Loan Management System (LMS) API

A production-grade, high-concurrency, multi-tenant financial engine built with .NET 9. This backend controls the lifecycle of short-term loans, automated interest/VAT snapshotting, multi-tier audit records, and live system logging.

---

🏗️ Architecture Design (Clean Architecture)

The system is decoupled into four explicit layout layers to protect domain integrity and enforce the separation of concerns:

• Domain: Independent layer holding system core objects (POCOs), Domain Enums (LoanStatus), and structural entity models.
• Application: Contains structural Data Transfer Objects (DTOs), processing contracts (IAuditService, IExcelService), and security engines.
• Infrastructure: Holds concrete framework implementations (ApplicationDbContext), multi-tenant token extractors (CurrentTenantService), real-time pipelines, background tasks (ChronosWorker), and reporting dependencies.
• Api: Web interface, request controllers, middleware processing pipelines, and explicit OpenApi/Scalar mappings.

---

🛠️ Core Technology Stack

• Framework: .NET 9.0 (Web API)
• Database Engine: Microsoft SQL Server
• ORM: Entity Framework Core 9.0
• Real-Time Transmission: ASP.NET Core SignalR (WebSockets)
• Cryptographic Hashing: BCrypt.Net-Next
• Reporting Engine: ClosedXML (OpenXML wrapper for Excel generation)
• Interactive API Docs: Microsoft.AspNetCore.OpenApi + Scalar API
• Containerization Engine: Docker & Docker Compose

---

⚡ Key System Rules & Principles

1. Multi-Tenancy (Data Isolation): Automated tenant filtering via EF Core HasQueryFilter tied to the current user's authenticated OrganizationId claim. Cross-tenant data leaks are structurally blocked at the database execution layer.
2. Financial Snapshotting: Interest and VAT values are permanently copied from the Organization row settings into the Loan row at the exact moment of contract creation to insulate historical ledger records against future configuration adjustments.
3. Soft Delete Integration: Data records are never physically stripped from the persistent storage. Rows are updated with an IsDeleted = true flag, stamped with the admin tracking ID (DeletedById), and automatically ignored by active query streams.
4. Descriptive Auditing: The IAuditService records explicit "Before" and "After" state data variations into the database rather than system codes, ensuring human-readable, compliant ledger reviews.

---

🏁 Getting Started

📋 Prerequisites

• .NET 9.0 SDK
• Docker Desktop or local Microsoft SQL Server instance
• Modern Terminal (PowerShell / Bash)

💾 Local Configuration

Update the configuration variables in LoanManagementSystem.Api/appsettings.json to link to your runtime database instance:

{
  "ConnectionStrings": {
    "DbConnection": "Server=YOUR_SERVER;Database=LMSDB;Trusted_Connection=True;TrustServerCertificate=True;"
  },
  "Jwt": {
    "Key": "PCuLYf7bWtAOvXejfHO5IuIhmWCMyzr7Bz3RKHuYf1d0VChhRIAbSvksszyuJx6H+VHxwp2PosDOgVF2uv3YXg==",
    "Issuer": "LoanManagementSystem",
    "Audience": "LoanManagementSystemUsers",
    "DurationInMinutes": 60
  }
}

⌨️ CLI Commands Execution

From the root folder containing your .sln file:

1. Restore dependencies and verify compilation:

dotnet restore
dotnet build

2. Generate a new database schema migration (if updates are introduced):

dotnet ef migrations add NameOfYourMigration --project LoanManagementSystem.Infrastructure --startup-project LoanManagementSystem.Api

3. Directly apply database updates:

dotnet ef database update --project LoanManagementSystem.Infrastructure --startup-project LoanManagementSystem.Api

---

🐳 Docker Deployment

The platform is configured with an automated multi-stage build script that orchestrates both the .NET API application and a fresh SQL Server container workspace instantly.

To spin up the entire backend container environment, run the following command inside the root folder:

docker-compose up --build

• Scalar API Interactive Panel: Navigate to http://localhost:5000/scalar/v1 inside your browser once compilation completes.
• Raw Document Endpoint: Extract your schema mapping data straight from http://localhost:5000/openapi/v1.json.

---

📡 API Endpoint Index

##NOTE!!!:Latest API full documentation is on docs/v1.json

Auth Routing

• POST /api/auth/login - Authenticates administrative or officer profiles. Returns signature JWT Bearer data token.

Branch Tenant Routing

• GET /api/organizations - Yields total master list of branches (Strict Access: System Root Branch Only).
• POST /api/organizations - Onboards a new operational tenant organization into the cloud ecosystem.
• PUT /api/organizations/{id} - Updates live baseline settings (VAT/Default Rates) for a branch footprint.

Workforce Directory Routing

• GET /api/users - Extracts active personnel rosters attached to the current company context.
• POST /api/users - Introduces a new employee context (Passwords run automatic underlying BCrypt salt hashes).
• PUT /api/users/{id}/reset-password - Overwrites employee access hashes during account lockouts.
• GET /api/users/export - Compiles a highly formatted, striped Excel list of total company staff profiles.

Capital Allocation & Ledger Routing

• GET /api/loans - Extracts tenant-isolated, open financial loans.
• POST /api/loans/auto-issue - Evaluates customer emails, auto-creates profiles if unrecognized, and secures the active loan under one operational transaction.
• PUT /api/loans/{id}/default - Manually shifts overdue lending assets into a frozen default state for collections tracking.
• GET /api/loans/export - Streams a polished, board-ready financial report excel spreadsheet down to the local machine.
• POST /api/payments - Records customer repayments. Automatically moves the master loan state into Paid if the ledger math clears the current TotalAmountDue.

WebSockets Hub Access Paths

• /hubs/notifications - Broadcasts generalized operational shifts to active staff nodes.

• /hubs/audit - Feeds a highly responsive security dashboard monitor with immediate ActivityLog and UserLoginLog data rows right after they commit to the core tables. AND MORE.

  PLEASE NOTE: if youre having issues with running the project unzip the LMS folder thats the back-up.