Add support for new endpoints for collections in hydrus

[sameshl]

I'm submitting a

• bug report.
• feature request.

Current Behaviour:

hydrus will support treating collections as a resource once PR HTTP-APIs/hydrus#488 gets merged.
This will bring in some changes to the endpoints at which hydrus is serving data.

Those changes need to be added to agent appropriately.

Expected Behaviour:

Brief description of major changes to the endpoints:

(Note: For below discussion, CommandCollection is a collection class, Command would be non-collection class / parsed class. The meaning of non-collection class would be any class which will not act as a 'collection' of items.)

1. GET on /collection/

Example endpoint: /CommandCollection/

This fetches the data from the 'CommandCollection' table.

Example response:

Will return a list of collections.

{
    "@context": "/serverapi/contexts/CommandCollection.jsonld",
    "@id": "/serverapi/CommandCollection/",
    "@type": "CommandCollection",
    "hydra:totalItems": 3,
    "hydra:view": {
        "@id": "/serverapi/CommandCollection?page=1",
        "@type": "hydra:PartialCollectionView",
        "hydra:first": "/serverapi/CommandCollection?page=1",
        "hydra:last": "/serverapi/CommandCollection?page=1"
    },
    "members": [
        {
            "@id": "/serverapi/CommandCollection/7d2cc88f-388a-43f1-80fc-0c2184de4784",
            "@type": "CommandCollection"
        },
        {
            "@id": "/serverapi/CommandCollection/50ed3b68-9437-4c68-93d4-b67013b9d412",
            "@type": "CommandCollection"
        },
        {
            "@id": "/serverapi/CommandCollection/c2e10f88-d205-41e7-aa61-338afd64f657",
            "@type": "CommandCollection"
        }
    ]
}

2. PUT on /collection/

Example endpoint: /CommandCollection/

The request body should have the list of ids of class instances which would be grouped into a collection.
For eg,

{
    "@type": "CommandCollection",
    "members": ["aaaaa",
                "bbbbb",
                "ccccc"]
}

In the above example, 'aaaaaa', 'bbbbb' and 'ccccc' are the ids(primary key) of the instances in Command table.
This adds data in the 'CommandCollection' table.

Example response:

{
    "@context": "http://www.w3.org/ns/hydra/context.jsonld",
    "@type": "Status",
    "description": "Object with ID 50ed3b68-9437-4c68-93d4-b67013b9d412 successfully added",
    "statusCode": 201,
    "title": "Object successfully added."
}

NOTE: The id returned is actually the value of the collection_id column in the table, not the primary key id.
3) GET on /collection/id

Example endpoint: /CommandCollection/50ed3b68-9437-4c68-93d4-b67013b9d412

Note: The id is corresponding to the collection_id column in the CommandCollection table, not the primary key id.

Example response:

Will return all the members belonging to the collection with given collection_id.

{
    "@context": "/serverapi/contexts/CommandCollection.jsonld",
    "@id": "/serverapi/CommandCollectionCollection/50ed3b68-9437-4c68-93d4-b67013b9d412",
    "@type": "CommandCollection",
    "members": [
        {
            "@id": "/serverapi/Command/aaaaaa",
            "@type": "Command"
        },
        {
            "@id": "/serverapi/Command/bbbbbb",
            "@type": "Command"
        },
        {
            "@id": "/serverapi/Command/cccccc",
            "@type": "Command"
        }
    ]
}

4. POST on /collection/id

Example endpoint: /CommandCollection/50ed3b68-9437-4c68-93d4-b67013b9d412

The request body should have the list of members to be updated for the given collection.
For eg,

{
    "@type": "CommandCollection",
    "members": ["ddd",
                "eee",
                "fff"]
}

Note: The id is corresponding to the collection_id column in the CommandCollection table, not the primary key id.

Example response:

Will update all the members belonging to the collection with given collection_id with the members given in the request body.

{
    "@context": "http://www.w3.org/ns/hydra/context.jsonld",
    "@type": "Status",
    "description": "Object with ID 50ed3b68-9437-4c68-93d4-b67013b9d412 successfully updated",
    "statusCode": 200,
    "title": "Object updated"
}

5. DELETE on /collection/id

Example endpoint: /CommandCollection/50ed3b68-9437-4c68-93d4-b67013b9d412

Note: The id is corresponding to the collection_id column in the CommandCollection table, not the primary key id.

Example response:

Will delete that collection from the table.

{
    "@context": "http://www.w3.org/ns/hydra/context.jsonld",
    "@type": "Status",
    "description": "Object with ID 50ed3b68-9437-4c68-93d4-b67013b9d412 successfully deleted",
    "statusCode": 200,
    "title": "Object successfully deleted."
}

6. GET, PUT, POST and DELETE on any /non-collection-class

Example endpoint: /Command/ or /Area

NOTE: All of these will have the same behaviour as what would have happened before on /CommandCollection/ endpoint

[priyanshunayan]

Seems like we need to discuss the Redis layer again due to the latest changes. Earlier, collection members were fetched from the server everytime a request was made to the Collection endpoint and only class instances were stored. And now since a class can have members just like collections, so we need to decide whether to cache them or not.