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♻️ refactor(accidental): extract parsable symbols from parse #216

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merged 2 commits into from
Jul 16, 2023
Merged

♻️ refactor(accidental): extract parsable symbols from parse #216

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70aace6
:recycle: refactor(accidental): rewrite parsable symbols declaratively
albertms10 Jul 16, 2023
e07896a
:zap: perf(accidental): use more performant `switch` expression
albertms10 Jul 16, 2023
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30 changes: 17 additions & 13 deletions lib/src/note/accidental.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,15 @@ final class Accidental implements Comparable<Accidental> {
static const String _flatSymbol = '♭';
static const String _doubleFlatSymbol = '𝄫';

static int? _semitonesFromSymbol(String symbol) => switch (symbol) {
_doubleSharpSymbol || 'x' => 2,
_sharpSymbol || '#' => 1,
_naturalSymbol || '' => 0,
_flatSymbol || 'b' => -1,
_doubleFlatSymbol => -2,
_ => null,
};

/// Parse [source] as an [Accidental] and return its value.
///
/// If the [source] string does not contain a valid [Accidental], a
Expand All @@ -40,19 +49,14 @@ final class Accidental implements Comparable<Accidental> {
/// ```
factory Accidental.parse(String source) {
// Safely split UTF-16 code units using `runes`.
final semitones = source.runes.fold(
0,
(acc, rune) =>
acc +
switch (String.fromCharCode(rune)) {
_doubleSharpSymbol || 'x' => 2,
_sharpSymbol || '#' => 1,
_naturalSymbol || '' => 0,
_flatSymbol || 'b' => -1,
_doubleFlatSymbol => -2,
_ => throw FormatException('Invalid Accidental', source),
},
);
final semitones = source.runes.fold(0, (acc, rune) {
final symbolSemitones = _semitonesFromSymbol(String.fromCharCode(rune));
if (symbolSemitones == null) {
throw FormatException('Invalid Accidental', source);
}

return acc + symbolSemitones;
});

return Accidental(semitones);
}
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