---
phase: 01-foundation
plan: 01
subsystem: database
tags: [sqlite, python, argparse, hatchling, textual]

# Dependency graph
requires: []
provides:
  - SQLite schema for rooms, categories, containers, items
  - DB connection module with path resolution (get_db_path, get_connection, init_db)
  - CLI entry point with --db flag and POSSESSION_DB env var support
  - pip-installable Python package via pyproject.toml
affects: [02-core-ui, 03-features]

# Tech tracking
tech-stack:
  added: [hatchling, textual>=0.47.0, sqlite3 (stdlib)]
  patterns: [Path(__file__).parent for resource location, sqlite WAL mode, foreign_keys PRAGMA]

key-files:
  created:
    - possession/__init__.py
    - possession/__main__.py
    - possession/db.py
    - possession/schema.sql
    - pyproject.toml
  modified: []

key-decisions:
  - "requires-python set to >=3.9 (not >=3.11 as planned) because only Python 3.9 is available in the environment; Optional[str] used instead of str | None union syntax"
  - "sqlite_sequence system table is present in DB alongside the 4 schema tables (created by SQLite AUTOINCREMENT) - this is expected and not a defect"
  - "Path(str(path)) used in get_connection to ensure compatibility with sqlite3.connect on Python 3.9"

patterns-established:
  - "Path resolution precedence: --db CLI arg > POSSESSION_DB env var > ~/.possession/possession.db"
  - "DB init is idempotent: CREATE TABLE IF NOT EXISTS means re-running never destroys data"
  - "schema.sql located via Path(__file__).parent to avoid hardcoded absolute paths"

requirements-completed: [STOR-01, STOR-02]

# Metrics
duration: 3min
completed: 2026-02-24
---

# Phase 1 Plan 01: Foundation Summary

**SQLite-backed Python package with 4-table schema (rooms/categories/containers/items) and configurable DB path via CLI flag, env var, or default ~/.possession location**

## Performance

- **Duration:** 3 min
- **Started:** 2026-02-24T06:28:11Z
- **Completed:** 2026-02-24T06:31:46Z
- **Tasks:** 2
- **Files modified:** 5

## Accomplishments

- pip-installable `possession-terminal` package with hatchling build system
- SQLite schema for all 4 entities with proper FK constraints and ON DELETE CASCADE/SET NULL semantics
- DB initialization module with WAL mode, foreign key enforcement, and idempotent schema application
- CLI entry point that resolves DB path from --db flag, POSSESSION_DB env var, or default ~/.possession/possession.db

## Task Commits

Each task was committed atomically:

1. **Task 1: Python package scaffold and CLI entry point** - `55f50f6` (feat)
2. **Task 2: SQLite schema and DB initialization module** - `3201eda` (feat)

**Plan metadata:** `c1c0e20` (docs: complete plan)

## Files Created/Modified

- `pyproject.toml` - Package definition with hatchling build, possession-terminal name, textual dependency, and `possession` script entry point
- `possession/__init__.py` - Package marker with `__version__ = "0.1.0"`
- `possession/__main__.py` - CLI entry point: argparse --db flag, POSSESSION_DB env var fallback, calls init_db(), prints "Database ready: {path}"
- `possession/schema.sql` - CREATE TABLE IF NOT EXISTS for rooms, categories, containers, items with FK references and ON DELETE behaviors
- `possession/db.py` - Three public functions: get_db_path() (path resolution), get_connection() (WAL + FK pragmas), init_db() (full initialization returning resolved path)

## Decisions Made

- **requires-python = ">=3.9"** instead of plan's ">=3.11" — only Python 3.9.6 is available on this machine. Code uses `Optional[str]` instead of `str | None` union syntax which requires Python 3.10+. Functionally identical.
- **ON DELETE CASCADE for containers** — if a room is deleted, its containers are removed automatically. Prevents orphaned containers.
- **ON DELETE SET NULL for items** — if a room, container, or category is deleted, item references become NULL (item is preserved but loses its location/category). Better UX than cascading deletion of items.
- **UNIQUE(name, room_id) on containers** — a room can have at most one container with a given name, but the same name can exist in different rooms.

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Bug] requires-python lowered from 3.11 to 3.9**
- **Found during:** Task 1 (package scaffold)
- **Issue:** Plan specified `requires-python = ">=3.11"` but only Python 3.9.6 is available in the environment. Using 3.11+ syntax would prevent running the code.
- **Fix:** Set `requires-python = ">=3.9"` in pyproject.toml; used `Optional[str]` from `typing` module instead of `str | None` union syntax (requires Python 3.10+)
- **Files modified:** pyproject.toml, possession/db.py
- **Verification:** `python3 -m possession` runs successfully, all tests pass
- **Committed in:** 55f50f6 and 3201eda (task commits)

---

**Total deviations:** 1 auto-fixed (1 environment adaptation)
**Impact on plan:** Minor version requirement change. All planned functionality delivered identically. Code runs successfully on Python 3.9.

## Issues Encountered

- Plan's automated verification script used exact set equality (`tables == {'rooms','containers','items','categories'}`) which fails because SQLite automatically creates `sqlite_sequence` when AUTOINCREMENT columns exist. Verified correct behavior using subset check — all 4 required tables are present.

## User Setup Required

None - no external service configuration required. Database file is created automatically on first run at `~/.possession/possession.db`.

## Next Phase Readiness

- DB layer is complete and verified — all Phase 2 features can import from `possession.db`
- `init_db(path)` is the single entry point for DB initialization; path resolution is centralized
- Schema supports all planned data relationships: rooms contain containers, items reference all three entities (room, container, category) via nullable FK
- No blockers for Phase 2 (core TUI) development

## Self-Check: PASSED

- FOUND: pyproject.toml
- FOUND: possession/__init__.py
- FOUND: possession/__main__.py
- FOUND: possession/db.py
- FOUND: possession/schema.sql
- FOUND: .planning/phases/01-foundation/01-01-SUMMARY.md
- FOUND: commit 55f50f6 (Task 1)
- FOUND: commit 3201eda (Task 2)

---
*Phase: 01-foundation*
*Completed: 2026-02-24*
