System Architecture
===================

High-Level Architecture
-----------------------

.. mermaid::

   graph TB
       subgraph Clients
           WEB[Web Dashboard<br/>Central Ops / Finance / Procurement / OEM Reporting]
           MOB[Mobile App<br/>Field Teams]
           OEM_PORTAL[OEM Portal<br/>Lead Submission & Reports]
           CUST[Customer Interface<br/>SMS / WhatsApp / Email]
       end

       subgraph API Layer
           GW[API Gateway<br/>JWT Auth + Rate Limiting]
           API[Django REST Framework<br/>api/v1/]
       end

       subgraph Django Apps
           ACC[accounts]
           LED[leads]
           SRV[surveys]
           INS[installations]
           PRO[procurement]
           FIN[finance]
           REP[reporting]
           NOT[notifications]
           EMG[emergency]
       end

       subgraph Data Layer
           DB[(PostgreSQL)]
           MEDIA[Media Storage<br/>S3 / MinIO]
           CACHE[Redis<br/>Cache + Celery Broker]
       end

       subgraph External Services
           SMS[SMS Gateway]
           WA[WhatsApp API]
           EMAIL[Email Service]
           PAY[Payment Gateway<br/>UPI / Bank Transfer]
       end

       WEB --> GW
       MOB --> GW
       OEM_PORTAL --> GW
       GW --> API
       API --> ACC
       API --> LED
       API --> SRV
       API --> INS
       API --> PRO
       API --> FIN
       API --> REP
       API --> NOT
       API --> EMG
       ACC --> DB
       LED --> DB
       SRV --> DB
       INS --> DB
       PRO --> DB
       FIN --> DB
       REP --> DB
       NOT --> DB
       EMG --> DB
       SRV --> MEDIA
       INS --> MEDIA
       NOT --> SMS
       NOT --> WA
       NOT --> EMAIL
       FIN --> PAY
       API --> CACHE

Technology Stack
----------------

.. list-table::
   :header-rows: 1
   :widths: 30 70

   * - Component
     - Technology
   * - Backend Framework
     - Django 5.x + Django REST Framework
   * - Database
     - PostgreSQL 16
   * - Task Queue
     - Celery + Redis
   * - Media Storage
     - S3-compatible (AWS S3 or MinIO for local dev)
   * - Authentication
     - JWT (SimpleJWT)
   * - API Documentation
     - drf-spectacular (OpenAPI 3.0)
   * - Notifications
     - SMS gateway, WhatsApp Business API, SMTP
   * - Payments
     - UPI integration, bank transfer APIs
   * - Containerization
     - Docker + Docker Compose
   * - Package Manager
     - uv

App Dependency Graph
--------------------

.. mermaid::

   graph LR
       accounts --> |"no deps"|accounts
       leads --> accounts
       surveys --> leads
       surveys --> accounts
       installations --> surveys
       installations --> accounts
       procurement --> installations
       finance --> procurement
       finance --> accounts
       reporting --> leads
       reporting --> surveys
       reporting --> installations
       notifications --> accounts
       emergency --> accounts
       emergency --> surveys
       emergency --> installations