---
phase: 04-folders-sharing-quotas-document-ux
plan: 03
type: execute
wave: 2
depends_on:
  - "04-01"
  - "04-02"
files_modified:
  - backend/services/audit.py
  - backend/api/folders.py
  - backend/api/documents.py
  - backend/main.py
autonomous: true
requirements:
  - FOLD-01
  - FOLD-02
  - FOLD-03
  - FOLD-04
  - FOLD-05

must_haves:
  truths:
    - "User can create, rename, delete, and list folders via REST API"
    - "Deleting a non-empty folder cascade-deletes all documents (MinIO + DB) and decrements quota atomically"
    - "GET /api/folders/{id} returns a breadcrumb array from root to the requested folder"
    - "Document list supports sort by name, date, size via ?sort= query param"
    - "Full-text search via ?q= uses plainto_tsquery on documents.extracted_text GIN index"
    - "write_audit_log() helper is available for all Phase 4 handlers"
    - "Duplicate folder name under same parent returns 409"
  artifacts:
    - path: "backend/services/audit.py"
      provides: "write_audit_log() async helper — flush-not-commit, never-raises"
      exports: ["write_audit_log"]
    - path: "backend/api/folders.py"
      provides: "FOLD-01..05 endpoints: POST /api/folders, GET /api/folders, GET /api/folders/{id}, PATCH /api/folders/{id}, DELETE /api/folders/{id}, PATCH /api/documents/{id}/folder"
    - path: "backend/main.py"
      provides: "folders router registered; all Phase 4 routers wired"
  key_links:
    - from: "backend/api/folders.py"
      to: "backend/services/audit.py"
      via: "write_audit_log() call after successful folder operations"
      pattern: "write_audit_log"
    - from: "backend/api/folders.py"
      to: "backend/db/models.py"
      via: "Folder, Document, Quota ORM models"
      pattern: "from db.models import Folder"
    - from: "backend/api/documents.py"
      to: "backend/api/folders.py"
      via: "PATCH /api/documents/{id}/folder uses same ownership assertion as documents.py"
      pattern: "get_regular_user"
---

<objective>
Implement the audit service helper and all folder backend endpoints (FOLD-01..05).
This plan introduces write_audit_log() which subsequent plans (shares, proxy, audit viewer) depend on.

Purpose: Deliver the complete folder CRUD and document organization API.
Output: backend/services/audit.py + backend/api/folders.py + main.py router registration.
</objective>

<execution_context>
@$HOME/.claude/get-shit-done/workflows/execute-plan.md
@$HOME/.claude/get-shit-done/templates/summary.md
</execution_context>

<context>
@.planning/phases/04-folders-sharing-quotas-document-ux/04-CONTEXT.md
@.planning/phases/04-folders-sharing-quotas-document-ux/04-PATTERNS.md
@.planning/phases/04-folders-sharing-quotas-document-ux/04-RESEARCH.md
@backend/api/documents.py
@backend/db/models.py
@backend/deps/auth.py
@backend/deps/db.py
</context>

<interfaces>
<!-- Key interfaces the executor must replicate exactly. Extracted from codebase. -->

<!-- From backend/deps/auth.py:
async def get_regular_user(...)  -> User:  # raises 403 for admin role
async def get_current_admin(...) -> User:  # raises 403 for non-admin
-->

<!-- From backend/db/models.py Folder model (lines ~120-145 approximately):
class Folder(Base):
    __tablename__ = "folders"
    id: Mapped[uuid.UUID]            # primary key, default uuid4
    user_id: Mapped[uuid.UUID]       # FK to users.id
    parent_id: Mapped[Optional[uuid.UUID]]  # FK to folders.id self-reference, nullable
    name: Mapped[str]                # String, not null
    created_at: Mapped[datetime]
    # UniqueConstraint("user_id", "parent_id", "name") — triggers 409 on duplicate
-->

<!-- Ownership assertion pattern (from backend/api/documents.py):
doc = await session.get(Document, uid)
if doc is None or doc.user_id != current_user.id:
    raise HTTPException(status_code=404, detail="Document not found")
-->

<!-- Atomic quota decrement (CASE WHEN for SQLite compat, established in STATE.md):
await session.execute(
    text(
        "UPDATE quotas SET used_bytes = "
        "CASE WHEN used_bytes > :delta THEN used_bytes - :delta ELSE 0 END "
        "WHERE user_id = :uid"
    ),
    {"delta": total_bytes, "uid": str(current_user.id)},
)
-->
</interfaces>

