import serial
import queue
import threading


class InductionHeater:
    """Interface to the MHS5200A function generator driving the LC tank"""
    def __init__(self, port, induction_min, induction_max):
        self.port = port
        self.induction_min = induction_min
        self.induction_max = induction_max
        self.queue = queue.Queue(1)

    def start(self):
        self.serial = serial.Serial(self.port, 57600)
        self.thread = threading.Thread(target=self.thread_target)
        self.thread.start()

    def thread_target(self):
        while True:
            amount = self.queue.get()
            if amount is None:
                break

            amount = max(min(amount, 0.5), -0.5)
            freq = ((self.induction_min + self.induction_max)/2
                    + amount*(self.induction_max - self.induction_min))

            command = ":s1f{:010d}\n".format(int(freq*1e2))
            self.serial.write(command.encode())
            self.serial.readline()

    def set(self, amount):
        self.queue.put(amount, block=False)

    def stop(self):
        self.queue.put(None, block=True)
        self.thread.join()
        self.serial.close()