The correct path for xapian database should be "X/fulltext/xapian",
not "Z//fulltextIndex/xapian".
So lets check for the right path and fallback to the wrong one (but
used in old zims).
The double '/' in the path is a bug of zimwriterfs and is specific
to the xapian database.
We must handle this correctly in `hasFulltextIndex` and not (buggly) in
`pathExists`.
(Hopefully, it seems that pathExists were used only by hasFulltextIndex)
The previous API suffer different problems:
- It was difficult to handle articles redirecting to other article.
- It was not possible to get few information (title) without getting
the whole content.
The new API introduce the new class `Entry` that act as a proxy to an
article in the zim file.
Methods of `Reader` now return an `Entry` and the user has to call
`Entry`'s methods to get useful information.
No redirection is made explicitly.
If an entry is not found, an exception is raised instead of returning
an invalid `Entry`.
The common pattern to get the content of an entry become :
```
std::string content;
try {
auto entry = reader.getEntryFromPath(path);
entry = entry.getFinalEntry();
content = entry.getContent();
} catch (NoEntry& e) {
...
}
```
Older methods are keep (with the same behavior) but are marked as
deprecated.
The library's books are created in the metadata in the opds.
As the opds stream is by definition a distant "library", there is no
zim to read to complete missing information.
This can lead to incomplete `library.xml`.
The downloader is using libaria2.
For now, only one download can be run a the time.
A download will start only if (and as soon as) no download is running.
If we check the later the `loopCounter` with 42, we must pre-increment the
content. Else, in case of infinite loop, the `loopCounter` will be 43.
Related to kiwix/kiwix-tools#168
