config.py

#!/usr/bin/python
import simplejson as json
import constants
import time
import sys
import copy
from shutil import copyfile
from collections import OrderedDict
import jsonschema
import os.path

config = None

# return all the configuration settings as an object
def get_config(validate=True):
	# load the configuration from the file
	load(validate)
	return config

# return all the configuration settings as a json object
def get_json_config(validate=True):
	return json.dumps(get_config(validate), default=lambda o: o.__dict__)

# reload the configuration
def reload(validate=True): 
	config = None
	load(validate)

# load the configuration from file
def load(validate):
	# if the config is already loaded return
	global config
	if config is not None: return
	# load the constants
	const = constants.get_constants()
	# create a config.json file if does not exist
	if not os.path.isfile(const['config_file']):
		copyfile(const['config_file_example'],const['config_file'])
	# open the config file and load it
	with open(const['config_file'], 'r') as file:
		config_file_content = file.read()
	file.close()
	config = json.loads(config_file_content, object_pairs_hook=OrderedDict)
	# store the raw configuration into a variable
	config["config_json"] = config_file_content
	# load config schema
	with open(const['config_file_schema'], 'r') as file:
		const['config_schema_json'] = file.read()
	file.close()
	# adapt the units if needed
	if "general" in config:
		if config["general"]["units"]["imperial"]:
			const["formats"]["length"]["suffix"] = "in"
			const["formats"]["length"]["formatter"] = "float_2"
			const["formats"]["speed"]["suffix"] = "m/h"
		if config["general"]["units"]["fahrenheit"]:
			const["formats"]["temperature"]["suffix"] = u'\u00B0F'
			const["formats"]["temperature"]["formatter"] = "int"
	else: 
		# probably this is the upgrade process
		config["general"] = {}
		config["general"]["timeframes"]= {}
		config["general"]["timeframes"]["realtime_hours"] = 0
		config["general"]["timeframes"]["recent_hours"] = 0
		config["general"]["timeframes"]["history_days"] = 0
	# attach the constants
	config['constants'] = const
	# validate the configuration against the schema
	if validate:
		try:
			jsonschema.validate(json.loads(config["config_json"]),json.loads(const['config_schema_json']))
		except Exception,e:
			print "The configuration file is not compliant with the schema or the schema is incorrect: "+str(e)
			sys.exit(1)

# save the configuration
def save(config_string):
	const = constants.get_constants()
	# validay the json file
	try:
		new_config = json.loads(config_string, object_pairs_hook=OrderedDict)
	except ValueError, e:
		print "unable to save configuration, invalid JSON provided: "+config_string
		return json.dumps("KO")
	# create a backup first
	copyfile(const['config_file'],const['config_file_backup'])
	# save the new config file
	with open(const['config_file'],'w') as file:
		file.write(json.dumps(new_config,indent=2))
	file.close()
	return json.dumps("OK")

# main
if __name__ == '__main__':
	get_config()