# Wotra — Working Time Tracker: Implementation Plan

## 1. High-Level Architecture

```
┌─────────────────────────┐         ┌──────────────────────────┐
│   Svelte PWA (client)   │ ◄─────► │    Go service (API)      │
│  - IndexedDB cache      │  HTTPS  │  - REST/JSON endpoints   │
│  - Service Worker       │  JSON   │  - Business logic        │
│  - Sync queue           │         │  - SQLite (modernc)      │
└─────────────────────────┘         └──────────────────────────┘
```

Single-user, self-hosted. One Go binary serves the Svelte SPA and the API.

## 2. Backend (Go)

### Stack

- `net/http` + `chi` for routing
- `modernc.org/sqlite` (pure Go, no CGO) with `database/sql`
- SQLite WAL mode, foreign keys on, busy timeout 5s
- `golang-migrate` or hand-rolled migrations
- Structured logging via `slog`

### Project Layout

```
cmd/wotra/main.go
internal/
  config/        # timezone, token, port
  domain/        # Entry, ClosedDay, ClosedWeek, Settings types
  store/         # sqlite repos + migrations
  handler/       # HTTP handlers, middleware
  service/       # business rules (close day/week, merge, overtime)
migrations/      # SQL migration files
web/             # SvelteKit app (embedded in binary at build time)
mise.toml        # task/tool runner (replaces Makefile)
PLAN.md
```

### Database Schema

```sql
-- Raw tracking events (source of truth for open days)
CREATE TABLE entries (
  id            TEXT PRIMARY KEY,           -- UUIDv7 (client-generated, sync-friendly)
  start_time    INTEGER NOT NULL,           -- unix epoch ms, UTC
  end_time      INTEGER,                    -- NULL while running
  auto_stopped  INTEGER NOT NULL DEFAULT 0, -- 1 = stopped at midnight automatically
  note          TEXT,
  day_key       TEXT NOT NULL,              -- 'YYYY-MM-DD' in configured local tz
  updated_at    INTEGER NOT NULL,
  deleted_at    INTEGER                     -- soft delete for sync
);
CREATE INDEX idx_entries_day ON entries(day_key);

-- Closed days: merged result, effectively immutable
CREATE TABLE closed_days (
  day_key       TEXT PRIMARY KEY,           -- 'YYYY-MM-DD'
  start_time    INTEGER,                    -- min(entries.start_time), NULL for non-work kinds
  end_time      INTEGER,                    -- max(entries.end_time), NULL for non-work kinds
  worked_ms     INTEGER NOT NULL,           -- sum of entry durations (breaks excluded)
  kind          TEXT NOT NULL,              -- 'work' | 'holiday' | 'vacation' | 'sick'
  closed_at     INTEGER NOT NULL,
  updated_at    INTEGER NOT NULL
);

-- Closed weeks: snapshot of expectations at close time
CREATE TABLE closed_weeks (
  week_key      TEXT PRIMARY KEY,           -- 'YYYY-Www' ISO week
  expected_ms   INTEGER NOT NULL,           -- frozen at close
  worked_ms     INTEGER NOT NULL,           -- sum of closed_days.worked_ms for the week
  delta_ms      INTEGER NOT NULL,           -- worked_ms - expected_ms (signed)
  closed_at     INTEGER NOT NULL,
  updated_at    INTEGER NOT NULL
);

-- Settings with effective-from semantics so past weeks aren't retroactively changed
-- Migration 003: switched to TEXT UUID primary key; added updated_at
CREATE TABLE settings_history (
  id              TEXT PRIMARY KEY,             -- UUID (client-generated, sync-friendly)
  effective_from  TEXT NOT NULL,                -- 'YYYY-MM-DD'
  hours_per_week  REAL NOT NULL,
  workdays_mask   INTEGER NOT NULL DEFAULT 31,  -- bits Mon=1..Sun=64; Mon-Fri = 31
  timezone        TEXT NOT NULL DEFAULT 'UTC',
  created_at      INTEGER NOT NULL,
  updated_at      INTEGER NOT NULL
);

-- Sync event log (append-only; TTL-pruned; prune marker for stale-client detection)
CREATE TABLE sync_log (
  entity        TEXT NOT NULL,              -- 'entries' | 'closed_days' | ... | '_pruned'
  entity_id     TEXT NOT NULL,
  op            TEXT NOT NULL,              -- 'upsert' | 'delete' | 'marker'
  version       INTEGER NOT NULL,           -- monotonic server-assigned
  payload       TEXT NOT NULL,              -- JSON snapshot
  logged_at     INTEGER NOT NULL,           -- unix ms; used for TTL pruning
  PRIMARY KEY (entity, entity_id, version)
);

-- Balance adjustments: manual corrective entries that modify the overall overtime balance
-- without touching week math. Signed delta_ms (positive = credit, negative = debit).
CREATE TABLE balance_adjustments (
  id           TEXT PRIMARY KEY,            -- client-generated UUIDv7 (sync-friendly)
  delta_ms     INTEGER NOT NULL,            -- signed; non-zero enforced at service layer
  note         TEXT NOT NULL DEFAULT '',    -- optional free-text reason
  effective_at INTEGER NOT NULL,            -- unix ms; backdatable
  created_at   INTEGER NOT NULL,
  updated_at   INTEGER NOT NULL
);
CREATE INDEX idx_balance_adjustments_effective_at ON balance_adjustments(effective_at);
```

