import { averageMoodScore, getMoodById, MOOD_CATALOG } from "../mood-catalog";
import { toDayKey } from "../day-key";

export type JournalEntryPoint = {
  id: string;
  recordedAt: string;
  moods: string[];
  stress: number | null;
  pillsTaken: boolean | null;
};

export function entryMoodScore(entry: Pick<JournalEntryPoint, "moods">): number | null {
  return averageMoodScore(entry.moods);
}

export function computeDayStreak(entryDays: string[]): number {
  if (entryDays.length === 0) return 0;

  const days = new Set(entryDays);
  const todayKey = toDayKey(new Date());
  let cursor = days.has(todayKey) ? new Date() : addDays(new Date(), -1);
  let streak = 0;

  while (days.has(toDayKey(cursor))) {
    streak += 1;
    cursor = addDays(cursor, -1);
  }

  return streak;
}

export function topMoodId(entries: Pick<JournalEntryPoint, "moods">[]): string | null {
  const counts = new Map<string, number>();
  for (const entry of entries) {
    for (const moodId of entry.moods) {
      counts.set(moodId, (counts.get(moodId) ?? 0) + 1);
    }
  }

  let best: string | null = null;
  let bestCount = 0;
  for (const [id, count] of counts) {
    if (count > bestCount) {
      best = id;
      bestCount = count;
    }
  }
  return best;
}

export function averageStress(entries: Pick<JournalEntryPoint, "stress">[]): number | null {
  const values = entries.map((e) => e.stress).filter((v): v is number => typeof v === "number");
  if (values.length === 0) return null;
  return values.reduce((sum, v) => sum + v, 0) / values.length;
}

export function pillsCorrelation(entries: JournalEntryPoint[]) {
  const withPills = entries.filter((e) => e.pillsTaken === true);
  const withoutPills = entries.filter((e) => e.pillsTaken === false);

  const avgWith = averageEntryMoodScores(withPills);
  const avgWithout = averageEntryMoodScores(withoutPills);

  return {
    withPillsCount: withPills.length,
    withoutPillsCount: withoutPills.length,
    avgMoodWithPills: avgWith,
    avgMoodWithoutPills: avgWithout,
  };
}

export function stressMoodCorrelation(entries: JournalEntryPoint[]) {
  const points = entries
    .map((entry) => {
      const moodScore = entryMoodScore(entry);
      if (moodScore === null || entry.stress === null) return null;
      return { stress: entry.stress, moodScore };
    })
    .filter((point): point is { stress: number; moodScore: number } => point !== null);

  if (points.length === 0) {
    return { points: [], avgStress: null, avgMood: null };
  }

  const avgStress = points.reduce((sum, p) => sum + p.stress, 0) / points.length;
  const avgMood = points.reduce((sum, p) => sum + p.moodScore, 0) / points.length;

  return { points, avgStress, avgMood };
}

export function weekOverWeekTrend(
  entries: JournalEntryPoint[],
  now = new Date(),
): { current: number | null; previous: number | null; delta: number | null } {
  const currentStart = startOfWeekMonday(now);
  const currentEnd = addDays(currentStart, 7);
  const previousStart = addDays(currentStart, -7);

  const currentScores = entries
    .filter((e) => inRange(new Date(e.recordedAt), currentStart, currentEnd))
    .map(entryMoodScore)
    .filter((v): v is number => v !== null);

  const previousScores = entries
    .filter((e) => inRange(new Date(e.recordedAt), previousStart, currentStart))
    .map(entryMoodScore)
    .filter((v): v is number => v !== null);

  const current =
    currentScores.length > 0
      ? currentScores.reduce((sum, v) => sum + v, 0) / currentScores.length
      : null;
  const previous =
    previousScores.length > 0
      ? previousScores.reduce((sum, v) => sum + v, 0) / previousScores.length
      : null;

  const delta = current !== null && previous !== null ? current - previous : null;
  return { current, previous, delta };
}

export function moodCatalogForClient() {
  return MOOD_CATALOG.map(({ id, label, emoji, color }) => ({ id, label, emoji, color }));
}

export function moodLabel(id: string): string {
  return getMoodById(id)?.label ?? id;
}

function averageEntryMoodScores(entries: JournalEntryPoint[]): number | null {
  const scores = entries.map(entryMoodScore).filter((v): v is number => v !== null);
  if (scores.length === 0) return null;
  return scores.reduce((sum, v) => sum + v, 0) / scores.length;
}

function addDays(date: Date, delta: number): Date {
  const next = new Date(date);
  next.setDate(next.getDate() + delta);
  return next;
}

function startOfWeekMonday(date: Date): Date {
  const next = new Date(date);
  const day = next.getDay();
  const diffToMonday = (day + 6) % 7;
  next.setHours(0, 0, 0, 0);
  next.setDate(next.getDate() - diffToMonday);
  return next;
}

function inRange(date: Date, start: Date, end: Date): boolean {
  return date >= start && date < end;
}