# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   ec2_instance_detailed_monitoring_enabled_check
# 
# Description:
#   This control checks whether an Amazon EC2 instance has detailed monitoring enabled.
# 
# Reports on:
#   AWS::EC2::Instance
# 
# Evaluates:
#   AWS CloudFormation, AWS CloudFormation hook
# 
# Rule Parameters:
#   None
# 
# Scenarios:
#   Scenario: 1
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document does not contain any EC2 instance resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an EC2 instance resource
#       And: 'Monitoring' has not been provided
#      Then: FAIL
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an EC2 instance resource
#       And: 'Monitoring' has been provided and set to a value other than bool(true)
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation Hook Document
#       And: The input document contains an EC2 instance resource
#       And: 'Monitoring' has been provided and set to bool(true)
#      Then: PASS

#
# Constants
#
let EC2_INSTANCE_TYPE = "AWS::EC2::Instance"
let INPUT_DOCUMENT = this

#
# Assignments
#
let ec2_instances = Resources.*[ Type == %EC2_INSTANCE_TYPE ]

#
# Primary Rules
#
rule ec2_instance_detailed_monitoring_enabled_check when is_cfn_template(%INPUT_DOCUMENT)
                                                         %ec2_instances not empty {
    check(%ec2_instances.Properties)
        <<
        [CT.EC2.PR.13]: Require an Amazon EC2 instance to have detailed monitoring enabled
        [FIX]: Set 'Monitoring' to 'true'.
        >>

}

rule ec2_instance_detailed_monitoring_enabled_check when is_cfn_hook(%INPUT_DOCUMENT, %EC2_INSTANCE_TYPE) {
    check(%INPUT_DOCUMENT.%EC2_INSTANCE_TYPE.resourceProperties)
        <<
        [CT.EC2.PR.13]: Require an Amazon EC2 instance to have detailed monitoring enabled
        [FIX]: Set 'Monitoring' to 'true'.
        >>
}

#
# Parameterized Rules
#
rule check(ec2_instance) {
    %ec2_instance {
        # Scenario 2
        Monitoring exists
        # Scenarios 3 and 4
        Monitoring == true
    }
}

#
# Utility Rules
#
rule is_cfn_template(doc) {
    %doc {
        AWSTemplateFormatVersion exists  or
        Resources exists
    }
}

rule is_cfn_hook(doc, RESOURCE_TYPE) {
    %doc.%RESOURCE_TYPE.resourceProperties exists
}