### API Surface (REST/JSON)

```
# Entries
POST   /api/entries/start              { note? }            -> Entry
POST   /api/entries/{id}/stop                               -> Entry
GET    /api/entries?from=YYYY-MM-DD&to=YYYY-MM-DD
POST   /api/entries                    { start_ms, end_ms, note? }  -> Entry (completed interval)
PUT    /api/entries/{id}               { start_time?, end_time?, note? }
DELETE /api/entries/{id}               (soft delete)

# Days
GET    /api/days?from=YYYY-MM-DD&to=YYYY-MM-DD
POST   /api/days/{day_key}/close                            -> ClosedDay
POST   /api/days/{day_key}/mark        { kind }             # holiday|vacation|sick
DELETE /api/days/{day_key}/close       (reopen day)

# Weeks
GET    /api/weeks?from=YYYY-Www&to=YYYY-Www
POST   /api/weeks/{week_key}/close                          -> ClosedWeek
DELETE /api/weeks/{week_key}/close     (reopen week)
GET    /api/weeks/balance                                   -> BalanceSummary

# Balance adjustments
GET    /api/balance/adjustments                             -> []BalanceAdjustment
POST   /api/balance/adjustments        { delta_ms, note?, effective_at }  -> BalanceAdjustment
PUT    /api/balance/adjustments/{id}   { delta_ms, note?, effective_at }  -> BalanceAdjustment
DELETE /api/balance/adjustments/{id}

# Settings
GET    /api/settings                                        # current effective settings
PUT    /api/settings                   { effective_from, hours_per_week, workdays_mask, timezone }
GET    /api/settings/history

# Sync
GET    /api/sync/pull?since=N                               -> { changes[], server_version } | 410 Gone
POST   /api/sync/push                  { changes[] }        -> { applied[], skipped[] }

# Health
GET    /healthz                                             (unauthenticated)
```

### Key Business Rules

- **day_key assignment**: based on `start_time` in the configured timezone.
- **Midnight enforcement**: `end_time` must be on the same calendar day as `start_time`. Server auto-stops any running entry at 23:59:59 local time via a background goroutine. Client warns the user.
- **Close day**: requires all entries for that day to have `end_time != NULL` (409 otherwise). Computes `worked_ms = sum(end_time - start_time)` across non-deleted entries. Entries are preserved but the day is now locked.
- **Mark day**: writes a `closed_days` row with `kind != 'work'`; `worked_ms` = expected daily ms (hours_per_week * 3600000 / popcount(workdays_mask)) for workdays, 0 for non-workdays.
- **Close week**: all workdays in the week must have a `closed_days` row. Sums `worked_ms`, snapshots `expected_ms` from settings effective at close time, stores signed `delta_ms`.
- **Settings change**: new row in `settings_history` with `effective_from`. Past closed weeks are unaffected because they store a frozen snapshot.
- **Future intervals**: server rejects `CreateInterval` and `Update` if the resulting day key is in the future (400 Bad Request).

