diff --git a/bin/generate-filters b/bin/generate-filters
index 8215e67..cdb2755 100755
--- a/bin/generate-filters
+++ b/bin/generate-filters
@@ -1,14 +1,4 @@
 #!/usr/bin/env php
 <?php
 
-use Opdavies\GmailFilterBuilder\Builder;
-
-if (file_exists(__DIR__.'/../../../../filters.php')) {
-    $filters = require(__DIR__.'/../../../../filters.php');
-} elseif (file_exists(__DIR__.'/../filters.php')) {
-    $filters = require(__DIR__.'/../filters.php');
-} else {
-    throw new \Exception('No filters.php file found.');
-}
-
-echo new Builder($filters);
+require_once __DIR__.'/generate-filters.php';
diff --git a/bin/generate-filters.php b/bin/generate-filters.php
new file mode 100644
index 0000000..00f7171
--- /dev/null
+++ b/bin/generate-filters.php
@@ -0,0 +1,14 @@
+<?php
+
+use Opdavies\GmailFilterBuilder\Console\Command\GenerateCommand;
+use Opdavies\GmailFilterBuilder\Container\Container;
+use Symfony\Component\Console\Application;
+
+require_once __DIR__.'/../vendor/autoload.php';
+
+$container = new Container();
+
+/** @var Application $application */
+$application = $container->get('app.cli');
+$application->setDefaultCommand(GenerateCommand::NAME);
+$application->run();
diff --git a/composer.json b/composer.json
index 04bc605..f6e6514 100644
--- a/composer.json
+++ b/composer.json
@@ -10,20 +10,34 @@
         }
     ],
     "require": {
+        "symfony/config": "^3.4",
+        "symfony/console": "^3.4",
+        "symfony/dependency-injection": "^3.4",
+        "symfony/filesystem": "^3.4",
+        "symfony/yaml": "^3.4",
         "tightenco/collect": "^5.4"
     },
     "require-dev": {
-        "phpunit/phpunit": "^5.7"
+        "phpunit/phpunit": "^5.7",
+        "symfony/var-dumper": "^3.4"
     },
     "autoload": {
         "psr-4": {
             "Opdavies\\GmailFilterBuilder\\": "src/"
         }
     },
+    "autoload-dev": {
+        "psr-4": {
+            "Tests\\Opdavies\\GmailFilterBuilder\\": "tests/"
+        }
+    },
     "extra": {
         "branch-alias": {
             "dev-master": "1.1-dev"
         }
     },
-    "bin": ["bin/generate-filters"]
+    "bin": ["bin/generate-filters"],
+    "config": {
+        "sort-packages": true
+    }
 }
diff --git a/config/services.yml b/config/services.yml
new file mode 100644
index 0000000..75f8706
--- /dev/null
+++ b/config/services.yml
@@ -0,0 +1,13 @@
+services:
+  app.cli:
+    class: Symfony\Component\Console\Application
+    autowire: true
+
+  app.builder:
+    class: Opdavies\GmailFilterBuilder\Service\Builder
+
+  app.generate.command:
+    class: Opdavies\GmailFilterBuilder\Console\Command\GenerateCommand
+    autowire: true
+    tags:
+      - { name: ConsoleCommand }
diff --git a/src/Builder.php b/src/Builder.php
index 8071191..a5cd6d7 100644
--- a/src/Builder.php
+++ b/src/Builder.php
@@ -2,89 +2,11 @@
 
 namespace Opdavies\GmailFilterBuilder;
 
-class Builder
+use Opdavies\GmailFilterBuilder\Service\Builder as NewBuilder;
+
+/**
+ * @deprecated
+ */
+class Builder extends NewBuilder
 {
-    /**
-     * @var array
-     */
-    private $filters = [];
-
-    public function __construct(array $filters)
-    {
-        $this->filters = $filters;
-    }
-
-    public function __toString()
-    {
-        return $this->build();
-    }
-
-    /**
-     * Build XML for a set of filters.
-     *
-     * @return string
-     */
-    private function build()
-    {
-        $prefix = "<?xml version='1.0' encoding='UTF-8'?>" . PHP_EOL . "<feed xmlns='http://www.w3.org/2005/Atom' xmlns:apps='http://schemas.google.com/apps/2006'>";
-        $suffix = '</feed>';
-
-        $xml = collect($this->filters)->map(function ($items) {
-            return $this->buildEntry($items);
-        })->implode(PHP_EOL);
-
-        return collect([$prefix, $xml, $suffix])->implode(PHP_EOL);
-    }
-
-    /**
-     * Build XML for an filter.
