require "yaml"
require "colorize"
require "file_utils"

require "passwd"

require "./context.cr"
require "./service_definition.cr"
require "./environment.cr"
require "./libc.cr"

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

		command = args[0]
		args.delete_at 0

		return command, args
end

lib C
	fun waitpid(pid : Int32, status_ptr : Int32*, options : Int32) : Int32
end

class Process
	def self.waitpid(pid)
		options = 0
		status_ptr = uninitialized Int32

		C.waitpid(pid, pointerof(status_ptr), options)
	end
end

class Service
	getter environment : Environment
	getter providers : ProvidersList

	setter name : String?
	property domain : String?
	getter ports = Hash(String, Int32).new

	@reference : ServiceDefinition

	# The place we’ll store configuration and data.
	@root : String?

	@context : Context

	class Exception < ::Exception
	end

	class ProvidersList < Hash(String, String)
		@context : Service::Context
		def initialize(@context)
			initialize
		end

		def []?(name)
			super(name).try { |x| @context.get_service_by_id x}
		end
	end

	struct Consumer
		getter token : String
		getter from : String
		def initialize(@token, @from)
		end
	end

	def initialize(@context : Context, name, environment_name : String?)
		@providers = ProvidersList.new @context
		@reference = context.get_service_definition_by_name name
		@environment = if environment_name.nil? || environment_name == ""
			@context.root_environment
		else
			@context.get_environment_by_name environment_name
		end
	end

	def initialize(@context : Context, specs : SpecParser)
		@providers = ProvidersList.new @context
		assignments = specs.assignments

		# Complicated because of compat with when services had no dedicated
		# name and their types were their name.
		type = assignments["type"]?.try &.as_s
		@name = (assignments["name"]?.try(&.as_s) || type).not_nil!
		@reference = context.get_service_definition_by_name (type || @name).not_nil!

		@domain = assignments["domain"]?.try &.as_s

		env = assignments["environment"]?.try &.as_s
		@environment = if env.nil? || env == ""
			@context.root_environment
		else
			@context.get_environment_by_name env
		end

		@root = assignments["root"]?.try &.as_s

		assignments["ports"]?.try &.as_a_or_s.each do |port_string|
			match = port_string.match /(.*)=(.*)/

			if match.nil?
				STDERR.puts "warning: '#{id}' has invalid port strings"
				next
			end

			_, name, number = match

			number = number.to_i

			@ports[name] = number
		end

		specs.sections.select(&.name.==("consumes")).each do |section|
			env, provider = Service.parse_id section.content["from"].as_s
			@providers[section.options[0]] = "#{env}/#{provider}"
		end
	end

	def to_spec
		file = [
			"type: #{@reference.name}",
			"environment: #{@environment.name}"
		]

		unless @name.nil?
			file << "name: #{@name}"
		end

		if @ports.size > 0
			ports_list = @ports.map do |name, number|
				"#{name}=#{number}"
			end.join ", "

			file << "ports: #{ports_list}"
		end

		if @root
			file << "root: #{@root}"
		end

		if @domain
			file << "domain: #{@domain}"
		end

		@providers.each do |token, provider|
			file << "%consumes #{token}"
			file << "    from: #{provider}"
		end

		file.join("\n") + "\n"
	end

	def full_id
		"#{@environment.name}/#{name}"
	end

	def id
		if @environment.name == "root"
			name
		else
			full_id
		end
	end

	# FIXME: At this point, macros would be both more readable and shorter.
	def name
		@name || @reference.name
	end
	def type
		@reference.name
	end
	def command
		@reference.command
	end
	def stop_command
		@reference.stop_command
	end
	def reload_command
		@reference.reload_command
	end
	def readiness_check_command
		@reference.readiness_check_command
	end
	def provides
		@reference.provides
	end
	def consumes
		@reference.consumes
	end
	def requires_domain
		@reference.requires_domain
	end
	def port_definitions
		@reference.port_definitions
	end
	def non_runnable
		@reference.non_runnable
	end

	def root
		@root || "#{@environment.root}/#{name}"
	end

	def provides?(token)
		provides.any? do |provider|
			provider.token == token
		end
	end

	@commands_environment : Hash(String, String)?
	private def build_commands_environment!
		env = {} of String => String

		env["SERVICE_NAME"] = name
		env["SERVICE_ROOT"] = root
		env["SERVICE_ID"] = full_id
		env["SERVICE_USER"] = user_name
		if _pid = pid @context.pid_directory
			env["SERVICE_PID"] = _pid.to_s
		end

		env["ENVIRONMENT"] = @environment.name
		env["ENVIRONMENT_TYPE"] = @environment.type.to_s

