#
#####################################
##           Gherkin               ##
#####################################
# Rule Identifier:
#   ELASTICSEARCH_DATA_NODE_FAULT_TOLERANCE
#
# Description:
#   Elasticsearch domains are configured with at least three data nodes and zone awareness enabled.
#
# Reports on:
#   AWS::Elasticsearch::Domain
#
# Evaluates:
#   AWS CloudFormation
#
# Rule Parameters:
#   NA
#
# Scenarios:
# a) SKIP: when there are no ElasticSearch Domain Resources 
# b) SKIP: when metadata has rule suppression for ELASTICSEARCH_DATA_NODE_FAULT_TOLERANCE
# c) FAIL: when ElasticSearch Domain Resources are missing ElasticsearchClusterConfig.ZoneAwarenessEnabled or ElasticsearchClusterConfig.InstanceCount
# d) FAIL: when ElasticSearch Domain Resources have ElasticsearchClusterConfig.ZoneAwarenessEnabled set to a value other than true 
# e) FAIL: when ElasticSearch Domain Resources have ElasticsearchClusterConfig.InstanceCount set to an integer value less than three (<3) 
# f) PASS: when ElasticSearch Domain Resources have ElasticsearchClusterConfig.ZoneAwarenessEnabled set to true and 
#          ElasticsearchClusterConfig.InstanceCount set to an integer value greater than or equal to three (>= 3) 

#
# Select all ElasticSearch domains from incoming template
#
let elasticsearch_data_node_fault_tolerance = Resources.*[ Type == "AWS::Elasticsearch::Domain"
  Metadata.guard.SuppressedRules not exists or
  Metadata.guard.SuppressedRules.* != "ELASTICSEARCH_DATA_NODE_FAULT_TOLERANCE"
]

rule ELASTICSEARCH_DATA_NODE_FAULT_TOLERANCE when %elasticsearch_data_node_fault_tolerance !empty {
    %elasticsearch_data_node_fault_tolerance.Properties { 
        ElasticsearchClusterConfig exists
        ElasticsearchClusterConfig is_struct

        ElasticsearchClusterConfig {
            ZoneAwarenessEnabled exists
            ZoneAwarenessEnabled == true
                <<
                    Violation: Elasticsearch domains are configured with at least three data nodes and zone awareness enabled
                    Fix: In ElasticsearchClusterConfig, set ZoneAwarenessEnabled to true and InstanceCount to an integer value greater than 3.
                >>
            InstanceCount exists
            InstanceCount >= 3
                <<
                    Violation: Elasticsearch domains are configured with at least three data nodes and zone awareness enabled
                    Fix: In ElasticsearchClusterConfig, set ZoneAwarenessEnabled to true and InstanceCount to an integer value greater than 3.
                >>
        }
    }
}