<tasks>

<task type="auto" tdd="true">
  <name>Task 1: Create backend/services/audit.py — write_audit_log() helper</name>
  <files>backend/services/audit.py</files>
  <read_first>
    backend/services/storage.py — read the entire file; extract the import pattern for async service modules and how AsyncSession is used; note the module-level logger pattern
    backend/db/models.py — search for the AuditLog class definition; read it fully to confirm attribute names: event_type, user_id, actor_id, resource_id, ip_address, metadata_ (ORM attribute; DB column name is "metadata" per CLAUDE.md note)
  </read_first>
  <behavior>
    - write_audit_log() called with all fields: session, event_type (str), user_id (Optional[uuid.UUID]), actor_id (Optional[uuid.UUID]), resource_id (Optional[uuid.UUID]), ip_address (Optional[str]), metadata_ (Optional[dict])
    - Function creates AuditLog ORM instance, adds to session, calls session.flush() (NOT commit)
    - Function NEVER raises — exception caught, logged as warning, then swallowed
    - AuditLog.metadata_ ORM attribute (not "metadata") used per CLAUDE.md note about reserved SQLAlchemy attribute name
  </behavior>
  <action>
    Create backend/services/audit.py.

    Imports: `from __future__ import annotations`, `import logging`, `import uuid`, `from typing import Optional`, `from sqlalchemy.ext.asyncio import AsyncSession`, `from db.models import AuditLog`.

    Module-level: `logger = logging.getLogger(__name__)`.

    Implement async def write_audit_log with signature: `(session: AsyncSession, event_type: str, user_id: Optional[uuid.UUID], actor_id: Optional[uuid.UUID], resource_id: Optional[uuid.UUID], ip_address: Optional[str], metadata_: Optional[dict] = None) -> None`.

    Body: try block that creates `AuditLog(event_type=event_type, user_id=user_id, actor_id=actor_id, resource_id=resource_id, ip_address=ip_address, metadata_=metadata_)`, calls `session.add(entry)`, then `await session.flush()`. Except block: `except Exception as exc: logger.warning("audit log write failed: %s", exc)`. No re-raise.

    Critical: use `session.flush()` not `session.commit()` — this is a hard architectural requirement (D-14).
  </action>
  <verify>
    <automated>cd /Users/nik/Documents/Progamming/document_scanner/backend && python -c "from services.audit import write_audit_log; import inspect; sig = inspect.signature(write_audit_log); print(list(sig.parameters.keys()))"</automated>
  </verify>
  <acceptance_criteria>
    - backend/services/audit.py exists and is importable
    - write_audit_log is an async function (grep: `async def write_audit_log`)
    - Function uses `await session.flush()` not `await session.commit()` (grep: `session.flush` present; `session.commit` absent from this file)
    - Function has a bare `except Exception` that logs and does NOT re-raise (grep: `logger.warning` inside except block)
    - `python -c "from services.audit import write_audit_log"` exits 0
  </acceptance_criteria>
  <done>write_audit_log() is importable; uses flush-not-commit; never raises.</done>
</task>

<task type="auto" tdd="true">
  <name>Task 2: Create backend/api/folders.py — all FOLD-01..05 endpoints</name>
  <files>backend/api/folders.py, backend/main.py</files>
  <read_first>
    backend/api/documents.py — read the entire file; extract the import block, UUID parse pattern (try/except ValueError → 404), ownership assertion pattern (resource is None or resource.user_id != current_user.id → 404), atomic quota UPDATE text(), and the list_documents handler signature for the sort/search extension
    backend/main.py — read the entire file; identify the include_router section to know where to add the folders router
    backend/db/models.py — read the Folder class and Document class fully to confirm all column names (parent_id, folder_id FK on Document)
  </read_first>
  <behavior>
    POST /api/folders:
    - Body: {name: str, parent_id: Optional[str] = null}
    - Auth: get_regular_user (403 for admin per CLAUDE.md)
    - If parent_id provided: assert parent folder exists and belongs to current_user (→ 404 if not)
    - Create Folder(user_id=current_user.id, name=name, parent_id=parsed_parent_uuid or None)
    - Catch IntegrityError → 409 "A folder with that name already exists here" (Pitfall 6)
    - Call write_audit_log after commit: event_type="folder.created", resource_id=folder.id, metadata_={"name": folder.name}
    - Return 201 with folder JSON

    GET /api/folders (list top-level): returns folders where user_id=current_user.id and parent_id IS NULL

    GET /api/folders/{id}: returns folder JSON + breadcrumb array
    - Breadcrumb: iterative Python walk up parent chain (not WITH RECURSIVE — avoids SQLite incompatibility in unit tests)
    - Walk: start from folder, load parent via session.get(Folder, folder.parent_id), repeat until parent_id is None
    - Breadcrumb array: [{id: str, name: str}, ...] from root to current folder (root first)
    - Response: {id, name, parent_id, user_id, created_at, breadcrumb: [...]}

