# Finance App

Personal finance tracker built on Next.js 16 (App Router), PostgreSQL, and Prisma. Bank statements are ingested automatically from Paperless-NGX via an N8N workflow that uses Gemini to extract structured data from PDF statements.

## Stack

- **Frontend**: Next.js 16 App Router, TypeScript, Tailwind CSS, Recharts
- **Backend**: Next.js API routes, raw PostgreSQL via `pg` + `@prisma/adapter-pg`
- **Database**: PostgreSQL (`postgres-personal` container)
- **Auth**: `X-Forwarded-User` header (email) set by Traefik forward-auth → mapped to `participants.email`
- **Ingestion**: N8N workflow → Gemini 2.5 Flash (PDF parsing) → PostgreSQL

---

## Data Model

### `statements`
The top-level document, one row per billing period per account.

| Column | Type | Description |
|--------|------|-------------|
| `id` | int | Primary key |
| `bank_name` | text | Normalised bank name (e.g. "American Express") |
| `card_name` | text | Product name (e.g. "Rewards Travel Adventures") |
| `account_number` | text | Account/card number (spaces stripped) |
| `account_type` | text | Raw account type string from statement |
| `statement_type` | text | Normalised type: `Credit Card`, `Business Card`, `multi-currency account`, etc. |
| `account_holder_name` | text | Name on the account if extracted |
| `billing_start_date` | date | Period start |
| `billing_end_date` | date | Period end — used as the deduplication anchor |
| `opening_balance` | numeric | Balance at start of period |
| `closing_balance` | numeric | Balance at end of period |
| `total_credits` | numeric | Sum of all credits in period |
| `total_debits` | numeric | Sum of all debits in period |
| `total_amount_due` | numeric | Amount due (credit cards) |
| `minimum_amount_due` | numeric | Minimum payment due (credit cards) |
| `payment_due_date` | date | Payment due date (credit cards) |
| `credit_limit` | numeric | Credit limit (credit cards) |
| `available_credit` | numeric | Available credit at statement date |
| `interest_charged` | numeric | Interest charged this period (from statement summary) |
| `fees_charged` | numeric | Fees charged this period (from statement summary) |
| `currency` | text | Statement currency (e.g. `AUD`, `USD`) |
| `exchange_rate_to_aud` | numeric | FX rate at ingestion time (live from open.er-api.com) |
| `owner_id` | int FK → `participants` | Which person owns this statement |
| `paperless_doc_id` | int | Paperless-NGX document ID — deduplication key |
| `tier_used` | text | AI model used for extraction (e.g. `gemini-2.5-flash`) |
| `event_created` | bool | Whether a Google Calendar reminder was created for payment due date |

**Deduplication**: unique index on `(bank_name, account_number, billing_end_date)` prevents re-ingestion of the same period. `paperless_doc_id` has a separate unique index for Paperless-linked documents.

**Credit card detection**: `statement_type ILIKE '%card%'`

---

### `transactions`
One row per line item within a statement. Cascade-deleted when the parent statement is deleted.

| Column | Type | Description |
|--------|------|-------------|
| `id` | int | Primary key |
| `statement_id` | int FK → `statements` | Parent statement |
| `transaction_date` | date | Date of transaction |
| `description` | text | Raw description from the statement |
| `amount` | numeric | Original amount in statement currency |
| `amount_aud` | numeric | AUD-converted amount (= amount if already AUD) |
| `transaction_type` | text | `debit`, `credit`, `payment`, `refund`, `fee`, `interest`, `transfer` |
| `merchant_name` | text | Raw merchant name extracted by Gemini |
| `merchant_normalized` | text | Cleaned/normalised merchant name (Gemini) |
| `location` | text | Location if present on statement |
| `foreign_currency_amount` | numeric | Original foreign amount if this was an FX transaction |
| `foreign_currency_code` | text | Foreign currency code (e.g. `USD`) |
| `category` | text | AI-assigned category (see category taxonomy below) |
| `row_index` | int | Position in statement — used for deduplication |

**Deduplication**: unique index on `(statement_id, transaction_date, description, amount, row_index)`.

**Analytics**: all spend queries use `amount_aud` for cross-currency consistency. Split-adjusted queries apply `amount_aud * share_percent / 100` where a split exists for the current user.

---

### `transaction_overrides`
User corrections to AI-extracted data. Stored separately to preserve the original extraction.

| Column | Type | Description |
|--------|------|-------------|
| `transaction_id` | int FK → `transactions` (unique) | One override per transaction |
| `merchant_normalized` | text | User-corrected merchant name |
| `category_override` | text | User-corrected category |
| `notes` | text | Free-text notes |

All analytics queries use `COALESCE(o.category_override, t.category)` and `COALESCE(o.merchant_normalized, t.merchant_normalized, t.merchant_name)` to prefer overrides over AI values.

