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question_4.php
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question_4.php
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<?php
namespace SoftwareEngineerTest;
// Question 2 & 3 & 4
/**
* Class Customer
*/
abstract class Customer {
protected $id;
protected $balance = 0;
public function __construct($id) {
$this->id = $id;
}
public function get_balance() {
return $this->balance;
}
}
// Write your code below
/**
* Abstract Class Typed_Customer
*
* This class covers the possibility to receive exrta deposit if the deposit() method is invoked
* and provides the generate_username() method for each subclasses.
*
* @author Csongor Halmai
*/
abstract class Typed_Customer extends Customer {
private static $last_username_index = 0; // incremented before each new username generation
protected $prefix = ""; // stores the B, S, G prefix of the customer
protected $extra = 1; // factor for deposit (1.0 = no extra deposit)
private static $used_usernames = array(); // stores the already used usernames
/*
* Multiplies the deposit with a factor.
*
* @param $amount double the value of the deposit
* @param $extra double the factor to multiple the deposit with
*/
public function deposit( $amount ) {
$this -> balance += $amount * $this -> extra;
}
/**
* Generates a unique username starting with the class prefix.
*
* It can revoke several username generator functions. Please, uncomment the
* one that you prefer.
*
* @return string the generated username
*/
public function generate_username() {
//return $this -> generate_username_incremented_decimal();
//return $this -> generate_username_incremented_base36();
//return $this -> generate_username_uniqid();
return $this -> generate_username_random();
}
/**
* It creates usernames by concatenating the prefix and an incremental decimal value.
* Results: S1, S2, G3, B4, ..., G9, B10, S11, ...
*
* Advantages:
* simple, quick, doesn't use much memory
* Disadvantages:
* user name is not random, tells the user how many user names were created before them.
*
* @return string the generated username
*/
private function generate_username_incremented_decimal() {
self::$last_username_index++;
if ( self::$last_username_index <= 0 ) {
throw new Exception( "Username-space is full" );
}
$tail = self::$last_username_index;
$ret = $this -> prefix. $tail;
return $ret;
}
/**
* It creates usernames by concatenating the prefix and an incremental
* value represented in base 36.
* Results: S1, S2, G3, B4, ..., G9, Ba, Sb, ..., Sz, B10, S11, ...
*
* Advantages:
* simple, quick, doesn't use much memory, shorter names than in case of generate_username_incremented_decimal()
* Disadvantages:
* user name is not random, tells the user how many user names were created before them.
*
* @return string the generated username
*/
private function generate_username_incremented_base36() {
self::$last_username_index++;
if ( self::$last_username_index <= 0 ) {
throw new Exception( "Username-space is full" );
}
$tail = base_convert( self::$last_username_index, 10, 36 );
$ret = $this -> prefix. $tail;
return $ret;
}
/**
* It creates usernames by concatenating the prefix and the result of the uniqid() function by eliminating the dot from it.
* Results: S569b949c67d70216698490, B569b949c68d10910181490, ...
*
* Advantages:
* simple, quick, doesn't use much memory, shorter names than in case of generate_username_incremented_decimal()
* Disadvantages:
* strongly relies on the uniqueness of uniquid()
*
* @return string the generated username
*/
private function generate_username_uniqid() {
$ret = str_replace( ".", "" , uniqid( $this -> prefix, TRUE ) );
return $ret;
}
/**
* It creates usernames by concatenating the prefix and a random string.
* The result's length changes between 2 and 30 characters.
*
* Results: Sa, G1fc3ewd4fg6h8jk64r, B325475836uq, ...
*
* This function remembers the already generated names and protects from generating the same one again.
*
* Advantages:
* creares really random user names.
* Disadvantages:
* conplicated, slow, uses much memory
*
* @return string the generated username
*/
private function generate_username_random() {
$total_length = 30;
do {
$ret = $this -> prefix;
$length = mt_rand( 1, $total_length - strlen( $this -> prefix ) );
$characters = "abcdefghijklmnopqrstuvwxyz0123456789";
for ( $i = 0; $i < $length; $i++ ) {
$ret .= $characters[ mt_rand( 0, strlen( $characters ) - 1 ) ];
}
} while ( isset( self::$used_usernames[ $ret ] ) );
self::$used_usernames[ $ret ] = 1;
return $ret;
}
}
/**
* Class Bronze_Customer
*
* @author Csongor Halmai
*/
class Bronze_Customer extends Typed_Customer {
function __construct() {
$this -> prefix = "B";
$this -> extra = 1;
}
}
/**
* Class Silver_Customer
*
* @author Csongor Halmai
*/
class Silver_Customer extends Typed_Customer {
function __construct() {
$this -> prefix = "S";
$this -> extra = 1.05;
}
}
/**
* Class Gold_Customer
*
* @author Csongor Halmai
*/
class Gold_Customer extends Typed_Customer {
function __construct() {
$this -> prefix = "G";
$this -> extra = 1.1;
}
}