# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   api_gw_xray_enabled_check
# 
# Description:
#   This control ensures that AWS X-Ray tracing is enabled on Amazon API Gateway REST APIs.
# 
# Reports on:
#   AWS::ApiGateway::Stage
# 
# 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 API Gateway stage resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an API Gateway stage resource
#       And: 'TracingEnabled' is not present on the API Gateway stage
#      Then: FAIL
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an API Gateway stage resource
#       And: 'TracingEnabled' is present on the API Gateway stage and is set to bool(false)
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an API Gateway stage resource
#       And: 'TracingEnabled' is present on the API Gateway stage and is set to bool(true)
#      Then: PASS

#
# Constants
#
let API_GW_STAGE_TYPE = "AWS::ApiGateway::Stage"
let INPUT_DOCUMENT = this

#
# Assignments
#
let api_gateway_stages = Resources.*[ Type == %API_GW_STAGE_TYPE ]

#
# Primary Rules
#
rule api_gw_xray_enabled_check when is_cfn_template(%INPUT_DOCUMENT)
                                    %api_gateway_stages not empty {
    check(%api_gateway_stages.Properties)
        <<
        [CT.APIGATEWAY.PR.2]: Require an Amazon API Gateway REST API stage to have AWS X-Ray tracing activated
        [FIX]: Set 'TracingEnabled' to 'true'.
        >>
}

rule api_gw_xray_enabled_check when is_cfn_hook(%INPUT_DOCUMENT, %API_GW_STAGE_TYPE) {
    check(%INPUT_DOCUMENT.%API_GW_STAGE_TYPE.resourceProperties)
        <<
        [CT.APIGATEWAY.PR.2]: Require an Amazon API Gateway REST API stage to have AWS X-Ray tracing activated
        [FIX]: Set 'TracingEnabled' to 'true'.
        >>
}

#
# Parameterized Rules
#
rule check(api_gateway_stage) {
    %api_gateway_stage {
        # Scenario 2, 3, 4
        TracingEnabled exists
        TracingEnabled == 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
}