<?php

namespace SilverStripe\ORM\Connect;

use mysqli_result;
use mysqli_stmt;

/**
 * Provides a record-view for mysqli statements
 *
 * By default streams unbuffered data, but seek(), rewind(), or numRecords() will force the statement to
 * buffer itself and sacrifice any potential performance benefit.
 */
class MySQLStatement extends Query
{

    /**
     * The related mysqli statement object if generated using a prepared query
     *
     * @var mysqli_stmt
     */
    protected $statement;

    /**
     * Metadata result for this statement
     *
     * @var mysqli_result
     */
    protected $metadata;

    /**
     * Is the statement bound to the current resultset?
     *
     * @var bool
     */
    protected $bound = false;

    /**
     * List of column names
     *
     * @var array
     */
    protected $columns = array();

    /**
     * List of bound variables in the current row
     *
     * @var array
     */
    protected $boundValues = array();

    /**
     * Binds this statement to the variables
     */
    protected function bind()
    {
        $variables = array();

        // Bind each field
        while ($field = $this->metadata->fetch_field()) {
            $this->columns[] = $field->name;
            // Note that while boundValues isn't initialised at this point,
            // later calls to $this->statement->fetch() Will populate
            // $this->boundValues later with the next result.
            $variables[] = &$this->boundValues[$field->name];
        }

        $this->bound = true;
        $this->metadata->free();

        // Buffer all results
        $this->statement->store_result();

        call_user_func_array(array($this->statement, 'bind_result'), $variables);
    }

    /**
     * Hook the result-set given into a Query class, suitable for use by SilverStripe.
     * @param mysqli_stmt $statement The related statement, if present
     * @param mysqli_result $metadata The metadata for this statement
     */
    public function __construct($statement, $metadata)
    {
        $this->statement = $statement;
        $this->metadata = $metadata;

        // Immediately bind and buffer
        $this->bind();
    }

    public function __destruct()
    {
        $this->statement->close();
        $this->currentRecord = false;
    }

    public function seek($row)
    {
        $this->rowNum = $row - 1;
        $this->statement->data_seek($row);
        return $this->next();
    }

    public function numRecords()
    {
        return $this->statement->num_rows();
    }

    public function nextRecord()
    {
        // Skip data if out of data
        if (!$this->statement->fetch()) {
            return false;
        }

        // Dereferenced row
        $row = array();
        foreach ($this->boundValues as $key => $value) {
            $row[$key] = $value;
        }
        return $row;
    }

    public function rewind()
    {
        return $this->seek(0);
    }
}