cfn

#!/bin/bash

set -fuo pipefail
IFS=$'\n\t'

export AWS_DEFAULT_OUTPUT="json"

DEFAULT_NAMESPACE='cfn'
DEFAULT_TEMPLATE='cfn.yaml'

function cached_value {
    local key=$1
    touch .cfn
    grep -m 1 -E "^$key=" .cfn | sed 's/.*=//'
}

function set_cached_value {
    local key=$1
    local value=$2
    touch .cfn
    new_cfn=$(mktemp)
    grep -v -E "^$key=" .cfn >> ${new_cfn}
    echo "$key=$value" >> ${new_cfn}
    mv ${new_cfn} .cfn
}

CFN_NAMESPACE=${CFN_NAMESPACE:-$(cached_value namespace)}
CFN_NAMESPACE=${CFN_NAMESPACE:-$DEFAULT_NAMESPACE}
CFN_STACK=${CFN_STACK:-$(cached_value stack)}
CFN_TEMPLATE=${CFN_TEMPLATE:-$(cached_value template)}
CFN_TEMPLATE=${CFN_TEMPLATE:-$DEFAULT_TEMPLATE}

function print_usage {
    cat <<EOF
usage: cfn [-h] [-n <namespace>] [-s <stack>] [-t <template>] [<command>]
EOF
}

function print_help {
    print_usage
    cat <<EOF
Manipulate AWS CloudFormation stacks.

  -n <namespace>
                 operate within namespace and remember for next time
                   (default $DEFAULT_NAMESPACE)
  -s <stack>
                 operate on stack and remember for next time
  -t <template>
                 relative local path to CloudFormation template and
                   remember for next time (default $DEFAULT_TEMPLATE)
  -h
                 print this message and exit

Valid commands are:

   create        create new stack
   update        update existing stack
   delete        delete stack
   doctor        help diagnose problems with stack
   status        check on status of stack
   list          list all stacks
EOF
}

while getopts ":hn:s:t:" opt; do
    case ${opt} in
        h )
            print_help
            exit 0
            ;;
        \? )
            echo "Invalid option: -${OPTARG}" 1>&2
            print_usage 1>&2
            exit 1
            ;;
        : )
            echo "Invalid option: ${OPTARG} requires an argument" 1>&2
            print_usage 1>&2
            exit 1
            ;;
        t )
	    if [[ ! -f ${OPTARG} ]]; then
		echo "File not found: ${OPTARG}" > /dev/stderr
		exit 2
	    fi
	    
            CFN_TEMPLATE=${OPTARG}
            set_cached_value template ${CFN_TEMPLATE}
            ;;
        s )
            CFN_STACK=${OPTARG}
            set_cached_value stack ${CFN_STACK}
            ;;
        n )
            CFN_NAMESPACE=${OPTARG}
            set_cached_value namespace ${CFN_NAMESPACE}
            ;;
    esac
done
shift $((OPTIND -1))

if [[ -z $CFN_STACK ]]; then
    echo "error: please specify a stack at least once with -s flag" 2>&1
    print_usage 2>&1
    exit 1
fi

STACK="$CFN_NAMESPACE-$CFN_STACK"

if ! (($# >= 1)); then
    # Allows user to do -s and stuff
    exit 0
fi

subcommand=$1
shift

function cfs {
    local cmd=$1
    shift
    if (($# > 0)); then
	if [[ $1 = '-'* ]]; then
	    aws cloudformation $cmd --stack-name $STACK "$@"
	else
	    local subcommand=$1
	    shift
	    aws cloudformation $cmd $subcommand --stack-name $STACK "$@"
	fi
    else
	aws cloudformation $cmd --stack-name $STACK "$@"
    fi
}

function validate_template {
    aws cloudformation validate-template --template-body "file://${CFN_TEMPLATE}"
}

function describe_stack {
    cfs describe-stacks \
	| jq -r '(["NAME", "STATUS", "DRIFT STATUS"] | (., map(length*"-"))), (.Stacks[0] | [.StackName, .StackStatus, .DriftInformation.StackDriftStatus]) | @tsv' \
	| column -s $'\t' -t
}

function doctor {
    cfs describe-stack-events | jq -r '.StackEvents[] | select(.ResourceStatus | test("FAILED")) | del(.StackId,.StackName,.EventId)'
}

case ${subcommand} in
    create )
        # Provide CAPABILITY_NAMED_IAM otherwise templates that create
        # IAM Roles won't work
	validate_template
        if cfs create-stack --template-body "file://${CFN_TEMPLATE}" --capabilities "CAPABILITY_NAMED_IAM"; then
	    if cfs wait "stack-create-complete"; then
		cfs describe-stacks
	    else
		doctor
	    fi
	fi
        exit
        ;;
    delete )
	cfs delete-stack
	exit
	;;
    drift )
	cfs detect-stack-drift
	exit
	;;
    start-session )
	instance_id=$(cfs describe-stack-resource --logical-resource-id $1 | jq -r '.StackResourceDetail.PhysicalResourceId')
	echo aws ssm start-session --target $instance_id
	aws ssm start-session --target $instance_id
	exit
	;;
    describe )
	cfs describe-stack-resource --logical-resource-id $1
	exit
	;;
    update )
        if cfs update-stack --template-body "file://${CFN_TEMPLATE}"  --capabilities "CAPABILITY_NAMED_IAM"; then
	    if cfs wait "stack-update-complete"; then
		cfs describe-stacks
	    else
		doctor
	    fi
	fi
        exit
        ;;
    status )
	describe_stack
	exit
	;;
    resources )
	cfs describe-stack-resources | jq -r '.StackResources[] | [.LogicalResourceId, (.ResourceType | sub("^AWS::"; "")), .ResourceStatus, .DriftInformation.StackResourceDriftStatus] | @tsv' | column -s $'\t' -t
	exit
	;;
    doctor )
	doctor
	exit
	;;
    list )
	aws cloudformation list-stacks | jq -r '(["NAME", "STATUS"] | (., map(length*"-"))), (.StackSummaries[] | select(.StackStatus | test("DELETE") | not) | [.StackName, .StackStatus]) | @tsv' | column -s $'\t' -t
	exit
	;;
    * )
        echo "error: unrecognized command: $subcommand" 2>&1
        print_usage 2>&1
        exit 1
esac
exit