-     *
-     * @param Filter $filter
-     *
-     * @return string
-     */
-    private function buildEntry(Filter $filter)
-    {
-        $entry = collect($filter->getProperties())->map(function ($value, $key) {
-            return $this->buildProperty($value, $key);
-        })->implode(PHP_EOL);
-
-        return collect(['<entry>', $entry, '</entry>'])->implode(PHP_EOL);
-    }
-
-    /**
-     * Build XML for a property.
-     *
-     * @param string $value
-     * @param string $key
-     *
-     * @return string
-     */
-    private function buildProperty($value, $key)
-    {
-        if (collect(['from', 'to'])->contains($key)) {
-            $value = $this->implode($value);
-        }
-
-        return vsprintf("<apps:property name='%s' value='%s'/>", [
-            $key,
-            htmlentities($this->implode($value)),
-        ]);
-    }
-
-    /**
-     * Implode values with the appropriate prefix, suffix and separator.
-     */
-    private function implode($value, $separator = '|')
-    {
-        if (is_string($value)) {
-            return $value;
-        }
-
-        if (is_array($value) && count($value) === 1) {
-            return reset($value);
-        }
-
-        return sprintf('(%s)', collect($value)->implode($separator));
-    }
 }
diff --git a/src/Console/Command/GenerateCommand.php b/src/Console/Command/GenerateCommand.php
new file mode 100644
index 0000000..0ea5751
--- /dev/null
+++ b/src/Console/Command/GenerateCommand.php
@@ -0,0 +1,58 @@
+<?php
+
+namespace Opdavies\GmailFilterBuilder\Console\Command;
+
+use Opdavies\GmailFilterBuilder\Builder;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Style\SymfonyStyle;
+use Symfony\Component\Filesystem\Exception\IOException;
+
+class GenerateCommand extends Command
+{
+    const NAME = 'generate';
+
+    /**
+     * {@inheritdoc}
+     */
+    public function configure()
+    {
+        $this
+            ->setName(self::NAME)
+            ->setDefinition([
+                new InputOption('input-file', null, InputOption::VALUE_OPTIONAL, 'The name of the PHP file containing your filters.', 'filters.php'),
+                new InputOption('output-file', null, InputOption::VALUE_OPTIONAL, 'The name of the XML file to generate.', 'filters.xml')
+            ])
+            ->setDescription('Generates XML for Gmail filters.')
+        ;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function execute(InputInterface $input, OutputInterface $output)
+    {
+        $inputFile = $input->getOption('input-file');
+        $outputFile = $input->getOption('output-file');
+
+        if (file_exists(__DIR__.'/../../../../'.$inputFile)) {
+            $filters = require(__DIR__.'/../../../../'.$inputFile);
+        } elseif (file_exists(__DIR__.'/../../../'.$inputFile)) {
+            $filters = require(__DIR__.'/../../../'.$inputFile);
+        } else {
+            throw new \Exception('No filters.php file found.');
+        }
+
+        $io = new SymfonyStyle($input, $output);
+
+        try {
+            new Builder($filters, $outputFile);
+
+            $io->success(sprintf('%s file generated.', $outputFile));
+        } catch (IOException $e) {
+            $io->error($e->getMessage());
+        }
+    }
+}
diff --git a/src/Container/CommandCompilerClass.php b/src/Container/CommandCompilerClass.php
new file mode 100644
index 0000000..2bf07b6
--- /dev/null
+++ b/src/Container/CommandCompilerClass.php
@@ -0,0 +1,22 @@
+<?php
+
+namespace Opdavies\GmailFilterBuilder\Container;
+
+use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Reference;
+
+class CommandCompilerClass implements CompilerPassInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function process(ContainerBuilder $container) {
+        $definition = $container->findDefinition('app.cli');
+        $taggedServices = $container->findTaggedServiceIds('ConsoleCommand');
+
+        foreach ($taggedServices as $id => $tags) {
+            $definition->addMethodCall('add', [new Reference($id)]);
+        }
+    }
+}
diff --git a/src/Container/Container.php b/src/Container/Container.php
new file mode 100644
index 0000000..905a9e4
--- /dev/null
+++ b/src/Container/Container.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace Opdavies\GmailFilterBuilder\Container;
+
+use Symfony\Component\Config\FileLocator;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Loader\YamlFileLoader;
