Sakai Development: Post Eight

This post follows straight on from the last, especially as I've missed a constant setting which goes with the ones listed at its end, a new line 857:

ACTIONS_ON_MULTIPLE_ITEMS.add(ActionType.ARCHIVE);

Looking at the next section I might need to change, where permissions are sorted out at lines 1721-1801, I don't think anything needs to be altered, because this draws in constant values which I have already altered. However, things do need to be changed where permissions are set for items. This is done with new lines 2203 and 2209:

boolean canArchive = ContentHostingService.allowArchiveResource(id);
item.setCanArchive(canArchive);

Of course, there will need to be corresponding alterations in the ContentHostingService class. I just need to find it - there is no ContentHostingService.java file in the source code. And searching online doesn't find anything useful. It's time to email those in the know, but meanwhile I can carry on with other bits of code. But I got a really quick answer - before I had a chance to do so, which tells me that I'm on the right lines:

"Yeah this one is in the kernel. The CHS Api lives there.
Sounds like what you are doing is correct. You'll need to add a method there that, most likely, checks some permission and returns true or false. If you want it set via a permission of course. You could just make it always available if that is what you wanted to, then you may not need to mod the kernel.

Then you could do item.canaddarchive(true)"

Thinking a bit more about this, I feel that perhaps I don't need a new kernel method, but I can be more sophisticated than making the service always available. To archive an item is basically making a copy, so what I really should do is to tie the archiving permission to the copy permission. So instead of the lines 2203 and 2209 above, I'll just check the canRead permission which is already there. (It strikes me, though, that in this world of DRM, read and copy are not necessarily the same thing, but never mind.) At least, I'm now at the end of the setting of permission booleans - the next bit of code should actually do something. (And no, I still have no idea why none of the kernel appears to be in the source code I downloaded, but this difficulty is one of the factors in my decision.)

What I want to work on now is to build the three archiving intermediate pages, which should be almost precisely like existing pages. The code for this starts at line 3961, which is where the delete confirmation page building code begins. To remind you, the three intermediate pages are the confirmation, collection metadata entry, and finish; the first and third will basically be copies of the equivalent delete pages and will therefore be built much in the same way. (I expected that most of the work for this little project would consist of copying and then amending existing code, nothing terribly difficult, and this is exactly what is being done here.) Since the code being copied is quite long, I'm not going to quote it all here. The two routines are very similar, so it looks as though copy and paste has already been used. I don't think I have time to look into the lines which are commented "//%%%% FIXME". I'll also need a third copy for MODE_ADD_ARCHIVE_METADATA. The new code becomes lines 4063 to 4207.

The code to call one of these new routines comes next, also a simple copy and modification of existing code. This comes in the context for the main page being re-displayed, as it will be on MODE_ARCHIVE_FINISH: lines 4823-7:

else if (mode.equals (MODE_ARCHIVE_FINISH))
{
  // build the context for the basic step of archive confirm page
  template = buildArchiveFinishContext (portlet, context, data, state);
}

This gives a total of about 200 lines of boilerplate code copied, modified slightly, and inserted back into the class. From this point onwards, we start getting into more exciting development (though there is still a little bit more to add, to call the code to create the context for the metadata form and for the confirmation page - which, it has just occurred to me, could sensibly be the same thing...I may want to revisit some of the above changes to do this, but for the moment I'll just leave things as they are, as it shouldn't do any harm to create constants but not use them).

The model I have used so far for these changes is the existing code for item deletion. Now, there is a slight problem: the actual deletion code appears to delete items one at a time when more than one is selected for deletion, and we can't do this for the archiving; we want one SWORD2 transaction whether there are one or more items. We now need to copy and modify two routines - doCopy, and doDeleteconfirm - which set the application state to doCopy or Deleteconfirm respectively. The first will set the doArchive state, and the second will set Archiveconfirm state, in both cases processing the list of items selected for archiving into a vector format, and these states should then be processed to make the actual archiving or the display of the confirmation page happen. This gives another hundred or so lines of code modified which doesn't really do much.

The next place where something needs to be added is now line 6288. The doDispatchItem method, of which this switch block forms part, is, like most of the rest this class, sparsely commented, but appears to be the part which determines what to do - hence the switch block, with cases corresponding to the different actions. The question is, whether the ARCHIVE case should be like the COPY case or the DELETE case? It's hard to tell without more documentation. The COPY case basically adds the ID of a selected item to a list of items to copy, while the DELETE case actually calls deleteItem - a method we have already decided isn't appropriate to copy directly (as we don't want to break down the archiving of a collection of items into a sequence of archiving actions on the individual items). So the ARCHIVE case needs to be something in between, something like this (I hope):

case ARCHIVE:
  List items_to_be_archived = new ArrayList();
  if(selectedItemId != null)
  {
    items_to_be_archived.add(selectedItemId);
  }
  state.removeAttribute(STATE_ITEMS_TO_BE_MOVED);
  state.setAttribute(STATE_ITEMS_TO_BE_ARCHIVED, items_to_be_archived);
  if (state.getAttribute(STATE_MESSAGE) == null)
  {
    // need new context
    state.setAttribute (STATE_MODE, MODE_ARCHIVE_FINISH);
  }
  break; 

which forms the new lines 6288 to 6301.