cluster_width;
        let last = &g[cluster_end - 1];
        if last.break_after() && last.len > 0 && kinsoku_allows(g, cluster_end - 1, kinsoku) && !splits_no_break(g, cluster_end) {
            if last.is_soft_hyphen() {
                if x + hyphen_glyph(last).adv <= width + EPS {
                    last_break = Some((cluster_end, true));
                }
            } else {
                last_break = Some((cluster_end, false));
            }
        }
        j = cluster_end;
    }
    if j >= g.len() {
        return (g.len(), false);
    }
    // Hyphenate the word that overflows. A list marker starting the line is not part of a word.
    let word_start = last_break.map_or(first, |b| b.0);
    let in_zone = |zone: f64| {
        let mut te = word_start;
        while te > first && g[te - 1].is_space() {
            te -= 1;
        }
        te > first && zone > 0.0 && width - g[i..te].iter().map(|g| g.adv).sum::<f64>() <= zone + EPS
    };
    if let Some((opts, zone)) = hyphenate
        && g[j].is_letter()
        && !in_zone(zone)
    {
        let mut we = j;
        while we < g.len() && !g[we].is_space() && !g[we].break_after() {
            we += 1;
        }
        let x_ws: f64 = g[i..word_start].iter().map(|g| g.adv).sum();
        let pts: Vec<usize> = hyphen_breaks(text, g, word_start, we, opts)
            .into_iter()
            .filter(|&k| k > 0 && kinsoku_allows(g, k - 1, kinsoku) && !splits_no_break(g, k))
            .collect();
        for &k in pts.iter().rev() {
            if k <= j && k > i {
                let w = x_ws + g[word_start..k].iter().map(|g| g.adv).sum::<f64>() + hyphen_glyph(&g[k - 1]).adv;
                if w <= width + EPS {
                    return (k, true);
                }
            }
        }
    }
    // Break candidates and greedy overflow are cluster boundaries; hyphenation also returns only
    // cluster starts, so the resulting end always keeps each source cluster together.
    let (end, hy) = match last_break {
        Some(b) if b.0 > i => b,
        _ => (j, false),
    };
    (end, hy)
}

/// Can glyph `g` hang outside the line (burasagari)? An East Asian comma or full stop, full width
/// (、。，．) or half width (､｡); not a closing bracket, nor Latin punctuation (Latin text keeps
/// its line breaks and composer). Never an inline graphic (U+FFFC).
pub(super) fn hangs(g: &SGlyph) -> bool {
    g.inline.is_none() && matches!(g.ch, '、' | '。' | '，' | '．' | '､' | '｡') && g.tcy.is_none()
}

/// Optical Margin Alignment: the share of glyph `g`'s advance that hangs outside the margin when
/// `g` starts or ends a line. Quotation marks, hyphens, full stops and commas hang whole, and
/// asterisks, tildes, ellipses, en and em dashes, colons and semicolons hang by half (the amounts
/// published for Roman Hanging Punctuation). A, V, W, Y, v, w and y hang by a tenth of their
/// advance, VectorCraft's own amount for their slanted sides. Other characters, East Asian
/// punctuation (which burasagari hangs) and inline graphics don't hang.
pub(super) fn optical_share(g: &SGlyph) -> f64 {
    if g.inline.is_some() || g.tcy.is_some() {
        return 0.0;
    }
    match g.ch {
        '-' | '\u{2010}' | '\u{2011}' | '.' | ',' => 1.0,
        c if is_quote(c) => 1.0,
        '*' | '~' | '…' | '–' | '—' | ':' | ';' => 0.5,
        'A' | 'V' | 'W' | 'Y' | 'v' | 'w' | 'y' => 0.1,
        _ => 0.0,
    }
}

/// Roman Hanging Punctuation: the share of glyph `g`'s advance that hangs outside the margin when
/// `g` starts or ends a line: [`optical_share`]'s punctuation, and no letters.
pub(super) fn roman_share(g: &SGlyph) -> f64 {
    if g.ch.is_alphabetic() { 0.0 } else { optical_share(g) }
}

