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

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

export type PeriodKey = PeriodType;

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

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

const PREFIX_TO_KEY: Record<string, PeriodKey> = {
  D: "daily",
  W: "weekly",
  M: "monthly",
  ALL: "all",
};

/**
 * 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] ?? "all";
}

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

export function getAmount(period: ReportPeriod): number {
  return period.metric.sum;
}

function mergeMetric(a: ReportPeriod["metric"], b: ReportPeriod["metric"]) {
  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,
          metric: { ...p.metric },
        });
      } else {
        map.set(p.id, {
          ...existing,
          metric: mergeMetric(existing.metric, p.metric),
        });
      }
    }
  }

  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];
    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));
}

export function extractFilteredTransactions(
  reportData: ReportData,
  selectedPeriodId: string | null | undefined,
  selectedGroupKey: GroupKey | null | undefined
): Transaction[] {
  let txns: Transaction[] = [];

  if (selectedPeriodId) {
    const key = periodIdToKey(selectedPeriodId);
    const periods = mergeBucketPeriods(reportData.buckets, key);
    const selected = periods.find((p) => p.id === selectedPeriodId);
    txns = selected?.metric.transactions || [];
  } else {
    const periods = mergeBucketPeriods(reportData.buckets, "all");
    if (periods.length > 0) {
      const period = periods.reduce((latest, p) =>
        new Date(p.start).getTime() > new Date(latest.start).getTime()
          ? p
          : latest
      , periods[0]);
      txns = period?.metric.transactions || [];
    }
  }

  if (selectedGroupKey) {
    txns = txns.filter((txn) => {
      let match = true;
      if (selectedGroupKey.tags && selectedGroupKey.tags.length > 0) {
        if (!txn.tags) {
          match = false;
        } else {
          const txnTags = txn.tags.map((t: any) =>
            typeof t === "string" ? t : t.name
          );
          if (
            !selectedGroupKey.tags.every((selectedTag) =>
              txnTags.includes(selectedTag)
            )
          ) {
            match = false;
          }
        }
      }
      if (match && selectedGroupKey.payee && selectedGroupKey.payee.length > 0) {
        if (!txn.payee || !txn.payee.name) {
          match = false;
        } else {
          if (!selectedGroupKey.payee.includes(txn.payee.name)) {
            match = false;
          }
        }
      }
      return match;
    });
  }

  return txns;
}

export function aggregateTransactions(
  transactions: Transaction[],
  keyExtractor: (txn: Transaction) => string[],
  limit = 4
): { items: { name: string; amount: number }[]; total: number } {
  const map = new Map<string, number>();

  for (const txn of transactions) {
    const keys = keyExtractor(txn);
    for (const key of keys) {
      map.set(key, (map.get(key) || 0) + txn.amount);
    }
  }

  const items = Array.from(map.entries()).map(([name, amount]) => ({
    name,
    amount,
  }));

  items.sort((a, b) => b.amount - a.amount);

  const top = items.slice(0, limit);
  const total = top.reduce((sum, item) => sum + item.amount, 0);

  return { items: top, total };
}