+
+class Container
+{
+    public function __construct()
+    {
+        $this->containerBuilder = new ContainerBuilder();
+        $loader = new YamlFileLoader($this->containerBuilder, new FileLocator(__DIR__.'/../../config'));
+        $loader->load('services.yml');
+        $this->containerBuilder->addCompilerPass(new CommandCompilerClass());
+        $this->containerBuilder->compile();
+    }
+
+    public function get($className)
+    {
+        return $this->containerBuilder->get($className);
+    }
+}
diff --git a/src/Filter.php b/src/Filter.php
index 1b37c4b..553fa89 100644
--- a/src/Filter.php
+++ b/src/Filter.php
@@ -2,240 +2,11 @@
 
 namespace Opdavies\GmailFilterBuilder;
 
-class Filter
+use Opdavies\GmailFilterBuilder\Model\Filter as NewFilter;
+
+/**
+ * @deprecated
+ */
+class Filter extends NewFilter
 {
-    /**
-     * @var array
-     */
-    private $properties = [];
-
-    /**
-     * @return static
-     */
-    public static function create()
-    {
-        return new static();
-    }
-
-    /**
-     * @param string $value
-     *
-     * @return $this
-     */
-    public function has($value)
-    {
-        $this->properties['hasTheWord'] = $value;
-
-        return $this;
-    }
-
-    /**
-     * @param string $value
-     *
-     * @return $this
-     */
-    public function hasNot($value)
-    {
-        $this->properties['doesNotHaveTheWord'] = $value;
-
-        return $this;
-    }
-
-    /**
-     * @param string|array $values
-     *
-     * @return $this
-     */
-    public function from($values)
-    {
-        $this->properties['from'] = collect($values)->map(function ($value) {
-            return trim($value);
-        })->all();
-
-        return $this;
-    }
-
-    /**
-     * @param string|array $values
-     *
-     * @return $this
-     */
-    public function to($values)
-    {
-        $this->properties['to'] = collect($values)->map(function ($value) {
-            return trim($value);
-        })->all();
-
-        return $this;
-    }
-
-    /**
-     * @param string $subject
-     *
-     * @return $this
-     */
-    public function subject($subject)
-    {
-        $this->properties['subject'] = $subject;
-
-        return $this;
-    }
-
-    /**
-     * @return $this
-     */
-    public function hasAttachment()
-    {
-        $this->properties['hasAttachment'] = 'true';
-
-        return $this;
-    }
-
-    /**
-     * @return $this
-     */
-    public function excludeChats()
-    {
-        $this->properties['excludeChats'] = 'true';
-
-        return $this;
-    }
-
-    /**
-     * @param string $label
-     *
-     * @return $this
-     */
-    public function label($label)
-    {
-        $this->properties['label'] = $label;
-
-        return $this;
-    }
-
-    /**
-     * @return $this
-     */
-    public function archive()
-    {
-        $this->properties['shouldArchive'] = 'true';
-
-        return $this;
-    }
-
-    /**
-     * @param string $label
-     *
-     * @return $this
-     */
-    public function labelAndArchive($label)
-    {
-        $this->label($label)->archive();
-
-        return $this;
-    }
-
-    /**
-     * @return $this
-     */
-    public function spam()
-    {
-        $this->properties['shouldSpam'] = 'true';
-        $this->properties['shouldNeverSpam'] = 'false';
-
-        return $this;
-    }
-
-    /**
-     * @return $this
-     */
-    public function neverSpam()
-    {
-        $this->properties['shouldSpam'] = 'false';
-        $this->properties['shouldNeverSpam'] = 'true';
-
-        return $this;
-    }
-
-    /**
-     * @return $this
-     */
-    public function trash()
-    {
-        $this->properties['shouldTrash'] = 'true';
-
-        return $this;
-    }
-
-    /**
-     * @return $this
-     */
-    public function read()
-    {
-        $this->properties['markAsRead'] = 'true';
-
-        return $this;
-    }
-
-    /**
-     * @return $this
-     */
-    public function star()
-    {
-        $this->properties['shouldStar'] = 'true';
-
-        return $this;
-    }
-
-    /**
-     * @param string $to
-     *
-     * @return $this
-     */
-    public function forward($to)
-    {
-        $this->properties['forwardTo'] = $to;
-
-        return $this;
-    }
-
-    /**
-     * @return $this
-     */
-    public function important()
-    {
-        $this->properties['shouldAlwaysMarkAsImportant'] = 'true';
