# TANRAIL ONE — Phase 3.2.2 Implementation Report

## 1. Overview
The Core Inventory Data Foundation has been successfully implemented according to the Phase 3.2 architectural blueprint. The implementation guarantees strict data isolation by Business Unit, enforces pessimistic locking on transactions, and respects the Human Decision of **STRICT REJECTION** for negative stock.

## 2. Implemented Components

### Models & Migrations
- `InventoryLocation`: Scoped strictly by `Branch`.
- `StockBalance`: Tracks physical quantity with a compound unique index on `[inventory_location_id, item_id]`.
- `StockMovement`: The immutable ledger capturing every quantity shift.
- `StockTransfer`: Facilitates internal transfers.

### Enums
- `MovementType`: `RECEIVE`, `ISSUE`, `TRANSFER`, `ADJUST`
- `TransferStatus`: `PENDING`, `IN_TRANSIT`, `COMPLETED`, `CANCELLED`

### Security Scopes & Policies
- **`InventoryScope`**: A unified Global Scope ensuring `StockBalance`, `StockMovement`, and `StockTransfer` are restricted to the active context's Business Unit via their relationship to `Item`. `InventoryLocation` is scoped via `Branch`.
- **`InventoryLocationPolicy`**, **`StockMovementPolicy`**, **`StockTransferPolicy`**: Policies preventing unauthorized cross-BU manipulation.
- Movements explicitly block `update()` and `delete()` in the policy.

### Core Engine
- **`InventoryService`**: Contains atomic methods (`receive`, `issue`, `transfer`, `adjust`).
- All methods operate within `DB::transaction()` utilizing `$balance->lockForUpdate()` to eliminate concurrency race conditions.

## 3. Negative Stock Policy Implementation
As mandated, `available_stock < requested_issue` throws a hard Exception from within the locked database transaction. No negative balance can ever be recorded.

## 4. Test Results
- **Inventory Tests Added:** 8 explicit tests targeting strict rejections, immutability, data constraints, adjustments, and cross-BU leakage.
- **Regression Tests:** Full system test ran successfully. 37/37 tests passed.

## 5. Architectural Decisions
- Stock adjustments do not use a separate model; they simply insert an `ADJUST` MovementType with a mandatory `reason`.
- No separate Item table was created; `StockBalance` seamlessly uses the existing Phase 3.1 `Item` model.

## 6. Risks & Unresolved Issues
- None at this time. The foundation strictly conforms to the architecture.