PCMS Outlook Add-In – Backend (Clean Architecture, .NET 8)

This repository contains the backend API implementation for the PCMS Outlook Add-In, built using .NET 8 with Clean Architecture principles. The API acts as a Backend-for-Frontend (BFF) and communicates with downstream PCMS Core APIs.

This service does not own a database. Instead, it focuses on:

• Authentication & Authorization (Advanced Identity / Keycloak JWT)
• Calling PCMS Core APIs and Microsoft Graph API
• Data mapping & transformation
• Caching (Redis cache-aside pattern)
• Document processing via Azure Service Bus
• Logging (Serilog + Application Insights)
• Resilience (Polly)
• Global exception handling
• DTO validation (FluentValidation)
• API Versioning

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Clean Architecture Overview

This project follows standard 4-layer Clean Architecture:

Presentation (API)
      ↓
Application (Services & Interfaces)
      ↓
Domain (Models, DTOs, Exceptions, Constants)
      ↓
Infrastructure (External Services, Caching, Auth, Repositories)

Key Rules:

• Domain has zero dependencies.
• Application depends only on Domain.
• Infrastructure implements Application interfaces.
• API references Application + Infrastructure.

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Solution Structure

PCMS.OutlookAddIn.sln
│
├── src/
│   ├── PCMS.OutlookAddIn.Api          → Presentation Layer (Controllers, Middleware, DI, Auth config)
│   ├── PCMS.OutlookAddin.Application  → Application Layer (Services, Interfaces, Mappers, Validators)
│   ├── PCMS.OutlookAddin.Domain       → Domain Layer (Models, DTOs, Exceptions, Constants)
│   ├── PCMS.OutlookAddin.Infrastructure → Infrastructure Layer (HTTP clients, Redis, SQL repos, Graph API, auth)
│   └── PCMS.OutlookAddin.Functions    → Azure Functions (Service Bus document processing)
│
└── tests/
    ├── PCMS.OutlookAddIn.Api.Tests
    ├── PCMS.OutlookAddIn.Application.Tests
    ├── PCMS.OutlookAddin.Domain.Tests
    ├── PCMS.OutlookAddIn.Infrastructure.Tests
    └── PCMS.OutlookAddin.Functions.Tests

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Layer Responsibilities

Layer	Responsibility
API	Controllers, middleware pipeline, DI registration, API versioning, Swagger
Application	Business logic services, interface contracts, mappers, FluentValidation validators
Domain	Models, DTOs, domain exceptions, constants — no external dependencies
Infrastructure	PCMS Core API clients, Redis caching, SQL repositories (Dapper), Microsoft Graph API, Advanced Identity token validation, Service Bus publisher
Functions	Azure Function triggered by Service Bus — fetches email via Graph, posts to PCMS

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Technology Stack

Core Framework

• .NET 8.0
• ASP.NET Core Web API
• C#

Azure Services

• Azure Functions (Isolated Worker) — Service Bus triggered document processing
• Azure Service Bus — Message queuing for async email saving
• Azure Key Vault — Secrets management (connection strings, client secrets)
• Application Insights — Monitoring and telemetry
• Azure Redis Cache — Cache-aside pattern for external API responses

Libraries & Patterns

• API Versioning (Asp.Versioning)
• FluentValidation — Request validation
• Serilog — Structured logging
• Polly — HTTP client resilience (timeouts)
• Dapper — Lightweight SQL data access
• MSAL (Microsoft.Identity.Client) — Graph API token acquisition
• StackExchange.Redis — Redis distributed cache

Testing

• xUnit — Unit testing framework
• Moq — Mocking framework
• FluentAssertions — Assertion library

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Running Locally

Restore dependencies

dotnet restore

Build the solution

dotnet build

Run the API project

dotnet run --project src/PCMS.OutlookAddIn.Api

Run unit tests

dotnet test

Swagger UI is available at https://localhost:{port}/swagger when running in Development or QA environments.

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Test Coverage

Project	Tests
Domain.Tests	159
Application.Tests	249
Api.Tests	407
Infrastructure.Tests	486
Functions.Tests	44
Total	1,345