Decorate Iterators - CSV Data Example

csv-keyed-spl.php

<?php
/**
 * @link http://stackoverflow.com/q/10181054/367456
 */


/**
 * Extending from a TraversableDecorator allows to decorate (change) the Iterator
 * being Traversed without changing the object.
 */
abstract class TraversableDecorator implements Iterator
{
    protected $subject;


    public function __construct($subject) {
        if (is_array($subject)) {
            $subject = new ArrayIterator($subject);
        } elseif (($subject instanceof Traversable) and !($subject instanceof iterator)) {
            $subject = new IteratorIterator($subject);
        }
        $this->subject = $subject;
    }

    public function current() {
        return $this->subject->current();
    }

    public function next() {
        $this->subject->next();
    }

    public function key() {
        return $this->subject->key();
    }

    public function valid() {
        return $this->subject->valid();
    }

    public function rewind() {
        $this->subject->rewind();
    }

    function __call($name, $arguments) {
        return call_user_func_array([$this->subject, $name], $arguments);
    }

    function __get($name) {
        return $this->subject->$name;
    }

    function __set($name, $value) {
        $this->subject->$name = $value;
    }

    function __isset($name) {
        return isset($this->subject->$name);
    }
}

/**
 * Decoration for the TraversableDecorator
 */
abstract class TraversableDecoration extends IteratorIterator
{
    public function __construct() {
    }

    public function setIterator(Traversable $iterator) {
        parent::__construct($iterator);
    }
}


/**
 * Decoration for skipping lines that are like the one given
 */
class SkipLines extends TraversableDecoration
{
    private $like;

    public function __construct(array $like) {
        $this->like = $like;
    }

    public function next() {
        parent::next();
        while(parent::valid()) {
            if (parent::current() !== $this->like) break;
            parent::next();
        }
    }
}

/**
 * Decoration for skipping empty lines
 */
class SkipEmptyLines extends SkipLines
{
    public function __construct() {
        parent::__construct([null]);
    }
}

/**
 * Decoration for setting field names
 */
class FieldNames extends TraversableDecoration
{
    private $fieldNames;

    public function __construct(array $fieldNames = null) {
        $this->fieldNames = $fieldNames;
    }

    public function current() {
        if ($this->fieldNames) {
            return array_combine($this->fieldNames, parent::current());
        }
        return parent::current();
    }

    public function setFieldNames(array $fieldNames) {
        $this->fieldNames = $fieldNames;
    }

    public function getFieldNames() {
        return $this->fieldNames;
    }
}


/**
 * Decoration for having field names in the first row
 */
class FieldNamesInFirstRow extends FieldNames
{
    public function rewind() {
        parent::rewind();
        $fieldNames = parent::current();
        parent::setFieldNames($fieldNames);
        parent::next();
    }
}


/**
 * CsvFile
 */
class CsvFile extends TraversableDecorator
{
    /**
     * @var Traversable
     */
    private $file;

    public function __construct($file = null) {
        $this->file = $this->filterInput($file);
        parent::__construct($this->file);
        $this->decorateWith(new SkipEmptyLines());
    }

    public function getFile() {
        return $this->file;
    }

    public function decorateWith(TraversableDecoration $iterator) {
        $iterator->setIterator($this->subject);
        $this->subject = $iterator;
    }

    public function removeDecoration() {
        parent::__construct($this->file);
    }

    /**
     * @param  mixed $file
     * @return Traversable
     * @throws InvalidArgumentException
     */
    private function filterInput($file) {

        if (null === $file) {
            $file = new SplTempFileObject();
        }

        if (is_string($file)) {
            try {
                $file = new SplFileObject($file);
            } catch (InvalidArgumentException $e) {
                throw $e;
            }
        }

        if ($file instanceof SplFileObject) {
            $file->setFlags(SplFileObject::READ_CSV);
        }

        return $file;
    }
}


/**
 * small helper function to display a csv file
 * @param CsvFile $csv
 */
$echoCsvFile = function(CsvFile $csv) {
    $counter = new IteratorIterator($csv);
    printf("CSV File with %d Line(s):\n", iterator_count($counter));
    foreach ($csv as $i => $line) {
        echo "$i:|";
        foreach($line as $key => $value) {
            ($value === NULL) && $value = 'NULL';
            echo "$key: $value|";
        }
        echo "\n";
    }
};


// Create a Temporary in-memory CSV file with two-line sample data
// and an empty line at the end
// Note: PHP eats non-standard \n for standard \r\n
$csv = new CsvFile();
/* @var $file SplTempFileObject */
$file = $csv->getFile();
$file->fwrite("A1,B1,C1\nA2,B2,C2\n\n");

$echoCsvFile($csv);

// as the example shows empty lines are dropped automatically as those
// are normally inside files in common scenarios, but this can be
// removed:
$csv->removeDecoration();
$echoCsvFile($csv);

// and added again:
$csv->decorateWith(new SkipEmptyLines());
$echoCsvFile($csv);

// for the moment take the CSV file as is and ignore empty lines
// this works because CsvFile can not only operate on an SplFileObject
// but anything that is Traversable
$csv = new CsvFile($csv);

// but tell that the first line contains the field names
$csv->decorateWith(new FieldNamesInFirstRow());
$echoCsvFile($csv);

// Let's change the field names, because in their current form it's not
// that nice
$csv->decorateWith(new FieldNames(['A', 'B', 'C']));
$echoCsvFile($csv);

// A full blown example
$csvData = <<<CSV
"Make","Model","Note"
"Chevy","1500","loaded"
"Chevy","2500",""
"Chevy","","loaded"
CSV;

$path = 'data://text/plain,' . $csvData;

$csv = new CsvFile($path);

$csv->decorateWith(new FieldNamesInFirstRow());
$echoCsvFile($csv);

// $csv->decorateWith(new SkipLines(["Chevy", "2500", ""]));
// $csv->decorateWith();
// $csv->decorateWith(new FieldNames(['make', 'model', 'note']));