<?php
define('DEBUG', true);
class Database{

    /**
    * Connection Informations.
    * @var string
    */
    private $host, $user, $pass, $db;

    /**
    * The PDO layer.
    * @var PDO
    */
    public $pdo;

    /**
    * If the class is initiated, pdo included.
    * @var bool
    */
    private $_init = false;

    /**
    * Le numero de requêtes que cette classe a executer.
    * @var int
    */
    private $queries = 0;

    public function __construct($host, $user, $db, $pass = '')
    {
        $this->host = $host;
        $this->user = $user;
        $this->db = $db;
        $this->pass = $pass;
        $this->construct_pdo();
    }

    /**
    * Construit PDO.
    * @return void
    */
    private function construct_pdo(){
        try{
            $this->pdo = new PDO("mysql:host=".$this->host.";dbname=".$this->db, $this->user, $this->pass);
            $this->_init = true;
        }
        catch(PDOException $e){
            exit("Erreur SQL: Impossible de se connecter au serveur.");
            $this->_init = false;
        }
    }

    /**
    * Execute une requête SELECT.
    * @see Database::genSelect
    * @return array
    */
    public function doSelect(array $fields, $from, array $conds = null){
        $stmt = $this->pdo->prepare($this->genSelect($fields, $from, $conds));
        if(!$stmt){
            if(DEBUG)
                exit('Erreur SQL !');
            return false;
        }
        if(!$stmt->execute()){
            if(DEBUG)
                exit('Erreur SQL !');
            return false;
        }
        ++$this->queries;
        if($stmt->rowCount() == 1)
        {
            return $stmt->fetch(PDO::FETCH_ASSOC);
        }
        if($stmt->rowCount() > 1)
        {
            return $stmt->fetchAll(PDO::FETCH_ASSOC);
        }
        if($stmt->rowCount() < 1)
        {
            return array();
        }
    }

    /**
    * Génère une requête SELECT.
    * @param array $fields Les noms des colonnes à récuperer.
    * @param string $from Le nom de la table.
    * @param array $conds [optional] Les conditions
    * @return string La requête généré.
    */
    private function genSelect(array $fields, $from, array $conds = null){
        // Initiation de la requête
        $query = 'SELECT ';
        // Premièrement parsing des fields
        $f = '';
        foreach($fields as $key => $field)
        {
            $field = $from.'.'.$field;
            if($key != (count($fields)-1))
                $field .= ',';
            $field .= ' ';
            // On ajoute
            $f .= $field;
        }
        // On ajoute les fields à la requête
        $query .= $f;
        // puis la clause from
        $query .= 'FROM '.$from;
        if(isset($conds))
        {
            $query .= ' WHERE ';
            $c = '';
            foreach($conds as $field => $val)
            {
                $cond = $from.".".$field." = '".$val."'";
                if(key($conds) != (count($conds)-1))
                    $cond .= ' AND ';
                $c .= $cond;
            }
            $query .= $c;
        }
        return $query;
    }

    /**
    * Execute une requête INSERT.
    * @see Database::genInsert
    * @param array $values Les valeurs à être inséré.
    * @return bool Résultat de l'opération.
    */
    public function doInsert(array $fields, $to, array $values){
        // Si le nombre de valeurs fournies sont pas conformes :/
        if(count($fields) !== count($values))
            throw new Exception("Le nombre de valeurs n'est pas conforme aux nombres de colonnes.");
        // On prépare la requête
        $query = $this->genInsert($fields, $to);
        $stmt = $this->pdo->prepare($query);
        if(!$stmt){
            if(DEBUG)
                exit('Erreur SQL !');
            return false;
        }
        $this->bindValues($stmt, $fields, $values);
        $this->pdo->beginTransaction();
        if(!$stmt->execute())
        {
            $this->pdo->rollBack();
            throw new Exception("Impossible d'éxecuter la requête: ".$query);
        }
        ++$this->queries;
        return $this->pdo->commit();
    }

    /**
    * Génère une requête insert.
    * @param array $fields Un tableau contenant les colonnes et leurs valeurs.
    * @param string $to La table concerné.
    * @return string
    */
    private function genInsert(array $fields, $to){
        // Init the query
        $query = 'INSERT INTO ';
        // Now parse the fields and the params
        $f = '';
        $v = '';
        foreach($fields as $k => $name)
        {
            $field = $name;
            if($k != (count($fields)-1))
                $field .= ', ';
            $f .= $field;
            // Now values
            $value = ":".$name;
            if($k != (count($fields)-1))
                $value .= ', ';
            $v .= $value;
        }
        $query .= $to.'('.$f.') ';
        $query .= 'VALUES('.$v.')';
        return $query;
    }

    /**
    * Ajoute les valeurs au statement.
    * @see Database::doInsert
    * @see Database::doUpdate
    * @return void
    */
    private function bindValues(PDOStatement &$stmt, $fields, $vals){
        foreach($fields as $k => $name)
        {
            $type = is_int($vals[$k]) ? PDO::PARAM_INT : PDO::PARAM_STR;
            $stmt->bindValue($name, $vals[$k], $type);
        }
        return ;
    }
}
?>