import type { ConsumptionChunk, DailyConsumption, Totals } from "./types.ts";

/**
 * Folds chunks into days, newest day first, each with its running lifetime total.
 * Pure, so the arithmetic is tested without a database.
 */
export function aggregateDays(chunks: ConsumptionChunk[]): DailyConsumption[] {
  const byDate = new Map<string, DailyConsumption & { sohAt: number }>();
  for (const chunk of chunks) {
    let day = byDate.get(chunk.date);
    if (!day) {
      day = {
        installationId: chunk.installationId,
        date: chunk.date,
        recordedAt: chunk.recordedAt,
        day: { km: 0, kwh: 0, hours: 0, socDrop: 0 },
        sohAt: -Infinity,
      };
      byDate.set(chunk.date, day);
    }
    day.day.km += chunk.day.km;
    day.day.kwh += chunk.day.kwh;
    day.day.hours += chunk.day.hours;
    day.day.socDrop += chunk.day.socDrop;
    const at = chunk.recordedAt.getTime();
    if (at > day.recordedAt.getTime()) day.recordedAt = chunk.recordedAt;
    // The newest manual SoH of the day wins.
    if (chunk.sohPercent !== undefined && at > day.sohAt) {
      day.sohPercent = chunk.sohPercent;
      day.sohAt = at;
    }
  }
  const ascending = [...byDate.values()].sort((a, b) => a.date.localeCompare(b.date));
  const running: Totals = { km: 0, kwh: 0, hours: 0, socDrop: 0 };
  const days = ascending.map(({ sohAt: _sohAt, ...day }) => {
    running.km += day.day.km;
    running.kwh += day.day.kwh;
    running.hours += day.day.hours;
    running.socDrop += day.day.socDrop;
    return { ...day, lifetime: { ...running } };
  });
  return days.reverse();
}