Provide method which builds the OPDS URL

[kelson42]

Currently the process is:
1 - client builds the OPDS URL
2 - client makes the OPDS URL call and retrieve the OPDS feed
3 - client shares the OPDS feed with libkiwix which parse it and in returns gives the list of books as object

I want that the first steps is done by the libkiwix as this is a common step to all clients. A first version of that code should be already available in Kiwix Desktop (and therefore should be migrated to libkiwix and replaced by a call to new libkiwix method).

The JNI should be updated as Kiwix Android needs it really soon.

[kelson42]

@mgautierfr Please let us know quickly if this does not make sense
@veloman-yunkan This is important to provide this soon as Kiwix Android next GSoC student will need it
@gouri-panda You will benefit of this. In the meantime you need to build the OPDS URL yourself for your first tests. See https://wiki.kiwix.org/wiki/OPDS

[veloman-yunkan]

@kelson42 I can't make sense of this ticket probably because I am missing some background.

I want that the first steps is done by the libkiwix as this is a common step to all clients

Can you please provide at least two examples in different clients?

[kelson42]

@veloman-yunkan Where is built the https://library.kiwix.org/catalog/search OPDS URL with all the filter arguments?

[veloman-yunkan]

This is what I found in kiwix-desktop searching for 'catalog': https://github.com/kiwix/kiwix-desktop/blob/1d8c556075df65999cbde690db7200b181f62df6/src/opdsrequestmanager.cpp#L10-L39

The same search in kiwix-android yields empty results.

[kelson42]

@veloman-yunkan This is what I meant with this ticket, each port should not do its own code to build the URL. Libkiwix shoukd provide a primitive taking the filters and returning the URL string.

[mgautierfr]

The idea here is to use kiwix-lib to fully encapsulate the opds catalog.
For now we have :

• Opds parsing/generation (generating a opds stream from a Library and the opposite).
• Handling of api' url on the server side (we can parse query and answer them).

What is missing is a handling of the urls on the client side. This need will become even more needed with all the changes on the (opds) api (#209, https://github.com/kiwix/kiwix-tools/issues/317, #421, ...)

This (cpp) API is not so easy to design.
For example, on kiwix-desktop we do OPDS query only to get a subset of the catalog (filtered by lang and category) but other filtering (search based on name, ...) is made locally (as it is a subset of what we get with the previous opds query).
But on kiwix-ios I think they do a OPDS query all the time. On android I don't know.
The API must allow the user to decide what filtering is made on locally and what is made with opds.
And the main catalog is on "http://library.kiwix.org/catalog/" but this may not be the case (every kiwix-serve can serve a catalog, so the address of the catalog must be configurable).

Maybe, we can extend kiwix::Manager, or create another object kiwix::OpdsManager or introduce a kiwix::RemoteLibrary...
I havn't fully think about this, I'm open to idea.

[kelson42]

The idea here is to use kiwix-lib to fully encapsulate the opds catalog.
For now we have :
* Opds parsing/generation (generating a opds stream from a Library and the opposite).
* Handling of api' url on the server side (we can parse query and answer them).

What is missing is a handling of the urls on the client side. This need will become even more needed with all the changes on the (opds) api (#209, kiwix/kiwix-tools#317, #421, ...)

Exactly

This (cpp) API is not so easy to design.
For example, on kiwix-desktop we do OPDS query only to get a subset of the catalog (filtered by lang and category) but other filtering (search based on name, ...) is made locally (as it is a subset of what we get with the previous opds query).
But on kiwix-ios I think they do a OPDS query all the time. On android I don't know.
The API must allow the user to decide what filtering is made on locally and what is made with opds.
And the main catalog is on "http://library.kiwix.org/catalog/" but this may not be the case (every kiwix-serve can serve a catalog, so the address of the catalog must be configurable).

Maybe, we can extend kiwix::Manager, or create another object kiwix::OpdsManager or introduce a kiwix::RemoteLibrary...
I havn't fully think about this, I'm open to idea.

This is an interesting discussion and indeed a complex topic. But IMO we should open a new ticket. This ticket is only about generating the URL string, this is neither complex nor subject to a discussion IMO.

[mgautierfr]

This ticket is only about generating the URL string, this is neither complex nor subject to a discussion IMO.

For now, the opds url is only root.xml or a search query.
I think we can have a function taking a Filter has argument. Then the filter could be use either locally on a existing library or to generate a url (to get a opds that can be parse to create a local library).

If we decide to change that when we design the whole system, it would be not difficult to do.

[kelson42]

@mgautierfr This ticket has been written with the search query in mind and agree with your last proposition. This is true that we might need an additional trivial method/api to get the root.xml URL if we want to be coherent.

[kelson42]

@veloman-yunkan Are things clear now for implementation?

[veloman-yunkan]

@kelson42 I think so. I will submit a PR soon, and we'll see if I understood everything correctly.