Controls PiFace Control And Display through a web browser. Returns the status of the switches and the LCD text in a JSON string. Set the text with GET variables and send various commands.

simplewebcontrolcad.py

"""
simplewebcontrolcad.py
Controls PiFace Control And Display through a web browser. Returns the status of the switches and the LCD text in a JSON string. Set the text with GET
variables and send various commands.

Copyright (C) 2013 Thomas Preston <thomas.preston@openlx.org.uk> simplewebcontrol.py
Copyright (C) 2014 Thomas Macpherson-Pope  <thomas.macpherson-pope@openlx.org.uk> simplewebcontrolcad.py


This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
"""
import sys
import subprocess
import http.server
import urllib.parse
import pifacecad


JSON_FORMAT = "{{'input_port': {input}, 'text_value': {text_value}, 'cursor_position': {cursor_position}}}"
DEFAULT_PORT = 8000
LCD_TEXT_GET_STRING = "lcd_text"
COMMAND_GET_STRING = "command"
GET_IP_CMD = "hostname -I"



class PiFaceWebHandler(http.server.BaseHTTPRequestHandler):

    """Handles PiFace web control requests"""
    def do_GET(self):
        output_value = "NULL"
        switches_value = self.pifacecad.switch_port.value

        # parse the query string
        qs = urllib.parse.urlparse(self.path).query
        query_components = urllib.parse.parse_qs(qs)
        # set the output
        if LCD_TEXT_GET_STRING in query_components:
            new_text_value = query_components[LCD_TEXT_GET_STRING][0]
            output_value = self.set_text_value(new_text_value)

        elif COMMAND_GET_STRING in query_components:
            command = query_components[COMMAND_GET_STRING][0]
            self.action_command(command)

        cursor_position = self.pifacecad.lcd.get_cursor()
        # reply with JSON
        self.send_response(200)
        self.send_header("Content-type", "application/json")
        self.end_headers()
        self.wfile.write(bytes(JSON_FORMAT.format(
            input=switches_value,
            text_value=output_value,
            cursor_position=cursor_position
        ), 'UTF-8'))

    def set_text_value(self, new_text_value):
        """Sets the text value to new_value."""
        print("Setting text port to {}.".format(new_text_value))
        port_value = new_text_value

        self.pifacecad.lcd.write(port_value)
        return port_value

    def action_command(self, command):
        print("Actioning command")
        if command == "backlight_on":
            self.pifacecad.lcd.backlight_on()
        elif command == "backlight_off":
            self.pifacecad.lcd.backlight_off()
        elif command == "blink_off":
            self.pifacecad.lcd.blink_off()
        elif command == "blink_on":
            self.pifacecad.lcd.blink_on()
        elif command == "clear":
            self.pifacecad.lcd.clear()
        elif command == "cursor_off":
            self.pifacecad.lcd.cursor_off()
        elif command == "cursor_on":
            self.pifacecad.lcd.cursor_on()
        elif command == "display_off":
            self.pifacecad.lcd.display_off()
        elif command == "display_on":
            self.pifacecad.lcd.display_on()
        elif command == "home":
            self.pifacecad.lcd.home()
        else:
            print(command + " is not an implemented command")


def get_my_ip():
    """Returns this computers IP address as a string."""
    ip = subprocess.check_output(GET_IP_CMD, shell=True).decode('utf-8')[:-1]
    return ip.strip()


if __name__ == "__main__":
    # get the port
    if len(sys.argv) > 1:
        port = int(sys.argv[1])
    else:
        port = DEFAULT_PORT

    # set up PiFace Digital
    PiFaceWebHandler.pifacecad = pifacecad.PiFaceCAD()

    print("Starting simple PiFace web control at:\n\n"
          "\thttp://{addr}:{port}\n\n"
          "Set text with:\n\n"
          "\thttp://{addr}:{port}/?lcd_text=Hello World\n"
          "Send commands with:\n\n"
          "\thttp://{addr}:{port}/?command=your_command\n\n"
          "Commands include:\n"
          "\tbacklight_off\n"
          "\tbacklight_on\n"
          "\tblink_off\n"
          "\tblink_on\n"
          "\tclear\n" 
          "\tdisplay_off\n"
          "\tdisplay_on\n"
          "\thome\n"
          .format(addr=get_my_ip(), port=port))
    PiFaceWebHandler.pifacecad.lcd.backlight_on()
    # run the server
    server_address = ('', port)
    try:
        httpd = http.server.HTTPServer(server_address, PiFaceWebHandler)
        httpd.serve_forever()
    except KeyboardInterrupt:
        print('^C received, shutting down server')
        httpd.socket.close()