# AGENTS.md - AI Coding Agent Guidelines

Guidelines for AI coding agents working on BillAI - a microservices bill analysis system.

## Architecture
- `web/` - SvelteKit 5 + TailwindCSS 4 + TypeScript (Frontend Proxy & UI, port 3000)
- `server/` - Go 1.21 + Gin + MongoDB (Main API & Data Storage, port 8080)
- `analyzer/` - Python 3.12 + FastAPI (Data Cleaning & Analysis Service, port 8001)

The SvelteKit frontend acts as a **proxy**: all `/api/*` browser requests are forwarded by
`web/src/routes/api/[...path]/+server.ts` to the Go backend. The browser never contacts Go
directly. `API_URL` env var controls the target (`http://server:8080` in Docker,
`http://localhost:8080` in local dev).

## Build/Lint/Test Commands

### Frontend (web/)
**Working Directory:** `/Users/clz/Projects/BillAI/web`

```bash
npm run dev                              # Start Vite dev server
npm run build                            # Production build (adapter-node)
npm run preview                          # Preview production build
npm run check                            # TypeScript check (svelte-check)
npm run lint                             # Prettier --check + ESLint
npm run format                           # Format with Prettier
npm run test                             # Run all unit tests once (CI mode)
npm run test:unit                        # Run unit tests in watch mode
npx vitest run src/routes/+page.spec.ts  # Run single test file
npx vitest run -t "test name pattern"    # Run tests by name pattern
```

### Backend (server/)
**Working Directory:** `/Users/clz/Projects/BillAI/server`

```bash
go run .                              # Start server
go build -o server .                  # Build binary
go mod tidy                           # Clean dependencies
go test ./...                         # Run all tests
go test ./handler/...                 # Run handler package tests
go test -run TestName ./...           # Run single test function
go test -v ./handler/...              # Verbose test output
```

### Analyzer (analyzer/)
**Working Directory:** `/Users/clz/Projects/BillAI/analyzer`

```bash
python server.py                      # Start FastAPI server directly
uvicorn server:app --reload           # Start with hot reload
pytest                                # Run all tests
pytest test_jd_cleaner.py            # Run single test file
pytest -k "test_name"                # Run test by name pattern
pip install -r requirements.txt      # Install dependencies
```

### Docker
**Working Directory:** `/Users/clz/Projects/BillAI`

```bash
docker-compose up -d --build          # Start/rebuild all services
docker-compose logs -f server         # Follow service logs
docker-compose down                   # Stop all services
```

## Code Style

### General
- **Comments:** Existing comments often use Chinese for business logic explanations. Maintain this
  style where appropriate; English is also acceptable for technical explanations.
- **Conventions:** Follow existing patterns strictly. Do not introduce new frameworks or libraries
  without checking `package.json` / `go.mod` / `requirements.txt`.

### TypeScript/Svelte (web/)
- **Formatting:** Prettier — tabs, single quotes, no trailing commas, printWidth 100,
  `prettier-plugin-svelte`.
- **Naming:** `PascalCase` for types/interfaces/components, `camelCase` for variables/functions.
- **Imports:** Use `$lib` alias for internal imports and `$app/*` for SvelteKit builtins. Never
  use relative paths for lib-level modules.
  ```typescript
  import { browser } from '$app/environment'
  import { goto } from '$app/navigation'
  import { auth } from '$lib/stores/auth'
  import type { UIBill } from '$lib/models/bill'
  import Upload from '@lucide/svelte/icons/upload'
  ```
- **Svelte 5 runes:** Use the new runes API — `$state`, `$derived`, `$effect`, `$props`. Event
  handlers use `onclick={fn}` syntax (not legacy `on:click`).
- **Types:** Define `export interface` for all data models. Frontend models use `camelCase` fields
  (`UIBill`); API responses use `snake_case` (`CleanedBill`). Provide explicit converter functions
  (e.g., `cleanedBillToUIBill`, `uiBillToUpdateBillRequest`) in `web/src/lib/models/bill.ts`.
- **Error Handling:** Check `response.ok`; throw `new Error(\`HTTP ${response.status}\`)` for the
  UI to catch. On 401, call `auth.logout()` and redirect to `/login`.
- **Auth pattern:** `createAuthStore()` factory in `$lib/stores/auth.ts`. Token stored in
  `localStorage` under key `auth`. All API calls go through `apiFetch()` in `$lib/api.ts`, which
  injects `Authorization: Bearer <token>` and handles 401 centrally.
- **Testing:** Vitest + `vitest-browser-svelte` + Playwright. Test files co-located with routes
  as `*.spec.ts`. Use `describe` / `it` / `expect` from vitest, `render` from
  `vitest-browser-svelte`.

