CakePHP Voucher/Discount code system - php

Question

I looked over Google for some samples/solutions about this, for example Creating Discount Code System (MySQL/php) but I haven't found a good solution.
My situation is such that I have a platform, where the user is supposed to have a balance in a virtual currency, and can buy virtual items for it. Now there's a wish to implement vouchers and discounts. There would be different kinds of codes, like one that gives 50% discount on purchasing items, x amount of extra items (with or without minimum item amount), just a code to get some currency, or a reference code that gives the referrer something.
I have implemented it as Campaign and CampaignType, where first holds the campaign info and second holds the action info.
Here's the structure:
-- Table structure for table `cake_campaigns`
CREATE TABLE IF NOT EXISTS `cake_campaigns` (
`id` bigint(20) NOT NULL AUTO_INCREMENT,
`name` varchar(50) CHARACTER SET utf8 NOT NULL,
`code` varchar(100) COLLATE utf8_bin NOT NULL,
`type_id` varchar(50) CHARACTER SET utf16 COLLATE utf16_bin NOT NULL DEFAULT '1',
`value` int(10) unsigned NOT NULL DEFAULT '5' COMMENT 'Percentage or amount',
`min_amount` bigint(20) unsigned NOT NULL DEFAULT '0',
`owner_id` bigint(20) unsigned NOT NULL,
`created` datetime NOT NULL,
`active` tinyint(1) unsigned NOT NULL DEFAULT '1',
`single_use` tinyint(1) unsigned NOT NULL DEFAULT '0',
PRIMARY KEY (`id`),
UNIQUE KEY `code` (`code`),
KEY `owner_id` (`owner_id`),
FULLTEXT KEY `name` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=4 ;
-- Table structure for table `cake_campaign_types`
CREATE TABLE IF NOT EXISTS `cake_campaign_types` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(50) CHARACTER SET utf8 NOT NULL,
`unit` varchar(10) CHARACTER SET utf16 NOT NULL DEFAULT '%',
`multiplier` double(10,8) NOT NULL DEFAULT '0.01000000',
`type` varchar(50) COLLATE utf8_bin DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `name` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=7 ;
Currently my logic is that when a campaign is used, then the action is according to CampaignType's name, for example in the purchase logic:
if (isset($this->request->data['Purchase']['code'])) {
$code = $this->request->data['Purchase']['code'];
$campaign = $this->Campaign->findByCode($code);
$this->Campaign->id = $campaign['Campaign']['id'];
// campaign no longer active
if ($this->Campaign->field('active') == 0) $code = false;
if ($this->CampaignLog->find('first', array('conditions' => array(
'user_id' => $this->User->field('id'),
'campaign_id' => $this->Campaign->field('id'),
'activated' => 1,
)))) $code = false; // code has already been used
unset($this->request->data['Purchase']['code']);
} else $code = false;
// Some purchasing logic here
if ($code) {
$this->CampaignLog->create();
$this->CampaignLog->save(array(
'campaign_id' => $this->Campaign->field('id'),
'user_id' => $this->User->field('id'),
'activated' => 1,
'source' => $this->Session->read('referrer'),
'earnings' => $earned,
'created' => strftime('%Y-%m-%d %H:%M:%S'),
));
if ($this->Campaign->field('single_use') == 1) {
$this->Campaign->saveField("active", 0);
}
// Apply code here
}
Now, my question is:
What would be the best course of action on going about applying those codes, because I'm a bit queasy on going with if-then-else or switch-case through all the possible code types. But right now, since there's so many things that can be different (ex. Discount - in percentage or set amount), then that seems to be the only option.
Maybe the structure/logic of the codes should be different?

Answer 1

It's already straightforward in my point of view, integrating it with the purchase would be the best bet in knowing further problems. Assuming that we have $this->request->data['price'] for the price, then we have an example type_id of 1 that represents as a discount.
All we have to do is to get value and do percentage equation so that would be like
$discount = floatval('0.' . $this->Campaign->value);
$finalPrice = $this->request->data['price'] * $discount;
Better if we implement it on a switch case to isolate their logic. It may depend on how you implement it but that's the gist of the concept.

Answer 2

Check the cart plugin it is using events for everything and nothing is hardcoded, it is pretty flexible by using this approach.
There is one method that is fired whenever the cart needs to be recalculated. Inside it calls other methods to calculate taxes and discounts.
Implementing this through events has the advantage that it is very easy to extend with additional discounts or tax calculations later.
Feel free to review the whole code of the plugin, it is not a simple implementation and covers cookie, session and database storage for the cart data and has events for a lot of things.