    PATCH /api/folders/{id}: rename folder
    - Body: {name: str}
    - Assert folder.user_id == current_user.id → 404 if not
    - Catch IntegrityError → 409 on duplicate name
    - Call write_audit_log: event_type="folder.renamed"

    DELETE /api/folders/{id}: delete folder
    - Assert folder.user_id == current_user.id → 404 if not
    - Collect all documents in this folder only (direct children — parent is not responsible for sub-folder docs via cascade; D-03 says cascade-delete but the UI only deletes the selected folder tree, not sub-folders of sub-folders; use WITH RECURSIVE via sqlalchemy text() for PostgreSQL; in test environment without PostgreSQL the recursive CTE will be skipped via a try/except fallback to direct children only)
    - Use WITH RECURSIVE CTE (via text()) to find all folder IDs in subtree (Pitfall 1) — wrap in try/except OperationalError for SQLite test compat, fallback collects only direct children
    - Sum size_bytes of all collected documents
    - Atomic quota decrement with CASE WHEN pattern
    - Delete MinIO objects best-effort (try/except per each object, per PATTERNS.md Pattern 2)
    - Delete all documents via ORM, then delete folder via session.delete(folder)
    - Call write_audit_log: event_type="folder.deleted", metadata_={"doc_count": len(docs), "name": folder.name}
    - Return 204

    PATCH /api/documents/{id}/folder (move document):
    - Body: {folder_id: Optional[str]} — null = move to root (no folder)
    - Assert doc.user_id == current_user.id → 404 if not
    - If folder_id provided: assert target folder.user_id == current_user.id → 404 if not (Pitfall from CONTEXT.md)
    - Update doc.folder_id and commit
    - Return 200 with updated doc JSON

    Extension to GET /api/documents list endpoint (in documents.py, not folders.py):
    - Add query params: sort (str, default "date"), order (str, default "desc"), folder_id (Optional[str]), q (Optional[str])
    - sort=name → order_by(Document.filename), sort=size → order_by(Document.size_bytes), sort=date → order_by(Document.created_at)
    - order=asc → .asc(), order=desc → .desc()
    - folder_id provided → add .where(Document.folder_id == parsed_uuid)
    - q provided and len >= 2: add FTS where clause using func.to_tsvector("english", func.coalesce(Document.extracted_text, "")).op("@@")(func.plainto_tsquery("english", q)) — import sqlalchemy.func
    - Add is_shared subquery: select(Share.document_id).where(Share.owner_id == current_user.id).scalar_subquery(); add Document.id.in_(shared_subq).label("is_shared") to select
  </behavior>
  <action>
    Create backend/api/folders.py with APIRouter(prefix="/api/folders", tags=["folders"]).

    Imports: `from __future__ import annotations`, `import uuid`, `from typing import Optional`, `from fastapi import APIRouter, Depends, HTTPException, Query, Request, status`, `from pydantic import BaseModel`, `from sqlalchemy import select, text, delete, func`, `from sqlalchemy.exc import IntegrityError, OperationalError`, `from sqlalchemy.ext.asyncio import AsyncSession`, `from db.models import Document, Folder, Quota, Share`, `from deps.auth import get_regular_user`, `from deps.db import get_db`, `from storage import get_storage_backend`, `from services.audit import write_audit_log`.

    Pydantic models: FolderCreate(name: str, parent_id: Optional[str] = None), FolderRename(name: str), DocumentMove(folder_id: Optional[str] = None).

    Implement all five endpoints as specified in the behavior block. For the WITH RECURSIVE CTE, use:
    `await session.execute(text("WITH RECURSIVE subtree AS (SELECT id FROM folders WHERE id = :root_id AND user_id = :uid UNION ALL SELECT f.id FROM folders f JOIN subtree s ON f.parent_id = s.id WHERE f.user_id = :uid) SELECT id FROM subtree"), {"root_id": str(folder.id), "uid": str(current_user.id)})`
    Wrap in try/except OperationalError and fallback to `select(Document).where(Document.folder_id == folder.id, Document.user_id == current_user.id)`.

    For the ip_address extraction pattern (per Pitfall 5): `ip_address = request.headers.get("X-Forwarded-For") or (request.client.host if request.client else None)`.

    After creating backend/api/folders.py, modify backend/main.py: add `from api.folders import router as folders_router` and `app.include_router(folders_router)` in the routes section alongside the other routers.

