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use crate::diagnostic::Span;
use crate::lower::{LoweringState, key_fifths, lowered_timed_note};
use crate::model::{Accidental, LoweredEventAtomKind};
use crate::parse::field::{AccidentalSign, KeySignature};
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) struct KeyAccidentalPolicy {
pub(crate) step: char,
pub(crate) accidental: Accidental,
pub(crate) span: Span,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) struct MeasureAccidental {
pub(crate) step: char,
pub(crate) octave: i8,
pub(crate) accidental: Accidental,
pub(crate) span: Span,
/// `true` when this entry was re-inserted by
/// `reset_measure_accidentals_at_barline` solely on behalf of a pending
/// tie. If that tie is later dropped without finding a stop note, the
/// entry is removed again (see `drop_pending_tie_carry`); a matched tie
/// consumes the entry after the stop note has resolved.
pub(crate) from_pending_tie: bool,
}
pub(crate) fn key_accidental_policy(key: Option<&KeySignature>) -> Vec<KeyAccidentalPolicy> {
let Some(key) = key else {
return Vec::new();
};
let mut accidentals = key_signature_accidentals(key);
for explicit in &key.accidentals {
let step = explicit.note.value.to_ascii_uppercase();
let accidental = accidental_from_field_sign(explicit.sign);
if let Some(existing) = accidentals.iter_mut().find(|entry| entry.step == step) {
existing.accidental = accidental;
existing.span = explicit.span;
} else {
accidentals.push(KeyAccidentalPolicy {
step,
accidental,
span: explicit.span,
});
}
}
accidentals
}
fn key_signature_accidentals(key: &KeySignature) -> Vec<KeyAccidentalPolicy> {
let fifths = key_fifths(key);
let key_span = Span::new(0, 0);
if fifths > 0 {
['F', 'C', 'G', 'D', 'A', 'E', 'B']
.into_iter()
.take(fifths as usize)
.map(|step| KeyAccidentalPolicy {
step,
accidental: Accidental::Sharp,
span: key_span,
})
.collect()
} else if fifths < 0 {
['B', 'E', 'A', 'D', 'G', 'C', 'F']
.into_iter()
.take(fifths.unsigned_abs() as usize)
.map(|step| KeyAccidentalPolicy {
step,
accidental: Accidental::Flat,
span: key_span,
})
.collect()
} else {
Vec::new()
}
}
pub(crate) fn accidental_from_field_sign(sign: AccidentalSign) -> Accidental {
match sign {
AccidentalSign::DoubleFlat => Accidental::DoubleFlat,
AccidentalSign::Flat => Accidental::Flat,
AccidentalSign::Natural => Accidental::Natural,
AccidentalSign::Sharp => Accidental::Sharp,
AccidentalSign::DoubleSharp => Accidental::DoubleSharp,
}
}
impl LoweringState {
pub(crate) fn effective_accidental(
&mut self,
step: char,
octave: i8,
written: Option<Accidental>,
written_span: Option<Span>,
) -> (Option<Accidental>, Option<Span>) {
let step = step.to_ascii_uppercase();
if let Some(accidental) = written {
let span = written_span
.unwrap_or_else(|| Span::new(self.source_span.end, self.source_span.end));
self.set_measure_accidental(step, octave, accidental, span);
return (Some(accidental), Some(span));
}
if let Some(accidental) = self
.accidental_state
.iter()
.rev()
.find(|entry| entry.step == step && entry.octave == octave)
{
return (Some(accidental.accidental), Some(accidental.span));
}
self.key_accidentals
.iter()
.find(|entry| entry.step == step)
.map(|entry| (Some(entry.accidental), Some(entry.span)))
.unwrap_or((None, None))
}
fn set_measure_accidental(
&mut self,
step: char,
octave: i8,
accidental: Accidental,
span: Span,
) {
if let Some(entry) = self
.accidental_state
.iter_mut()
.find(|entry| entry.step == step && entry.octave == octave)
{
entry.accidental = accidental;
entry.span = span;
// A fresh written accidental re-legitimizes the entry: it must
// survive even if a pending tie on the same pitch is later dropped.
entry.from_pending_tie = false;
} else {
self.accidental_state.push(MeasureAccidental {
step,
octave,
accidental,
span,
from_pending_tie: false,
});
}
}
/// Reset measure accidentals at a bar line, but preserve the accidental of a
/// note whose tie is still open.
///
/// Per ABC 2.1 §4.20 a tie continues the same sounding pitch across the bar
/// line; the bar must not cancel it. Without this, the stop note would be
/// re-resolved against the key signature, changing the tied pitch. Normal
/// (non-tied) accidentals are still cleared as usual.
