added ability to reference array elements when the root element is an array

Changing form [] to () because of Nagios issues. Fixes.

README.md

@@ -89,10 +89,28 @@ optional arguments:
                         (key,UnitOfMeasure,Min,Max).
   -s, --ssl             HTTPS mode.
   -f SEPARATOR, --field_separator SEPARATOR
-                        Json Field separator, defaults to "."
+                        Json Field separator, defaults to "." ; Select element
+                        in an array with "(" ")"
   -d, --debug           Debug mode.
 ```
 
+Access a specific JSON field by following this syntax: `alpha.beta.gamma(3).theta.omega(0)`
+Dots are field separators (changeable), parantheses are for entering arrays.
+
+If the root of the JSON data is itself an array like the following:
+
+```
+[
+{ "gauges": { "jvm.buffers.direct.capacity": {"value": 215415}}}
+]
+```
+
+The beginning of the key should start with ($index) as in this example:
+
+```
+./check_http_json.py -H localhost:8081 -p metrics --key_exists "(0)_gauges_jvm.buffers.direct.capacity_value" -f _
+```
+
 More info about Nagios Range format and Units of Measure can be found at [https://nagios-plugins.org/doc/guidelines.html](https://nagios-plugins.org/doc/guidelines.html).
 
 ### Docker Info Example Plugin

check_http_json.py

@@ -45,6 +45,35 @@ class JsonHelper:
 	def __init__(self, json_data, separator):
 		self.data = json_data
 		self.separator = separator
+		self.arrayOpener = '('
+		self.arrayCloser = ')'
+
+	def getSubElement(self, key, data):
+		separatorIndex = key.find(self.separator)
+		partialKey = key[:separatorIndex]
+		remainingKey = key[separatorIndex + 1:]
+		if partialKey in data:
+			return self.get(remainingKey, data[partialKey])
+		else:
+			return (None, 'not_found')
+
+	def getSubArrayElement(self, key, data):
+		subElemKey = key[:key.find(self.arrayOpener)]
+		index = int(key[key.find(self.arrayOpener) + 1:key.find(self.arrayCloser)])
+		remainingKey = key[key.find(self.arrayCloser + self.separator) + 2:]
+		if key.find(self.arrayCloser + self.separator) == -1:
+			remainingKey = key[key.find(self.arrayCloser) + 1:]
+
+		if subElemKey in data:
+			if index < len(data[subElemKey]):
+				return self.get(remainingKey, data[subElemKey][index])
+			else:
+				return (None, 'not_found')
+		else:
+			if not subElemKey:
+				return self.get(remainingKey, data[index])
+			else:
+				return (None, 'not_found')
 			
 	def equals(self, key, value): return self.exists(key) and str(self.get(key)) == value
 	def lte(self, key, value): return self.exists(key) and float(self.get(key)) <= float(value)
@@ -57,13 +86,25 @@ class JsonHelper:
 		else:
 			data = self.data
 
-		if self.separator in key:
+		if len(key) <= 0:
-			return self.get(key[key.find(self.separator) + 1:], data[key[:key.find(self.separator)]])
+			return data
-		else:
+
-			if key in data:
+		if key.find(self.separator) != -1 and key.find(self.arrayOpener) != -1 :
-				return  data[key]
+			if key.find(self.separator) < key.find(self.arrayOpener) :
+				return self.getSubElement(key, data)
 			else:
-				return (None, 'not_found')
+				return self.getSubArrayElement(key, data)
+		else:
+			if key.find(self.separator) != -1 : 
+				return self.getSubElement(key, data)
+			else:
+				if key.find(self.arrayOpener) != -1 :
+					return self.getSubArrayElement(key, data)
+				else:
+					if key in data:
+						return data[key]
+					else:
+						return (None, 'not_found')
 
 class JsonRuleProcessor:
 	"""Perform checks and gather values from a JSON dict given rules and metrics definitions"""
@@ -163,7 +204,7 @@ def parseArgs():
 		More information about Range format and units of measure for nagios can be found at https://nagios-plugins.org/doc/guidelines.html\
 		Additional formats for this parameter are: (key), (key,UnitOfMeasure), (key,UnitOfMeasure,Min,Max).')
 	parser.add_argument('-s', '--ssl', action='store_true', help='HTTPS mode.')
-	parser.add_argument('-f', '--field_separator', dest='separator', help='Json Field separator, defaults to "."')
+	parser.add_argument('-f', '--field_separator', dest='separator', help='Json Field separator, defaults to "." ; Select element in an array with "(" ")"')
 	parser.add_argument('-d', '--debug', action='store_true', help='Debug mode.')
 
 	return parser.parse_args()