// Counts the score denominator, not a playable-note timeline.
// SUS headers supply playable categories, including generated continuation ticks.
// Body family 3 kinds 4/5 supply non-playable bezier / inactive relay points.
const alphabet = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
const categories = ['NORMAL', 'FLICK', 'LONG_START', 'LONG_END', 'LONG_FLICK_END', 'LONG_RELAY', 'LONG_CONTINUE'];

export function susScoreWeight(text) {
  const headers = new Map();
  let invisibleRelayCount = 0;
  let bezierPointCount = 0;
  let starts = 0, ends = 0, relays = 0;
  for (const line of text.split(/\r?\n/)) {
    const header = line.match(/^#([A-Z_]+)\s+(\S+)\s*$/);
    if (header) {
      if (headers.has(header[1])) throw new Error(`Duplicate SUS header: ${header[1]}`);
      headers.set(header[1], header[2]);
    }
    const match = line.match(/^#\d{3}3[0-9a-zA-Z]{2}:(.*)$/);
    if (!match) continue;
    const body = match[1].trim();
    // Repeated channel lines are additive; do not overwrite them in a map.
    for (let index = 0; index < body.length;) {
      if (body.startsWith('0x', index)) {
        const run = body.slice(index + 2, index + 4);
        if (run.length !== 2 || [...run].some((char) => !alphabet.includes(char))) throw new Error('Malformed SUS empty run');
        index += 4; // Empty cells have no denominator contribution.
        continue;
      }
      const token = body.slice(index, index + 2);
      if (token.length !== 2 || [...token].some((char) => !alphabet.includes(char))) throw new Error('Malformed SUS note token');
      const kind = token[0];
      if (kind === '1') starts += 1;
      else if (kind === '2') ends += 1;
      else if (kind === '3') relays += 1;
      else if (kind === '4') bezierPointCount += 1;
      else if (kind === '5') invisibleRelayCount += 1;
      else if (kind !== '0') throw new Error(`Unsupported SUS hold kind: ${kind}`);
      index += 2;
    }
  }
  function integer(name) {
    const raw = headers.get(name);
    if (!raw || !/^\d+$/.test(raw) || !Number.isSafeInteger(Number(raw))) throw new Error(`Invalid SUS header: ${name}`);
    return Number(raw);
  }
  const counts = Object.fromEntries(categories.map((kind) => [kind, integer(`${kind}_NOTE_COUNT`)]));
  // Ghosts are visual guides, not invisible hold relays; they add no score weight.
  integer('GHOST_NOTE_COUNT');
  for (const unsupported of ['DAMAGE_NOTE_COUNT']) {
    if (integer(unsupported) !== 0) throw new Error(`Unsupported scoring category: ${unsupported}`);
  }
  const fullComboNoteCount = integer('FULL_COMBO_NOTE_COUNT');
  if (Object.values(counts).reduce((sum, count) => sum + count, 0) !== fullComboNoteCount ||
    integer('TOTAL_NOTE_COUNT') !== fullComboNoteCount + integer('GHOST_NOTE_COUNT') ||
    starts !== counts.LONG_START || ends !== counts.LONG_END + counts.LONG_FLICK_END || relays !== counts.LONG_RELAY) {
    throw new Error('SUS header/body category mismatch');
  }
  const songId = headers.get('MUSIC_ID');
  if (!songId || !/^m\d{4}$/.test(songId)) throw new Error('Invalid SUS music ID');
  const baseWeight = 1000 * (counts.NORMAL + counts.LONG_START + counts.LONG_END + counts.LONG_FLICK_END)
    + 1050 * counts.FLICK + 100 * (counts.LONG_RELAY + counts.LONG_CONTINUE);
  return {
    songId, fullComboNoteCount, counts, invisibleRelayCount, bezierPointCount, baseWeight,
    perfectNoteWeight: baseWeight + 100 * (invisibleRelayCount + bezierPointCount)
  };
}