initial scaffold

src/stores/eqStore.ts

@@ -0,0 +1,44 @@
+import { create } from 'zustand';
+import type { EQBand } from '@/types/audio';
+
+/**
+ * EQ state — M0 stub. The biquad chain is implemented as a Media3 AudioProcessor
+ * at M4; for now this just holds the band model (ported `EQBand`) so the EQ
+ * screen and later DSP wiring share one shape.
+ */
+const DEFAULT_FREQUENCIES = [32, 64, 125, 250, 500, 1000, 2000, 4000, 8000, 16000];
+
+function makeDefaultBands(): EQBand[] {
+  return DEFAULT_FREQUENCIES.map((frequency) => ({
+    id: `band-${frequency}`,
+    type: 'peaking',
+    frequency,
+    gain: 0,
+    Q: 1.0,
+  }));
+}
+
+interface EQStore {
+  enabled: boolean;
+  preamp: number; // dB
+  bands: EQBand[];
+
+  setEnabled: (enabled: boolean) => void;
+  setPreamp: (preamp: number) => void;
+  setBandGain: (id: string, gain: number) => void;
+  reset: () => void;
+}
+
+export const useEQStore = create<EQStore>((set) => ({
+  enabled: false,
+  preamp: 0,
+  bands: makeDefaultBands(),
+
+  setEnabled: (enabled) => set({ enabled }),
+  setPreamp: (preamp) => set({ preamp }),
+  setBandGain: (id, gain) =>
+    set((state) => ({
+      bands: state.bands.map((b) => (b.id === id ? { ...b, gain } : b)),
+    })),
+  reset: () => set({ enabled: false, preamp: 0, bands: makeDefaultBands() }),
+}));