-
-        return $this;
-    }
-
-    /**
-     * @return $this
-     */
-    public function notImportant()
-    {
-        $this->properties['shouldNeverMarkAsImportant'] = 'true';
-
-        return $this;
-    }
-
-    /**
-     * @param string $category
-     *
-     * @return $this
-     */
-    public function categorise($category)
-    {
-        $this->properties['smartLabelToApply'] = $category;
-
-        return $this;
-    }
-
-    /**
-     * @return array
-     */
-    public function getProperties()
-    {
-        return $this->properties;
-    }
 }
diff --git a/src/Model/Filter.php b/src/Model/Filter.php
new file mode 100644
index 0000000..75d036f
--- /dev/null
+++ b/src/Model/Filter.php
@@ -0,0 +1,241 @@
+<?php
+
+namespace Opdavies\GmailFilterBuilder\Model;
+
+class Filter
+{
+    /**
+     * @var array
+     */
+    private $properties = [];
+
+    /**
+     * @return static
+     */
+    public static function create()
+    {
+        return new static();
+    }
+
+    /**
+     * @param string $value
+     *
+     * @return $this
+     */
+    public function has($value)
+    {
+        $this->properties['hasTheWord'] = $value;
+
+        return $this;
+    }
+
+    /**
+     * @param string $value
+     *
+     * @return $this
+     */
+    public function hasNot($value)
+    {
+        $this->properties['doesNotHaveTheWord'] = $value;
+
+        return $this;
+    }
+
+    /**
+     * @param string|array $values
+     *
+     * @return $this
+     */
+    public function from($values)
+    {
+        $this->properties['from'] = collect($values)->map(function ($value) {
+            return trim($value);
+        })->all();
+
+        return $this;
+    }
+
+    /**
+     * @param string|array $values
+     *
+     * @return $this
+     */
+    public function to($values)
+    {
+        $this->properties['to'] = collect($values)->map(function ($value) {
+            return trim($value);
+        })->all();
+
+        return $this;
+    }
+
+    /**
+     * @param string $subject
+     *
+     * @return $this
+     */
+    public function subject($subject)
+    {
+        $this->properties['subject'] = $subject;
+
+        return $this;
+    }
+
+    /**
+     * @return $this
+     */
+    public function hasAttachment()
+    {
+        $this->properties['hasAttachment'] = 'true';
+
+        return $this;
+    }
+
+    /**
+     * @return $this
+     */
+    public function excludeChats()
+    {
+        $this->properties['excludeChats'] = 'true';
+
+        return $this;
+    }
+
+    /**
+     * @param string $label
+     *
+     * @return $this
+     */
+    public function label($label)
+    {
+        $this->properties['label'] = $label;
+
+        return $this;
+    }
+
+    /**
+     * @return $this
+     */
+    public function archive()
+    {
+        $this->properties['shouldArchive'] = 'true';
+
+        return $this;
+    }
+
+    /**
+     * @param string $label
+     *
+     * @return $this
+     */
+    public function labelAndArchive($label)
+    {
+        $this->label($label)->archive();
+
+        return $this;
+    }
+
+    /**
+     * @return $this
+     */
+    public function spam()
+    {
+        $this->properties['shouldSpam'] = 'true';
+        $this->properties['shouldNeverSpam'] = 'false';
+
+        return $this;
+    }
+
+    /**
+     * @return $this
+     */
+    public function neverSpam()
+    {
+        $this->properties['shouldSpam'] = 'false';
+        $this->properties['shouldNeverSpam'] = 'true';
+
+        return $this;
+    }
+
+    /**
+     * @return $this
+     */
+    public function trash()
+    {
+        $this->properties['shouldTrash'] = 'true';
+
+        return $this;
+    }
+
+    /**
+     * @return $this
+     */
+    public function read()
+    {
+        $this->properties['markAsRead'] = 'true';
+
+        return $this;
+    }
+
+    /**
+     * @return $this
+     */
+    public function star()
+    {
+        $this->properties['shouldStar'] = 'true';
+
+        return $this;
+    }
+
+    /**
+     * @param string $to
+     *
+     * @return $this
+     */
+    public function forward($to)
+    {
+        $this->properties['forwardTo'] = $to;
+
+        return $this;
+    }
+
+    /**
+     * @return $this
+     */
+    public function important()
+    {
+        $this->properties['shouldAlwaysMarkAsImportant'] = 'true';
