import type { UploadFile } from './common';
import { audioExt } from './files';

type SummaryFile = Pick<UploadFile, 'format' | 'original_name' | 'bitrate' | 'sample_rate' | 'bit_depth'>;

function range(values: (number | null)[], divisor: number, decimals: number, unit: string): string | null {
  const known = values.filter((value): value is number => value !== null && Number.isFinite(value) && value > 0);
  if (!known.length) return null;
  const format = (value: number) => String(Number((value / divisor).toFixed(decimals)));
  const min = format(Math.min(...known));
  const max = format(Math.max(...known));
  return `${min === max ? min : `${min}–${max}`} ${unit}`;
}

/** Only measured positive values contribute to quality ranges; absent metadata is not zero. */
export function batchSummary(files: SummaryFile[]) {
  const counts = new Map<string, number>();
  for (const file of files) {
    const format = (file.format?.trim() || audioExt(file.original_name)).toUpperCase();
    counts.set(format, (counts.get(format) ?? 0) + 1);
  }
  return {
    formats: [...counts].sort(([a, ac], [b, bc]) => bc - ac || a.localeCompare(b)),
    quality: [
      range(files.map((file) => file.bitrate), 1000, 0, 'kbps'),
      range(files.map((file) => file.sample_rate), 1000, 3, 'kHz'),
      range(files.map((file) => file.bit_depth), 1, 0, 'bit'),
    ].filter(Boolean).join(' · '),
  };
}