    Also extend backend/api/documents.py: add sort, order, folder_id, q query params to the list_documents handler. Add import for func and Share. Add the is_shared subquery to the select. Add FTS where clause when q is present. Do NOT break existing tests — these are additive changes.
  </action>
  <verify>
    <automated>cd /Users/nik/Documents/Progamming/document_scanner/backend && python -m pytest tests/test_folders.py -x -v --no-header 2>&1 | tail -30</automated>
  </verify>
  <acceptance_criteria>
    - backend/api/folders.py exists with all five endpoint functions (grep: `async def create_folder`, `async def list_folders`, `async def get_folder`, `async def rename_folder`, `async def delete_folder`)
    - backend/api/folders.py contains PATCH /api/documents/{id}/folder endpoint (grep: `move_document` or equivalent)
    - backend/main.py includes folders router (grep: `folders_router`)
    - `python -c "from api.folders import router"` exits 0
    - All folder ownership assertions use 404 not 403 (grep: `status_code=404` in folders.py; no `status_code=403`)
    - IntegrityError caught and returns 409 (grep: `IntegrityError` and `409` in folders.py)
    - write_audit_log called after folder create, rename, delete (grep: `write_audit_log` appears at least 3 times)
    - test_create_folder and test_rename_folder turn green (xpass) or remain xfail — no FAILED
    - `cd backend && python -m pytest tests/ -x --no-header 2>&1 | grep -E "^FAILED"` returns nothing
  </acceptance_criteria>
  <done>Folders API endpoints are implemented; document list has sort/search; all existing tests still pass.</done>
</task>

</tasks>

<threat_model>
## Trust Boundaries

| Boundary | Description |
|----------|-------------|
| Client → POST /api/folders | Untrusted name/parent_id input; Pydantic validates types; IntegrityError → 409 |
| Client → DELETE /api/folders/{id} | Untrusted folder_id path parameter; UUID parse → 404; ownership assertion → 404 |
| Client → GET /api/documents?q= | Untrusted search query; plainto_tsquery is injection-safe (parameterized via SQLAlchemy func) |
| Client → PATCH /api/documents/{id}/folder | Untrusted doc_id + folder_id; both validated via ownership assertion |

## STRIDE Threat Register

| Threat ID | Category | Component | Disposition | Mitigation Plan |
|-----------|----------|-----------|-------------|-----------------|
| T-04-03-01 | Elevation of Privilege | POST/PATCH/DELETE /api/folders | mitigate | get_regular_user dep: admin role returns 403; regular user passes through |
| T-04-03-02 | Information Disclosure | GET /api/documents?q= (FTS scope) | mitigate | FTS query MUST include Document.user_id == current_user.id filter; plainto_tsquery is parameterized (no injection) |
| T-04-03-03 | Tampering | DELETE /api/folders/{id} cascade-delete | mitigate | Ownership assertion on folder before cascade; atomic quota decrement (CASE WHEN); MinIO deletion is best-effort (does not abort primary operation on failure) |
| T-04-03-04 | Information Disclosure | folder IDOR via path parameter | mitigate | All folder endpoints assert folder.user_id == current_user.id → 404 (not 403 — prevents attacker enumeration of folder IDs) |
| T-04-03-05 | Information Disclosure | PATCH /api/documents/{id}/folder cross-user target folder | mitigate | Both document ownership AND target folder ownership asserted → 404 on mismatch |
| T-04-03-06 | Tampering | folder name UniqueConstraint violation surfaced as 500 | mitigate | IntegrityError caught → 409 Conflict with clear error message (Pitfall 6) |
| T-04-SC | Tampering | npm/pip/cargo installs | accept | No new packages installed in this plan |
</threat_model>

<verification>
1. Endpoint smoke: `cd backend && python -m pytest tests/test_folders.py -v --no-header 2>&1 | tail -30`
2. Full suite: `cd backend && python -m pytest -v --no-header 2>&1 | grep -E "FAILED|ERROR"` — expect empty
3. Import check: `cd backend && python -c "from api.folders import router; from services.audit import write_audit_log; print('OK')"`
4. Security grep: `grep -n "get_regular_user\|status_code=404\|IntegrityError\|write_audit_log\|plainto_tsquery" backend/api/folders.py`
</verification>

<success_criteria>
- write_audit_log() is importable from services.audit; uses session.flush(); never raises
- All five folder endpoints exist in api/folders.py; router registered in main.py
- Document list endpoint supports sort, folder_id, q params; is_shared field returned
- test_folders.py tests turn from xfail to xpass (green) or remain xfail — zero FAILED
- Full pytest suite is green
</success_criteria>

<output>
Create `.planning/phases/04-folders-sharing-quotas-document-ux/04-03-SUMMARY.md` when done.
</output>