diff --git a/CHANGELOG.md b/CHANGELOG.md
index b7d93d6e..4d80f4a9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 - Fix wildfly_resource's with array of hashes values.
 - Allow custom templates or file for module.xml.
 - Support for jgroups stacks.
+- Rewrite functions in Puppet language.
 
 ## 2.0.1
 
diff --git a/functions/service_config.pp b/functions/service_config.pp
new file mode 100644
index 00000000..6041daa6
--- /dev/null
+++ b/functions/service_config.pp
@@ -0,0 +1,68 @@
+function wildfly::service_config(
+  Enum['wildfly', 'jboss-eap'] $distribution,
+  String $version,
+  Enum['standalone', 'domain'] $mode,
+  Enum['sysvinit', 'systemd', 'upstart'] $init_system) {
+
+  case $distribution {
+
+    # intentionally not using $facts (see rspec-puppet #503)
+
+    'wildfly' : {
+      $conf_file = $::osfamily ? {
+        'Debian' => '/etc/default/wildfly',
+        default  => '/etc/default/wildfly.conf'
+      }
+
+      $service_file = "wildfly-init-${downcase($::osfamily)}.sh"
+
+      case [versioncmp($version, '10'), $init_system] {
+        [-1, default] : {
+          {
+            'service_name'     => 'wildfly',
+            'conf_file'        => $conf_file,
+            'conf_template'    => 'wildfly/wildfly.sysvinit.conf',
+            'service_file'     => "bin/init.d/${service_file}",
+          }
+        }
+        [default, 'systemd'] : {
+          {
+            'service_name'     => 'wildfly',
+            'conf_file'        => '/etc/wildfly/wildfly.conf',
+            'conf_template'    => 'wildfly/wildfly.systemd.conf',
+            'service_file'     => "docs/contrib/scripts/init.d/${service_file}",
+            'systemd_template' => 'wildfly/wildfly.systemd.service',
+          }
+        }
+        [default, default] : {
+          {
+            'service_name'     => 'wildfly',
+            'conf_file'        => $conf_file,
+            'conf_template'    => 'wildfly/wildfly.sysvinit.conf',
+            'service_file'     => "docs/contrib/scripts/init.d/${service_file}",
+          }
+        }
+      }
+    }
+    'jboss-eap' : {
+      case versioncmp($version, '7') {
+        -1 : {
+          {
+            'service_name'     => 'jboss-as',
+            'conf_file'        => '/etc/jboss-as/jboss-as.conf',
+            'conf_template'    => 'wildfly/wildfly.sysvinit.conf',
+            'service_file'     => "bin/init.d/jboss-as-${mode}.sh",
+          }
+        }
+        default : {
+          {
+            'service_name'     => 'jboss-eap',
+            'conf_file'        => '/etc/default/jboss-eap.conf',
+            'conf_template'    => 'wildfly/wildfly.sysvinit.conf',
+            'service_file'     => 'bin/init.d/jboss-eap-rhel.sh',
+          }
+        }
+      }
+    }
+  }
+}
diff --git a/lib/puppet/parser/functions/service_config.rb b/lib/puppet/parser/functions/service_config.rb
deleted file mode 100644
index 42797f82..00000000
--- a/lib/puppet/parser/functions/service_config.rb
+++ /dev/null
@@ -1,58 +0,0 @@
-module Puppet::Parser::Functions
-  newfunction(:service_config, :type => :rvalue) do |args|
-    distribution = args[0]
-    version = args[1]
-    mode = args[2]
-    init_system = args[3]
-
-    config = {}
-
-    case distribution
-    when 'wildfly'
-      if function_versioncmp([version, '10']) >= 0
-        if init_system == 'systemd'
-          config['systemd_native'] = true
-          config['systemd_template'] = 'wildfly/wildfly.systemd.service'
-          config['conf_file'] = '/etc/wildfly/wildfly.conf'
-          config['conf_template'] = 'wildfly/wildfly.systemd.conf'
-        else
-          path = 'docs/contrib/scripts/init.d'
-        end
-      else
-        path = 'bin/init.d'
-      end
-
-      osfamily = lookupvar('osfamily')
-      config['service_file'] = "#{path}/wildfly-init-#{osfamily.downcase}.sh"
-
-      unless config['systemd_native']
-        case osfamily
-        when 'RedHat'
-          config['conf_file'] = '/etc/default/wildfly.conf'
-        when 'Debian'
-          config['conf_file'] = '/etc/default/wildfly'
-        end
-        config['conf_template'] = 'wildfly/wildfly.sysvinit.conf'
-      end
-
-      config['service_name'] = 'wildfly'
-    when 'jboss-eap'
-      if function_versioncmp([version, '7']) >= 0
-        config['service_file'] = 'bin/init.d/jboss-eap-rhel.sh'
-        config['conf_file'] = '/etc/default/jboss-eap.conf'
-        config['service_name'] = 'jboss-eap'
-      else
-        config['service_file'] = "bin/init.d/jboss-as-#{mode}.sh"
-        config['conf_file'] = '/etc/jboss-as/jboss-as.conf'
-        config['service_name'] = 'jboss-as'
-      end
-      config['conf_template'] = 'wildfly/wildfly.sysvinit.conf'
-    end
-
-    if init_system == 'systemd' && config['systemd_template'].nil?
-      config['systemd_template'] = 'wildfly/wildfly.sysvinit.service'
-    end
-
-    config
-  end
-end
diff --git a/manifests/service.pp b/manifests/service.pp
index 750627e1..74679503 100644
--- a/manifests/service.pp
+++ b/manifests/service.pp
@@ -1,7 +1,7 @@
 # Manages Wildfly service.
 class wildfly::service {
 
