Improved checks.

- Environments can have checks, that are run before the service’s
    checks.
  - Directories can now be checked as well as files.
  - Failing checks now stop the start process with a Service::Exception.
  - Some variable substitution is done in check commands and tests.
  - Some environment variables related to the environment to run the
    service in are also exported.

src/main.cr

@@ -39,7 +39,8 @@ class ServiceDefinition
 	struct Checks
 		YAML.mapping({
 			name: String,
-			file: String, # FIXME: -> String? and add directory:?
+			file: String?,
+			directory: String?,
 			command: String
 		})
 	end
@@ -115,12 +116,25 @@ class Environment
 		domain_name: {
 			type: String?,
 			key: "domain-name"
+		},
+		checks: {
+			# FIXME: Would probably need a more neutral namespace.
+			type: Array(ServiceDefinition::Checks),
+			default: Array(ServiceDefinition::Checks).new
 		}
 	})
 
 	def initialize()
 		@name = "root"
 		@type = Type::Prefix
+		@checks = Array(ServiceDefinition::Checks).new
+
+		# FIXME: Should this *really* be here?
+		@checks << ServiceDefinition::Checks.from_yaml <<-EOF
+		name: Creating data directory
+		directory: /srv/%{ENVIRONMENT}
+		command: mkdir -p /srv/%{ENVIRONMENT} && chmod a+rwt /srv/%{ENVIRONMENT}
+		EOF
 	end
 
 	class_getter root = Environment.new
@@ -242,13 +256,34 @@ class Service
 		@reference.provides
 	end
 
+	def export_environment_variables
+		ENV["SERVICE_ENVIRONMENT"] = @environment.name
+		ENV["SERVICE_ENVIRONMENT_TYPE"] = @environment.type.to_s
+	end
+	private def evaluate(string)
+		string.sub /%{[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)
-		@reference.checks.each do |check|
+		export_environment_variables
+
+		(@environment.checks + @reference.checks).each do |check|
 			run_check = false
 
-			# Other tests will likely come later.
-			if check.file && ! File.exists? check.file
-				run_check = true
+			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
@@ -258,10 +293,17 @@ class Service
 			puts "  - #{check.name}"
 
 			# FIXME: Output? Only in debug mode?
-			Process.run "sh", ["-c", check.command], output: Process::Redirect::Inherit, error: Process::Redirect::Inherit
+			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}"