HostedOSM.py

#!/usr/local/bin/python3


import urllib.request
import xmltodict
import xml.etree.ElementTree as ET

import json

import cgi, cgitb

cgitb.enable()


form = cgi.FieldStorage()

class SpeedLimitOutput():
    def __init__(self,camera_id,geo_long,geo_lat,road_name,speed):
        self.camera_id = camera_id
        self.geo_long = geo_long
        self.geo_lat = geo_lat
        self.road_name = road_name
        self.speed = speed

    def ToJson(self):
        return '{"camera_speed_limit": '+json.dumps(self.__dict__)+"}"

def XMLfromOSMSpeedCall(long1,lat1,long2,lat2):
        api_url = 'http://www.overpass-api.de/api/xapi?*[maxspeed=*][bbox={long1},{lat1},{long2},{lat2}]'

        api_request = api_url.format(long1=long1,  lat1=lat1,long2=long2,  lat2=lat2)
        speed_limits = urllib.request.urlretrieve(api_request)

        return ET.parse(speed_limits[0])

def JSONfromTFLCall(camera_id):
        api_url = 'https://api.tfl.gov.uk/Place/JamCams_00001.{camera_id}'

        api_request = api_url.format(camera_id=camera_id)
        camera_api_response = urllib.request.urlretrieve(api_request)

        d = ""

        with open(camera_api_response[0]) as json_data:
                d = json.load(json_data)


        return d


def OSMLongLatSpeedLimit(cam_long,cam_lat,start_box_size = 0.00000002, step_dist =  0.0001,attempt_count = 10 ):

        ways = []

        step = start_box_size
        while ((len(ways) != 1) and attempt_count > 0 and step > 0):
                box_long = str(float(cam_long) - step)

                box_lat = str(float(cam_lat) - step)

                box_long2 = str(float(cam_long) + step)

                box_lat2 = str(float(cam_lat) + step)

                tree = XMLfromOSMSpeedCall(box_long,box_lat,box_long2,box_lat2)

                road_speeds = {}

                unknown_counter = 0

                ways = tree.getroot().findall('way')

                if(len(ways) != 1):
                        if(len(ways) > 1):
                                step -= step_dist
                        else:
                                step += step_dist

                attempt_count -= 1

        for way in ways:
                way_tags = way.findall('tag')
                for tag in way_tags:
                        pass
                        #print(tag.attrib.get('k'),tag.attrib.get('v'))

                max_speeds = [tag.attrib.get('v') for tag in way_tags if tag.attrib.get('k') == "maxspeed"]
                names = [tag.attrib.get('v') for tag in way_tags if tag.attrib.get('k') == "name"]

                if(len(names) > 0 ):
                        name= names[0]
                else:
                        unknown_counter += 1
                        name = "?-"+str(unknown_counter)


                if(len(max_speeds) > 0):
                        road_speeds[name] = max_speeds[0]
                else:
                        road_speeds[name] = -1
        return road_speeds



def LongLatFromTFLid(tfl_id):
        json = JSONfromTFLCall(tfl_id)

        cam_lat = json["lat"]
        cam_long = json["lon"]

        return cam_long,cam_lat

def CameraSpeedLimits(camera_id):
        camera_long,camera_lat = LongLatFromTFLid(camera_id)
        road_dict = OSMLongLatSpeedLimit(camera_long,camera_lat)

        speed_limits=[]
        for key,value in road_dict.items():
                speed_limits.append( (camera_id,str(camera_lat),str(camera_long),key,value) )
        return speed_limits


camera_id = form.getvalue("camera_id")

speed_limits = CameraSpeedLimits(camera_id)

speed_limit = SpeedLimitOutput(speed_limits[0][0],speed_limits[0][1],speed_limits[0][2],speed_limits[0][3],speed_limits[0][4])

print("Content-type: application/json")
print ("")
print(speed_limit.ToJson())
#print('{ "test": "'+str(camera_id)+'" }')