Using the Logger from Fair
==========================

For a complete documentation please refer to the FairLogger `documentation <https://github.com/FairRootGroup/FairLogger>`_.

Usage inside the Code
---------------------

The basic syntax is

.. code-block:: C++

  LOG(info) << "My information";

**Severity keywords**

With `LOG(<keyword>)` you can mark the messaged by severity. The higher severity levels also print the lower levels, e.g. `info` will print `warn`, too.
Most people in Panda use `info`, `warn` and `error`.

.. code-block:: C++

  "trace"
  "debug4"
  "debug3"
  "debug2"
  "debug1"
  "debug"
  "info"
  "state"
  "warn"
  "error"
  "fatal"
  "nolog"

Options in a ROOT macro
-----------------------

To set the Logger options inside your Root macro follow this structure, which will give a lot of information 

.. code-block:: C++

  #include <fairlogger/Logger.h>
  int myacro()
  {
    fair::Logger::SetConsoleColor(true);
    fair::Logger::SetVerbosity("veryhigh");
    ...
  }


**Coloured console output**

Adds a nice and easy way to spot errors by the colored keywords.
`fair::Logger::SetConsoleColor(true);` Be aware that this should be off when logging to a file, because the coloring is performed by escape sequences which will clog your logs.

**Logger Verbosity**

Here you can adjust what the logger puts in front of the actual message. There are custom verbosity levels as well, if needed.::

  verylow:  message
  low:      [severity] message
  medium:   [HH:MM:SS][severity] message
  high:     [process_name][HH:MM:SS][severity] message
  veryhigh: [process_name][HH:MM:SS:µS][severity][file:line:function] message
  user1:    [severity] message
  user2:    [severity] message
  user3:    [severity] message
  user4:    [severity] message


When running a root macro e.g. for simulations, the process will always be ``root.exe`` and the time stamps are only in a few cases of use. 
This example may be most practical for debugging and results in `[severity][file:line:function] message`

.. code-block:: C++

  auto spec = fair::VerbositySpec::Make(fair::VerbositySpec::Info::severity,
                                        fair::VerbositySpec::Info::file_line_function);
  fair::Logger::DefineVerbosity("user1", spec);
  fair::Logger::SetVerbosity("user1");

Here is the list of available::
  
  +-----------------------------------------------+----------------------+
  | Argument                                      | Result               |
  +===============================================|======================|
  | fair::VerbositySpec::Info::process_name       | [process_name]       |
  | fair::VerbositySpec::Info::timestamp_s        | [HH:MM:SS]           |
  | fair::VerbositySpec::Info::timestamp_us       | [HH:MM:SS:µS]        |
  | fair::VerbositySpec::Info::severity           | [severity]           |
  | fair::VerbositySpec::Info::file               | [file]               |
  | fair::VerbositySpec::Info::file_line          | [file:line]          |
  | fair::VerbositySpec::Info::file_line_function | [file:line:function] |
  +-----------------------------------------------+----------------------+