/// A punctuation mark that hangs ([`optical_share`]), not a letter.
pub(super) fn optical_punct(g: &SGlyph) -> bool {
    !g.ch.is_alphabetic() && optical_share(g) > 0.0
}

/// A single or double quotation mark: straight, curly, low-9 or reversed-9.
fn is_quote(c: char) -> bool {
    matches!(c, '\'' | '"' | '‘' | '’' | '‚' | '‛' | '“' | '”' | '„' | '‟')
}

/// Optical Margin Alignment and Roman Hanging Punctuation: how far a line hangs outside its left
/// and right margins, from the glyph at each end of `line` (its glyphs in visual order, each with
/// the advance it is set with) and its `share` ([`optical_share`] or [`roman_share`]), and how many glyphs hang at each end → (left, right, left glyphs,
/// right glyphs). A punctuation mark followed by a quotation mark hangs together with it: `."`
/// ending a line and `'"` starting one hang both their glyphs. A line of one glyph hangs at
/// neither end.
pub(super) fn optical_hangs(line: &[(&SGlyph, f64)], share: fn(&SGlyph) -> f64) -> (f64, f64, usize, usize) {
    let n = line.len();
    if n < 2 {
        return (0.0, 0.0, 0, 0);
    }
    let hang = |k: usize| line.get(k).map_or(0.0, |&(g, adv)| share(g) * adv.max(0.0));
    let punct = |k: usize| line.get(k).is_some_and(|&(g, _)| optical_punct(g));
    let quote = |k: usize| line.get(k).is_some_and(|&(g, _)| is_quote(g.ch) && share(g) > 0.0);
    let mut left = hang(0);
    // The glyphs that hang at the left; the right end takes none of them.
    let mut taken = usize::from(left > 0.0);
    if left > 0.0 && n > 2 && punct(0) && quote(1) {
        left += hang(1);
        taken = 2;
    }
    let mut right = hang(n - 1);
    let mut right_glyphs = usize::from(right > 0.0);
    if right > 0.0 && n > 2 && n - 2 >= taken && punct(n - 2) && quote(n - 1) {
        right += hang(n - 2);
        right_glyphs = 2;
    }
    (left, right, taken, right_glyphs)
}

/// Works as [`optical_hangs`] does for a right-to-left line, whose `line` is also in visual order.
/// The line is read from right to left: `."` ending it hangs both its glyphs at the left, `'"` starting it hangs both at
/// the right, and the right end takes its glyphs first.
pub(super) fn optical_hangs_rtl(line: &[(&SGlyph, f64)], share: fn(&SGlyph) -> f64) -> (f64, f64, usize, usize) {
    let reversed: Vec<(&SGlyph, f64)> = line.iter().rev().copied().collect();
    let (right, left, right_glyphs, left_glyphs) = optical_hangs(&reversed, share);
    (left, right, left_glyphs, right_glyphs)
}

/// How much narrower a line whose last character is glyph `end - 1` is set: `line_end` of that
/// glyph ([`break_line`]), at most its advance, and 0 when it is not finite.
fn line_end_credit(g: &[SGlyph], line_end: &[f64], end: usize) -> f64 {
    let Some(k) = end.checked_sub(1) else { return 0.0 };
    match (line_end.get(k), g.get(k)) {
        (Some(&credit), Some(gl)) if credit.is_finite() && credit > 0.0 => credit.min(gl.adv.max(0.0)),
        _ => 0.0,
    }
}

/// May [`break_line`] end a line after glyph `end - 1` (and the spaces after it)? At the paragraph's
/// end or a forced line break, and where it records a break without a hyphen.
fn may_end_after(g: &[SGlyph], end: usize, kinsoku: Kinsoku) -> bool {
    let mut e = end;
    while g.get(e).is_some_and(SGlyph::is_space) {
        e += 1;
    }
    if e >= g.len() || g[e].ch == '\u{2028}' {
        return true;
    }
    let Some(last) = e.checked_sub(1).and_then(|k| g.get(k)) else { return false };
    last.break_after() && last.len > 0 && !last.is_soft_hyphen() && kinsoku_allows(g, e - 1, kinsoku) && !splits_no_break(g, e)
}