		@providers.each do |token, provider|
			service_provider = @context.get_service_by_id provider

			# FIXME: Warning if mandatory?
			next if service_provider.nil?

			env["#{token.upcase}_PROVIDER"] = provider
			env["#{token.upcase}_ENVIRONMENT"] = service_provider.environment.name
			env["#{token.upcase}_ROOT"] = service_provider.root
		end

		env["SERVICE_TOKENS"] = @providers.to_a.map(&.[0]).join ':'

		@ports.each do |name, number|
			name = name.upcase

			env["PORT_#{name}"] = number.to_s
		end

		# 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

		@commands_environment = env
	end
	def commands_environment : Hash(String, String)
		@commands_environment || build_commands_environment!
	end

	# FIXME: Is working on ${} really a good idea?
	# FIXME: There should be a unified way of obtaining a service’s
	#        environment, and we should take our variables from that
	#        instead of hardcoding everything.
	private def evaluate(string)
		env = commands_environment

		string.gsub /\${[a-zA-Z_]+}/ do |match|
			match = match[2..match.size-2]

			env[match.upcase]? || ""
		end
	end

	def files
		@environment.files + @reference.files
	end

	def build_files!(context : Context)
		files.each do |file|
			run_hook = false

			next unless creation_command = file.creation_command

			path = evaluate file.file_path
			if path[0] != '/'
				path = "#{root}/#{path}"
			end

			run_hook = (!File.exists? path) || file.is_configuration?

			next unless run_hook

			context.info "Creating #{file.name}"

			uid, gid = get_uid_gid

			child = Process.fork do
				Dir.cd root

				System.become_user user_name

				Process.exec "sh", ["-c", creation_command],
					output: Process::Redirect::Inherit,
					error: Process::Redirect::Inherit,
					env: commands_environment
			end.wait

			unless child.success?
				raise Service::Exception.new "Child process exited with status “#{(child.exit_status/256).to_i}”."
				break
			end
		end
	end

	def start(context : Context)
		return if running? context.pid_directory

		if non_runnable
			context.title "Setting up #{to_s}"
		else
			context.title "Starting #{to_s}"
		end

		create_user_and_group!

		uid, gid = get_uid_gid
		FileUtils.mkdir_p root
		File.chown root, uid, gid

		build_files! context

		return if non_runnable

		# 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 = "#{context.log_directory}/#{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

			unless @reference.start_as_root
				System.become_user user_name
			end

			Process.exec command, args,
				chdir: (@reference.directory.try { |x| evaluate x } || root),
				env: commands_environment
		end

		self.save_pid context.pid_directory, process.pid

		# FIXME: At this point, let’s wait a few seconds for the service to be ready.
		if command = readiness_check_command
			context.info "Waiting for service to become ready…"

			start_time = Time.local
			now = Time.local

			while (now - start_time).seconds < 5
				r = Process.run "sh", ["-c", command],
					output: Process::Redirect::Inherit,
					error: Process::Redirect::Inherit,
					env: commands_environment

				if r.success?
					break
				end

				sleep 0.05

				now = Time.local
			end
		end

		provides.each do |token_definition|
			reverse_dependencies = get_consumers(token_definition.token)
				.map(&.id)
				.compact_map do |id|
					context.get_service_by_id id
				end

			reverse_dependencies.each do |service|
				next unless service.non_runnable

				should_start = service
					.dependency_tree.flatten
					.select(&.!=(self))
					.map(&.status(context))
					.map do |status|
						status.running? || status.non_runnable?
					end
					.reduce do |a, b| a && b end

				if should_start
					service.start context
				end
			end
		end
	end

	# TODO:
	#   - Custom shutdown commands.
	#   - Should we wait for the process to die?
	#   - Shouldn’t we remove the pid file?
	def stop(context : Context)
		return if non_runnable

		context.title "Stopping #{to_s}"

		_pid = pid context.pid_directory

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

				Process.run(command, args)
			else
				Process.kill Signal::TERM, _pid
			end

			Process.waitpid _pid
			File.delete(get_pid_file context.pid_directory)
		else
			# Already stopped or dead, nothing to be done here.
		end
	end

	def reloadable?
		!@reload_command.nil?
	end
	def reload(context : Context)
		build_files! context

		command = reload_command

		unless command
			raise Exception.new "This service cannot be reloaded!"
		end

		Process.fork do
			Dir.cd root

			Process.exec "sh", ["-c", command],
				output: Process::Redirect::Inherit,
				error: Process::Redirect::Inherit,
				env: commands_environment
		end.wait
	end

