"""
CLI Meter
====================================================================
Takes a reading of the light using the meter attached via to the
intended Raspberry PI. The reading is the sent to a server where the
reading is stored. The intended use for this script is to be run via
the command-line without the need for a G.U.I. This should be the
version used when the "Return to Ritherdon" project is live.
"""

import json
import RPi.GPIO as GPIO
import time, math
import requests
from datetime import datetime
import pdb

# Using BCM (Broadcom) names when referencing the GPIO pins.
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(True)

a_pin = 18 # Charges the capacitor.
b_pin = 23 # Discharges the capacitor.

api_url = "http://35.176.14.135/api/readings/add/1"

def discharge():
    GPIO.setup(a_pin, GPIO.IN)
    GPIO.setup(b_pin, GPIO.OUT)
    GPIO.output(b_pin, False)
    time.sleep(0.01) # 0.01 -- initial value

def charge_time():
    GPIO.setup(b_pin, GPIO.IN)
    GPIO.setup(a_pin, GPIO.OUT)
    GPIO.output(a_pin, True)
    t1 = time.time()
    while not GPIO.input(b_pin):
        pass
    t2 = time.time()
    return (t2 - t1) * 1000000

def analog_read():
    discharge()
    return charge_time()

def read_resistance():
    n = 20
    total = 0;
    for i in range(1, n):
        total = total + analog_read()
    reading = total / float(n)
    resistance = reading * 6.05 - 939
    return resistance

def light_from_r(R):
    return math.log(1000000.0/R) * 10.0

def get_timestamp():
    return datetime.now().strftime(("%Y-%m-%d %H:%M:%S"))

def push_reading(lvalue):
    time = get_timestamp()
    headers = {"content-type": "application/json"}
    payload = { "reading": int(lvalue), "time": time}
    print(payload)
    res = requests.post(api_url, data=json.dumps(payload), headers=headers)

def update_reading():
    light = light_from_r(read_resistance())
    reading_str = "{:.0f}".format(light)
    print(reading_str)
    push_reading(light)

def main():
    try:
        while True:
            #pdb.set_trace()
            update_reading()
    except KeyboardInterrupt:
        print("Keyboard Interrupt: quitting program.")
    except:
        print("Error updating light reading...")
    finally:
        print("Cleaning up GPIO before closing...")
        GPIO.cleanup()

if __name__ == "__main__":
    main()