Note that this change makes the user-facing change of renaming
the 'numConnectionForBtc' (singular 'Connection') to
'numConnectionsForBtc' (plural 'Connections'). It is presumed that not
many users are relying on this option for day-to-day operations, and the
singular version was pretty clearly a typo / oversight.
Note that the default value of 600 advertised in BisqExecutable's option
handling was incorrect. The actual value had since become 1200 MB. This
correct default is now reflected in Config's option handling.
Prior to this commit, BisqExecutable has been responsible for parsing
command line and config file options and BisqEnvironment has been
responsible for assigning default values to those options and providing
access to option values to callers throughout the codebase.
This approach has worked, but at considerable costs in complexity,
verbosity, and lack of any type-safety in option values. BisqEnvironment
is based on the Spring Framework's Environment abstraction, which
provides a great deal of flexibility in handling command line options,
environment variables, and more, but also operates on the assumption
that such inputs have String-based values.
After having this infrastructure in place for years now, it has become
evident that using Spring's Environment abstraction was both overkill
for what we needed and limited us from getting the kind of concision and
type saftey that we want. The Environment abstraction is by default
actually too flexible. For example, Bisq does not want or need to have
environment variables potentially overriding configuration file values,
as this increases our attack surface and makes our threat model more
complex. This is why we explicitly removed support for handling
environment variables quite some time ago.
The BisqEnvironment class has also organically evolved toward becoming a
kind of "God object", responsible for more than just option handling. It
is also, for example, responsible for tracking the status of the user's
local Bitcoin node, if any. It is also responsible for writing values to
the bisq.properties config file when certain ban filters arrive via the
p2p network. In the commits that follow, these unrelated functions will
be factored out appropriately in order to separate concerns.
As a solution to these problems, this commit begins the process of
eliminating BisqEnvironment in favor of a new, bespoke Config class
custom-tailored to Bisq's needs. Config removes the responsibility for
option parsing from BisqExecutable, and in the end provides "one-stop
shopping" for all option parsing and access needs.
The changes included in this commit represent a proof of concept for the
Config class, where handling of a number of options has been moved from
BisqEnvironment and BisqExecutable over to Config. Because the migration
is only partial, both Config and BisqEnvironment are injected
side-by-side into calling code that needs access to options. As the
migration is completed, BisqEnvironment will be removed entirely, and
only the Config object will remain.
An additional benefit of the elimination of BisqEnvironment is that it
will allow us to remove our dependency on the Spring Framework (with the
exception of the standalone pricenode application, which is Spring-based
by design).
Note that while this change and those that follow it are principally a
refactoring effort, certain functional changes have been introduced. For
example, Bisq now supports a `--configFile` argument at the command line
that functions very similarly to Bitcoin Core's `-conf` option.
