#!/usr/bin/env python
##########################################################################
# elasticlog.py - Enable/disable logging to an elasticsearch environment
##########################################################################
# Copyright 2017 Todd Shadburn <tshadburn@opencomputingsolutions.com>
##########################################################################
# Python environment requirements:
#  - Python 2.7+ or 3.x+
#  - Install CMRESHandler module
#      pip install CMRESHandler
#
# Environment variables required:
#    ELASTICLOG_ENABLE	 - 1=enable, 0=disable(default)
#    ELASTICLOG_HOST	 - hostname(s) for the elastic cluster
#    ELASTICLOG_USERNAME - elastic login username
#    ELASTICLOG_PASSWORD - elastic login password
#    ELASTICLOG_INDEXNAME - elastic index name to use
##########################################################################

import os
import logging


def setup_elasticsearch_logging(logger=None, appname=None, owner=None, deploymentstage=None, *args, **kwargs):
	"""
	Enable elaseticsearch logging if we have all our config items
	appname/owner/deploymentstage are required arguments (for ES logging fields)
	Additional user-specified ES logging fields can be passed in kwargs (name=value)
	"""
	if not appname or not owner or not deploymentstage:
		# Missing a required argument, don't continue
		raise ValueError('elasticlog: Missing a required argument, not enabling.')
		return None

	# setup basic logging (to the console anyway) if not already configured
	log = None
	if logger:
		# Use the logging already setup by the application
		log = logger
	else:
		# Create a basic console logger for the application
		log = logging.getLogger(appname)
		log.setLevel(logging.INFO)
		formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
		console_handler = logging.StreamHandler()
		console_handler.setLevel(logging.INFO)
		console_handler.setFormatter(formatter)
		log.addHandler(console_handler)

	# Pull in cmreshandler which supports ElasticSearch
	try:
		from cmreslogging.handlers import CMRESHandler
	except:
		# No cmredhandler, just return the console logger
		return log

	# Process environment variables for elasticlog
	# This makes use of this module; 1)easy and 2)consistent
	ELASTICLOG_ENABLE=0
	if 'ELASTICLOG_ENABLE' in os.environ:
		ELASTICLOG_ENABLE=int(os.environ['ELASTICLOG_ENABLE'])
	if ELASTICLOG_ENABLE == 0:
		# don't enable elasticsearch logging but return
		# the console logger
		return log
	ELASTICLOG_HOST=''
	if 'ELASTICLOG_HOST' in os.environ:
		ELASTICLOG_HOST = os.environ['ELASTICLOG_HOST']
	ELASTICLOG_USERNAME=''
	if 'ELASTICLOG_USERNAME' in os.environ:
		ELASTICLOG_USERNAME = os.environ['ELASTICLOG_USERNAME']
	ELASTICLOG_PASSWORD=''
	if 'ELASTICLOG_PASSWORD' in os.environ:
		ELASTICLOG_PASSWORD = os.environ['ELASTICLOG_PASSWORD']
	ELASTICLOG_INDEXNAME=''
	if 'ELASTICLOG_INDEXNAME' in os.environ:
		ELASTICLOG_INDEXNAME = os.environ['ELASTICLOG_INDEXNAME']
	if (ELASTICLOG_HOST == '' or
	    ELASTICLOG_USERNAME == '' or
	    ELASTICLOG_PASSWORD == '' or
	    ELASTICLOG_INDEXNAME == ''):
		# Missing a parameter, don't continue
		raise ValueError('elasticlog: Missing a required environment variable, not enabling.')
		# Return the console logger
		return log

	# We've got all the info we need to add the elasticsearch log handler

	# Build additional fields for ES, starting with required fields
	es_addl_fields = {
		'AppName': appname,
		'Owner': owner,
		'DeploymentStage': deploymentstage,
	}
	# Then add any user-specified fields
	for n,v in kwargs:
		es_addl_fields[n] = k

	# Now, connect to ElasticSearch and add the handler
	ehandler = CMRESHandler(hosts=[{'host': ELASTICLOG_HOST, 'port': 9200}],
                       auth_type=CMRESHandler.AuthType.BASIC_AUTH,
                       auth_details=(ELASTICLOG_USERNAME,ELASTICLOG_PASSWORD),
                       use_ssl=True,
                       verify_ssl=False,
                       es_index_name=ELASTICLOG_INDEXNAME,
                       es_additional_fields=es_addl_fields,
                       )
	ehandler.setLevel(logging.INFO)
	log.addHandler(elastic_handler)
	return log