import { Signal } from "@char/aftercare";
import { canonBeat, type Track } from "../project/model.ts";
import { project } from "../project/store.ts";

export const ROW_H = 10;
export const STRIP_H = 48;
export const HEADER_W = 190;

/** where typed chords go and playback starts, in beats. on chord tracks, the chord starting
 * here is the one that keyboard edits apply to */
export const cursor = new (class extends Signal<number> {
  // it's compared against chord boundaries, so it lives on the same grid as they do
  override set(beats: number) {
    super.set(canonBeat(beats));
  }
})(0);
// "none" is null rather than undefined in signals: aftercare doesn't notify changes away from undefined
export const activeTrackId = new Signal<string | null>(project.get().tracks[0]?.id ?? null);
/** selected notes, on note tracks */
export const selection = new Signal<{ trackId: string; ids: readonly string[] } | null>(null);
export type ChordEdit = { trackId: string; initial: string; selectAll: boolean };
export const chordEdit = new Signal<ChordEdit | null>(null);
export const pxPerBeat = new Signal(64);
/** a signal kept in localStorage: for preferences about the app rather than a project */
function remembered<T>(name: string, initial: T): Signal<T> {
  const key = `chord-pad/ui/${name}`;
  let value = initial;
  try {
    value = JSON.parse(localStorage.getItem(key) ?? "null") ?? initial;
  } catch {
    // unreadable: start over
  }
  const signal = new Signal(value);
  signal.subscribe(v => localStorage.setItem(key, JSON.stringify(v)));
  return signal;
}

export const paletteSevenths = remembered("palette-sevenths", false);
export const chordPanelOpen = remembered("chord-panel-open", true);
export const mixtureOpen = remembered("mixture-open", false);

export const rollHeight = (t: Track): number => (t.view.high - t.view.low + 1) * ROW_H;
export const laneHeight = (t: Track): number =>
  (t.kind === "chords" ? STRIP_H : 0) + rollHeight(t);

export const selectedIds = (trackId: string): readonly string[] => {
  const sel = selection.get();
  return sel?.trackId === trackId ? sel.ids : [];
};

project.subscribe((p, old) => {
  if (p.id === old.id) return;
  cursor.set(0);
  selection.set(null);
  chordEdit.set(null);
  activeTrackId.set(p.tracks[0]?.id ?? null);
});