> ## Documentation Index
> Fetch the complete documentation index at: https://methodscenter.mintlify.app/llms.txt
> Use this file to discover all available pages before exploring further.

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  If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback via POST to:
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# Architecture

## System Overview

* **Runtime Stack:** Django REST Framework application served from Docker containers, backed by PostgreSQL, with analytics powered by a custom modelling module.
* **Hosting Pattern:** Container stack deployed on AWS EC2, fronted by Nginx for TLS termination, caching, and static asset delivery.
* **Automation:** Cron-driven background jobs create surveys, execute modelling pipelines, and issue alerts without blocking API requests.
* **Observability:** Application logs streamed via Docker, PostgreSQL introspection through pgAdmin, and health endpoints ready for integration into CloudWatch or Datadog.

## Infrastructure Topology

```mermaid  theme={null}
flowchart LR
    A[Student Browser] --> D[Internet]
    B[Lecturer Browser] --> D
    C[Researcher Tools] --> D
    D --> E[Route 53 DNS]
    E --> F[AWS Security Group]
    F --> G[EC2 Instance]

    subgraph EC2[EC2 Instance]
        H[Nginx Reverse Proxy] --> I[Django App Server]
        I --> J[PostgreSQL Database]
        K[pgAdmin] -.-> J
        L[django-cron] -.-> I
        M[Analytics Engine] -.-> I
        I --> M
    end

    G --> H
```

## Full Stack Request Flow

```mermaid  theme={null}
flowchart LR
    A[Next.js Frontend<br/>Vercel] -->|HTTPS API Calls| B[Internet]
    B --> C[Route 53 DNS]
    C --> D[AWS Security Group]
    D --> E[Nginx Reverse Proxy<br/>EC2]
    E --> F[Django REST API<br/>Docker Container]
    F --> G[PostgreSQL<br/>Database]

    H[Background Jobs<br/>django-cron] -.-> F
    F -.-> I[Analytics Engine<br/>Kalman Filter]
```

### Nginx Responsibilities

* Terminate HTTPS and enforce secure headers (HSTS, CSP).
* Reverse proxy API traffic to `web` container on port `8000`.
* Serve cached static files from `/var/www/luna/static/` for low latency.
* Expose `/admin` and `/api` under the same domain for simplicity; consider subdomains when scaling.

## Application Layer

| Layer                 | Responsibilities                                                  | Key Components                   |
| --------------------- | ----------------------------------------------------------------- | -------------------------------- |
| **API Gateway**       | REST routing, serializers, authentication, permission enforcement | API endpoints, DRF views         |
| **Domain Layer**      | User management, course modules, surveys, and forms               | Core business logic, data models |
| **Modelling Layer**   | Kalman filter computations, analytics persistence, exports        | Statistical analysis engine      |
| **Cron & Scheduling** | Periodic job orchestration for surveys and analytics              | Background job scheduler         |

## Request Lifecycle Flow

```mermaid  theme={null}
sequenceDiagram
    participant Student as Student
    participant Nginx as Nginx Reverse Proxy
    participant API as Django API
    participant DB as PostgreSQL
    participant Cron as Cron Runner
    participant Model as Modelling Engine

    Student->>Nginx: POST /api/modules/{id}/surveys
    Nginx->>API: Forward request
    API->>DB: Create survey record (status=ACTIVE)
    API-->>Student: 201 Created + survey metadata

    Cron->>API: Trigger weekly survey generation job
    API->>DB: Insert new survey records
    Cron->>Model: Invoke modelling task
    Model->>DB: Update results with smoothed metrics
    Model-->>API: Model status reported for dashboards
```

## Data Model Overview

### Entity Relationship Diagram

```mermaid  theme={null}
erDiagram
    User ||--o{ Student : "extends as"
    User ||--o{ Module : "owns/teaches"
    University ||--|{ Module : "offers"
    University ||--|{ Faculty : "contains"
    Module ||--o{ Enrollment : "has"
    Student ||--o{ Enrollment : "participates in"
    Module ||--o{ Survey : "generates"
    Student ||--o{ Survey : "completes"
    Form ||--o{ FormResponse : "collects"
    Student ||--o{ FormResponse : "submits"

    User {
        string email
        string role
        string university
    }

    Student {
        string demographics
        string language
        string background
    }

    Module {
        string name
        string code
        string semester
        date schedule
        string status
    }

    Enrollment {
        date enrolled_date
        string status
    }

    Survey {
        int sequence_number
        json responses
        string completion_status
        date submitted_at
    }

    Form {
        string name
        json structure
    }

    FormResponse {
        json answers
        date submitted_at
        string status
    }
```

