<?php

class Connection
{
    // Internal variable to hold the connection
    private static $db;

    final private function __construct() {}

    /**
     * @param $query
     * @param bool $throw_error
     * @return OdbcResultSet|resource|string
     * @throws SqlException
     */
    public static function execute($query, $throw_error = false)
    {
        $result = odbc_exec(self::get(), utf8_decode($query));
        $result = new OdbcResultSet($result);

        if ($result->is_error()) {
            if($throw_error) {
                throw new SqlException($result->get_error(), $query);
            }

            return $result->get_error();
        }

        return $result;
    }

    public static function get()
    {
        if (is_null(self::$db)) {
            $dsn = sprintf(
                "Driver={%s};Server=%s,%s;Database=%s;",
                Configuration::get('db.driver'),
                Configuration::get('db.server'),
                Configuration::get('db.port'),
                Configuration::get('db.name')
            );
            self::$db = odbc_pconnect($dsn, Configuration::get('db.username'), Configuration::get('db.password'));

            if (self::$db === false) {
                throw new SqlException("Unable to connect to the server.");
            }
        }
        // Return the connection
        return self::$db;
    }

    final private function __clone() {}
}

class OdbcResultSet implements Iterator, ArrayAccess
{
    public $length;

    private $results;
    private $error;
    private $num_fields;
    private $cursor_index;

    public function __construct($odbc_result)
    {
        if ($odbc_result === false) {
            $this->error = odbc_errormsg(Connection::get());
        } else {
            try {
                $this->results = array();
                $this->num_fields = odbc_num_fields($odbc_result);

                if ($this->num_fields > 0) {
                    while ($row = odbc_fetch_row($odbc_result)) {
                        $data = array();
                        for ($i = 1; $i <= $this->num_fields; ++$i) {
                            $data[odbc_field_name($odbc_result, $i)] = utf8_encode(odbc_result($odbc_result, $i));
                        }
                        $this->results[] = $data;
                    }
                };
            } catch (Exception $e) {
                print($e->getMessage());
            }

            $this->cursor_index = 0;
            $this->length = count($this->results);
            odbc_free_result($odbc_result);
        }
    }

    public function is_error()
    {
        return ($this->error ? true : false);
    }

    public function get_error()
    {
        return $this->error;
    }

    public function get_row()
    {
        return $this->current();
    }

    public function to_array()
    {
        return $this->results;
    }

    // ArrayAccess
    /**
     * @param int $offset
     * @return bool
     */
    public function offsetExists($offset)
    {
        return !$this->error && $this->cursor_index < $this->length && $this->cursor_index >= 0;
    }

    /**
     * @param int $offset
     * @return bool|array
     */
    public function offsetGet($offset)
    {
        return $this->offsetExists($offset) ? $this->results[$offset] : false;
    }

    public function offsetSet($offset, $value)
    {
        if($this->offsetExists($offset)) {
            $this->results[$offset] = $value;
        }
    }

    public function offsetUnset($offset)
    {
        throw new RuntimeException("This makes no sense at all.");
    }

    // Iterator
    /**
     * @return bool|array
     */
    public function current()
    {
        return $this->offsetGet($this->cursor_index);
    }

    /**
     * @return int
     */
    public function key()
    {
        return $this->cursor_index;
    }

    /**
     * @return array|bool
     */
    public function next()
    {
        $current = $this->current();
        ++$this->cursor_index;
        return $current;
    }

    public function rewind()
    {
        $this->cursor_index = 0;
    }

    /**
     * @return bool
     */
    public function valid()
    {
        return $this->offsetExists($this->cursor_index);
    }
}