---

### `transaction_splits`
Shared expense tracking — records that a transaction was split between participants.

| Column | Type | Description |
|--------|------|-------------|
| `transaction_id` | int FK → `transactions` | The transaction being split |
| `participant_id` | int FK → `participants` | Who shares in this transaction |
| `share_percent` | numeric(5,2) | Their percentage (1–100) |
| `settled` | bool | Whether this share has been settled |
| `settled_at` | timestamptz | When it was settled |

A transaction can be split across multiple participants. The statement owner's own share is implicit (`100 - SUM(other shares)`). Analytics queries LEFT JOIN `transaction_splits` on `participant_id = current_user.id` — if no split row exists, the full amount belongs to the owner.

---

### `transaction_tags`
Many-to-many join between transactions and tags.

| Column | Type |
|--------|------|
| `transaction_id` | int FK → `transactions` |
| `tag_id` | int FK → `tags` |

---

### `tags`
User-defined coloured labels for ad-hoc transaction grouping beyond the fixed category taxonomy.

| Column | Type | Description |
|--------|------|-------------|
| `id` | int | Primary key |
| `name` | text (unique) | Tag name |
| `color` | text | Hex colour (default `#6366f1`) |

---

### `participants`
People who own statements or share expenses.

| Column | Type | Description |
|--------|------|-------------|
| `id` | int | Primary key |
| `name` | text (unique) | Display name |
| `email` | text (unique) | Login identity — matched against `X-Forwarded-User` header |

---

### `account_owner_mappings`
Persists `(bank, account_number) → owner` assignments so future ingestion auto-assigns the correct owner without manual intervention.

| Column | Type | Description |
|--------|------|-------------|
| `bank_name` | text | |
| `account_number` | text | |
| `owner_id` | int FK → `participants` | |

Written when a user reassigns a statement owner in the UI. Consulted by the N8N workflow on every new statement insert.

---

### `rules`
Saved auto-categorisation rules. Applied in bulk via the Rules page.

| Column | Type | Description |
|--------|------|-------------|
| `owner_id` | int FK → `participants` | Rule belongs to this user |
| `name` | text | Rule label |
| `conditions` | jsonb | Array of `{field, operator, value}` — AND logic |
| `actions` | jsonb | `{set_category, add_tag_ids, set_merchant}` |
| `enabled` | bool | |
| `priority` | int | Higher priority rules run first |

**Condition fields**: `merchant_normalized`, `description`, `category`, `bank_name`, `amount`
**Condition operators**: `contains`, `equals`, `starts_with`, `gt`, `lt`, `not_equals`

---

### `budgets`
Monthly spend targets per category. Stored but currently unused in the UI (replaced by the analytics/insights views).

| Column | Type | Description |
|--------|------|-------------|
| `owner_id` | int FK → `participants` | |
| `category` | text | Category name |
| `month` | date | Always first of month (e.g. `2026-03-01`) |
| `amount_limit` | numeric | Spend target for that category/month |

---

## Category Taxonomy

Fixed set defined in `src/lib/categories.ts`. Applied by Gemini at ingestion and overridable by the user or rules engine:

`groceries` · `dining` · `transport` · `fuel` · `shopping` · `utilities` · `entertainment` · `travel` · `health` · `insurance` · `subscriptions` · `cash_advance` · `government` · `education` · `rent` · `home_goods` · `home_maintenance` · `transfers` · `income` · `investment` · `personal_care` · `pets` · `gifts` · `charity` · `other`

- **home_goods** — items purchased for the house (appliances, furniture, kitchenware, electronics)
- **home_maintenance** — services on the property (cleaning, mowing, repairs)

**Committed spend** (Insights page): `rent`, `utilities`, `insurance`, `subscriptions`
**Excluded from spend analytics**: `transfers`, `investment`

---

## API Routes

All routes require authentication via `X-Forwarded-User` header (set by Traefik). Responses are always scoped to the authenticated user's `owner_id`.