-  $config = service_config($wildfly::distribution, $wildfly::version, $wildfly::mode, $wildfly::init_system)
+  $config = wildfly::service_config($wildfly::distribution, $wildfly::version, $wildfly::mode, $wildfly::init_system)
 
   debug("${wildfly::distribution}.${wildfly::version}.${wildfly::mode}.${wildfly::init_system}: ${config}")
 
@@ -9,9 +9,7 @@
   $conf_template = pick($wildfly::conf_template, $config['conf_template'])
   $service_name = pick($wildfly::service_name, $config['service_name'])
   $service_file = pick($wildfly::service_file, $config['service_file'])
-
-  $systemd_template = $config['systemd_template']
-  $systemd_native = $config['systemd_native']
+  $systemd_template = pick($wildfly::systemd_template, $config['systemd_template'], 'wildfly/wildfly.sysvinit.service')
 
   if !$wildfly::package_name {
     contain "wildfly::service::${wildfly::init_system}"
diff --git a/manifests/service/systemd.pp b/manifests/service/systemd.pp
index 3df8302d..22f24477 100644
--- a/manifests/service/systemd.pp
+++ b/manifests/service/systemd.pp
@@ -1,9 +1,9 @@
 # Wildfly systemd configuration
 #
 class wildfly::service::systemd {
-  $systemd_template = pick($wildfly::systemd_template, $wildfly::service::systemd_template)
 
-  if $wildfly::service::systemd_native {
+  if $wildfly::service::systemd_template == 'wildfly/wildfly.systemd.service' {
+    # Use native script
     file { "${wildfly::dirname}/bin/launch.sh" :
       ensure  => present,
       mode    => '0755',
diff --git a/spec/functions/service_config_spec.rb b/spec/functions/service_config_spec.rb
index 9801f790..e0e9ccd4 100644
--- a/spec/functions/service_config_spec.rb
+++ b/spec/functions/service_config_spec.rb
@@ -1,16 +1,18 @@
-describe 'service_config' do
+describe 'wildfly::service_config' do
   context 'Wildfly 10' do
     let(:distribution) { 'wildfly' }
     let(:version) { '10.0' }
 
-    before(:each) { scope.expects(:lookupvar).at_most_once.with('osfamily').returns('RedHat') }
+    let(:facts) do
+      { :osfamily => 'RedHat' }
+    end
 
     it 'using sysvinit' do
-      is_expected.to run.with_params(distribution, version, 'standalone', 'sysvinit').and_return('service_name' => 'wildfly', 'conf_file' => '/etc/default/wildfly.conf', 'service_file' => 'docs/contrib/scripts/init.d/wildfly-init-redhat.sh', 'conf_template' => 'wildfly/wildfly.sysvinit.conf')
+      is_expected.to run.with_params(distribution, version, 'standalone', 'sysvinit').and_return('service_name' => 'wildfly', 'conf_file' => '/etc/default/wildfly.conf', 'conf_template' => 'wildfly/wildfly.sysvinit.conf', 'service_file' => 'docs/contrib/scripts/init.d/wildfly-init-redhat.sh')
     end
 