/// Would a line ending at glyph index `end` split a No Break run, or an inseparable pair that
/// Bunri-Kinshi keeps together ([`SGlyph::keeps_next`])?
fn splits_no_break(g: &[SGlyph], end: usize) -> bool {
    end > 0 && g.get(end - 1).is_some_and(|a| (a.no_break && g.get(end).is_some_and(|b| b.no_break)) || (a.keeps_next && g.get(end).is_some()))
}

/// Does kinsoku allow a line break after glyph `j`? Not after an opening bracket, nor before a
/// closing one, a comma, a full stop, a small kana… (the character is pushed to the next line
/// with the one before it).
fn kinsoku_allows(g: &[SGlyph], j: usize, kinsoku: Kinsoku) -> bool {
    g.get(j).is_some_and(|gl| kinsoku_between(gl.ch, g.get(j + 1).map(|n| n.ch), kinsoku))
}

/// Kinsoku for a break between `before` and `after` (none: the end of the paragraph): Hard keeps
/// every character of the set off the line start and end, Soft lets 々, ー and small kana start a
/// line, None allows the break.
fn kinsoku_between(before: char, after: Option<char>, kinsoku: Kinsoku) -> bool {
    match kinsoku {
        Kinsoku::None => true,
        Kinsoku::Hard => !no_line_end(before) && after.is_none_or(|c| !no_line_start(c)),
        Kinsoku::Soft => !no_line_end(before) && after.is_none_or(|c| !no_line_start(c) || soft_line_start(c)),
    }
}

/// The share of an em by which a push-in ([`push_in`]) may close each gap next to a CJK character
/// on the line, measured on the character before the gap.
pub(super) const PUSH_IN_SQUEEZE: f64 = 0.1;

/// The most glyphs after the overflowing cluster a push-in ([`push_in`]) takes onto the line; a
/// longer run of characters kinsoku keeps together pushes out.
const PUSH_IN_RUN: usize = 16;

