Recorder-Tabber/src/lib/line.ts

import { DURATION_PRESETS, type DurationPreset } from "@/lib/duration";
import { newId } from "@/lib/score";

export type LineKind = "note" | "rest" | "space";

export type LineNote = {
  id: string;
  kind: LineKind;
  pitch: string;
  quarters: number;
  label: string;
};

export const LINE_BOX = {
  minWidth: 280,
  minHeight: 200,
  maxHeight: 880,
};

const QUARTER = DURATION_PRESETS.find((preset) => preset.quarters === 1) ?? DURATION_PRESETS[3];

export function createNote(pitch: string, preset: DurationPreset = QUARTER, id = newId("n")): LineNote {
  return { id, kind: "note", pitch, quarters: preset.quarters, label: preset.label };
}

export function createRest(preset: DurationPreset = QUARTER, id = newId("r")): LineNote {
  return { id, kind: "rest", pitch: "", quarters: preset.quarters, label: preset.label };
}

export function createSpace(preset: DurationPreset = QUARTER, id = newId("s")): LineNote {
  return { id, kind: "space", pitch: "", quarters: preset.quarters, label: preset.label };
}

/** Keep a resized line box on the page. `maxWidth` is the room the page actually has. */
export function clampLineBox(
  width: number,
  height: number,
  maxWidth: number,
): { width: number; height: number } {
  const limit = Math.max(160, maxWidth);
  const minWidth = Math.min(LINE_BOX.minWidth, limit);
  return {
    width: Math.round(Math.min(limit, Math.max(minWidth, width))),
    height: Math.round(Math.min(LINE_BOX.maxHeight, Math.max(LINE_BOX.minHeight, height))),
  };
}

export function insertNote(notes: LineNote[], index: number, note: LineNote): LineNote[] {
  const next = notes.slice();
  const at = Math.max(0, Math.min(index, next.length));
  next.splice(at, 0, note);
  return next;
}

/** `toIndex` is the slot in the current list, counting the note that is moving. */
export function moveNote(notes: LineNote[], id: string, toIndex: number): LineNote[] {
  const from = notes.findIndex((note) => note.id === id);
  if (from < 0) return notes;
  const next = notes.filter((note) => note.id !== id);
  const adjusted = toIndex > from ? toIndex - 1 : toIndex;
  const at = Math.max(0, Math.min(adjusted, next.length));
  next.splice(at, 0, notes[from]);
  return next;
}

export function removeNote(notes: LineNote[], id: string): LineNote[] {
  return notes.filter((note) => note.id !== id);
}

const DURATION_ORDER = [...DURATION_PRESETS].sort((a, b) => a.quarters - b.quarters);

/** The next longer or shorter preset. Null at either end of the list. */
export function neighborDuration(quarters: number, direction: -1 | 1): DurationPreset | null {
  const index = DURATION_ORDER.findIndex((preset) => Math.abs(preset.quarters - quarters) < 0.001);
  if (index < 0) return null;
  return DURATION_ORDER[index + direction] ?? null;
}

export function setDuration(notes: LineNote[], id: string, preset: DurationPreset): LineNote[] {
  return notes.map((note) =>
    note.id === id ? { ...note, quarters: preset.quarters, label: preset.label } : note,
  );
}

export function cloneLine(notes: LineNote[]): LineNote[] {
  return notes.map((note) => ({ ...note, id: newId("n") }));
}

/** -1 when the pointer is outside the line. Otherwise the insertion slot from left to right. */
export function dropIndexFromPoint(
  pointerX: number,
  pointerY: number,
  line: { left: number; right: number; top: number; bottom: number },
  noteCenters: number[],
  slack = 36,
): number {
  const inside =
    pointerX >= line.left - slack &&
    pointerX <= line.right + slack &&
    pointerY >= line.top - slack &&
    pointerY <= line.bottom + slack;
  if (!inside) return -1;
  for (let index = 0; index < noteCenters.length; index += 1) {
    if (pointerX < noteCenters[index]) return index;
  }
  return noteCenters.length;
}

function preset(quarters: number, label: string): DurationPreset {
  return { quarters, label };
}

/** Two short lines to edit. They are not a full tune. */
export const LINE_EXAMPLES = [
  {
    id: "twinkle",
    title: "Twinkle, opening",
    blurb: "Seven notes. The last one is held.",
    notes: [
      createNote("C5", preset(1, "quarter"), "twinkle-1"),
      createNote("C5", preset(1, "quarter"), "twinkle-2"),
      createNote("G5", preset(1, "quarter"), "twinkle-3"),
      createNote("G5", preset(1, "quarter"), "twinkle-4"),
      createNote("A5", preset(1, "quarter"), "twinkle-5"),
      createNote("A5", preset(1, "quarter"), "twinkle-6"),
      createNote("G5", preset(2, "half"), "twinkle-7"),
    ],
  },
  {
    id: "ode",
    title: "Ode, held note",
    blurb: "A dotted quarter, an eighth, and a half note.",
    notes: [
      createNote("E5", preset(1.5, "dotted quarter"), "ode-1"),
      createNote("D5", preset(0.5, "eighth"), "ode-2"),
      createNote("D5", preset(2, "half"), "ode-3"),
    ],
  },
] as const;