Data Cart Restructuring Pt. 2

[RayPlante]

As part of the on-going restructuring of the landing page code, PR #166 ("ODD-940: Data Cart code restructuring") was aimed at improving encapsulation of the code that manages the data cart. That PR centered on the introduction of the DataCart class that controls the list of items currently in the cart. This follow-on PR focuses on improving the encapsulation, particularly around the communication between components that use the cart as well as improving the separation of concerns for the different classes within the data cart module.

This PR attempts to address the these main concerns:

• several classes manipulated the state of the data cart by directly analyzing or manipulating a TreeNode data structure.
  • as TreeNode is part of the primeng TreeTable widget, that made multiple non-display classes dependent on primeng; this would make it harder to change to a different widget for the display.
  • for good encapsulation/separation-of-concerns in a MVC architecture, all such manipulations should go through the DataCart interface.
• There are several communication channels and techniques used to communicate changes in the cart and the download status which could be consolidated around separation-of-conern principles. (For example, the BundleplanComponent used the DownloadService to download data, but then used the TreetableComponent to tell the DownloadService that the download is complete, so that it can update the cart.)

This PR addresses these concerns primarily through these design changes:

• The DataCart class is now watchable; thus all communications about changes in the cart, including the download state, goes through the DataCart.
• The role of the CartService has been redefined to be about obtaining an instance of a DataCart.

I have also added a description of the Cart framework into datacart/README.md that attempts to describe the role of the key classes and explain the communication between them.

[chuanlin2018]

I found three issues and two of them were fixed:

1. For ediid starts with "ark:", zip file name and download status do not show up in tree table (fixed);
2. Download status in the tree table is always green (fixed);
3. In the tree table, select/deselect the root of a dataset is not working properly. this.dataTree.children = [...this.dataTree.children] doesn't seem to be working. Function refreshTree() can be used as a work around but the tree table will fresh every time user select/deselect a treenode. So far I didn't find a better way to fix this.

[RayPlante]

This is great--thanks for doing this. The refreshTree() looks fairly inexpensive--nice! Hopefully it won't cause any weird blinking. I'll follow up with you on the next step.

[chuanlin2018]

It does cause blinking :( So I didn't implement the change in this check in. You can try it to see if it's acceptable.

[RayPlante]

@chuanlin2018: This last commit (2f9e6d6) hopefully fixes the buggy selection behavior we were seeing (including # 3 in you list above). Can you confirm?

[chuanlin2018]

Will do.

[RayPlante]

I'll note that this fix did not require the "who" capability that I shared in the restruct/cartservice-selwho branch, so I left that out.

[chuanlin2018]

OK. I am reading your code while compiling locally.

[chuanlin2018]

The problem seems to be fixed. I didn't see it happen again when running locally. Need a while to understand your code though:)

[chuanlin2018]

Thanks for the explanation. Now I understand. Seems the conflicts need be resolved before I can approve the changes...

[chuanlin2018]

Just ran into couple of minor issues while going through your code:

1. "Remove Downloaded" and "Remove Selected" did the same thing - both buttons call the same function.
2. Direct download in datacart was not working - problem with the parameters in this.dataCart.setDownloadStatus().

[chuanlin2018]

I fixed the following:

1. "Remove Downloaded" - now calls right function.
2. Direct download in datacart
3. gaTrackEvent() in Google Analytics service - handle the use case that event = undefined while action = undefined. So far this never happened.