#!/usr/bin/env python3

import RPi.GPIO as gpio
import time
import logging
import re
import subprocess


class amp_controller:
    """Amp controller class to hold certain attributes and methods for automatically
    turning on and off the amplifier.
    """

    SHUTOFF_TIMER_DURATION = 5 * 60  # in seconds
    SHORT_TIMER_DURATION = 60
    CHECK_FREQUENCY = 1  # in seconds
    MPD_LOG_FILE = "/var/log/mpd/mpd.log"
    PULSE_CARD_PATH = "/proc/asound/card0/pcm0p/sub0/status"
    GPIO_PINS = {"Relay": 2, "Phono": 4, "Tape": 14, "CD": 15}

    powered = False
    last_mpd_output = ""

    gpio.setmode(gpio.BCM)
    logging.basicConfig(level=logging.DEBUG)

    def setup_pins(self) -> None:
        """Set all GPIO pins to output."""
        for pin in self.GPIO_PINS.values():
            gpio.setup(pin, gpio.OUT)

    def set_channel(self, channel_name) -> None:
        """Set the channel on the amplifier."""
        pin = self.GPIO_PINS[channel_name]
        gpio.output(pin, True)
        time.sleep(0.5)
        gpio.output(pin, False)

    def power(self, state) -> None:
        """Turn the amplifier on or off via the GPIO pins."""
        if state == "on":
            gpio.output(self.GPIO_PINS["Relay"], True)
            time.sleep(0.5)
            self.powered = True
        else:
            gpio.output(self.GPIO_PINS["Relay"], False)
            self.powered = False

    def pulse_playing(self) -> bool:
        """Return True if there is something playing on the specified Pulseaudio card.
        Return False in every other case.
        """
        output = subprocess.check_output(
            "cat " + self.PULSE_CARD_PATH, shell=True, universal_newlines=True
        )

        state = output.split("\n")[0]

        if "RUNNING" in state:
            logging.debug("Pulseaudio connected")
            return True

        return False

    def mpd_client_connected(self) -> bool:
        """Return True if an mpd client is connected and False if not.
        Requires 'log_level="secure"' or "debug" to be set in mpd.conf.
        """
        output = subprocess.check_output(
            ["tail", "-1", self.MPD_LOG_FILE], universal_newlines=True
        )

        if output != self.last_mpd_output:
            self.last_mpd_output = output
            if re.match(".* opened from .*", output):
                logging.debug("mpd client connected")
                return True

        return False


if __name__ == "__main__":
    ac = amp_controller()
    ac.setup_pins()
    ac.power("on")
    ac.set_channel("CD")

    timer = ac.SHUTOFF_TIMER_DURATION
    while True:
        # Check for changes every second.
        time.sleep(ac.CHECK_FREQUENCY)

        # Only connected, nothing playing.
        if ac.mpd_client_connected():
            if not ac.powered:
                ac.power("on")
                ac.set_channel("CD")

            # (Re)set the timer to the short duration if a client connects. Don't
            # overwrite a running timer currently greater than the short duration one.
            if timer > 0 and timer <= ac.SHORT_TIMER_DURATION:
                timer = ac.SHORT_TIMER_DURATION
            elif timer < 0:
                timer = ac.SHORT_TIMER_DURATION

            logging.debug("Timer set to {}".format(timer))

        if timer == 0:
            logging.debug("Timer ran out")
            ac.power("off")

        if ac.pulse_playing() and not ac.powered:
            ac.power("on")
            ac.set_channel("CD")

            # Reset the timer.
            timer = ac.SHUTOFF_TIMER_DURATION

        # Start the counter if nothing is currently playing.
        if not ac.pulse_playing():
            timer -= ac.CHECK_FREQUENCY
            logging.debug("Nothing playing.")
            logging.debug("Timer: " + str(timer))
            continue

            if timer < -1000:  # Just to be safe and avoid weird overflows.
                timer = -1

        # If there is something playing (no ifs matched) just reset the counter.
        timer = ac.SHUTOFF_TIMER_DURATION
        logging.debug("Something is playing.")
        logging.debug("Timer: " + str(timer))