     it 'using systemd' do
-      is_expected.to run.with_params(distribution, version, 'standalone', 'systemd').and_return('systemd_native' => true, 'systemd_template' => 'wildfly/wildfly.systemd.service', 'conf_file' => '/etc/wildfly/wildfly.conf', 'conf_template' => 'wildfly/wildfly.systemd.conf', 'service_file' => '/wildfly-init-redhat.sh', 'service_name' => 'wildfly')
+      is_expected.to run.with_params(distribution, version, 'standalone', 'systemd').and_return('service_name' => 'wildfly', 'conf_file' => '/etc/wildfly/wildfly.conf', 'conf_template' => 'wildfly/wildfly.systemd.conf', 'service_file' => 'docs/contrib/scripts/init.d/wildfly-init-redhat.sh', 'systemd_template' => 'wildfly/wildfly.systemd.service')
     end
   end
 
@@ -18,14 +20,16 @@
     let(:distribution) { 'wildfly' }
     let(:version) { '9.0.2' }
 
-    before(:each) { scope.expects(:lookupvar).with('osfamily').returns('RedHat') }
+    let(:facts) do
+      { :osfamily => 'RedHat' }
+    end
 
     it 'using sysvinit' do
       is_expected.to run.with_params(distribution, version, 'standalone', 'sysvinit').and_return('service_name' => 'wildfly', 'conf_file' => '/etc/default/wildfly.conf', 'service_file' => 'bin/init.d/wildfly-init-redhat.sh', 'conf_template' => 'wildfly/wildfly.sysvinit.conf')
     end
 
     it 'using systemd' do
-      is_expected.to run.with_params(distribution, version, 'standalone', 'systemd').and_return('service_name' => 'wildfly', 'conf_file' => '/etc/default/wildfly.conf', 'service_file' => 'bin/init.d/wildfly-init-redhat.sh', 'conf_template' => 'wildfly/wildfly.sysvinit.conf', 'systemd_template' => 'wildfly/wildfly.sysvinit.service')
+      is_expected.to run.with_params(distribution, version, 'standalone', 'systemd').and_return('service_name' => 'wildfly', 'conf_file' => '/etc/default/wildfly.conf', 'service_file' => 'bin/init.d/wildfly-init-redhat.sh', 'conf_template' => 'wildfly/wildfly.sysvinit.conf')
     end
   end
 
@@ -38,7 +42,7 @@
     end
 
     it 'using systemd' do
-      is_expected.to run.with_params(distribution, version, 'standalone', 'systemd').and_return('service_file' => 'bin/init.d/jboss-eap-rhel.sh', 'conf_file' => '/etc/default/jboss-eap.conf', 'service_name' => 'jboss-eap', 'conf_template' => 'wildfly/wildfly.sysvinit.conf', 'systemd_template' => 'wildfly/wildfly.sysvinit.service')
+      is_expected.to run.with_params(distribution, version, 'standalone', 'systemd').and_return('service_file' => 'bin/init.d/jboss-eap-rhel.sh', 'conf_file' => '/etc/default/jboss-eap.conf', 'service_name' => 'jboss-eap', 'conf_template' => 'wildfly/wildfly.sysvinit.conf')
     end
   end
 
@@ -51,7 +55,7 @@
     end
 
     it 'using systemd' do
-      is_expected.to run.with_params(distribution, version, 'standalone', 'systemd').and_return('service_file' => 'bin/init.d/jboss-as-standalone.sh', 'conf_file' => '/etc/jboss-as/jboss-as.conf', 'service_name' => 'jboss-as', 'conf_template' => 'wildfly/wildfly.sysvinit.conf', 'systemd_template' => 'wildfly/wildfly.sysvinit.service')
+      is_expected.to run.with_params(distribution, version, 'standalone', 'systemd').and_return('service_file' => 'bin/init.d/jboss-as-standalone.sh', 'conf_file' => '/etc/jboss-as/jboss-as.conf', 'service_name' => 'jboss-as', 'conf_template' => 'wildfly/wildfly.sysvinit.conf')
     end
   end
 end