///
/// The carry must be preserved eagerly here and undone later if the tie is
/// dropped (rather than added only once a tie matches) because the stop
/// note's accidental is resolved via `effective_accidental` when the note
/// is lowered, BEFORE `finish_pending_tie_if_possible` runs — so the carry
/// must already exist at the barline and a drop can only be retroactive.
pub(crate) fn reset_measure_accidentals_at_barline(&mut self) {
let preserved: Vec<MeasureAccidental> = self
.pending_ties
.iter()
.filter_map(|tie| {
lowered_timed_note(self.lowered.get(tie.event_index)).and_then(|timed| {
if let LoweredEventAtomKind::Note {
step,
octave,
effective_accidental,
accidental_source,
..
} = timed.event.kind
{
effective_accidental.map(|accidental| MeasureAccidental {
step: step.to_ascii_uppercase(),
octave,
accidental,
span: accidental_source.unwrap_or_else(|| {
Span::new(self.source_span.end, self.source_span.end)
}),
from_pending_tie: true,
})
} else {
None
}
})
})
.collect();
self.accidental_state.clear();
self.accidental_state.extend(preserved);
}
/// Preserve the effective pitch of a note that is about to start a pending
/// tie. This matters for chains such as `^G-|G-G`: the first stop note gets
/// its sharp from a synthetic cross-bar carry, then immediately starts a new
/// tie before any later same-pitch note can re-resolve naturally.
pub(crate) fn preserve_pending_tie_carry_from_event(&mut self, event_index: usize) {
let Some((step, octave, accidental, span)) =
lowered_timed_note(self.lowered.get(event_index)).and_then(|timed| {
if let LoweredEventAtomKind::Note {
step,
octave,
effective_accidental,
accidental_source,
..
} = timed.event.kind
{
effective_accidental.map(|accidental| {
(
step.to_ascii_uppercase(),
octave,
accidental,
accidental_source.unwrap_or_else(|| {
Span::new(self.source_span.end, self.source_span.end)
}),
)
})
} else {
None
}
})
else {
return;
};
if let Some(entry) = self
.accidental_state
.iter_mut()
.find(|entry| entry.step == step && entry.octave == octave)
{
if entry.from_pending_tie {
entry.accidental = accidental;
entry.span = span;
}
return;
}
self.accidental_state.push(MeasureAccidental {
step,
octave,
accidental,
span,
from_pending_tie: true,
});
}
/// Preserve open-tie pitches across a mid-measure key change: per ABC 2.1
/// §4.20 a tie continues the same sounding pitch, so the stop note must
/// not re-resolve under the NEW key. Unlike the barline rule above (which
/// carries only explicit/ledger accidentals — key-derived pitches
/// re-resolve identically across a barline), a key change also re-pitches
/// key-derived notes, so the resolved alter under the OLD key — effective
/// accidental, else the old key policy's accidental, else an explicit
/// natural — is materialized into the measure ledger before the swap.
pub(crate) fn preserve_tie_pitches_for_key_change(&mut self) {
let preserved: Vec<MeasureAccidental> = self
.pending_ties
.iter()
.filter_map(|tie| {
lowered_timed_note(self.lowered.get(tie.event_index)).and_then(|timed| {
if let LoweredEventAtomKind::Note {
step,
octave,
effective_accidental,
accidental_source,
..
} = timed.event.kind
{
let step = step.to_ascii_uppercase();
let resolved = effective_accidental.unwrap_or_else(|| {
self.key_accidentals
.iter()
.find(|entry| entry.step == step)
.map(|entry| entry.accidental)
.unwrap_or(Accidental::Natural)
});
Some(MeasureAccidental {
step,
octave,
accidental: resolved,
span: accidental_source.unwrap_or_else(|| {
Span::new(self.source_span.end, self.source_span.end)
}),
from_pending_tie: true,
})
} else {
None
}
})
})
.collect();
self.accidental_state.extend(preserved);
}
/// Undo the accidental carry that `reset_measure_accidentals_at_barline`
/// preserved on behalf of a pending tie that was dropped without finding a
/// stop note. Entries that come from a written accidental in the current
/// measure (`from_pending_tie == false`) are left untouched.
pub(crate) fn drop_pending_tie_carry(&mut self, signature: (char, i8)) {
// Comparing `entry.step == signature.0` raw is sound: note signatures
// are always uppercase (`LoweredEventAtomKind::Note` constructors
// uppercase the step), as are `MeasureAccidental` entries.
self.accidental_state.retain(|entry| {
!(entry.from_pending_tie && entry.step == signature.0 && entry.octave == signature.1)
});
}
/// Consume the synthetic carry for a matched cross-bar tie. The carry is
/// needed before matching so the stop note resolves to the tied pitch, but
/// it must not become an ordinary measure accidental for later same-pitch
/// notes in the stop note's bar. A freshly written accidental on the stop
/// note has already re-legitimized the entry (`from_pending_tie == false`)
/// and is intentionally preserved.
pub(crate) fn consume_pending_tie_carry(&mut self, signature: (char, i8)) {
self.accidental_state.retain(|entry| {
!(entry.from_pending_tie && entry.step == signature.0 && entry.octave == signature.1)
});
}
}