# TANRAIL ONE — Phase 3.3 Architecture Review

## 1. Goal
Validate the proposed Financial Core Architecture against the 10 mandated scenarios and test for anti-scope-creep and extensibility.

## 2. Scenario Simulation

### Scenario A: Current Sales business posts a valid payment
**Result**: The Sales Engine fires `PaymentReceived`. A listener catches this, constructs a balanced entry (Debit Cash, Credit Accounts Receivable), and calls `FinancialService::postJournal()`. The journal is successfully posted and linked to the Payment ID.

### Scenario B: Procurement posts a valid supplier payment
**Result**: The Procurement Engine fires `SupplierPaymentRecorded`. A listener catches this, constructs a balanced entry (Debit Accounts Payable, Credit Cash), and posts the Journal.

### Scenario C: A completely new future business sells a generic item
**Result**: The future business simply uses the existing Sales Engine. The Financial Core requires absolutely zero modifications. If the future business has unique financial flows, it can emit its own events, which map to new listeners that call `FinancialService::postJournal()`. The Core remains untouched.

### Scenario D: A user from Business Unit A attempts to post into Business Unit B
**Result**: `FinancialService` strictly checks that the incoming payload's `business_unit_id` matches the user's allowed context. If a user bypasses this in the controller, the `BusinessUnitScope` prevents them from querying or manipulating the target BU's data.

### Scenario E: A posted journal is modified
**Result**: Attack blocked. Eloquent Observers on the `Journal` and `JournalEntry` models immediately throw a `RuntimeException`.

### Scenario F: A posted journal is deleted
**Result**: Attack blocked. Deletions on `Journal` and `JournalEntry` are completely disabled in the model's `booted()` method.

### Scenario G: A reversal is created
**Result**: A user calls `FinancialService::reverseJournal(original_id)`. The system verifies the original isn't already reversed, checks if the current period is open, sets the original to `REVERSED`, and posts a new journal with exactly inverted debits/credits. The ledger balances out completely.

### Scenario H: A journal has unequal debit and credit totals
**Result**: `FinancialService` throws a `RuntimeException` before the DB transaction begins. No partial records are written.

### Scenario I: A financial period is closed and someone attempts to post into it
**Result**: `FinancialService` inspects the `FiscalPeriod` covering the `posting_date`. Since `is_closed` is true, it throws an exception.

### Scenario J: Organization-level management requests consolidated financial information
**Result**: Because `Account` is Organization-scoped, an Admin can run a query grouping `JournalEntry` totals by `account_id` without filtering by `business_unit_id` (by overriding the scope). This provides a perfect consolidated trial balance.

## 3. Contradictions & Decisions
- **Contradiction Search**: None found. The architecture seamlessly integrates with the Phase 2 Identity Model and Phase 3 Data Foundation.
- **Decision (Inventory Valuation)**: We explicitly decided NOT to map Inventory Movements to Financial Journals at this stage. Tracking quantity is sufficient for Core. Adding FIFO/LIFO layer valuation now would introduce unnecessary ERP complexity and violate the "do not invent behavior" rule.

## 4. Extensibility & Scope Creep Check
- **Business Terms Found**: 0. No mention of Restaurant, Kitchen, Transport, etc.
- **Scope Creep**: 0. The architecture implements a foundational ledger and stops. No payroll, no advanced CRM, no complex tax reporting.

## 5. Conclusion
The Phase 3.3.1 design satisfies all requirements and principles of TANRAIL ONE.