/// Kinsoku Shori Type: the end of the line from `i` that overflows `width` at the cluster
/// `j..cluster_end` (the line is `x` wide through it) when the line pushes in, or None when it
/// pushes out. A line pushes in only where kinsoku rules out the break before `j`: a character
/// that may not end a line comes before it (an opening bracket or quotation mark, Latin ones
/// included), or one that may not start a line comes at `j`. It then takes the characters up to
/// the next break kinsoku allows (not at a soft hyphen), and the spaces after it, when closing
/// its gaps next to CJK characters, each by up to [`PUSH_IN_SQUEEZE`] of an em of the character
/// before it, makes room for them. Push In First tries this before it pushes out. Push Out First
/// tries it only when pushing out, to the line's last allowed break `pushed_out`, would leave the
/// line short by more than an em of the character before `j`. Push Out Only never pushes in, and
/// neither does a line holding a tab or right-to-left text, nor one where the characters taken in
/// reach a space after a character that may not end a line. With `hanging` (Optical Margin
/// Alignment or Roman Hanging Punctuation), the gaps that hanging punctuation keeps open are not
/// counted. `vertical`: the line is a column of vertical type ([`squeeze_em`]). Both lines are
/// measured with their last character set as narrow as `line_end` sets it ([`break_line`]).
#[allow(clippy::too_many_arguments)]
fn push_in(
    g: &[SGlyph],
    i: usize,
    j: usize,
    cluster_end: usize,
    x: f64,
    width: f64,
    pushed_out: Option<usize>,
    kinsoku: Kinsoku,
    kinsoku_type: KinsokuShoriType,
    hanging: bool,
    vertical: bool,
    line_end: &[f64],
) -> Option<usize> {
    if kinsoku == Kinsoku::None || kinsoku_type == KinsokuShoriType::PushOutOnly {
        return None;
    }
    let before = g.get(j.checked_sub(1)?)?;
    if before.len == 0 || g.get(j)?.no_break || splits_no_break(g, j) || kinsoku_allows(g, j - 1, kinsoku) {
        return None;
    }
    let allowed = |k: usize| {
        k >= g.len()
            || (g[k].byte != g[k - 1].byte
                && kinsoku_allows(g, k - 1, kinsoku)
                && !splits_no_break(g, k)
                && (g[k].is_space() || (g[k - 1].break_after() && !g[k - 1].is_soft_hyphen())))
    };
    let (mut end, mut x) = (cluster_end, x);
    while !allowed(end) {
        let gl = &g[end];
        // A space here follows a character kinsoku keeps off a line's end: the line pushes out.
        if gl.is_space() || gl.ch == '\t' || gl.ch == '\u{2028}' || gl.no_break || end - cluster_end >= PUSH_IN_RUN {
            return None;
        }
        x += gl.adv;
        end += 1;
    }
    // A tab's width depends on where it falls; a line with one (other than a list marker's)
    // pushes out.
    if g[i..end].iter().any(|h| h.ch == '\t' && h.len > 0) {
        return None;
    }
    // With `hanging`, punctuation keeps the gap after a mark that may hang at the line's start,
    // and the gap before one that may hang at its end ([`optical_hangs`]): those gaps are not
    // counted.
    let mut last = end;
    while last > i && g[last - 1].is_space() {
        last -= 1;
    }
    // A line holding right-to-left text is reordered before it is drawn, and justification closes
    // the gaps between its glyphs in that order: it pushes out.
    if g[i..last].iter().any(|h| h.len > 0 && h.level.is_rtl()) {
        return None;
    }
    let punct = |k: usize| g.get(k).is_some_and(optical_punct);
    let quote = |k: usize| g.get(k).is_some_and(|h| is_quote(h.ch));
    let may_hang = |a: usize| {
        hanging
            && ((a == i && punct(i))
                || (a == i + 1 && punct(i) && quote(i + 1))
                || (a + 2 == last && punct(last - 1))
                || (a + 3 == last && punct(last - 2) && quote(last - 1)))
    };
    let room: f64 = (i..end - 1).filter(|&a| closes(g, a, end) && !may_hang(a)).map(|a| PUSH_IN_SQUEEZE * squeeze_em(&g[a], vertical)).sum();
    if x - line_end_credit(g, line_end, last) - width > room + EPS {
        return None;
    }
    if kinsoku_type == KinsokuShoriType::PushOutFirst {
        let mut kept = pushed_out.filter(|&b| b > i).unwrap_or(i);
        while kept > i && g[kept - 1].is_space() {
            kept -= 1;
        }
        let set = if kept > i { line_end_credit(g, line_end, kept) } else { 0.0 };
        let short = width - (g[i..kept].iter().map(|h| h.adv).sum::<f64>() - set);
        if short <= squeeze_em(before, vertical) + EPS {
            return None;
        }
    }
    while g.get(end).is_some_and(SGlyph::is_space) {
        end += 1;
    }
    if g.get(end).is_some_and(|h| h.ch == '\u{2028}') {
        end += 1;
    }
    Some(end)
}

/// May a push-in close the gap after glyph `a`? A gap between two characters, at least one of them
/// CJK, outside a tate-chu-yoko block, a list marker and a shaped cluster, and not next to a space,
/// a tab or an inline graphic before it, nor inside an inseparable pair that Bunri-Kinshi keeps
/// together. Zero-width format controls take no gap: the gap is the one between the visible
/// characters on either side, before `end`, as the layout justifies it.
fn closes(g: &[SGlyph], a: usize, end: usize) -> bool {
    let Some(p) = g.get(a).filter(|p| !is_format_control(p.ch)) else { return false };
    let Some(n) = g.get(a + 1..end).and_then(|rest| rest.iter().find(|n| !is_format_control(n.ch))) else { return false };
    p.len > 0
        && !p.keeps_next
        && p.byte != n.byte
        && p.inline.is_none()
        && !p.is_space()
        && !n.is_space()
        && p.ch != '\t'
        && !n.continues_tcy()
        && (is_cjk(p.ch) || is_cjk(n.ch))
}

