# EQ Custom Presets Specification

## Purpose

User-defined preset save/name/list on top of the existing 6 fixed presets,
a per-station EQ entry point from the player's tool tray, and a
"stations with their own EQ" drill-down. **Band count stays 5** — resolved
by spike (Engram id 2498), not a pending decision. Traceable to WU13
(Settings screen) and WU14 (player tool tray, shares WU13's editor
component).

## Requirements

### Requirement: Five-Band Equalizer (Regression Guard, First-Class)

The equalizer screen MUST render exactly **5** vertical sliders.
`assert(bandas.length == 5)` in `preset_ecualizador.dart` MUST remain
unchanged. Band count is device-reported via `just_audio`'s
`AndroidEqualizer` (`params.bands`), not app-chosen; any requirement or
implementation asserting 7 bands is rejected on sight.

#### Scenario: Ecualizador screen renders 5 sliders

- GIVEN the user opens the Ecualizador settings screen
- WHEN it renders
- THEN exactly 5 vertical sliders are shown, one per band

#### Scenario: Band-count regression is rejected (edge case)

- GIVEN a future change proposes 7 sliders or a modified `bandas.length` assert
- WHEN that change is reviewed against this requirement
- THEN it fails: 5 is the resolved, binding band count for this change

### Requirement: Custom Preset Save

The user MUST be able to save the current 5-band configuration as a new,
named custom preset, which then appears alongside the 6 fixed presets in
the preset chip row.

#### Scenario: Saving a custom preset

- GIVEN the user has adjusted the 5 sliders from a fixed preset
- WHEN they choose "Guardar como preset" and enter the name "Mi preset"
- THEN a new preset named "Mi preset" is persisted
- AND it appears in the preset chip row on next render

### Requirement: Custom Preset Naming Validates Non-Empty Input

The system MUST reject an empty or whitespace-only preset name without
crashing, and MUST NOT persist a preset in that case.

#### Scenario: Empty name is rejected

- GIVEN the "Guardar como preset" flow is open
- WHEN the user submits an empty name
- THEN a validation message is shown and no preset is saved

### Requirement: Per-Station EQ Entry Point From the Player

The player's tool tray MUST expose an "EQ propio" tile that opens a
per-station EQ bottom sheet. That sheet MUST reuse the same 5-band editor
component used by the Settings Ecualizador screen (not a separate
implementation).

#### Scenario: Opening per-station EQ from the player

- GIVEN a station is currently playing
- WHEN the user taps "EQ propio" in the tool tray
- THEN a bottom sheet opens with 5 sliders bound to that station's resolved preset
- AND changes made there apply through the existing per-station EQ persistence path

### Requirement: Stations-With-Own-EQ Drill-Down

The Settings Ecualizador screen MUST expose a row that navigates to a list
of stations that currently have a station-specific preset override,
sourced from the existing `presetsPorEmisora` map.

#### Scenario: Drill-down lists exactly the overridden stations

- GIVEN 2 stations have entries in `presetsPorEmisora` and N others do not
- WHEN the user opens the drill-down
- THEN exactly those 2 stations are listed

### Requirement: Base-vs-Per-Station Explainer Preserved

An info banner distinguishing the base (global/device) EQ from per-station
overrides MUST remain visible on the Ecualizador screen.

#### Scenario: Banner is visible on screen open

- GIVEN the user opens the Ecualizador screen
- WHEN it renders
- THEN the base-vs-per-station explainer banner is visible

### Requirement: Active Output Surfaced on the Main Screen

The "Salida activa" (active output device) row MUST be visible on the main
Ecualizador screen, not only in the Advanced sub-section.

#### Scenario: Output row updates on device change

- GIVEN the Ecualizador screen is open
- WHEN the active audio output device changes (e.g. Bluetooth connects)
- THEN the "Salida activa" row updates to reflect the new device