### Go Backend (server/)
- **Layer structure:** `handler` (HTTP) → `service` (logic) → `adapter` (external Python service)
  and `repository` (DB) → `model` (structs). Handlers must not contain business logic.
- **Struct tags:** JSON uses `snake_case`. `omitempty` on optional response fields. Use `form` tags
  for query/form binding. Use pointer fields (`*string`) for optional patch request fields. Sensitive
  fields get `json:"-"`.
  ```go
  type CleanedBill struct {
      ID            primitive.ObjectID `bson:"_id,omitempty" json:"id,omitempty"`
      BillType      string             `bson:"bill_type" json:"bill_type"`
  }
  type UpdateBillRequest struct {
      Category *string `json:"category,omitempty"`
  }
  ```
- **Error Handling:** Return `500` for DB/internal errors, `400` for bad requests, `404` for not
  found. Wrap errors with context using `fmt.Errorf("context: %w", err)`. Check
  `err == repository.ErrNotFound` for 404 disambiguation. Use `Result bool` (not `Success`) in
  response envelopes.
  ```go
  if err != nil {
      c.JSON(http.StatusInternalServerError, Response{Result: false, Message: err.Error()})
      return
  }
  ```
- **Response envelope:** Most endpoints: `Result bool`, `Message string`, `Data *T`. Auth endpoints
  use `success bool`, `error string`, `data interface{}`.
- **Interfaces:** Use `adapter.Cleaner` and `repository.BillRepository` interfaces. Access global
  singletons via `adapter.GetCleaner()` and `repository.GetRepository()`.
- **Time:** Use the custom `LocalTime` type (wraps `time.Time`) for all timestamp fields. It
  serializes as `"2006-01-02 15:04:05"` in both JSON and BSON, preserving local time.
- **Soft delete:** Bills are never hard-deleted. All queries must filter `is_deleted: false`.

### Python Analyzer (analyzer/)
- **Style:** PEP 8. `snake_case` for variables, functions, and filenames. `UPPER_CASE` for
  module-level constants. Prefix private module globals with `_`.
- **Type Hints:** Mandatory for all function arguments and return types. Use `Optional[str]` from
  `typing` or `str | None` (Python 3.10+ union syntax).
- **Models:** Use `pydantic.BaseModel` for all API request/response schemas.
  ```python
  class CleanRequest(BaseModel):
      input_path: str
      output_path: str
      year: Optional[str] = None
      bill_type: Optional[str] = "auto"
  ```
- **FastAPI patterns:** Use `HTTPException(status_code=400, detail=message)` for user errors.
  Manage temporary files with `tempfile.NamedTemporaryFile` + `os.unlink` in `finally` blocks.
- **Cleaner classes:** Extend `BaseCleaner(ABC)` from `cleaners/base.py`. Implement `clean()` and
  optionally `reclassify()`. Category inference reads rules from `config/category.yaml` via
  `yaml.safe_load`.
- **Docstrings:** Triple-quoted. Chinese descriptions are common for API endpoint docs.

## Key Patterns

### API Flow
```
Browser → SvelteKit proxy (/api/[...path]/+server.ts)
        → Go server (Gin, AuthRequired middleware)
          → handler → service → adapter.GetCleaner() → HTTP POST to Python FastAPI
                              → repository.GetRepository() → MongoDB
```

### Authentication
- JWT (HS256). Token in `localStorage` under key `auth`.
- Header: `Authorization: Bearer <token>`.
- `middleware.AuthRequired()` wraps all `/api/*` routes except `/api/auth/*`.
- Passwords in `config.yaml` support plaintext or SHA-256 hashed values.
- 401 anywhere → `auth.logout()` + redirect to `/login`.

### File Processing
Upload flow: Upload (ZIP/XLSX) → Extract → Convert to UTF-8 CSV (Python `/convert`) →
Auto-detect bill type → Deduplicate against DB → Clean/normalize (Python `/clean/upload`) →
Save raw + cleaned bills to MongoDB.

Deduplication: raw bills check `transaction_id`; cleaned bills check
`transaction_id + merchant_order_no`. JD bills trigger soft-deletion of overlapping records in
other sources to prevent double-counting.

### Adapter (Go ↔ Python)
`adapter.Cleaner` interface has two implementations: HTTP-based (`adapter/http`, default) and
subprocess-based (`adapter/python`, legacy). Controlled by `ANALYZER_MODE` env var.

## Important Files
| File | Role |
|---|---|
| `web/src/lib/api.ts` | Central API client; `apiFetch()` injects auth and handles 401 |
| `web/src/lib/stores/auth.ts` | Auth state; JWT in localStorage; login/logout/validate |
| `web/src/lib/models/bill.ts` | `UIBill` model + converters to/from API `CleanedBill` shape |
| `web/src/routes/api/[...path]/+server.ts` | SvelteKit proxy to Go backend |
| `server/main.go` | Entry point; wires config, adapters, repository, router |
| `server/config/config.go` | YAML + env config; priority: defaults → config.yaml → env vars |
| `server/router/router.go` | All route definitions and middleware assignment |
| `server/middleware/auth.go` | JWT validation + user context injection |
| `server/handler/upload.go` | Full upload pipeline (extract → convert → clean → store) |
| `server/handler/bills.go` | List/filter bills with pagination and monthly stats |
| `server/model/bill.go` | `RawBill`, `CleanedBill`, `MonthlyStat`; custom `LocalTime` type |
| `server/adapter/adapter.go` | `Cleaner` interface definition |
| `server/repository/repository.go` | `BillRepository` interface (14 persistence methods) |
| `server/repository/mongo/repository.go` | MongoDB implementation with aggregation pipelines |
| `analyzer/server.py` | FastAPI entry point; `/health`, `/clean`, `/convert`, `/detect` routes |
| `analyzer/cleaners/base.py` | `BaseCleaner` ABC; shared filtering and output logic |
| `analyzer/cleaners/alipay.py` | Alipay-specific normalization |
| `analyzer/cleaners/wechat.py` | WeChat-specific normalization |
| `analyzer/cleaners/jd.py` | JD (京东) normalization and 3-level review scoring |
| `analyzer/category.py` | `infer_category()` using YAML keyword rules |
| `analyzer/converter.py` | xlsx→csv (openpyxl), GBK→UTF-8 re-encoding, type detection |
| `server/config.yaml` | Server port, MongoDB URI, JWT settings, user list |
| `docker-compose.yaml` | 5 services: web, server, analyzer, mongodb, mongo-express |