### Auth

- `AUTH_TOKEN` environment variable on the server.
- All `/api/*` routes require `Authorization: Bearer <token>`.
- Client stores token in `localStorage` after a one-time setup screen.
- `/healthz` is unauthenticated.

## 3. Frontend (Svelte PWA)

### Stack

- SvelteKit (static adapter for embedding in Go binary)
- TypeScript
- `vite-plugin-pwa` + Workbox for service worker and manifest
- `dexie` for typed IndexedDB access
- `vitest` for unit tests

### Screens

| Screen | Purpose |
|--------|---------|
| **Week** | Week picker, 7-day chip strip, day detail panel for selected day. Default: today selected (if in week) else Monday. Today tab in bottom nav is a shortcut that selects today. |
| **History** | Month/week list of closed days and weeks with overtime indicators |
| **Settings** | hours/week, workdays mask, timezone, effective-from, token setup |

The old dedicated **Today** route is merged into the Week view (see § Merged Week+Today View below).

### Merged Week+Today View (`/week`)

Three regions:

1. **Week header** — week picker, week totals, Close Week button, closed-week banner.
2. **Day strip** — 7 chips (Mon–Sun), each showing: weekday label + date, mini progress bar (worked/expected), kind icon, closed badge, today highlight. Horizontal scroll-snap on mobile. Selected chip scrolls into view. `role="tablist"` with keyboard arrow navigation.
3. **Day detail panel** — for the selected day, capabilities gated per table:

| Condition | canStartStop | canAddInterval | canEditEntries | canMarkKind | canCloseDay |
|---|---|---|---|---|---|
| Future | false | false | false | true | false |
| Today, open | true | true | true | true | true* |
| Today, closed | false | false | false | true | reopen |
| Past, open | false | true | true | true | true |
| Past, closed | false | false | false | true | reopen |

*Close Day button disabled with tooltip while a running entry exists.

**URL state**: `?week=2026-W18&day=2026-04-30`. Bare `/week` canonicalizes via `replaceState`. Chip clicks use `replaceState` (no history push). Week navigation (prev/next) uses `goto` (history push). Default day selection on week change: today if in week, else Monday.

**Bottom nav**: "Today" tab is a shortcut link to `/week?week=<currentWeek>&day=<todayKey>`. Active when route is `/week` and `?day === todayKey()`.

### Offline Strategy

1. App shell precached by Workbox.
2. All reads come from Dexie (IndexedDB); a sync worker reconciles with the server in the background.
3. All mutations create a local Dexie record with a client-generated UUIDv7 and an entry in a local `outbox` table.
4. When online, the outbox is flushed via `/api/sync/push`; responses update the local cache.
5. `/api/sync/pull` fetches any server-side changes since `last_pulled_version`.

## 4. Sync Protocol

- Every mutable row carries `updated_at` (ms) on the client and `version` (server monotonic int) once accepted.
- **Pull**: `POST /api/sync/pull { since_version: N }` → rows with `version > N` + `server_version`.
- **Push**: client sends batched upsert/delete events with `updated_at`. Server applies last-write-wins per row. Conflicts returned to client, which re-pulls those rows.

## 5. Build & Deployment

```sh
# Single-binary production build (via mise)
mise run build
# 1. npm run build  (inside web/)
# 2. go build -tags production -o wotra ./cmd/wotra
#    -> embeds web/build via go:embed
```

Dev mode: Go on `:8080`, Vite dev server on `:5173` with `/api` proxied to Go.

Environment variables:
| Variable | Default | Description |
|----------|---------|-------------|
| `AUTH_TOKEN` | required | Bearer token for API access |
| `PORT` | `8080` | Server port |
| `DB_PATH` | `wotra.db` | SQLite file path |
| `TZ` | `UTC` | Server timezone for day-key calculation |

## 6. Milestones

### M1–M6 — Done
Full backend + frontend implemented, PWA offline sync, single-binary build, `mise.toml` task runner.

### M7 — Merge Today+Week views ✅ in progress

Staged implementation:

| Stage | Goal | Status |
|---|---|---|
| 0 | Add Vitest setup | pending |
| 1 | Day strip on week view (read-only) | pending |
| 2 | Extract DayDetail component; render today in week view | pending |
| 3 | Day selection + URL-driven state | pending |
| 4 | Backend guard: reject future-day intervals | pending |
| 5 | Bottom nav Today shortcut; delete /today route | pending |

### M8 — Balance adjustments ✅

Manual corrective entries on the History page that adjust the overall overtime balance without touching week math. Separate `balance_adjustments` table with signed `delta_ms`, optional `note`, and `effective_at` (backdatable). Balance summary combines `Σ closed_weeks.delta_ms + Σ balance_adjustments.delta_ms`.

