pluriwave/test/servicios/servicio_audio_eq_ganancia_test.dart

import 'package:flutter_test/flutter_test.dart';
import 'package:pluriwave/servicios/servicio_audio.dart';

/// eq-estado-unico item E — `mapearGananciaNativa`, the translation from the
/// app's fixed ±12 dB slider scale to whatever range the device's native
/// `Equalizer.getBandLevelRange()` reports.
///
/// This is the only source-plausible explanation for the reported «suena muy
/// alto» half of the bug. The original implementation normalised the input
/// across the WHOLE range and mapped it linearly:
///
///     normalizado = (db.clamp(-12, 12) + 12) / 24
///     return minDecibels + normalizado * (maxDecibels - minDecibels)
///
/// which sends 0 dB to the MIDPOINT of the native range. That is only 0 when
/// the range happens to be symmetric. Android does not guarantee that: the
/// AudioEffect Equalizer contract only requires a min/max pair, and real
/// devices ship asymmetric ranges. On such a device a FLAT preset — every
/// band 0 dB — was silently pushing a positive boost into every band, which
/// is audibly louder while the on/off button still reads "off".
///
/// The contract asserted here: 0 dB always maps to exactly 0, and the two
/// sides of the scale are stretched INDEPENDENTLY against their own end of
/// the native range, so the sign of the user's intent is never inverted and
/// the extremes still reach the device's real limits.
void main() {
  group('mapearGananciaNativa — 0 dB is always exactly 0', () {
    test('symmetric range (the common case) is unchanged', () {
      expect(
        mapearGananciaNativa(0, minDecibels: -15, maxDecibels: 15),
        0,
      );
    });

    test('asymmetric range no longer boosts a FLAT preset', () {
      // The reported symptom: on a device reporting [-12, +19] the old
      // midpoint mapping turned every 0 dB band into +3.5 dB of real boost.
      expect(
        mapearGananciaNativa(0, minDecibels: -12, maxDecibels: 19),
        0,
        reason: 'a FLAT preset must be inaudible, on every device',
      );
    });

    test('a wholly positive range still cannot boost a FLAT preset', () {
      expect(mapearGananciaNativa(0, minDecibels: 3, maxDecibels: 19), 0);
    });

    test('a wholly negative range still cannot cut a FLAT preset', () {
      expect(mapearGananciaNativa(0, minDecibels: -19, maxDecibels: -3), 0);
    });
  });

  group('mapearGananciaNativa — the extremes reach the native limits', () {
    test('+12 dB maps to the native maximum', () {
      expect(mapearGananciaNativa(12, minDecibels: -12, maxDecibels: 19), 19);
    });

    test('-12 dB maps to the native minimum', () {
      expect(mapearGananciaNativa(-12, minDecibels: -12, maxDecibels: 19), -12);
    });

    test('values beyond the slider scale are clamped, not extrapolated', () {
      expect(mapearGananciaNativa(40, minDecibels: -15, maxDecibels: 15), 15);
      expect(mapearGananciaNativa(-40, minDecibels: -15, maxDecibels: 15), -15);
    });
  });

  group('mapearGananciaNativa — each side scales against its own end', () {
    test('half boost is half of the positive headroom', () {
      expect(
        mapearGananciaNativa(6, minDecibels: -12, maxDecibels: 20),
        closeTo(10, 1e-9),
      );
    });

    test('half cut is half of the negative headroom', () {
      expect(
        mapearGananciaNativa(-6, minDecibels: -12, maxDecibels: 20),
        closeTo(-6, 1e-9),
      );
    });

    test('the sign of the user intent is never inverted', () {
      for (final db in [-12.0, -6.0, -1.0, 1.0, 6.0, 12.0]) {
        final nativo = mapearGananciaNativa(
          db,
          minDecibels: -12,
          maxDecibels: 19,
        );
        expect(
          nativo.sign,
          db.sign,
          reason: 'a cut must never become a boost ($db dB -> $nativo)',
        );
      }
    });
  });

  group('mapearGananciaNativa — degenerate ranges reported by the device', () {
    test('a range with no headroom on one side clamps that side to 0', () {
      // A device that reports max == 0 can only cut. Asking for a boost must
      // resolve to "no change", never to a negative value.
      expect(mapearGananciaNativa(12, minDecibels: -15, maxDecibels: 0), 0);
      expect(mapearGananciaNativa(-12, minDecibels: -15, maxDecibels: 0), -15);
    });

    test('a zero-width range collapses everything to 0', () {
      expect(mapearGananciaNativa(12, minDecibels: 0, maxDecibels: 0), 0);
      expect(mapearGananciaNativa(-12, minDecibels: 0, maxDecibels: 0), 0);
    });

    test('the result never escapes the native range', () {
      for (final db in [-12.0, -3.0, 0.0, 3.0, 12.0]) {
        final nativo = mapearGananciaNativa(
          db,
          minDecibels: -3,
          maxDecibels: 19,
        );
        expect(nativo, greaterThanOrEqualTo(-3));
        expect(nativo, lessThanOrEqualTo(19));
      }
    });
  });
}