	def get_pid_file(pid_dir)
		"#{pid_dir}/#{name}.#{environment.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)
		FileUtils.mkdir_p pid_dir
		File.write get_pid_file(pid_dir), new_pid
	end

	enum Status
		Running
		Dead
		Stopped
		NonRunnable
	end

	def status(pid_dir)
		return Status::NonRunnable if non_runnable
		_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
		"%-16s #{name.colorize(:white).to_s}\n" % "Name:" +
		"%-16s #{type.colorize(:white).to_s}\n" % "Type:" +
			"%-16s #{environment.name.colorize(:white).to_s} (#{environment.type.to_s.downcase})\n" % "Environment:" +
			(
				if provides.size > 0
					"Provides:\n" +
					(provides.map { |x|
						consumers = get_consumers(x.token)

						consumers_string = if consumers.size > 0
							consumers.map(&.full_id.colorize(:green).to_s).join ", "
						else
							"n/a".colorize(:yellow).to_s
						end

						"  - %-12s #{consumers_string}\n" % "#{x.token}:"
					}).join
				else
					""
				end
			) +
			(
				if @reference.consumes.size > 0
					"Consumes:\n" +
					(@reference.consumes.map { |x|
						provider = @providers[x.token]?

						provider_string = if provider
							provider.full_id.colorize(:green).to_s
						elsif x.optional
							"n/a".colorize(:yellow).to_s
						else
							"MISSING".colorize(:red).to_s
						end

						"  - %-12s #{provider_string}\n" % x.token
					}).join
				else
					""
				end
			) +
			(
				if @ports.size > 0
					"Ports:\n" +
					(@ports.map { |name, number|
						"  - %-12s #{number.colorize(:magenta).to_s}\n" % "#{name}:"
					}).join
				else
					""
				end
			)
	end

	def write(path)
		FileUtils.mkdir_p "#{path}"
		File.write "#{path}/#{name}.#{@environment.name}.spec", to_spec
	end

	def remove(context)
		context.title "Removing #{to_s}"

		files.reverse.each do |file|
			file_path = evaluate file.file_path

			context.info "Removing #{file.name}"
			command = file.deletion_command

			child = Process.fork do
				Dir.cd root

				exit 0 unless File.exists? file_path

				if command
					Process.exec "sh", ["-c", command],
						output: Process::Redirect::Inherit,
						error: Process::Redirect::Inherit,
						env: commands_environment
				else
					FileUtils.rm_rf file_path
				end
			end.wait

			unless child.success?
				raise Service::Exception.new "Child process exited with status “#{(child.exit_status/256).to_i}”."
				break
			end
		end

		remove_user_and_group!

		File.delete "#{context.services_directory}/#{name}.#{@environment.name}.spec"

		FileUtils.rm_rf root
	end

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

	def self.parse_id(id) : Tuple(String, String)
		s = id.split '/'

		environment = s[0]
		service = s[1]?

		if service.nil?
			service = environment
			environment = "root"
		end

		{environment, service}
	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

		@providers.each do |token, provider_id|
			service = @context.get_service_by_id provider_id

			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_dependencies
		rdeps = [self]

		i = 0
		while i < rdeps.size
			item = rdeps[i]

			@context.services.each do |service|
				service.providers.any? do |token, id|
					if item.is_id?(id) && ! rdeps.any? service
						rdeps << service
					end
				end
			end

			i += 1
		end

		rdeps
	end

	def get_default_provider(token) : String?
		@environment.get_provider(token) || @context.root_environment.get_provider(token)
	end

	def consumes?(token, origin)
		providers.select do |_token, provider|
			token == _token && origin.is_id?(provider)
		end.size > 0
	end

	def get_consumers(token)
		@context.services.select(&.consumes?(token, self))
	end

	def default_user_name
		full_id.sub('/', '.')
	end
	def user_name
		@reference.user || default_user_name
	end
	def group_name
		@reference.group || default_user_name
	end

	def get_uid_gid
		passwd = Passwd.new("/etc/passwd", "/etc/group")

		user = passwd.get_user(user_name).not_nil!

		{user.uid, user.gid}
	end

	def create_user_and_group!
		Passwd.new("/etc/passwd", "/etc/group").tap do |passwd|
			if user = passwd.get_user user_name
				group = passwd.get_group user_name

				return if group.nil?

				group.users = reverse_dependencies.map &.user_name

				passwd.mod_group group
			else
				passwd.add_user user_name,
					full_name: "Service[#{id}]"
			end
		end
	end

	def remove_user_and_group!
		Passwd.new("/etc/passwd", "/etc/group").tap do |passwd|
			passwd.remove_user user_name
			passwd.remove_group user_name
		end
	end
end