service/src/service.cr

require "yaml"
require "colorize"

def split_command(string)
		args = string.split /\ (?=([^\"]*\"[^\"]*\")*[^\"]*$)/

		command = args[0]
		args.delete_at 0

		return command, args
end

class Service
	getter environment : Environment
	getter providers = ProvidersList.new

	class Exception < ::Exception
	end

	class ProvidersList < Hash(String, String)
		def []?(name)
			super(name).try { |x| Service.get_by_id x}
		end
	end

	struct AsYAML
		YAML.mapping({
			name: String,
			environment: String,
			consumes: {
				type: Array(YAMLConsumes),
				default: [] of YAMLConsumes
			}
		})
	end
	struct YAMLConsumes
		YAML.mapping({
			token: String,
			from: String
		})
	end

	def initialize(name, environment_name : String?, @consumes = [] of YAMLConsumes)
		@reference = ServiceDefinition.get name
		@environment = if environment_name.nil? || environment_name == ""
			Environment.root
		else
			Environment.get environment_name
		end

		@consumes.each do |consume|
			@providers[consume.token] = consume.from
		end
	end

	def self.from_yaml(yaml)
		yaml = AsYAML.from_yaml yaml
		

		self.new yaml.name, yaml.environment, yaml.consumes
	end
	def to_yaml
		{
			name: name,
			environment: @environment.name
		}.to_yaml
	end

	def id
		if @environment.name == "root"
			name
		else
			"#{@environment.name}/#{name}"
		end
	end

	# FIXME: At this point, macros would be both more readable and shorter.
	def name
		@reference.name
	end
	def type
		@reference.type
	end
	def command
		@reference.command
	end
	def stop_command
		@reference.stop_command
	end
	def provides
		@reference.provides
	end

	def export_environment_variables
		ENV["SERVICE_ENVIRONMENT"] = @environment.name
		ENV["SERVICE_ENVIRONMENT_TYPE"] = @environment.type.to_s

		# FIXME: Parsing should probably be done… when parsing the file.
		# FIXME: Parsing is probably a bit primitive. Maybe this isn’t the right way of defining this.
		@reference.environment_variables.each do |string|
			# FIXME: Should probably deserve a warning.
			variable = string.match(/^[^=]*=/).not_nil![0]
			value = string[variable.size..string.size]
			variable = variable[0..variable.size-2]

			ENV[variable] = value
		end
	end
	private def evaluate(string)
		string.gsub /%{[a-zA-Z]+}/ do |match|
			match = match[2..match.size-2]

			if match.downcase == "environment"
				@environment.name
			else
				""
			end
		end
	end

	def start(pid_dir : String, log_dir : String)
		export_environment_variables

		(@environment.checks + @reference.checks).each do |check|
			run_check = false

			check.file.try do |file|
				run_check = true if ! File.exists? evaluate file
			end

			check.directory.try do |directory|
				run_check = true if ! Dir.exists? evaluate directory
			end

			unless run_check
				next
			end

			puts "  - #{check.name}"

			# FIXME: Output? Only in debug mode?
			child = Process.run "sh", ["-c", evaluate check.command], output: Process::Redirect::Inherit, error: Process::Redirect::Inherit

			if child.exit_status != 0
				raise Service::Exception.new "Child process exited with status “#{child.exit_status}”."
				break
			end
		end

		# FIXME: Should evaluate be used in split_command? What namespace should split_command use?
		command, args = split_command command
		args.map! do |arg| evaluate arg end

		process = Process.fork do
			base_log_name = "#{log_dir}/#{name}.#{@environment.name}"
			stdout_file = File.open "#{base_log_name}.out", "w"
			stderr_file = File.open "#{base_log_name}.err", "w"

			LibC.dup2 stdout_file.fd, 1
			LibC.dup2 stderr_file.fd, 2

			Process.exec command, args, chdir: @reference.directory
		end

		self.save_pid pid_dir, process.pid
	end

	# TODO:
	#   - Custom shutdown commands.
	#   - Should we wait for the process to die?
	#   - Shouldn’t we remove the pid file?
	def stop(pid_dir : String)
		_pid = pid pid_dir

		if _pid
			command = stop_command
			if command
				command, args = split_command command

				Process.run(command, args)
			else
				Process.kill Signal::TERM, _pid
			end
		else
			# Already stopped or dead, nothing to be done here.
		end
	end

	def get_pid_file(pid_dir)
		"#{pid_dir}/#{name}.pid"
	end

	def pid(pid_dir)
		File.read(get_pid_file pid_dir).to_i
	rescue e # pid file missing, corrupted or otherwise not readable
		nil
	end

	def save_pid(pid_dir, new_pid)
		File.write get_pid_file(pid_dir), new_pid
	end

	enum Status
		Running
		Dead
		Stopped
	end

	def status(pid_dir)
		_pid = pid pid_dir

		if _pid
			if Process.exists? _pid
				Status::Running
			else
				Status::Dead
			end
		else
			Status::Stopped
		end
	end
	def running?(pid_dir)
		status(pid_dir) == Service::Status::Running
	end

	def to_s
		"#{name} (in #{@environment.name})"
	end

	def summary
		"Name: #{name}\n" +
			"Environment: #{environment.name} (#{environment.type.to_s.downcase})\n" +
			(
				if provides.size > 0
					"Provides:\n" +
					(provides.map { |x| "  - " + x.token + "\n" }).join
				else
					""
				end
			) +
			(
				if @reference.consumes.size > 0
					"Consumes:\n" +
					(@reference.consumes.map { |x|
						provider = @providers[x.token]?
						if provider
							"  - #{x.token} (from #{provider.id})\n"
						else
							"  - #{x.token} " +
								"(NOT CURRENTLY PROVIDED)".colorize(:red).to_s +
								"\n"
						end
					}).join
				else
					""
				end
			)
	end

	class_getter all = [] of Service
	def self.load(path)
		Dir.each_child path do |child|
			unless child.match /\.yaml$/
				next
			end

			@@all << Service.from_yaml File.read "#{path}/#{child}"
		end
	end

	def write(path)
		File.write "#{path}/#{name}.#{@environment.name}.yaml", to_yaml
	end

	def remove(path)
		File.delete "#{path}/#{name}.#{@environment.name}.yaml"
	end

	def self.get_by_id(id)
		matches = id.match /[^\/]*/
		unless matches # Should not happen, above regex would always match.
			raise Exception.new "FIXME"
		end
		environment_name = matches[0]
		service_name = if environment_name == id
			environment_name = "root"
			id
		else
			id.sub 0..matches[0].size, ""
		end

		@@all.find do |service|
			service.name == service_name
		end
	end
	def is_id?(id)
		id == self.id || (@environment.name == "root" && id == "root/#{name}")
	end

	alias ServiceTree = Array(ServiceTree) | Service

	# Returns a dependency tree.
	# You’ll probably want to flatten and reverse it afterwards.
	def dependency_tree
		tree = [self] of ServiceTree

		@consumes.each do |token|
			service = Service.get_by_id token.from

			unless service
				# FIXME: Does it make the dep tree invalid?
				# FIXME: Only optional deps should be fine.
				next
			end

			tree << service.dependency_tree
		end

		tree
	end

	def reverse_dependency_tree
		tree = [self] of ServiceTree

		@@all.each do |service|
			service.providers.any? do |token, id|
				if self.is_id?(id) && ! tree.any? service
					tree << service
				end
			end
		end

		tree
	end
end