====== Create Payment Method Module ======
Check this thread for more info.
http://www.magentocommerce.com/boards/viewthread/832/P60/

===== Introduction =====

Each payment method can be done as separate module or few methods can be combined in same module if they share functionality or could be used together.

Let's create a module with one payment method that will:
  * accept credit card information
  * authorize it when order is submitted
  * save transaction ID in order payment record

Our new module will be called NewModule.

Replace all instances of 'NewModule' with name of your module and 'newmodule' with simplified code, that contains only alphanumeric characters and underscore.

To make this tutorial most concise, it's implied that mentioned folders will be created when needed.

Make sure that app/code/local is in include_path.

If you are using configuration cache, don't forget to clean it after modifying config xml files by deleting the contents of var/cache/config/

===== Module Declaration =====

Create ''app/etc/modules/Mage_NewModule.xml'':
<code xml>
<config>
    <modules>
<!-- declare Mage_NewModule module -->
        <Mage_NewModule>
<!-- this is an active module -->
            <active>true</active>
<!-- this module will be located in app/code/local code pool -->
            <codePool>local</codePool>
<!-- specify dependencies for correct module loading order -->
            <depends>
                <Mage_Payment />
            </depends>
<!-- declare module's version information for database updates -->
            <version>0.1.0</version>
        </Mage_NewModule>
    </modules>
</config>
</code>

Now that the application is aware of the module, we will let Magento know about details of our module.

===== Module Configuration =====

Create ''app/code/local/Mage/NewModule/etc/config.xml'':
<code xml>
<?xml version="1.0"?>
<config>
    <global>
<!-- declare model group for new module -->
        <models>
<!-- model group alias to be used in Mage::getModel('newmodule/...') -->
            <newmodule>
<!-- base class name for the model group -->
                <class>Mage_NewModule_Model</class>
            </newmodule>
        </models>

<!-- declare resource setup for new module -->
        <resources>
<!-- resource identifier -->
            <newmodule_setup>
<!-- specify that this resource is a setup resource and used for upgrades -->
                <setup>
<!-- which module to look for install/upgrade files in -->
                    <module>Mage_NewModule</module>
                </setup>
<!-- specify database connection for this resource -->
                <connection>
<!-- do not create new connection, use predefined core setup connection -->
                    <use>core_setup</use>
                </connection>
            </newmodule_setup>
            <newmodule_write>
                <use>core_write</use>
            </newmodule_write>
            <newmodule_read>
                <use>core_read</use>
            </newmodule_read>
        </resources>
    </global>

<!-- declare default configuration values for this module -->
    <default>
<!-- 'payment' configuration section (tab) -->
        <payment>
<!-- 'newmodule' configuration group (fieldset) -->
            <newmodule>
<!-- by default this payment method is inactive -->
                <active>0</active>
<!-- model to handle logic for this payment method -->
                <model>newmodule/paymentMethod</model>
<!-- order status for new orders paid by this payment method -->
                <order_status>1</order_status>
<!-- default title for payment checkout page and order view page -->
                <title>Credit Card (Authorize.net)</title>
            </newmodule>
         </payment>
    </default>
</config>
</code>

===== Adapter model =====

Note: PaymentMethod name is arbitrary and is up to your decision.

Create ''app/code/local/Mage/NewModule/Model/PaymentMethod.php'':
<code php>
<?php

/**
 * Our test CC module adapter
 */
class Mage_NewModule_Model_PaymentMethod extends Mage_Payment_Model_Method_Cc
{
    /**
    * unique internal payment method identifier
    * 
    * @var string [a-z0-9_]
    */
    protected $_code = 'newmodule';

    /**
     * Here are examples of flags that will determine functionality availability
     * of this module to be used by frontend and backend.
     * 
     * @see all flags and their defaults in Mage_Payment_Model_Method_Abstract
     *
     * It is possible to have a custom dynamic logic by overloading
     * public function can* for each flag respectively
     */
     
    /**
     * Is this payment method a gateway (online auth/charge) ?
     */
    protected $_isGateway               = true;

    /**
     * Can authorize online?
     */
    protected $_canAuthorize            = true;

    /**
     * Can capture funds online?
     */
    protected $_canCapture              = true;

    /**
     * Can capture partial amounts online?
     */
    protected $_canCapturePartial       = false;

    /**
     * Can refund online?
     */
    protected $_canRefund               = false;

    /**
     * Can void transactions online?
     */
    protected $_canVoid                 = true;

    /**
     * Can use this payment method in administration panel?
     */
    protected $_canUseInternal          = true;

    /**
     * Can show this payment method as an option on checkout payment page?
     */
    protected $_canUseCheckout          = true;

    /**
     * Is this payment method suitable for multi-shipping checkout?
     */
    protected $_canUseForMultishipping  = true;

    /**
     * Can save credit card information for future processing?
     */
    protected $_canSaveCc = false;

    /**
     * Here you will need to implement authorize, capture and void public methods
     * 
     * @see examples of transaction specific public methods such as
     * authorize, capture and void in Mage_Paygate_Model_Authorizenet
     */
}
</code>
Now that we have the model let's give admin a way to configure it and also make checkout process aware of this method.

===== Declare configuration options for admin panel =====

This file will define how you see configuration options in Magento admin panel
System > Configuration

Create ''app/code/local/Mage/NewModule/etc/system.xml'':
<code xml>
<?xml version="1.0"?>
<config>
   <sections>
<!-- payment tab -->
        <payment>
            <groups>
<!-- newmodule fieldset -->
                <newmodule translate="label" module="paygate">
<!-- will have title 'New Module' -->
                    <label>New Module</label>
<!-- position between other payment methods -->
                    <sort_order>670</sort_order>
<!-- do not show this configuration options in store scope -->
                    <show_in_default>1</show_in_default>
                    <show_in_website>1</show_in_website>
                    <show_in_store>0</show_in_store>
                    <fields>
<!-- is this payment method active for the website? -->
                        <active translate="label">
<!-- label for the field -->
                            <label>Enabled</label>
<!-- input type for configuration value -->
                            <frontend_type>select</frontend_type>
<!-- model to take the option values from -->
                            <source_model>adminhtml/system_config_source_yesno</source_model>
<!-- field position -->
                            <sort_order>1</sort_order>
<!-- do not show this field in store scope -->
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>0</show_in_store>
                        </active>
                        <order_status translate="label">
                            <label>New order status</label>
                            <frontend_type>select</frontend_type>
                            <source_model>adminhtml/system_config_source_order_status_processing</source_model>
                            <sort_order>4</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>0</show_in_store>
                        </order_status>
                        <title translate="label">
                            <label>Title</label>
                            <frontend_type>text</frontend_type>
                            <sort_order>2</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>0</show_in_store>
                        </title>
                    </fields>
                </newmodule>
            </groups>
        </payment>
    </sections>
</config>
</code>

If you go now to Admin / System / Configuration / Payment Methods, you should see "New Module" group. 
Enable it and try to checkout. On payment methods page you should see "New Module" payment method with credit card form.

===== Database updates =====
Create ''app/code/local/Mage/NewModule/sql/newmodule_setup/mysql4-install-0.1.0.php'':
<code php>
<?php
// here are the table creation/updates for this module
</code>