/// The em a push-in measures in, along the line: `g`'s em at its Horizontal Scale, as Mojikumi's
/// spacing is, or at its Vertical Scale when it stands upright in vertical type and the font's
/// vertical metrics set its length down the column ([`super::vertical::upright_cell`]).
pub(super) fn squeeze_em(g: &SGlyph, vertical: bool) -> f64 {
    let down_the_column = vertical && stands_upright(g) && g.face.vertical_glyph(g.gid).is_some();
    g.face.units_per_em() * if down_the_column { g.sy } else { g.sx }
}

#[cfg(test)]
#[test]
fn kinsoku_keeps_closing_marks_off_line_starts_and_opening_ones_off_line_ends() {
    for (a, b) in [('字', '。'), ('弧', '」'), ('」', '、'), ('ャ', 'ー'), ('カ', 'ッ'), ('「', 'か'), ('（', '雅')] {
        assert!(!kinsoku_between(a, Some(b), Kinsoku::Hard), "{a}{b}");
    }
    for (a, b) in [('。', '雅'), ('」', 'は'), ('字', '「'), ('の', '演')] {
        assert!(kinsoku_between(a, Some(b), Kinsoku::Hard), "{a}{b}");
    }
    assert!(kinsoku_between('。', None, Kinsoku::Hard));
}

/// Soft kinsoku lets 々, ー and small kana (JLREQ cl-09's 々, cl-10, cl-11) start a line and keeps
/// the rest of the set (half-width forms aren't in those classes); None allows any break.
#[cfg(test)]
#[test]
fn soft_kinsoku_lets_small_kana_and_the_prolonged_sound_mark_start_a_line() {
    for (a, b) in [('ャ', 'ー'), ('カ', 'ッ'), ('時', '々'), ('ト', 'ㇰ'), ('か', 'ゃ')] {
        assert!(!kinsoku_between(a, Some(b), Kinsoku::Hard), "{a}{b}");
        assert!(kinsoku_between(a, Some(b), Kinsoku::Soft), "{a}{b}");
    }
    for (a, b) in [('字', '。'), ('弧', '」'), ('「', 'か'), ('ｶ', 'ｯ'), ('ｶ', 'ｰ'), ('字', 'ゝ')] {
        assert!(!kinsoku_between(a, Some(b), Kinsoku::Soft), "{a}{b}");
        assert!(kinsoku_between(a, Some(b), Kinsoku::None), "{a}{b}");
    }
}

/// Glyph indices inside `g[ws..we]` (a word) where a hyphenated break may go under `opts`, in the
/// language of the word's first letter; never next to a Hangul letter, which takes no hyphen, and
/// nowhere in a Korean word that Korean Line Break Anywhere off keeps whole.
fn hyphen_breaks(text: &str, g: &[SGlyph], ws: usize, we: usize, opts: &HyphenationOptions) -> Vec<usize> {
    if g.get(ws..we).is_some_and(|word| word.iter().any(|h| h.keeps_word)) {
        return Vec::new();
    }
    let mut points = word_hyphen_breaks(text, g, ws, we, opts);
    let hangul = |i: usize| g.get(i).is_some_and(|h| h.inline.is_none() && crate::shape::is_hangul(h.ch));
    points.retain(|&k| !hangul(k.wrapping_sub(1)) && !hangul(k));
    points
}

