.. _custom:


=======================
Writing a Custom Plugin
=======================

.. toctree::
    :hidden:

    RPC_method
    subscription
    tracer


Before setting out to write a plugin it will be helpful to be familiar with the :ref:`types`. Different plugins will require different implementation.

Basic Implementation
====================

All plugins will share some common aspects. 

Package
-------

Any plugin will need its own package located in ``plugeth-plugins/packages``. The package will need to include a ``main.go`` from which the ``.so`` file will be built. The package and main file should share the same name and the name should be a word that describes the basic functionality of the plugin. 

Initialize
----------

Most plugins will need to be initialized with a ``func Initialize``. The initialize function will need to be passed at least three arguments: ``cli.Context``, ``core.PluginLoader``, ``core.Logger``.  

All plugins could have an intial template that looks something like this: 

.. code-block:: Go

   package main

   import (
	   "github.com/openrelayxyz/plugeth-utils/core"
	   "gopkg.in/urfave/cli.v1"
   )

   var log core.Logger

   func Initialize(ctx *cli.Context, loader core.PluginLoader, logger core.Logger) {
	   log = logger
	   log.Info("loaded New Custom Plugin")
   }

InitializeNode
--------------

Many plugins will make use of ``func InitializeNode``.

.. code-block:: Go

   func InitializeNode(stack core.Node, b core.Backend) {
           backend = b
           log.Info("Initialized node and backend")
   }


``InitializeNode`` is called as soon as the Geth node is initialized. The ``core.Node`` object represents the running node with P2P and RPC capabilities, while the ``core.Backend`` gives you access to blocks and other data you may need to access.    

Specialization
==============

From this point implimentation becomes more specialized to the particular plugin type. Continue from here for specific instructions for the following plugins:

* :ref:`RPC_method`
* :ref:`subscription`
* :ref:`tracer`










.. _blockupdates: https://github.com/openrelayxyz/plugeth-plugins/blob/master/packages/blockupdates/main.go
.. _hello: https://github.com/openrelayxyz/plugeth-plugins/blob/master/packages/hello/main.go