# Configurable Multi-Tenant LMS — Domain-Driven Design (DDD)
*System Architecture & Bounded Context Specifications*

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## 1. Domain Map & Ubiquitous Language

To support hundreds of lenders dynamically, all domain concepts are bounded and read from configuration metadata rather than code-defined defaults.

### Ubiquitous Language Definitions
*   **Lender (Tenant)**: The owner of the lending products. Identified by `lender_id`.
*   **Product**: A financial model offered by a Lender (e.g. "Personal Loan - Tier 1 Salaried").
*   **Product Configuration**: The metadata that defines rules, workflows, fees, and engines for a Product.
*   **Amortization Schedule (RPS)**: The collection of repayment installments (Principal + Interest + Charges) mapped over time.
*   **Allocation Sequence**: The priority order in which received payments are distributed across outstanding balances (e.g. Interest -> Principal -> Charges).
*   **Charge Entry**: An individual fee applied to a loan (e.g. Processing Fee, Cheque Bounce Fee, Restructure Fee).
*   **NPA (Non-Performing Asset)**: A loan state determined by consecutive days past due (DPD) exceeding a product-specific threshold.

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## 2. Bounded Contexts

```
┌────────────────────────────────────────────────────────────────────────┐
│                        Multi-Tenant LMS Bounded Contexts               │
├────────────────────────────────────────────────────────────────────────┤
│  ┌────────────────────────┐            ┌────────────────────────────┐  │
│  │ Configuration Context  │            │        Loan Context        │  │
│  │ - Lenders & Products   ├───────────►│ - Amortization Schedules   │  │
│  │ - Dynamic Rule Sets    │            │ - Loan Accounts & States   │  │
│  └───────────┬────────────┘            └─────────────┬──────────────┘  │
│              │                                       │                 │
│              ▼                                       ▼                 │
│  ┌────────────────────────┐            ┌────────────────────────────┐  │
│  │ Repayment & Allocation │            │       Charge Context       │  │
│  │ - IPC/PIC Allocation   │◄───────────┤ - Fixed/Percentage Fees    │  │
│  │ - Payment Receipts     │            │ - Penalties & Grace Days   │  │
│  └───────────┬────────────┘            └─────────────┬──────────────┘  │
│              │                                       │                 │
│              ▼                                       ▼                 │
│  ┌────────────────────────┐            ┌────────────────────────────┐  │
│  │ Settlement Context     │            │        NPA Context         │  │
│  │ - Foreclosures         │◄───────────┤ - DPD Tracking             │  │
│  │ - Maker-Checker Entry  │            │ - Bucket Classification    │  │
│  └────────────────────────┘            └────────────────────────────┘  │
└────────────────────────────────────────────────────────────────────────┘
```

### Context Details

#### A. Configuration Context (Central Source of Truth)
*   **Aggregate Roots**: `Lender`, `Product`, `ProductConfiguration`.
*   **Entities & Value Objects**: `ChargeMaster`, `AllocationPriority`, `DisbursementScheduleConfig`, `InterestConfig`.
*   **Responsibilities**: Defines the parameters governing calculation methods, allocation hierarchies, fee matrices, and state transition workflows.
*   **Temporal Rules**: Enforces version control using `version`, `effective_from`, and `effective_to`.

#### B. Loan Context
*   **Aggregate Roots**: `Loan`.
*   **Entities & Value Objects**: `RepaymentSchedule` (Installment), `AmortizationParameters`.
*   **Responsibilities**: Generates schedules on disbursement, computes due dates, and manages loan status transitions (e.g. active -> foreclosure_pending -> closed).

#### C. Repayment & Allocation Context
*   **Aggregate Roots**: `Payment`.
*   **Entities & Value Objects**: `PaymentAllocation`, `AllocationSequence`.
*   **Responsibilities**: Records receipts from payment gateways (Razorpay, Paytm) and dynamically splits funds across interest, principal, and penalties according to the configured rule (IPC, PIC, etc.).

#### D. Charge Context
*   **Aggregate Roots**: `ChargeEntry`.
*   **Entities & Value Objects**: `PenaltyRule`, `WaiverEntry`.
*   **Responsibilities**: Calculates and applies charges (Fixed / Percentage) on triggers (NACH bounce, cheque bounce, restructuring) and manages grace periods.

#### E. Settlement & Foreclosure Context
*   **Aggregate Roots**: `SettlementEntry`.
*   **Entities & Value Objects**: `ForeclosureCalculation`, `MakerCheckerApproval`.
*   **Responsibilities**: Computes total outstanding, applies foreclosure penalties, and enforces checker approvals before closing accounts.

#### F. NPA Context
*   **Aggregate Roots**: `NPAClassification`.
*   **Entities & Value Objects**: `DPDBucket`.
*   **Responsibilities**: Evaluates loan portfolios daily, tracks DPD counts, and transitions loans to NPA status when thresholds are breached.