<?php

class DatabaseQuery
{
  const COMBINE_TYPE_AND = ' AND ';
  const COMBINE_TYPE_OR = ' OR ';
  const JOIN_TYPE_INNER = ' INNER ';
  const JOIN_TYPE_LEFT = ' LEFT ';

  private $table;
  private $columns = array();
  private $where = array();
  private $order = array();
  private $limit;
  private $offset;
  private $join = array();
  
  private $db;
  
  public function __construct(Database $db)
  {
    $this->db = $db;
  }

  public function from($table, $columns = null)
  {
    $this->table = (string)$table;
    $this->columns = (array)$columns;
    return $this;
  }

  public function where($condition, $values = null, $conditionName = null)
  {
    $condition = (string)$condition;
    if ($values !== null)
      $condition = $this->db->quoteInto($condition, $values);
    if ($conditionName !== null && !is_numeric($conditionName))
      $this->where[$conditionName] = $condition;
    else
      $this->where[] = $condition;
    return $this;
  }

  public function combineWhere($conditionName1, $conditionName2, $combineType = self::COMBINE_TYPE_AND, $conditionName = null)
  {
    $condition1 = isset($this->where[$conditionName1]) ? $this->where[$conditionName1] : null;
    $condition2 = isset($this->where[$conditionName2]) ? $this->where[$conditionName2] : null;

    if ($condition1 !== null && $condition2 !== null) {
      unset($this->where[$conditionName1], $this->where[$conditionName2]);
      $this->where($condition1 . ' ' . $combineType . ' ' . $condition2, null, $conditionName);
    }
    return $this;
  }

  public function resetWhere()
  {
    $this->where = array();
    return $this;
  }

  public function order($column)
  {
    $this->order[] = (string)$column;
    return $this;
  }

  public function resetOrder()
  {
    $this->order = array();
    return $this;
  }

  public function limit($limit, $offset = null)
  {
    $this->limit = ($limit === null) ? null : (int)$limit;
    $this->offset = ($offset === null) ? null : (int)$offset;
    return $this;
  }
  
  public function innerJoin($tableName, $on, array $columns = array())
  {
    $this->join(self::JOIN_TYPE_INNER, $tableName, $on, $columns);
    return $this;
  }
  
  public function leftJoin($tableName, $on, array $columns = array())
  {
    $this->join(self::JOIN_TYPE_LEFT, $tableName, $on, $columns);
    return $this;
  }
  
  private function join($type, $tableName, $on, $columns)
  {
    $this->columns = array_merge($this->columns, (array)$columns);
    $this->join[] = array('type' => $type, 'tableName' => $tableName, 'on' => $on);
  }

  private function renderWhereClause()
  {
    if ($this->where)
      return ' WHERE ' . implode(self::COMBINE_TYPE_AND, $this->where);
    return '';
  }

  private function renderOrderClause()
  {
    if ($this->order)
      return ' ORDER BY ' . implode(', ', $this->order);
    return '';
  }

  private function renderLimitClause($useOffset = true)
  {
    if ($this->limit !== null) {
      $sql = ' LIMIT ';
      if ($useOffset && ($this->offset !== null))
        $sql .= $this->offset . ', ';
      $sql .= $this->limit;

      return $sql;
    }
    return '';
  }
  
  private function renderJoinClause()
  {
    if ($this->join) {
      $sql = '';
      foreach ($this->join as $join)
        $sql .= " {$join['type']} JOIN {$join['tableName']} ON ({$join['on']}) ";
      return $sql;
    }
    return '';
  }
  

  public function renderSelectSql()
  {
    $sql = 'SELECT ' . implode(', ', $this->columns) . ' FROM ' . $this->table
         . $this->renderJoinClause()
         . $this->renderWhereClause()
         . $this->renderOrderClause()
         . $this->renderLimitClause();

    return $sql;
  }
/*
  public function update(array $values = array())
  {
    $sql = 'UPDATE ' . $this->table; // Not Working
    $sql .= $this->renderWhereClause();
    $sql .= $this->renderOrderClause();
    $sql .= $this->renderLimitClause(false);
  }

  public function delete()
  {
    $sql = 'DELETE FROM ' . $this->table;
    $sql .= $this->renderWhereClause();
    $sql .= $this->renderOrderClause();
    $sql .= $this->renderLimitClause(false);

    return $sql;
  }
*/
}