<?php

class DB_Query {
    protected $table;
    protected $columns;
    protected $joins;
    protected $conditions;
    protected $order;
    protected $offset;
    protected $limit;
    protected $values;

    public function __construct($table, $columns = null) {
        $this->table = $table;
        $this->columns($columns);
    }

    public function columns($columns) {
        $this->columns = $columns;
    }

    public function where($field, $value, $op = '=') {
        $this->conditions[] = "$field $op ?";
        $this->values[] = $value;
        return $this;
    }

    public function like($field, $value) {
        return $this->where($field, "%$value%", "LIKE");
    }

    public function orderBy($order) {
        $this->order = $order;
        return $this;
    }

    public function join($table, $alias, $condition, $type = null) {
        $this->joins[] = ($type ? "$type " : "") . "JOIN $table AS $alias ON $condition";
    }

    public function limit($offset, $limit) {
        $this->offset = (int) $offset;
        $this->limit = (int) $limit;
    }

    public function page($page, $per_page) {
        $page = (int) $page;
        $per_page = (int) $per_page;
        $offset = $per_page * $page - $per_page;
        $this->limit($offset, $per_page);
        return $this;
    }

    public function execute() {
        $t = $this;
        $sql = 'SELECT ' . (is_null($t->columns) ? '*' : $t->columns) . ' FROM ' . $t->table;
        if ($t->joins) {
            $sql .= ' ' . implode(' ', $t->joins);
        }
        if ($t->conditions) {
            $sql .= ' WHERE ' . implode(' AND ', $t->conditions);
        }
        if ($t->order) {
            $sql .= " ORDER BY {$t->order}";
        }
        if ($t->limit) {
            $sql .= " LIMIT {$t->offset},{$t->limit}";
        }
        // echo $sql . '<br>';
        $stm = db::prepare($sql);
        $stm->execute($t->values);
        return $stm;
    }

    public function reset() {
        foreach (array('columns', 'joins', 'conditions', 'order', 'offset', 'limit', 'values') as $p) {
            $this->{$p} = null;
        }
    }

    public function __call($method, $args) {
        if (preg_match('/^fetch(all|column|object)?$/i', $method)) {
            $stm = $this->execute();
            $callback = array($stm, $method);
            return call_user_func_array($callback, $args);
        }
        throw new BadMethodCallException("Method $method not exists");
    }
}