# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   cloudwatch_alarm_action_check
# 
# Description:
#   This control checks whether an Amazon CloudWatch alarm has at least one action configured for the alarm state.
# 
# Reports on:
#   AWS::CloudWatch::Alarm
# 
# 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 CloudWatch alarm resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains a CloudWatch alarm resource
#       And: 'AlarmActions' 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 a CloudWatch alarm resource
#       And: 'AlarmActions' has been provided as an empty list
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation Hook Document
#       And: The input document contains a CloudWatch alarm resource
#       And: 'AlarmActions' has been provided as a non-empty list
#      Then: PASS

#
# Constants
#
let CLOUDWATCH_ALARM_TYPE = "AWS::CloudWatch::Alarm"
let INPUT_DOCUMENT = this

#
# Assignments
#
let cloudwatch_alarms = Resources.*[ Type == %CLOUDWATCH_ALARM_TYPE ]

#
# Primary Rules
#
rule cloudwatch_alarm_action_check when is_cfn_template(%INPUT_DOCUMENT)
                                        %cloudwatch_alarms not empty {
    check(%cloudwatch_alarms.Properties)
        <<
        [CT.CLOUDWATCH.PR.1]: Require an Amazon CloudWatch alarm to have an action configured for the alarm state
        [FIX]: Set 'AlarmActions' to a list with one or more alarm action values.
        >>
}

rule cloudwatch_alarm_action_check when is_cfn_hook(%INPUT_DOCUMENT, %CLOUDWATCH_ALARM_TYPE) {
    check(%INPUT_DOCUMENT.%CLOUDWATCH_ALARM_TYPE.resourceProperties)
        <<
        [CT.CLOUDWATCH.PR.1]: Require an Amazon CloudWatch alarm to have an action configured for the alarm state
        [FIX]: Set 'AlarmActions' to a list with one or more alarm action values.
        >>
}

#
# Parameterized Rules
#
rule check(cloudwatch_alarm){
    %cloudwatch_alarm {
        # Scenario 2
        AlarmActions exists
        # Scenarios 3 and 4
        AlarmActions is_list
        AlarmActions not empty
    }
}

#
# 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
}