SignBridge uses Flask-SQLAlchemy with a single models.py to define the data layer, and Flask-Migrate to manage schema evolution against a PostgreSQL database.

Model Introduction

Learn how models are structured and used in the application.

Introduction to models

ERD Diagram

View the entity relationship diagram for the database schema.

Entity Relationship Diagram

Flask-Migrate Introduction

Learn how database migrations work with Flask-Migrate.

Introduction to Flask-Migrate

Running migrations

Step-by-step guide for creating and applying migrations.

How to run migrations

PostgreSQL Configuration

Configure PostgreSQL for production and deployment environments.

PostgreSQL Setup

SQLite for Local Development

Use SQLite for lightweight local development and testing.

SQLite for Local Development

Seeding Initial Data

Populate the database with default or sample application data.

Seeding Initial Data

SQLAlchemy Queries

Learn how to create and execute queries using SQLAlchemy.

Making Queries with SQLAlchemy

Blueprints¶

SignBridge has the concept of blueprints to encapsulate the logic responsible for processing a user’s request and returning a response. The application is divided into the following blueprints: main, auth, call, user, admin, help, and errors.

Blueprint reference: main | auth | call | user | admin | help | error

Templates¶

The template layer provides a Jinja2-based syntax for rendering the information to be presented to the user. SignBridge templates are organised around a shared base.html and blueprint-specific subdirectories.

Template Overview

Learn the basics of working with templates in the application.

Template Overview

styles.css Reference

Explore the available CSS styles and design utilities.

styles.css Reference

Forms¶

SignBridge uses Flask-WTF for all form handling, with form classes defined in each blueprint’s forms.py module.

Form class reference: auth/forms.py | call/forms.py | user/forms.py | main/forms.py | admin/forms.py

Authentication¶

SignBridge provides full user lifecycle management — registration, login, and email-based password reset — alongside a token-based REST API authentication system.

Overview: Authentication overview | Login & registration flows | Password reset by email
Tokens: api/tokens.py | Token generation & revocation | Protecting API routes
Email: auth/email.py | core/email.py | Email template reference

The REST API¶

SignBridge exposes a REST API under the api/ blueprint for programmatic access to users, rooms, and tokens.

Endpoint reference: API endpoint reference
Authentication: Authentication
How-to: How-to guides

The sign language model¶

SignBridge ships with a MobileNet-based Sri Lanka Sign Language (SLSL) classifier that runs client-side via TensorFlow.js. Model files live in static/models/.

Overview: How the model works
Architecture: MobileNet model architecture | Input preprocessing |
Customisation: Adding new sign classes | Retraining guide
Help pages: SLSL chart | Video tutorial page

The development process¶

Learn about the various components and tools that support local development of SignBridge.

Configuration: config.py overview |
App factory: app/__init__.py | extensions.py
Logging: Logging setup
Static files: CSS overview | JS module overview

Testing¶

SignBridge’s test suite is built with pytest, covering models, authentication flows, the REST API, room logic, and end-to-end Selenium tests.

Introduction: Running the test suite | conftest.py
Test module reference: test_models.py | test_auth.py | test_api.py | test_rooms.py | test_selenium.py

Deployment¶

Overview: Deployment overview | Pre-deployment checklist
WSGI: Gunicorn configuration | Nginx as reverse proxy
Socket.IO: Deploying with eventlet / gevent |
Database: PostgreSQL setup & running migrations |

Security¶

Security is highly important in a real-time video application, and SignBridge provides several layers of protection.

Indices and Search¶

The SignBridge project¶

Design: Architecture overview | ERD diagram | GitHub repository
SignBridge over time: Changelog | About this documentation