/// [`hyphen_breaks`] before the points next to Hangul are left out.
fn word_hyphen_breaks(text: &str, g: &[SGlyph], ws: usize, we: usize, opts: &HyphenationOptions) -> Vec<usize> {
    // Strip leading/trailing punctuation (quotes, commas).
    let (mut a, mut b) = (ws, we);
    while a < b && !g[a].is_letter() {
        a += 1;
    }
    while b > a && !g[b - 1].is_letter() {
        b -= 1;
    }
    if b <= a || g[a..b].iter().any(|g| !g.is_letter()) {
        return vec![];
    }
    let (s, e) = (g[a].byte, g[b - 1].byte + g[b - 1].len);
    let Some(word) = text.get(s..e) else { return vec![] };
    let offs: Vec<usize> = word.char_indices().map(|(o, _)| s + o).collect();
    // The first glyph of each cluster start (not inside a ligature), by its byte: one pass, not a
    // search for each point.
    let mut starts = std::collections::HashMap::new();
    for k in a + 1..b {
        if g[k].byte != g[k - 1].byte {
            starts.entry(g[k].byte).or_insert(k);
        }
    }
    points_for(word, opts, g[a].hyphen_language).into_iter().filter_map(|ci| starts.get(offs.get(ci)?).copied()).collect()
}

/// Break candidates for the every-line composer: hyphenation points under `hyphenate` (the
/// paragraph's Hyphenation options) when it is given. No break comes before a space: a line that
/// may end after a dash, a Thai word or a space ends after the spaces that follow it, as in
/// [`break_line`].
pub(super) fn candidates(text: &str, g: &[SGlyph], hyphenate: Option<&HyphenationOptions>, kinsoku: Kinsoku) -> Vec<Breakpoint> {
    let mut v = vec![];
    let mut ws = 0;
    for (j, gl) in g.iter().enumerate() {
        // A list marker (the glyphs of length 0 here) ends before the first word.
        let marker_end = gl.len == 0 && g.get(j + 1).is_some_and(|n| n.len > 0);
        let end_of_word = gl.is_space() || gl.break_after() || marker_end;
        if end_of_word {
            if let Some(opts) = hyphenate
                && j > ws
            {
                for k in
                    hyphen_breaks(text, g, ws, j, opts).into_iter().filter(|&k| k > 0 && kinsoku_allows(g, k - 1, kinsoku) && !splits_no_break(g, k))
                {
                    v.push(Breakpoint { end: k, hyphen: hyphen_glyph(&g[k - 1]).adv });
                }
            }
            let hy = if gl.is_soft_hyphen() { hyphen_glyph(gl).adv } else { 0.0 };
            if j + 1 < g.len() && g[j + 1].byte != gl.byte && !g[j + 1].is_space() && kinsoku_allows(g, j, kinsoku) && !splits_no_break(g, j + 1) {
                v.push(Breakpoint { end: j + 1, hyphen: hy });
            }
            ws = j + 1;
        }
    }
    if let Some(opts) = hyphenate
        && g.len() > ws
    {
        for k in
            hyphen_breaks(text, g, ws, g.len(), opts).into_iter().filter(|&k| k > 0 && kinsoku_allows(g, k - 1, kinsoku) && !splits_no_break(g, k))
        {
            v.push(Breakpoint { end: k, hyphen: hyphen_glyph(&g[k - 1]).adv });
        }
    }
    v.sort_by_key(|b| b.end);
    v.dedup_by_key(|b| b.end);
    v
}

#[cfg(test)]
#[test]
fn a_pen_out_of_baseline_steps_finds_no_room() {
    let frame = kurbo::Shape::to_path(&kurbo::Rect::new(0.0, 0.0, 400.0, 400.0), 0.1);
    let regions = Region::cells(&frame, &super::LayoutOptions::default(), &[]);
    let est = Metrics { asc: 10.0, desc: 3.0, lead: 14.0, cap: 7.0, xh: 5.0, top: 10.0 };
    let pen = |steps| Pen {
        regions: Some(&regions),
        ri: 0,
        prev: None,
        pending: 0.0,
        fb: FirstBaseline::Ascent,
        fb_min: 0.0,
        queued: vec![],
        model: LeadingModel::default(),
        next_top: None,
        no_room_for: f64::INFINITY,
        steps_left: std::rc::Rc::new(std::cell::Cell::new(steps)),
        search: Default::default(),
    };
    assert!(pen(MAX_TOTAL_STEPS).place(est, 0.0, 0.0, 0.0).is_some());
    assert!(pen(0).place(est, 0.0, 0.0, 0.0).is_none());
}