server.py

import os
from flask import Flask, jsonify, render_template, request
from flask_sqlalchemy import SQLAlchemy
from model import DisasterEvent, db, connect_to_db
from datetime import date, datetime

app = Flask(__name__)

@app.route('/')
def displays_events():
    """
    Renders table filter page.

    """
    
    return render_template('/events.html')


@app.route('/api/events', methods=['GET'])
def get_events():
    """
    Takes in date and event type parameters to query database
    and return Json.

    """

    events_info = []

    from_date = parse_date_input(request.args.get('from'))

    to_date = parse_date_input(request.args.get('to'))

    if validate_date_params(from_date, to_date) is 'invalid':
        return jsonify({}), 400

    event_types = [event.lower() for event in request.args.getlist('event_type')]
    
    queried_events = make_query_to_db(from_date, to_date, event_types)

    for event in queried_events:
        date = event.start_date.strftime('%Y/%m/%d')
        events_info.append({ 'disasterId': event.disaster_id,
                             'state': event.state,
                             'incidentType': event.incident_type,
                             'startDate': date,
                             'count': event.count })

    return jsonify(events_info)


def parse_date_input(date):
    """
    Converts string to datetime object.

    """
    try:
        return datetime.strptime(date, '%Y-%m-%d')
    except ValueError:
        return 'invalid'


def validate_date_params(from_date, to_date):
    """
    Checks that dates entered by user are valid.

    """
    if to_date < from_date:
        return 'invalid'
    elif from_date == 'invalid' or to_date == 'invalid':
        return 'invalid'


def make_query_to_db(from_date, to_date, event_types):
    """
    Makes database query based on validated form inputs.

    """

    q = DisasterEvent.query

    filtered_events = q.filter( (DisasterEvent.incident_type.in_(event_types))
                                & (DisasterEvent.start_date >= from_date)
                                & (DisasterEvent.start_date <= to_date)
                              ).order_by('start_date').all()

    return filtered_events


@app.route('/event_types')
def get_distinct_event_types():
    """
    Gets list of distinct event types in database.

    """

    event_types = db.session.query(DisasterEvent.incident_type).distinct().order_by('incident_type').all()

    return jsonify(event_types)


if __name__ == '__main__':
    connect_to_db(app, os.environ.get('DATABASE_URL'))

    db.create_all()

    PORT = int(os.environ.get('PORT', 5000))

    DEBUG = "NO_DEBUG" not in os.environ
    
    app.run(debug=DEBUG, host='0.0.0.0', port=PORT)