lab_app_v8.py

'''
FILE NAME
lab_app.py
Version 8

1. WHAT IT DOES
This version passes the date/time strings to the template.
 
2. REQUIRES
* Any Raspberry Pi

3. ORIGINAL WORK
Raspberry Full Stack 2018, Peter Dalmaris

4. HARDWARE
* Any Raspberry Pi
* DHT11 or 22
* 10KOhm resistor
* Breadboard
* Wires

5. SOFTWARE
Command line terminal
Simple text editor
Libraries:
from flask import Flask, request, render_template, sqlite3

6. WARNING!
None

7. CREATED 

8. TYPICAL OUTPUT
A simple web page served by this flask application in the user's browser.
The page contains the current temperature and humidity.
A second page that displays historical environment data from the SQLite3 database.
The historical records can be selected by specifying a date range in the request URL.
The user can now click on one of the date/time buttons to quickly select one of the available record ranges.
The user can use Jquery widgets to select a date/time range.

 // 9. COMMENTS
--
 // 10. END
'''

from flask import Flask, request, render_template
import time
import datetime
import sys
import Adafruit_DHT
import sqlite3

app = Flask(__name__)
app.debug = True # Make this False if you are no longer debugging

@app.route("/")
def hello():
    return "Hello World!"

@app.route("/lab_temp")
def lab_temp():
	humidity, temperature = Adafruit_DHT.read_retry(Adafruit_DHT.AM2302, 17)
	if humidity is not None and temperature is not None:
		return render_template("lab_temp.html",temp=temperature,hum=humidity)
	else:
		return render_template("no_sensor.html")

@app.route("/lab_env_db", methods=['GET']) 
def lab_env_db():
	temperatures, humidities, from_date_str, to_date_str = get_records()
	return render_template(	"lab_env_db.html", 	temp 			= temperatures,
							hum 			= humidities,
							from_date 		= from_date_str, 
							to_date 		= to_date_str,
							temp_items 		= len(temperatures),
							hum_items 		= len(humidities))
	
def get_records():
	from_date_str 	= request.args.get('from',time.strftime("%Y-%m-%d 00:00")) #Get the from date value from the URL
	to_date_str 	= request.args.get('to',time.strftime("%Y-%m-%d %H:%M"))   #Get the to date value from the URL
	range_h_form	= request.args.get('range_h','');  #This will return a string, if field range_h exists in the request

	range_h_int 	= "nan"  #initialise this variable with not a number

	try: 
		range_h_int	= int(range_h_form)
	except:
		print ("range_h_form not a number")

	if not validate_date(from_date_str):			# Validate date before sending it to the DB
		from_date_str 	= time.strftime("%Y-%m-%d 00:00")
	if not validate_date(to_date_str):
		to_date_str 	= time.strftime("%Y-%m-%d %H:%M")		# Validate date before sending it to the DB

		# If range_h is defined, we don't need the from and to times
	if isinstance(range_h_int,int):	
		time_now		= datetime.datetime.now()
		time_from 		= time_now - datetime.timedelta(hours = range_h_int)
		time_to   		= time_now
		from_date_str   = time_from.strftime("%Y-%m-%d %H:%M")
		to_date_str	    = time_to.strftime("%Y-%m-%d %H:%M")
	
	conn=sqlite3.connect('/var/www/lab_app/lab_app.db')
	curs=conn.cursor()
	curs.execute("SELECT * FROM temperatures WHERE rDateTime BETWEEN ? AND ?", (from_date_str, to_date_str))
	temperatures 	= curs.fetchall()
	curs.execute("SELECT * FROM humidities WHERE rDateTime BETWEEN ? AND ?", (from_date_str, to_date_str))
	humidities 		= curs.fetchall()
	conn.close()
	return [temperatures, humidities, from_date_str, to_date_str]

def validate_date(d):
    try:
        datetime.datetime.strptime(d, '%Y-%m-%d %H:%M')
        return True
    except ValueError:
        return False

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=8080)