+
+        return $this;
+    }
+
+    /**
+     * @return $this
+     */
+    public function notImportant()
+    {
+        $this->properties['shouldNeverMarkAsImportant'] = 'true';
+
+        return $this;
+    }
+
+    /**
+     * @param string $category
+     *
+     * @return $this
+     */
+    public function categorise($category)
+    {
+        $this->properties['smartLabelToApply'] = $category;
+
+        return $this;
+    }
+
+    /**
+     * @return array
+     */
+    public function getProperties()
+    {
+        return $this->properties;
+    }
+}
diff --git a/src/Service/Builder.php b/src/Service/Builder.php
new file mode 100644
index 0000000..9acdbb7
--- /dev/null
+++ b/src/Service/Builder.php
@@ -0,0 +1,128 @@
+<?php
+
+namespace Opdavies\GmailFilterBuilder\Service;
+
+use Opdavies\GmailFilterBuilder\Filter;
+use Symfony\Component\Filesystem\Filesystem;
+
+class Builder
+{
+    private $filesystem;
+
+    /**
+     * @var array
+     */
+    private $filters = [];
+
+    /**
+     * @var
+     */
+    private $outputFile;
+
+    /**
+     * @var bool
+     */
+    private $writeFile;
+
+    /**
+     * @var string
+     */
+    private $xml;
+
+    public function __construct(array $filters, $outputFile = 'filters.xml', $writeFile = true) {
+        $this->filesystem = new Filesystem();
+        $this->filters = $filters;
+        $this->outputFile = $outputFile;
+        $this->writeFile = $writeFile;
+
+        $this->build();
+    }
+
+    public function __toString()
+    {
+        return $this->build();
+    }
+
+    /**
+     * Returns the generated XML.
+     *
+     * @return string
+     */
+    public function getXml()
+    {
+        return $this->xml;
+    }
+
+    /**
+     * Build XML for a set of filters.
+     *
+     * @return string
+     */
+    private function build()
+    {
+        $prefix = "<?xml version='1.0' encoding='UTF-8'?>" . PHP_EOL . "<feed xmlns='http://www.w3.org/2005/Atom' xmlns:apps='http://schemas.google.com/apps/2006'>";
+        $suffix = '</feed>';
+
+        $xml = collect($this->filters)->map(function ($items) {
+            return $this->buildEntry($items);
+        })->implode(PHP_EOL);
+
+        $this->xml = collect([$prefix, $xml, $suffix])->implode(PHP_EOL);
+
+        if ($this->writeFile) {
+            $this->filesystem->dumpFile($this->outputFile, $this->xml);
+        }
+    }
+
+    /**
+     * Build XML for an filter.
+     *
+     * @param Filter $filter
+     *
+     * @return string
+     */
+    private function buildEntry(Filter $filter)
+    {
+        $entry = collect($filter->getProperties())->map(function ($value, $key) {
+            return $this->buildProperty($value, $key);
+        })->implode(PHP_EOL);
+
+        return collect(['<entry>', $entry, '</entry>'])->implode(PHP_EOL);
+    }
+
+    /**
+     * Build XML for a property.
+     *
+     * @param string $value
+     * @param string $key
+     *
+     * @return string
+     */
+    private function buildProperty($value, $key)
+    {
+        if (collect(['from', 'to'])->contains($key)) {
+            $value = $this->implode($value);
+        }
+
+        return vsprintf("<apps:property name='%s' value='%s'/>", [
+            $key,
+            htmlentities($this->implode($value)),
+        ]);
+    }
+
+    /**
+     * Implode values with the appropriate prefix, suffix and separator.
+     */
+    private function implode($value, $separator = '|')
+    {
+        if (is_string($value)) {
+            return $value;
+        }
+
+        if (is_array($value) && count($value) === 1) {
+            return reset($value);
+        }
+
+        return sprintf('(%s)', collect($value)->implode($separator));
+    }
+}
diff --git a/tests/Unit/BuilderTest.php b/tests/Unit/BuilderTest.php
index 25f24d3..cf70229 100644
--- a/tests/Unit/BuilderTest.php
+++ b/tests/Unit/BuilderTest.php
@@ -18,7 +18,7 @@ class BuilderTest extends TestCase
             ->star()
             ->important();
 
-        $result = new Builder([$filterA, $filterB]);
+        $result = new Builder([$filterA, $filterB], '', false);
 
         $expected = <<<EOF
 <?xml version='1.0' encoding='UTF-8'?>
@@ -36,6 +36,6 @@ class BuilderTest extends TestCase
 </feed>
 EOF;
 
-        $this->assertEquals($expected, $result->__toString());
+        $this->assertEquals($expected, $result->getXml());
     }
 }