---
phase: 02-dashboard-charts-and-layout
plan: 01
subsystem: ui
tags: [react, react-router, i18n, dashboard, charts]

# Dependency graph
requires:
  - phase: 01-design-foundation-and-primitives
    provides: PageShell, design tokens, shadcn chart primitive
provides:
  - useMonthParam hook for URL-based month navigation
  - MonthNavigator component with prev/next arrows and Select dropdown
  - Chart and month navigation i18n keys (EN + DE)
affects: [02-dashboard-charts-and-layout, 03-collapsible-dashboard-sections]

# Tech tracking
tech-stack:
  added: []
  patterns: [URL-based state via useSearchParams, locale-aware month formatting]

key-files:
  created:
    - src/hooks/useMonthParam.ts
    - src/components/dashboard/MonthNavigator.tsx
  modified:
    - src/i18n/en.json
    - src/i18n/de.json

key-decisions:
  - "useMonthParam preserves other URL params via setSearchParams callback form"
  - "navigateMonth uses Date constructor for automatic year rollover"
  - "MonthNavigator accepts t prop but dropdown uses locale-aware Intl formatting"
  - "ChartEmptyState already existed from Phase 1 — skipped creation, added i18n keys only"

patterns-established:
  - "URL-based month state: useMonthParam hook as single source of truth for month selection"
  - "Month formatting: Date.toLocaleDateString with month:'long', year:'numeric'"

requirements-completed: [UI-DASH-01]

# Metrics
duration: 2min
completed: 2026-03-16
---

# Phase 02, Plan 01: Month Navigation and Chart Infrastructure Summary

**useMonthParam hook and MonthNavigator component for URL-based month selection, plus 10 new chart/navigation i18n keys in EN and DE**

## Performance

- **Duration:** ~2 min
- **Started:** 2026-03-16T12:02:00Z
- **Completed:** 2026-03-16T12:03:06Z
- **Tasks:** 2
- **Files modified:** 4

## Accomplishments
- useMonthParam hook reads/writes `?month=YYYY-MM` URL param with current-month fallback and year-rollover navigation
- MonthNavigator renders prev/next chevron buttons and a Select dropdown of available budget months with locale-aware formatting
- 10 new i18n keys added for chart labels, month navigation, and empty states in both EN and DE

## Task Commits

Each task was committed atomically:

1. **Task 1: Create useMonthParam hook and MonthNavigator component** - `4481950` (feat)
2. **Task 2: Add chart and month navigation i18n keys** - `42bf1f9` (feat)

## Files Created/Modified
- `src/hooks/useMonthParam.ts` - URL-based month state hook with navigateMonth for year rollover
- `src/components/dashboard/MonthNavigator.tsx` - Prev/next arrows + Select dropdown for month selection
- `src/i18n/en.json` - 10 new dashboard chart and navigation keys
- `src/i18n/de.json` - Matching German translations

## Decisions Made
- ChartEmptyState component already existed from Phase 1 — only i18n keys were added, component creation skipped
- useMonthParam uses setSearchParams callback form to preserve other URL params
- MonthNavigator uses Date.toLocaleDateString for locale-aware month display

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Already Exists] Skipped ChartEmptyState component creation**
- **Found during:** Task 2 (ChartEmptyState and i18n keys)
- **Issue:** ChartEmptyState component already existed from Phase 1 setup
- **Fix:** Skipped creation, added only the i18n keys
- **Verification:** Component exists and exports correctly
- **Committed in:** 42bf1f9 (Task 2 commit)

---

**Total deviations:** 1 auto-fixed (1 already exists)
**Impact on plan:** No scope creep — component existed, only i18n work needed.

## Issues Encountered
None

## User Setup Required
None - no external service configuration required.

## Next Phase Readiness
- Month navigation infrastructure ready for dashboard integration (Plan 03)
- Chart components (Plan 02) can reference i18n keys
- All foundational pieces in place for DashboardPage wiring

---
*Phase: 02-dashboard-charts-and-layout*
*Completed: 2026-03-16*