import {
  ReportPeriod,
  ReportBucket,
  GroupKey,
} from "../features/report";

// ─── Types ────────────────────────────────────────────────────

export type PeriodKey = "weekly" | "monthly" | "yearly" | "fyly" | "full";

export type DecoratedPeriod = ReportPeriod & {
  id: string;
  label: string;
};

// ─── Period helpers ───────────────────────────────────────────

const PREFIX_TO_KEY: Record<string, PeriodKey> = {
  W: "weekly",
  M: "monthly",
  Y: "yearly",
  FY: "fyly",
  FULL: "full",
};

/**
 * Derive the period key from a decorated-period id.
 * E.g. `"W:2026-04-28_2026-05-04"` → `"weekly"`
 */
export function periodIdToKey(periodId: string): PeriodKey {
  const prefix = periodId.split(":")[0];
  return PREFIX_TO_KEY[prefix] ?? "full";
}

// ─── Metric helpers ───────────────────────────────────────────

export function getAmount(
  period: ReportPeriod,
  mode: "expense" | "income"
): number {
  return mode === "expense" ? period.expenses.sum : period.incomes.sum;
}

function mergeMetric(a: ReportPeriod["expenses"], b: ReportPeriod["expenses"]) {
  const sum = a.sum + b.sum;
  const count = a.count + b.count;

  return {
    ...a,
    sum,
    count,
    average: count > 0 ? sum / count : 0,
    transactions:
      a.transactions || b.transactions
        ? [...(a.transactions || []), ...(b.transactions || [])]
        : undefined,
  };
}

/**
 * Merge periods with the same id across all buckets, summing
 * their metrics and concatenating transactions.
 *
 * Returns sorted by start date ascending.
 */
export function mergeBucketPeriods(
  buckets: ReportBucket[],
  key: PeriodKey
): DecoratedPeriod[] {
  const map = new Map<string, DecoratedPeriod>();

  for (const bucket of buckets) {
    const periods = (bucket.periods[key] || []) as DecoratedPeriod[];

    for (const p of periods) {
      const existing = map.get(p.id);

      if (!existing) {
        map.set(p.id, {
          ...p,
          expenses: { ...p.expenses },
          incomes: { ...p.incomes },
        });
      } else {
        map.set(p.id, {
          ...existing,
          expenses: mergeMetric(existing.expenses, p.expenses),
          incomes: mergeMetric(existing.incomes, p.incomes),
        });
      }
    }
  }

  return Array.from(map.values()).sort(
    (a, b) => new Date(a.start).getTime() - new Date(b.start).getTime()
  );
}

// ─── Formatting ───────────────────────────────────────────────

export const formatCurrency = (val: number) => {
  const absVal = Math.abs(val);
  if (absVal >= 100000) {
    return `₹ ${(val / 100000).toFixed(2)}L`;
  }
  if (absVal >= 1000) {
    return `₹ ${(val / 1000).toFixed(2)}k`;
  }
  return `₹ ${val.toFixed(2)}`;
};

export const getPercentage = (progressAmount: number, totalAmount: number) => {
  if (!totalAmount) return 0;
  return Math.min(100, Math.max(0, (progressAmount / totalAmount) * 100));
};

// ─── Group filtering ──────────────────────────────────────────

/**
 * Check if a bucket's group_key matches the selected GroupKey.
 * Every dimension present in `selected` must exist in the bucket
 * and contain all the selected values.
 */
export function matchesGroupKey(
  bucket: ReportBucket,
  selected: GroupKey
): boolean {
  for (const [dim, values] of Object.entries(selected)) {
    const bucketValues = bucket.group_key[dim as keyof GroupKey];
    if (!bucketValues) return false;
    if (!(values as string[]).every((v) => bucketValues.includes(v)))
      return false;
  }
  return true;
}

/**
 * Return only buckets matching the selected group key,
 * or all buckets if no selection.
 */
export function filterBuckets(
  buckets: ReportBucket[],
  selectedGroupKey: GroupKey | null
): ReportBucket[] {
  if (!selectedGroupKey) return buckets;
  return buckets.filter((b) => matchesGroupKey(b, selectedGroupKey));
}