webapp.py

webapp.py WebApp

This document describes the detailed step-by-step process of how the webapp.py script works, including the specific methods, classes, and functions used at each step.

Initialization and Start of WebApp

Importing Modules

• The webapp.py script imports several modules, including standard libraries (threading, http.server, socketserver, logging, sys, signal, os, json, subprocess) and custom modules (Logger, shared_data).

Global Variables

• should_exit: A flag used to signal when the server should shut down.

Logger Initialization

• The logger is initialized to capture events and errors.

CustomHandler Class

__init__ Method

• Purpose: Initializes the request handler with shared data.
• Key Steps:
  1. Initialize Shared Data:
     • Sets up self.shared_data with shared data.
  2. Call Parent Constructor:
     • Calls the parent constructor to complete initialization.

log_message Method

• Purpose: Overrides the default logging behavior to suppress logging of GET requests.
• Key Steps:
  1. Log Non-GET Requests:
     • Logs messages that are not GET requests.

do_GET Method

• Purpose: Handles GET requests to serve HTML files, configuration data, and the display image.
• Key Steps:
  1. Serve HTML Files:
     • Calls serve_file for index.html and config.html.
  2. Serve Configuration Data:
     • Calls serve_current_config to serve the current configuration as JSON.
  3. Restore Default Configuration:
     • Calls restore_default_config to reset configurations to default.
  4. Scan Wi-Fi Networks:
     • Calls scan_wifi to scan for available Wi-Fi networks.
  5. Serve Display Image:
     • Calls serve_image to serve the current display image.

do_POST Method

• Purpose: Handles POST requests to save configuration data and connect to Wi-Fi.
• Key Steps:
  1. Save Configuration:
     • Calls save_configuration to save posted configuration data.
  2. Connect to Wi-Fi:
     • Calls connect_wifi to connect to a specified Wi-Fi network.

serve_file Method

• Purpose: Serves an HTML file with dynamic content injection.
• Key Steps:
  1. Read and Serve File:
     • Reads the file, injects dynamic content, and serves it.

serve_current_config Method

• Purpose: Serves the current configuration as JSON.
• Key Steps:
  1. Read and Serve Configuration:
     • Reads the configuration file and sends it as JSON.

restore_default_config Method

• Purpose: Restores the default configuration and saves it to JSON.
• Key Steps:
  1. Restore and Save Configuration:
     • Resets configurations to default, saves them, and serves the updated configuration.

serve_image Method

• Purpose: Handles requests to serve the display image.
• Key Steps:
  1. Read and Serve Image:
     • Reads and serves the current display image file.

scan_wifi Method

• Purpose: Scans for available Wi-Fi networks and returns the results as JSON.
• Key Steps:
  1. Scan Networks:
     • Runs the iwlist command to scan for Wi-Fi networks.
  2. Parse and Serve Results:
     • Parses the scan results and serves them as JSON.

parse_scan_result Method

• Purpose: Parses the scan output from iwlist to extract SSIDs.
• Key Steps:
  1. Extract SSIDs:
     • Parses the scan output to extract and return a list of SSIDs.

connect_wifi Method

• Purpose: Connects to a specified Wi-Fi network using the provided SSID and password.
• Key Steps:
  1. Read Credentials:
     • Reads the SSID and password from the POST request.
  2. Update Network Configuration:
     • Updates the NetworkManager configuration with the new credentials.
  3. Connect to Network:
     • Runs the nmcli command to connect to the network.

update_nmconnection Method

• Purpose: Updates the preconfigured.nmconnection file with the new SSID and password.
• Key Steps:
  1. Write Configuration:
     • Writes the new network configuration to the file.
  2. Set Permissions:
     • Sets the correct permissions on the configuration file.
  3. Reload Connection:
     • Reloads the NetworkManager connections.

save_configuration Method

• Purpose: Saves the configuration posted from the client.
• Key Steps:
  1. Read and Update Configuration:
     • Reads the posted configuration data, updates the current configuration, and saves it.
  2. Reload Configuration:
     • Reloads the configuration to apply the changes.

WebThread Class

__init__ Method

• Purpose: Initializes the web server thread with the specified handler class and port.
• Key Steps:
  1. Initialize Attributes:
     • Sets up self.shared_data, self.port, and self.handler_class.

run Method

• Purpose: Runs the web server in a separate thread.
• Key Steps:
  1. Start Server:
     • Starts the web server and handles requests until should_exit is set to True.
  2. Handle Port Conflicts:
     • If the port is already in use, increments the port number and retries.
  3. Graceful Shutdown:
     • Ensures the server is closed properly when shutting down.

shutdown Method

• Purpose: Shuts down the web server gracefully.
• Key Steps:
  1. Shutdown Server:
     • Shuts down and closes the server.

handle_exit_web Function

Purpose

• Handles exit signals to shut down the web server cleanly.
• Key Steps:
  1. Set Exit Flag:
     • Sets should_exit to True to signal the server to stop.
  2. Shutdown Server:
     • Calls shutdown on the web server thread and waits for it to finish.

Execution Flow when webapp.py is Run

Step 1: Initialize Web Thread

• An instance of the WebThread class is created with the CustomHandler and the specified port.

Step 2: Start Main Loop

• The main loop is started in a separate thread to handle web server requests.

Step 3: Handle Requests

• The web server handles GET and POST requests, serving HTML files, configuration data, and images, and processing configuration updates and Wi-Fi connections.

Step 4: Handle Exit Signal

• When an exit signal is received, the handle_exit_web function sets the exit flag and shuts down the server cleanly.

Summary

The webapp.py script manages the web interface of the e-ink display, serving HTML interface pages and the EPD image, handling GET and POST requests, and running a multithreaded web server for concurrent request handling. It ensures a clean exit on receiving system signals and captures events and errors for maintainability and ease of debugging.