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helloanoop/database.php

Last active January 1, 2019 18:34
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  1. helloanoop revised this gist Jan 1, 2019. No changes.
  2. helloanoop created this gist Jan 1, 2019.
    139 changes: 139 additions & 0 deletions database.php
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    <?php

    class Database
    {
    /**
    * Storage
    * @var array
    */
    protected $database = array();

    /**
    * Transactions
    * @var array
    */
    protected $transactions = array();

    /**
    * Value usage counter
    * @var array
    */
    protected $valueUsage = array();

    /**
    * Set value
    * @param $name
    * @param bool $value
    */
    protected function setValue($name,$value=false)
    {
    if(isset($this->database[$name])) {
    $this->valueUsage[$this->database[$name]] -= 1;
    unset($this->database[$name]);
    }

    if ($value) {
    $this->database[$name] = $value;
    // IDEA: if values are mostly large, we can keep their hashes as $valueUsage key
    $this->valueUsage[$value] = isset($this->valueUsage[$value]) ? $this->valueUsage[$value] + 1 : 1;
    }
    }

    /**
    * Keep records about value change
    * @param $name
    */
    protected function addTransactionChange($name)
    {
    if ($this->transactions) {
    $lastTransaction = end($this->transactions);
    if (!isset($lastTransaction[$name])) {
    $this->transactions[key($this->transactions)][$name] = $this->get($name);
    }
    }
    }

    /**
    * Open a transactional block
    */
    public function begin()
    {
    array_push($this->transactions, array());
    }

    /**
    * Rollback all of the commands from the most recent transaction block
    *
    * @throws Exception
    */
    public function rollback()
    {
    if ($this->transactions) {
    $lastTransaction = end($this->transactions);
    foreach($lastTransaction as $name => $value) {
    $this->setValue($name,$value);
    }
    unset($this->transactions[key($this->transactions)]);
    } else {
    throw new Exception("INVALID ROLLBACK");
    }
    }

    /**
    * Permanently store all of the operations from any presently open transactional blocks
    */
    public function commit()
    {
    $this->transactions = array();
    }

    /**
    * Return the value stored under the variable $name
    * @param $name
    * @return string
    */
    public function get($name)
    {
    return isset($this->database[$name]) ? $this->database[$name] : 'null';
    }

    /**
    * Set variable
    * @param $name
    * @param $value
    */
    public function set($name,$value)
    {
    $this->addTransactionChange($name);
    $this->setValue($name,$value);
    }

    /**
    * Unset variable
    * @param $name
    */
    public function delete($name)
    {
    $this->addTransactionChange($name);
    $this->setValue($name);
    }

    /**
    * Returns the number of variables equal to $value
    * @param $value
    * @return int
    */
    public function numEqualTo($value)
    {
    return isset($this->valueUsage[$value]) ? $this->valueUsage[$value] : 0;
    }
    }
    55 changes: 55 additions & 0 deletions index.php
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    <?php

    require_once('database.php');

    $database = new Database();
    if(!defined('STDIN')) define('STDIN', fopen('php://stdin', 'r'));
    if(!defined('STDOUT')) define('STDOUT', fopen('php://stdout', 'w'));
    if(!defined('STDERR')) define('STDERR', fopen('php://stderr', 'w'));
    fwrite(STDOUT, "\nHey! Program will terminate on command 'END'\n\n");

    $data = array();

    do {
    $command = trim(fgets(STDIN));
    $data[] = explode(' ', $command);
    } while ($command != 'END');

    fwrite(STDOUT, "-- OUTPUT --\n");

    try {
    foreach ($data as $cmd) {
    switch ($cmd[0]) {
    case 'BEGIN':
    $database->begin();
    break;
    case 'ROLLBACK':
    $database->rollback();
    break;
    case 'COMMIT':
    $database->commit();
    break;
    case 'GET':
    echo $database->get($cmd[1])."\n";
    break;
    case 'SET':
    $database->set($cmd[1],@$cmd[2]);
    break;
    case 'UNSET':
    $database->delete($cmd[1]);
    break;
    case 'NUMEQUALTO':
    echo $database->numEqualTo($cmd[1])."\n";
    break;
    case 'END':
    exit(0);
    break;
    default:
    fwrite(STDOUT, "There is no command $cmd[0]!\n");
    exit(0);
    break;
    }
    }
    } catch(Exception $e) {
    fwrite(STDOUT, $e->getMessage());
    }