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/*
 * #%L
 * **********************************************************************
 * ORGANIZATION  :  Pi4J
 * PROJECT       :  Pi4J :: Java Examples
 * FILENAME      :  GpioInputPollingExample.java
 *
 * This file is part of the Pi4J project. More information about
 * this project can be found here:  https://pi4j.com/
 * **********************************************************************
 * %%
 * Copyright (C) 2012 - 2021 Pi4J
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */

import com.pi4j.io.gpio.*;
import com.pi4j.platform.PlatformAlreadyAssignedException;
import com.pi4j.util.CommandArgumentParser;
import com.pi4j.util.Console;
import com.pi4j.util.ConsoleColor;

/**
 * This example code demonstrates how to perform simple GPIO
 * pin state reading using a polling loop on the Raspberry Pi.
 *
 * @author Robert Savage
 */
public class GpioInputPollingExample {

    /**
     * [ARGUMENT/OPTION "--pin (#)" | "-p (#)" ]
     * This example program accepts an optional argument for specifying the GPIO pin (by number)
     * to use with this GPIO listener example. If no argument is provided, then GPIO #1 will be used.
     * -- EXAMPLE: "--pin 4" or "-p 0".
     *
     * [ARGUMENT/OPTION "--pull (up|down|off)" | "-l (up|down|off)" | "--up" | "--down" ]
     * This example program accepts an optional argument for specifying pin pull resistance.
     * Supported values: "up|down" (or simply "1|0").   If no value is specified in the command
     * argument, then the pin pull resistance will be set to PULL_UP by default.
     * -- EXAMPLES: "--pull up", "-pull down", "--pull off", "--up", "--down", "-pull 0", "--pull 1", "-l up", "-l down".
     *
     * @param args
     * @throws InterruptedException
     * @throws PlatformAlreadyAssignedException
     */
    public static void main(String[] args) throws InterruptedException, PlatformAlreadyAssignedException {

        // create Pi4J console wrapper/helper
        // (This is a utility class to abstract some of the boilerplate code)
        final Console console = new Console();

        // state tracking variable
        PinState lastKnownState = null;

        // print program title/header
        console.title("<-- The Pi4J Project -->", "GPIO Input Polling Example");

        // allow for user to exit program using CTRL-C
        console.promptForExit();

        // create gpio controller
        final GpioController gpio = GpioFactory.getInstance();

        // by default we will use gpio pin #01; however, if an argument
        // has been provided, then lookup the pin by address
        Pin pin = CommandArgumentParser.getPin(
                RaspiPin.class,    // pin provider class to obtain pin instance from
                RaspiPin.GPIO_01,  // default pin if no pin argument found
                args);             // argument array to search in

        // by default we will use gpio pin PULL-UP; however, if an argument
        // has been provided, then use the specified pull resistance
        PinPullResistance pull = CommandArgumentParser.getPinPullResistance(
                PinPullResistance.PULL_UP,  // default pin pull resistance if no pull argument found
                args);                      // argument array to search in

        // provision gpio pin as an input pin
        final GpioPinDigitalInput input = gpio.provisionDigitalInputPin(pin, "MyInput", pull);

        // set shutdown state for this pin: unexport the pin
        input.setShutdownOptions(true);

        // prompt user that we are ready
        console.println("Successfully provisioned [" + pin + "] with PULL resistance = [" + pull + "]");
        console.emptyLine();
        console.box("Polling for GPIO state changes.", "The GPIO input pin states will be displayed below.");
        console.emptyLine();

        // display pin state
        while(!console.exiting()) {
            if(lastKnownState != input.getState()) {
                lastKnownState = input.getState();
                console.println(" [" + input.toString() + "] digital state is: " + ConsoleColor.conditional(
                        lastKnownState.isHigh(), // conditional expression
                        ConsoleColor.GREEN,        // positive conditional color
                        ConsoleColor.RED,          // negative conditional color
                        input.getState()));
                Thread.sleep(100);
            }
        }

        // stop all GPIO activity/threads by shutting down the GPIO controller
        // (this method will forcefully shutdown all GPIO monitoring threads and scheduled tasks)
        gpio.shutdown();
    }
}