Extract volume init and removal from project.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

compose/volume.py

@@ -3,8 +3,10 @@ from __future__ import unicode_literals
 
 import logging
 
+from docker.errors import APIError
 from docker.errors import NotFound
 
+from .config import ConfigurationError
 
 log = logging.getLogger(__name__)
 
@@ -50,3 +52,71 @@ class Volume(object):
         if self.external_name:
             return self.external_name
         return '{0}_{1}'.format(self.project, self.name)
+
+
+class ProjectVolumes(object):
+
+    def __init__(self, volumes):
+        self.volumes = volumes
+
+    @classmethod
+    def from_config(cls, name, config_data, client):
+        config_volumes = config_data.volumes or {}
+        volumes = {
+            vol_name: Volume(
+                    client=client,
+                    project=name,
+                    name=vol_name,
+                    driver=data.get('driver'),
+                    driver_opts=data.get('driver_opts'),
+                    external_name=data.get('external_name'))
+            for vol_name, data in config_volumes.items()
+        }
+        return cls(volumes)
+
+    def remove(self):
+        for volume in self.volumes.values():
+            volume.remove()
+
+    def initialize(self):
+        try:
+            for volume in self.volumes.values():
+                if volume.external:
+                    log.debug(
+                        'Volume {0} declared as external. No new '
+                        'volume will be created.'.format(volume.name)
+                    )
+                    if not volume.exists():
+                        raise ConfigurationError(
+                            'Volume {name} declared as external, but could'
+                            ' not be found. Please create the volume manually'
+                            ' using `{command}{name}` and try again.'.format(
+                                name=volume.full_name,
+                                command='docker volume create --name='
+                            )
+                        )
+                    continue
+                volume.create()
+        except NotFound:
+            raise ConfigurationError(
+                'Volume %s specifies nonexistent driver %s' % (volume.name, volume.driver)
+            )
+        except APIError as e:
+            if 'Choose a different volume name' in str(e):
+                raise ConfigurationError(
+                    'Configuration for volume {0} specifies driver {1}, but '
+                    'a volume with the same name uses a different driver '
+                    '({3}). If you wish to use the new configuration, please '
+                    'remove the existing volume "{2}" first:\n'
+                    '$ docker volume rm {2}'.format(
+                        volume.name, volume.driver, volume.full_name,
+                        volume.inspect()['Driver']
+                    )
+                )
+
+    def namespace_spec(self, volume_spec):
+        if not volume_spec.is_named_volume:
+            return volume_spec
+
+        volume = self.volumes[volume_spec.external]
+        return volume_spec._replace(external=volume.full_name)