| Method | Route | Description |
|--------|-------|-------------|
| GET | `/api/statements` | All statements for current user |
| GET / PATCH | `/api/statements/[id]` | Get statement; PATCH to reassign owner (also writes `account_owner_mappings`) |
| GET | `/api/transactions` | Paginated transactions with filters: `from`, `to`, `category`, `merchant`, `statement_id`, `search`, `sort`, `dir` |
| GET / PATCH | `/api/transactions/[id]` | Get transaction; PATCH to upsert override (category, merchant, notes) |
| GET / POST | `/api/transactions/[id]/splits` | List or create splits on a transaction |
| GET / POST | `/api/transactions/[id]/tags` | List or apply tags to a transaction |
| POST | `/api/transactions/bulk` | Bulk update category/merchant across multiple transactions |
| GET | `/api/analytics/monthly` | Split-adjusted monthly spend by category + income + investments. Params: `months` (1–24, default 6) |
| GET | `/api/analytics/subscriptions` | Recurring charge detection — merchants with ≥3 occurrences at consistent intervals |
| GET | `/api/analytics/fees` | Fees and interest from statement summaries + individual fee/interest transactions |
| GET | `/api/shared-transactions` | Transactions that have active splits |
| POST | `/api/splits/settle` | Mark a split as settled |
| GET / POST | `/api/participants` | List participants; POST to create (with optional `email`) |
| GET | `/api/participants/[id]/balance` | Net balance owed by/to a specific participant |
| GET | `/api/participants/balances` | All participant balances |
| GET / POST | `/api/rules` | List or create rules |
| PATCH / DELETE | `/api/rules/[id]` | Update or delete a rule |
| POST | `/api/rules/apply` | Run all enabled rules against all transactions; returns `{matched, transactions_affected}` |
| GET / POST | `/api/budgets` | List budgets for a month (`?month=YYYY-MM`); upsert budget |
| DELETE | `/api/budgets/[id]` | Delete a budget |
| GET | `/api/merchants` | Merchant name autocomplete suggestions |
| GET | `/api/me` | Current user info derived from `X-Forwarded-User` header |
| GET / POST | `/api/tags` | List or create tags |
| PATCH / DELETE | `/api/tags/[id]` | Update or delete a tag |

---

## Ingestion Pipeline

```
Paperless-NGX
  └─ documents tagged "Bank Statement" + "Credit Card" (without "cc-processor")
       │
       ▼
  N8N workflow — polls every 5 minutes (workflow ID: FysADdFwEtwONQl4)
       │
       ├─ Duplicate check: SELECT WHERE paperless_doc_id = <id>
       │    └─ Already processed → skip, mark in Paperless
       │
       ├─ Download PDF binary from Paperless API
       │
       ├─ Gemini 2.5 Flash — PDF → structured JSON
       │    responseSchema: { summary: {...}, transactions: [...] }
       │    timeout: 180s, retryOnFail: 3×, delay: 30s
       │
       ├─ Parse & normalise
       │    account_number: strip spaces
       │    bank_name: title-case
       │    FX rate: fetch live from open.er-api.com if non-AUD
       │
       ├─ Statement exists? (bank + account + billing_end_date)
       │    └─ Duplicate → skip, mark in Paperless
       │
       ├─ New bank? → Slack approval gate (human confirms before insert)
       │
       ├─ Lookup account_owner_mappings → resolve owner_id (default: 1 = "Me")
       │
       ├─ INSERT statements + transactions
       │
       ├─ Google Calendar reminder for payment_due_date (credit cards)
       │
       └─ Paperless: PATCH document to add "cc-processor" tag
```

N8N workflow JSON: `docker/automation/workflows/cc-statement-processor-paperless.json` in the smarthome repo.

---

## Schema Migrations

Located in `prisma/migrations/`. Applied manually against the running container:

```bash
docker exec postgres-personal psql -U personal -d personal \
  < prisma/migrations/<migration>/migration.sql
```

| Migration | What it adds |
|-----------|-------------|
| `0001_init` | `statements`, `transactions`, `participants` |
| `0002_splits` | `transaction_splits` |
| `0003_owner_segregation` | `owner_id` on statements, `account_owner_mappings`, `email` on participants |
| `0004_tags` | `tags`, `transaction_tags` |
| `0005_rules` | `rules` |
| `0006_budgets` | `budgets` |
| `0007_cashflow` | `amount_aud`, `exchange_rate_to_aud` on transactions; `exchange_rate_to_aud` on statements |

> `paperless_doc_id` on statements and the `uq_statements_paperless_doc_id` index were added directly (not tracked in a migration file).

---

## Deployment

Runs as a Docker container alongside the rest of the home lab stack. Build and deploy:

```bash
# From smarthome repo root
docker compose --env-file docker/common.env --env-file docker/finance/.env \
  -f docker/finance/docker-compose.yml up -d --build
```

The container uses Next.js standalone output. `@prisma/adapter-pg` and `pg` are listed in `serverExternalPackages` in `next.config.ts` to ensure they are included in the standalone bundle.