Function computeReadingHabits

Source

export function computeReadingHabits(
  history: ReadingHistory,
  timeRange: TimeRange,
): {
  byDayOfWeek: Array<{ day: string; chapters: number }>;
  byTimeOfDay: Array<{ hour: string; chapters: number }>;
  peakDay: string | null;
  peakHour: string | null;
} {
  const filtered = filterHistoryByTimeRange(history, timeRange);
  if (!filtered.length) {
    return {
      byDayOfWeek: [],
      byTimeOfDay: [],
      peakDay: null,
      peakHour: null,
    };
  }

  // Establish baseline from pre-range history
  const now = Date.now();
  const ranges = {
    "7d": 7 * 24 * 60 * 60 * 1000,
    "30d": 30 * 24 * 60 * 60 * 1000,
    "90d": 90 * 24 * 60 * 60 * 1000,
  };
  const cutoff = timeRange === "all" ? 0 : now - ranges[timeRange];
  const preRangeBaseline =
    timeRange === "all" ? new Map() : getPreRangeBaseline(history, cutoff);

  const dayNames = [
    "Sunday",
    "Monday",
    "Tuesday",
    "Wednesday",
    "Thursday",
    "Friday",
    "Saturday",
  ];
  const dayMap = new Map<number, number>();
  const hourMap = new Map<number, number>();

  // Calculate deltas and group by day/hour
  const sorted = [...filtered].sort((a, b) => a.timestamp - b.timestamp);
  const previousChapters = new Map<string | number, number>(preRangeBaseline);

  for (const entry of sorted) {
    const prev = previousChapters.get(entry.mangaId) ?? 0;
    const delta = Math.max(0, entry.chaptersRead - prev);

    if (delta > 0) {
      const date = new Date(entry.timestamp);
      const dayOfWeek = date.getDay();
      const hour = date.getHours();

      dayMap.set(dayOfWeek, (dayMap.get(dayOfWeek) ?? 0) + delta);
      hourMap.set(hour, (hourMap.get(hour) ?? 0) + delta);
    }

    previousChapters.set(entry.mangaId, entry.chaptersRead);
  }

  // Convert to arrays
  const byDayOfWeek = Array.from({ length: 7 }, (_, i) => ({
    day: dayNames[i],
    chapters: dayMap.get(i) ?? 0,
  }));

  const byTimeOfDay = Array.from({ length: 24 }, (_, i) => ({
    hour: `${i.toString().padStart(2, "0")}:00`,
    chapters: hourMap.get(i) ?? 0,
  }));

  // Find peaks
  const maxDay = Math.max(...byDayOfWeek.map((d) => d.chapters));
  const maxHour = Math.max(...byTimeOfDay.map((h) => h.chapters));

  const peakDay = byDayOfWeek.find((d) => d.chapters === maxDay)?.day ?? null;
  const peakHour =
    byTimeOfDay.find((h) => h.chapters === maxHour)?.hour ?? null;

  return {
    byDayOfWeek,
    byTimeOfDay,
    peakDay,
    peakHour,
  };
}
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