import type { NoteInputEvent } from './webmidi.ts';

// Typing-keyboard piano: the a..' row plays white keys from C, the row
// above plays the black keys, z/x shift the octave. Active only when
// enabled and when focus is not in a text field.

const KEY_TO_SEMITONE: Record<string, number> = {
  a: 0, w: 1, s: 2, e: 3, d: 4, f: 5, t: 6, g: 7, y: 8, h: 9, u: 10, j: 11,
  k: 12, o: 13, l: 14, p: 15, ';': 16, "'": 17,
};

type Listener = (e: NoteInputEvent) => void;

class KeyboardPiano {
  enabled = false;
  octave = 4; // 'a' plays C4 by default (MIDI 60 at octave 4)
  private listeners = new Set<Listener>();
  private stateListeners = new Set<() => void>();
  private held = new Map<string, number>();
  private attached = false;

  subscribe(cb: Listener): () => void {
    this.listeners.add(cb);
    return () => this.listeners.delete(cb);
  }

  subscribeState(cb: () => void): () => void {
    this.stateListeners.add(cb);
    return () => this.stateListeners.delete(cb);
  }

  private emitState() { for (const cb of this.stateListeners) cb(); }

  setEnabled(v: boolean) {
    this.enabled = v;
    if (!v) this.releaseAll();
    this.attach();
    this.emitState();
  }

  private attach() {
    if (this.attached) return;
    this.attached = true;
    window.addEventListener('keydown', this.onKeyDown);
    window.addEventListener('keyup', this.onKeyUp);
    window.addEventListener('blur', () => this.releaseAll());
  }

  private inTextField(): boolean {
    const el = document.activeElement;
    return !!el && (el.tagName === 'INPUT' || el.tagName === 'TEXTAREA' || (el as HTMLElement).isContentEditable);
  }

  private onKeyDown = (ev: KeyboardEvent) => {
    if (!this.enabled || ev.repeat || ev.ctrlKey || ev.metaKey || ev.altKey || this.inTextField()) return;
    const key = ev.key.toLowerCase();
    if (key === 'z') { this.octave = Math.max(0, this.octave - 1); this.emitState(); return; }
    if (key === 'x') { this.octave = Math.min(8, this.octave + 1); this.emitState(); return; }
    const semi = KEY_TO_SEMITONE[key];
    if (semi === undefined || this.held.has(key)) return;
    const pitch = (this.octave + 1) * 12 + semi;
    if (pitch > 127) return;
    ev.preventDefault();
    this.held.set(key, pitch);
    this.emit({ on: true, pitch, velocity: 100, source: 'keyboard' });
  };

  private onKeyUp = (ev: KeyboardEvent) => {
    const key = ev.key.toLowerCase();
    const pitch = this.held.get(key);
    if (pitch === undefined) return;
    this.held.delete(key);
    this.emit({ on: false, pitch, velocity: 0, source: 'keyboard' });
  };

  private releaseAll() {
    for (const [key, pitch] of this.held) {
      void key;
      this.emit({ on: false, pitch, velocity: 0, source: 'keyboard' });
    }
    this.held.clear();
  }

  private emit(e: NoteInputEvent) {
    for (const cb of this.listeners) cb(e);
  }
}

export const keyboardPiano = new KeyboardPiano();