# Doc Service — Status

## What it is

PDF document management microservice. Handles upload, storage, async AI-powered extraction, tagging, categorisation, and retrieval of PDF documents on a per-user basis.

Port: `8001` (internal only, not exposed to host). All traffic arrives via the backend proxy (`backend/app/routers/documents_proxy.py`), which injects the authenticated `x-user-id` header.

Database: shared PostgreSQL instance, isolated via `alembic_version_doc_service` Alembic version table. Storage: `/data/documents/` (Docker named volume `doc_data`).

---

## Current functionality

### Document lifecycle

1. `POST /documents/upload` — validate PDF, persist file to `/data/documents/{user_id}/{doc_id}.pdf`, create DB row with `status=pending`, enqueue background extraction
2. Background task: extract text with `pdfplumber` → POST to ai-service `/chat` → parse JSON result → update `status=done` (or `failed`)
3. AI extracts: `title`, `document_type`, `tags`, `suggested_categories`, plus domain fields (vendor, customer, dates, amounts, etc.) into `extracted_data` (JSON string)

### Endpoints

| Method | Path | Description |
|--------|------|-------------|
| `POST` | `/documents/upload` | Upload PDF; returns 202 with initial doc row |
| `GET` | `/documents` | Paginated list with filters and sort |
| `GET` | `/documents/{id}` | Single document |
| `GET` | `/documents/{id}/status` | Lightweight status poll |
| `GET` | `/documents/{id}/download` | Stream file bytes |
| `DELETE` | `/documents/{id}` | Delete document and file |
| `PATCH` | `/documents/{id}/type` | Update document type |
| `PATCH` | `/documents/{id}/tags` | Replace tag list (dedup, preserve order) |
| `PATCH` | `/documents/{id}/title` | Update editable title |
| `GET` | `/documents/categories` | List all categories for the user |
| `POST` | `/documents/categories` | Create a category |
| `POST` | `/documents/{id}/categories/{cat_id}` | Assign category to document |
| `DELETE` | `/documents/{id}/categories/{cat_id}` | Remove category from document |

### Pagination & filtering (`GET /documents`)

Query params:

| Param | Default | Notes |
|-------|---------|-------|
| `page` | 1 | ≥ 1 |
| `per_page` | 20 | 1–100 |
| `sort` | `created_at` | `created_at`, `processed_at`, `filename`, `title`, `file_size`, `status`, `document_type` |
| `order` | `desc` | `asc` \| `desc` |
| `status` | — | filter by status string |
| `document_type` | — | filter by document type |
| `search` | — | case-insensitive ILIKE on `title`, `filename`, `tags`, `document_type` |

Response: `{ items: [...], total: N, page: N, pages: N }`

### Document schema

```
id            UUID
user_id       string (from x-user-id header)
filename      original filename
title         AI-suggested editable title (nullable)
file_size     bytes
status        pending | processing | done | failed
document_type AI-classified type (nullable)
extracted_data JSON string — all AI-extracted fields
tags          JSON array string — editable tags
error_message set if status=failed
created_at    upload timestamp
processed_at  when extraction finished
categories    many-to-many via category_assignments
```

### AI extraction (via ai-service)

Prompt sends the first 50 000 chars of extracted text. Expected JSON response includes:
- `title` — suggested human-readable title
- `document_type` — invoice / bill / receipt / order / expense / revenue / unknown
- `tags` — list of keyword tags
- `suggested_categories` — list of category names to suggest in the UI
- Domain fields: `vendor`, `customer`, `invoice_number`, `due_date`, `total_amount`, `currency`, etc.

### Config (runtime, persisted to shared volume)

`/config/doc_service_config.json`:
```json
{ "documents": { "max_pdf_bytes": 20971520 } }
```
Env override: `DOC_MAX_PDF_MB`

### Database migrations

| Revision | Description |
|----------|-------------|
| 0001 | Initial schema (documents, categories, category_assignments) |
| 0002 | Add `title` column to documents |

Run automatically on container start via `alembic upgrade head`.

---

## Architecture

```
backend (proxy)  →  doc-service:8001
                        │
                   documents.py router
                        │
               ┌────────┴────────┐
          upload              list/get/patch
               │
        save_upload()        pdfplumber extraction
               │                    │
         Document(status=pending)   ai_client.classify_document()
               │                    │
        BackgroundTask         ai-service:8010/chat
               │                    │
         process_document()   JSON result → update doc row
```

---

## Known limitations / not implemented

- **Re-process** — no endpoint to re-trigger AI extraction on an existing document (e.g. after changing the AI model or prompt)
- **Advanced field-level search** — `search` param matches text fields via ILIKE but does not query into `extracted_data` JSON (e.g. filter by `vendor` or `due_date`)
- **Bulk operations** — no bulk category assign/remove, no bulk delete
- **Document sharing** — documents are strictly per-user; no group sharing yet
- **Pagination in categories** — categories are returned as a full list (no pagination)
- **File type** — only PDF supported
- **Concurrent uploads** — no rate limiting per user

---

## Future work

- [ ] `POST /documents/{id}/reprocess` — re-run AI extraction
- [ ] Advanced filter: query `extracted_data` JSON fields (vendor, due_date, amount) — requires PostgreSQL `jsonb` column or indexed virtual columns
- [ ] Bulk operations endpoint
- [ ] Document sharing via groups (blocked on groups/permissions system in backend)
- [ ] Support additional file types (images via OCR, DOCX)
- [ ] Rate limiting on upload endpoint
- [ ] Soft delete with restore
- [ ] Category rename / delete with cascade handling