#!/usr/bin/env ruby

require "bundler/inline"
gemfile do
  source "https://rubygems.org"
  gem "optimist"
  gem "colorize"
end
require "pp"

SUB_COMMANDS = {
  "execute"   => "Execute an .asl file through the stepfunctions simulator.",
  "intrinsic" => "Execute an intrinsic function or JSONPath standalone."
}.freeze
Optimist.options do
  banner "Run the aws stepfunctions simulator."
  banner ""
  banner "Notes:"
  banner "  This tool requires the stepfunctions simulator to be installed locally and running."
  banner "  Installation instructions can be found at https://docs.aws.amazon.com/step-functions/latest/dg/sfn-local.html."
  banner ""
  banner "Commands:"
  SUB_COMMANDS.each { |k, v| banner "  #{k.ljust(14)}#{v}" }
  banner ""
  banner "  For more help with a specific command use #{$PROGRAM_NAME} <command> --help"
  banner ""
  banner "Global Options:"
  stop_on SUB_COMMANDS.keys
end
cmd = ARGV.shift
Optimist.educate if cmd.nil?
Optimist.die "unknown subcommand #{cmd.inspect}" unless SUB_COMMANDS.include?(cmd)

def aws_stepfunctions(args)
  cmd = "aws stepfunctions --endpoint-url http://localhost:8083 #{args}"
  puts "** #{cmd}".light_black if ENV["DEBUG"]
  output = `#{cmd}`.chomp
  output = output.empty? ? {} : JSON.parse(output)
  puts output.pretty_inspect.light_black if ENV["DEBUG"]
  output
rescue JSON::ParserError => err
  warn "ERROR: #{err}".light_red if ENV["DEBUG"]
  {}
end

def execute_stepfunction(definition, input)
  require "json"
  require "shellwords"

  begin
    state_machine_arn = aws_stepfunctions("create-state-machine --definition #{Shellwords.escape(definition)} --name 'StateMachine' --role-arn 'arn:aws:iam::012345678901:role/DummyRole'")["stateMachineArn"]
    exit 1 if state_machine_arn.nil?

    input = input ? "--input #{Shellwords.escape(input)}" : ""
    execution_arn = aws_stepfunctions("start-execution --state-machine-arn #{state_machine_arn} #{input}")["executionArn"]
    exit 1 if execution_arn.nil?

    status, output = aws_stepfunctions("describe-execution --execution-arn #{execution_arn}").values_at("status", "output")
    if status == "FAILED"
      warn "ERROR: Execution failed. See simulator for reason.".light_red
      exit 1
    end
  ensure
    aws_stepfunctions("stop-execution --execution-arn #{execution_arn}") if execution_arn
    aws_stepfunctions("delete-state-machine --state-machine-arn #{state_machine_arn}") if state_machine_arn
  end

  puts output if output
end

def execute
  opts = Optimist.options do
    banner SUB_COMMANDS["execute"]
    banner ""

    opt :file,  "The .asl file to execute", :default => "definition.asl"
    opt :input, "Input to the execution", :type => :string
  end

  definition = File.read(opts[:file]).chomp
  execute_stepfunction(definition, opts[:input])
end

def intrinsic
  opts = Optimist.options do
    banner SUB_COMMANDS["intrinsic"]
    banner ""

    opt :function, "The intrinsic function or JSONPath to run", :type => :string, :required => true
    opt :input, "Input to the execution", :type => :string
  end

  require "json"

  definition = {
    "StartAt" => "ExecState",
    "States"  => {
      "ExecState" => {
        "Type"       => "Pass",
        "Parameters" => {"data.$" => opts[:function]},
        "OutputPath" => "$.data",
        "End"        => true
      }
    }
  }.to_json

  execute_stepfunction(definition, opts[:input])
end

send(cmd)