Dashboard Refactor: Flow-based Metrics + Unified Data Model (#4)

# Dashboard Refactor: Flow-based Metrics + Unified Data Model

## Summary

This MR transforms the dashboard into a **flow-driven, backend-powered analytics system** with a significantly cleaner architecture and improved UX.

## Overview

This MR introduces a **major refactor of the dashboard and report data model**, transitioning from separate `expense/income` handling to a unified **flow-based (`outflows` / `inflows`) system** backed by a single `metric` structure.

It simplifies data handling, improves UI consistency, and enables better extensibility for future analytics.

---

## Key Changes

### 1. Data Model Simplification

* Replaced:

  * `expenses` / `incomes`
* With:

  * `metric`

```ts
ReportPeriod {
  start: string;
  end: string;
  metric: {
    sum: number;
    count: number;
    transactions: Transaction[];
  }
}
```

* Eliminates duplication across logic paths
* Flow is now controlled at query level instead of data shape

---

### 2. Flow-based System (Core Change)

* Introduced:

  ```ts
  type DashboardFlow = "outflows" | "inflows";
  ```

* Replaced all references of:

  * `expense` → `outflows`
  * `income` → `inflows`

* Flow is now:

  * Controlled at **Dashboard level**
  * Propagated to **API query (`useReport`)**

---

### 3. API Changes

#### `useReport`

* Removed legacy params:

  * `group_by`, `rolling`, `include_transactions`, etc.

* New structure:

```ts
useReport({
  periods: ["daily", "weekly", "monthly", "all"],
  flow,
  payee,
  tags
})
```

* Backend now handles:

  * Flow filtering
  * Aggregation

---

### 4. Period System Update

* Removed:

  * yearly, fyly, full

* Added:

  * `daily`
  * `all`

```ts
type PeriodType = "daily" | "weekly" | "monthly" | "all";
```

* Updated helpers:

  * `periodIdToKey`
  * `buildPeriodId`
  * `buildLabel`

---

### 5. React Query UX Improvement

* Added:

```ts
placeholderData: keepPreviousData
```

* Prevents UI flicker on filter/flow changes
* Enables smooth transitions

---

### 6. Dashboard State Refactor

#### Before

```ts
mode: "expense" | "income"
```

#### After

```ts
flow: "outflows" | "inflows"
```

* Introduced `onFlowChange` callback
* Lifted flow state to parent (`Dashboard.tsx`)
* Flow change triggers API refetch

---

### 7. UI Improvements

#### Flow Toggle

* Replaced mode toggle with:

  * Outflows / Inflows switch

#### Loading State Handling

* Added `isFetching` across components
* UI behavior during fetch:

  * Reduced opacity
  * Disabled interactions

#### Drill-down UX

* Added:

  * "Clear Drill-down" button

---

### 8. New Components

#### TopPayees

* New analytics card

* Shows top payees based on:

  * Selected period
  * Drill-down filters

* Supports:

  * Click-to-filter (drill-down)

---

### 9. Adapter Layer Simplification

#### Removed mode branching everywhere

Examples:

* `getAmount(period)` now uses:

  ```ts
  period.metric.sum
  ```

* `LatestItems`, `TopTags`, `HistoryChart`:

  * No longer split logic by expense/income
  * Work on unified transaction stream

---

### 10. GroupKey Generalization

#### Before

```ts
{
  payee?: string[];
  tags?: string[];
}
```

#### After

```ts
{
  [dimension: string]: string[];
}
```

* Enables future dimensions without refactor

---

## Behavioral Changes

* Flow selection now **controls backend query**
* All components consume **filtered data only**
* No client-side filtering for expense/income

---

## Benefits

* Single source of truth (`metric`)
* Cleaner adapters (no branching explosion)
* Easier feature additions (new dimensions, filters)
* Better UX (no flicker, smoother transitions)
* Backend-driven correctness

---

## Migration Notes

* Replace all `mode` usages with `flow`
* Update adapters to use `metric`
* Remove assumptions about:

  * `expenses`
  * `incomes`
* Ensure API supports:

  * `flow`
  * new period types

---

## Future Scope

* Add more dimensions (account, category hierarchy)
* Multi-flow comparison (inflows vs outflows together)
* Snapshot-based caching (already partially supported)

---

## Testing Notes

Verify:

* Flow toggle updates API calls
* No UI flicker on filter change
* Drill-down works across:

  * tags
  * payees
* Daily / Weekly / Monthly / All tabs behave correctly
* Loading state disables interaction properly

---

Reviewed-on: #4
Co-authored-by: Vishesh 'ironeagle' Bangotra <aetoskia@gmail.com>
Co-committed-by: Vishesh 'ironeagle' Bangotra <aetoskia@gmail.com>

src/components/report.helpers.ts

@@ -2,11 +2,12 @@ import {
   ReportPeriod,
   ReportBucket,
   GroupKey,
+  PeriodType,
 } from "../features/report";
 
 // ─── Types ────────────────────────────────────────────────────
 
-export type PeriodKey = "weekly" | "monthly" | "yearly" | "fyly" | "full";
+export type PeriodKey = PeriodType;
 
 export type DecoratedPeriod = ReportPeriod & {
   id: string;
@@ -16,11 +17,10 @@ export type DecoratedPeriod = ReportPeriod & {
 // ─── Period helpers ───────────────────────────────────────────
 
 const PREFIX_TO_KEY: Record<string, PeriodKey> = {
+  D: "daily",
   W: "weekly",
   M: "monthly",
-  Y: "yearly",
-  FY: "fyly",
-  FULL: "full",
+  ALL: "all",
 };
 
 /**
@@ -29,19 +29,16 @@ const PREFIX_TO_KEY: Record<string, PeriodKey> = {
  */
 export function periodIdToKey(periodId: string): PeriodKey {
   const prefix = periodId.split(":")[0];
-  return PREFIX_TO_KEY[prefix] ?? "full";
+  return PREFIX_TO_KEY[prefix] ?? "all";
 }
 
 // ─── Metric helpers ───────────────────────────────────────────
 
-export function getAmount(
-  period: ReportPeriod,
-  mode: "expense" | "income"
-): number {
-  return mode === "expense" ? period.expenses.sum : period.incomes.sum;
+export function getAmount(period: ReportPeriod): number {
+  return period.metric.sum;
 }
 
-function mergeMetric(a: ReportPeriod["expenses"], b: ReportPeriod["expenses"]) {
+function mergeMetric(a: ReportPeriod["metric"], b: ReportPeriod["metric"]) {
   const sum = a.sum + b.sum;
   const count = a.count + b.count;
 
@@ -78,14 +75,12 @@ export function mergeBucketPeriods(
       if (!existing) {
         map.set(p.id, {
           ...p,
-          expenses: { ...p.expenses },
-          incomes: { ...p.incomes },
+          metric: { ...p.metric },
         });
       } else {
         map.set(p.id, {
           ...existing,
-          expenses: mergeMetric(existing.expenses, p.expenses),
-          incomes: mergeMetric(existing.incomes, p.incomes),
+          metric: mergeMetric(existing.metric, p.metric),
         });
       }
     }
@@ -126,7 +121,7 @@ export function matchesGroupKey(
   selected: GroupKey
 ): boolean {
   for (const [dim, values] of Object.entries(selected)) {
-    const bucketValues = bucket.group_key[dim as keyof GroupKey];
+    const bucketValues = bucket.group_key[dim];
     if (!bucketValues) return false;
     if (!(values as string[]).every((v) => bucketValues.includes(v)))
       return false;