### M9 — Sync redesign ✅

Full offline support with online-first, offline-fallback mutation strategy.

**Backend:**
- Migration 003: `logged_at` on `sync_log`; `settings_history` migrated to UUID TEXT PK with `updated_at`.
- `SyncStore.Prune(ctx, ttl)`: deletes rows older than TTL and writes a `_pruned` marker at the boundary version. Clients pulling with `since < marker_version` receive `ErrSyncStale` → `410 Gone`.
- `GET /api/sync/pull?since=N`: calls Prune lazily (30-day TTL), returns changes or 410.
- `POST /api/sync/push`: accepts batched outbox items; applies last-`updated_at`-wins for `entries`, `balance_adjustments`, `settings_history`. `closed_days`/`closed_weeks` are server-only and skipped. Returns `{applied, skipped}`.

**Frontend:**
- `client.ts`: all mutation methods (`entries`, `balance`, `settings`) catch `TypeError` (network error) and fall back to writing directly to Dexie + enqueuing in the outbox. IDs for offline creates are generated client-side via `crypto.randomUUID()`.
- `sync.ts`: `pushOutbox` sends outbox to `POST /api/sync/push`; on success removes applied items. `pullChanges` uses `GET /api/sync/pull?since=N`; on 410 calls `coldStart()` and retries. `coldStart()` clears all Dexie tables and resets `last_version=0`.
- `db.ts`: Dexie v3 — `settings_history` key path changed to `id` (string); upgrade handler clears the table for repopulation via pull.
- Settings page: `editingId` and ID params updated from `number` to `string`.

### M10 — Future
CSV/JSON export, monthly summary view.

## 7. Decisions & Rationale

| Decision | Choice | Reason |
|----------|--------|--------|
| Midnight crossing | Disallow; auto-stop at 23:59:59 | Keeps day-boundary logic simple and lossless |
| Running entry at close | Refuse with 409 | Explicit is better than implicit |
| Expected hours split | Even across workdays | Simplest correct model; per-day config out of scope |
| Auth v1 | Single shared bearer token | Single-user self-hosted; minimal friction |
| Deployment | Single Go binary embeds SPA | Simplest self-hosting story |
| SQLite driver | modernc.org/sqlite (pure Go) | No CGO; easy cross-compilation |
| Breaks in closed day | Not included in worked_ms | Sum of entry durations only; gaps between entries are breaks |
| Week close settings | Use close-time date, not week Monday | Settings changed mid-week apply to that week's close |
| weekDayKeys formula | `(weekday+6)%7` for days-since-Monday | Avoids sign bug when Jan 4 is Sunday (affects year 2026) |
| Merged Today+Week | Single `/week` route with day selection | Reduces duplication; week context always visible |
| Balance adjustments | Separate `balance_adjustments` table | Avoids conflating measured deltas with manual corrections; preserves week math invariant (`delta_ms = worked - expected`) |
| Balance adjustment scope | Closed weeks only for auto balance | In-progress week delta shown separately in week view; mixing would make balance jitter |
| Balance adjustment IDs | TEXT (UUIDv7, client-generated) | Consistent with `entries`; allows offline creation and sync |
| Settings history PK | TEXT UUID (migration 003) | Consistent with other entities; enables offline create; `updated_at` enables last-write-wins sync |
| Sync prune strategy | Prune marker row at boundary version | No extra table; client detects stale state from the log itself; 410 triggers full re-sync |
| Sync conflict resolution | Last `updated_at` wins | Server is authoritative; simple to implement and reason about for single-user |
| Offline mutation flow | Online-first, offline-fallback | Server is primary; client writes to Dexie+outbox only on network failure; simpler than full local-first |