items-by-period (#2)

Reviewed-on: #2
Co-authored-by: Vishesh 'ironeagle' Bangotra <aetoskia@gmail.com>
Co-committed-by: Vishesh 'ironeagle' Bangotra <aetoskia@gmail.com>

src/components/report.helpers.ts

@@ -0,0 +1,147 @@
+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));
+}