### Core Entities

**University**

* Represents educational institutions
* Contains multiple faculties and departments
* Supports multi-tenant platform architecture

**User**

* Email-based authentication system
* Three roles: Student, Lecturer, Administrator
* Linked to university affiliation

**Student**

* Extended user profile for student participants
* Stores demographic and academic background
* Tracks language preferences and financial support

**Module (Course)**

* Represents academic courses/subjects
* Configurable semester periods (Winter/Summer)
* Password-protected enrollment system
* Scheduled survey deployment days
* Active/Inactive status management

**Enrollment**

* Links students to their enrolled courses
* Prevents duplicate enrollments
* Tracks enrollment timeline

**Survey**

* Time-series survey instances for longitudinal data collection
* Auto-incremented sequence numbers per student
* Flexible JSON structure for diverse question types
* Completion tracking (Completed/Not Completed)
* Lifecycle status (Active/Archived)

**Form Template**

* Reusable questionnaire blueprints
* JSON-based flexible structure
* Created by lecturers and administrators

**Form Response**

* Student submissions to forms
* Tracks completion status and timestamps
* JSON storage for answers

**Faculty**

* Organizational units within universities
* Groups related departments and programs

## Technology Stack

### Backend Framework

* **Django 4.2.5** - Model-View-Template architecture
* **Django REST Framework 3.14.0** - RESTful API design
* **Custom authentication** - Email-based user system

### Database

* **PostgreSQL** - ACID-compliant relational storage
* **JSON fields** - Flexible survey and form content
* **Database adapter** - psycopg2-binary

### API & Documentation

* **OpenAPI/Swagger** - Interactive API documentation (drf-yasg)
* **CORS support** - Cross-origin resource sharing (django-cors-headers)

### Task Scheduling

* **django-cron** - Periodic job execution
* **Survey automation** - Scheduled deployment system

### Configuration & Deployment

* **Environment management** - python-decouple, python-dotenv
* **Containerization** - Docker, Docker Compose
* **Web server** - Nginx (reverse proxy, SSL termination)

### Cloud Infrastructure

* **Compute** - AWS EC2 instances
* **Deployment** - Dockerized application on EC2
* **Networking** - Nginx reverse proxy with SSL/TLS

## Deployment Architecture

```mermaid  theme={null}
flowchart LR
    A[Internet] --> B[Route 53 DNS]
    B --> C[AWS Security Group]
    C --> D[EC2 Instance]

    subgraph EC2 Instance
        E[Nginx<br/>SSL/TLS] --> F[Luna App<br/>Django]
        F <--> G[PostgreSQL<br/>Database]
    end

    D --> E
```

## Background Processing

1. **Survey Generation** - Runs twice daily; creates upcoming survey records based on module schedule and student enrollment.
2. **Analytics Pipeline** - Ingests completed surveys, executes Kalman smoothing, writes metrics to analytics tables for dashboards.

## Security Architecture

### Authentication & Authorization

* Email-based authentication (no username required)
* Secure password hashing using Django's PBKDF2 algorithm
* Role-based access control (Student, Lecturer, Administrator)
* Session-based authentication framework

### Data Protection

* Environment-based configuration (no hardcoded secrets)
* CORS policy enforcement for API security
* SQL injection prevention via ORM parameterization
* XSS protection through template auto-escaping

### Infrastructure Security

* Container isolation and separation
* Docker bridge network segmentation
* HTTPS/TLS encryption in production (Nginx)
* Database access restricted to internal network

## Related Documentation

* [Overview](./overview.md) - Platform introduction and research context
* [Installation Guide](./installation.md) - Environment setup instructions
* [Student Experience](./student-experience.md) - Student user workflows
* [Lecturer Experience](./lecturer-experience.md) - Lecturer and researcher workflows


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