--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pyams_sequence/reference.py	Thu Jul 12 16:00:06 2018 +0200
@@ -0,0 +1,146 @@
+#
+# Copyright (c) 2008-2018 Thierry Florac <tflorac AT ulthar.net>
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+
+__docformat__ = 'restructuredtext'
+
+
+# import standard library
+
+# import interfaces
+from hypatia.interfaces import ICatalog
+from pyams_i18n.interfaces import II18n
+from pyams_sequence.interfaces import IInternalReference, ISequentialIdInfo, ISequentialIntIds
+from pyams_skin.layer import IPyAMSUserLayer
+from zope.lifecycleevent.interfaces import IObjectModifiedEvent
+
+try:
+    from pyams_workflow.interfaces import IWorkflow, IWorkflowVersions, IWorkflowVersion, \
+        IWorkflowState, IWorkflowManagedContent, IWorkflowPublicationInfo, IWorkflowTransitionEvent
+except ImportError:
+    handle_workflow = False
+else:
+    handle_workflow = True
+
+# import packages
+from hypatia.catalog import CatalogQuery
+from hypatia.query import Eq
+from pyams_catalog.query import CatalogResultSet
+from pyams_utils.registry import get_utility
+from pyams_utils.request import check_request
+from pyramid.events import subscriber
+
+
+@subscriber(IObjectModifiedEvent, context_selector=IInternalReference)
+def handle_modified_reference(event):
+    """Handle modified reference"""
+    for description in event.descriptions:
+        for attribute in description.attributes:
+            if attribute == 'reference':
+                del event.object.target
+                return
+
+
+if handle_workflow:
+    # Target is handled as a volatile property to keep references in memory
+    # Reference must be updated when a content is published or retired while being in version
+    # greater than 1
+    @subscriber(IWorkflowTransitionEvent)
+    def handle_workflow_transition(event):
+        """Handle workflow transition to update internal references"""
+        workflow_state = IWorkflowState(event.object, None)
+        if (workflow_state is None) or (workflow_state.version_id == 1):
+            return  # don't update references on first version
+        sequence_info = ISequentialIdInfo(event.object, None)
+        if sequence_info is not None:
+            catalog = get_utility(ICatalog)
+            params = Eq(catalog['link_reference'], sequence_info.hex_oid)
+            for result in CatalogResultSet(CatalogQuery(catalog).query(params)):
+                del result.target
+
+
+def get_last_version(content):
+    """Check for last available version"""
+    if handle_workflow and (IWorkflowVersion.providedBy(content) or IWorkflowManagedContent.providedBy(content)):
+        content = IWorkflowVersions(content).get_last_versions()[0]
+    if ISequentialIdInfo(content, None) is not None:
+        return content
+    else:
+        return None
+
+
+def get_visible_version(content):
+    """Check for visible version"""
+    if handle_workflow:
+        if IWorkflowVersion.providedBy(content) or IWorkflowManagedContent.providedBy(content):
+            workflow = IWorkflow(content)
+            versions = IWorkflowVersions(content).get_versions(workflow.published_states, sort=True)
+            if versions:
+                return versions[-1]
+        publication_info = IWorkflowPublicationInfo(content, None)
+        if publication_info is not None:
+            if publication_info.is_visible():
+                return content
+            else:
+                return None
+    return content
+
+
+def get_version_in_state(content, state):
+    """Check for versions in given status"""
+    if handle_workflow and (IWorkflowVersion.providedBy(content) or IWorkflowManagedContent.providedBy(content)):
+        versions = IWorkflowVersions(content).get_versions(state)
+        if versions:
+            content = versions[0]
+    if ISequentialIdInfo(content, None) is not None:
+        return content
+    else:
+        return None
+
+
+def get_sequence_dict(version, attribute='title', request=None):
+    """Get OID and label matching given version"""
+    sequence = get_utility(ISequentialIntIds)
+    info = ISequentialIdInfo(version)
+    return {'id': info.hex_oid,
+            'text': '{0} ({1})'.format(II18n(version).query_attribute(attribute, request=request),
+                                       sequence.get_short_oid(info.oid))}
+
+
+def get_sequence_target(oid, state):
+    """Get content matching given OID"""
+    sequence = get_utility(ISequentialIntIds)
+    content = sequence.query_object_from_oid(oid)
+    if handle_workflow and (IWorkflowVersion.providedBy(content) or IWorkflowManagedContent.providedBy(content)):
+        versions = IWorkflowVersions(content).get_versions(state, sort=True)
+        if versions:
+            content = versions[0]
+            return content
+
+
+def get_reference_target(reference, state=None, request=None):
+    """Get target of given reference OID"""
+    catalog = get_utility(ICatalog)
+    params = Eq(catalog['oid'], reference)
+    results = list(CatalogResultSet(CatalogQuery(catalog).query(params)))
+    if results:
+        if state:
+            results = list(filter(lambda x: get_version_in_state(x, state), results))
+        else:
+            if request is None:
+                request = check_request()
+            if IPyAMSUserLayer.providedBy(request):
+                getter = get_visible_version
+            else:
+                getter = get_last_version
+            results = list(map(getter, results))
+        if results:
+            return results[0]