AwsUploadPolicy.php

<?php

/**
 * Class AwsUploadPolicy
 * @see http://docs.aws.amazon.com/AmazonS3/latest/dev/HTTPPOSTForms.html
 * @package Urahara
 */
class AwsUploadPolicy implements \JsonSerializable
{
    const ACL_PRIVATE       = 'private';
    const ACL_PUBLIC_READ   = 'public-read';
    const ACL_PUBLIC_RW     = 'public-read-write';
    const ACL_AUTH_READ     = 'authenticated-read';
    const ACL_OWNER_READ    = 'bucket-owner-read';
    const ACL_OWNER_FULL    = 'bucket-owner-full-control';

    const MATCH_EXACT   = 'eq';
    const MATCH_PREFIX  = 'starts-with';

    private static $BUCKET                  = 'bucket';
    private static $ACL                     = 'acl';
    private static $KEY                     = 'key';
    private static $CONTENT_LENGTH_RANGE    = 'content-length-range';
    private static $CONTENT_TYPE            = 'Content-Type';

    /**
     * @var \DateTime
     */
    private $expiry;

    private $conditions = array();

    public function __construct(\DateTime $expiry)
    {
        $this->expiry = $expiry;
    }

    public function setBucket($value)
    {
        $this->addExactMatchCondition(self::$BUCKET, $value);
    }

    public function setACL($value)
    {
        $this->addExactMatchCondition(self::$ACL, $value);
    }

    public function setKey($value, $prefix = self::MATCH_EXACT)
    {
        if ($prefix === self::MATCH_PREFIX) {
            $this->addStartsWithCondition(self::$KEY, $value);
        } else {
            $this->addExactMatchCondition(self::$KEY, $value);
        }
    }

    public function setContentLength($value)
    {
        $this->addRangeCondition(self::$CONTENT_LENGTH_RANGE, $value, $value);
    }

    public function setContentType($value, $prefix = self::MATCH_EXACT)
    {
        if ($prefix === self::MATCH_PREFIX) {
            $this->addStartsWithCondition(self::$CONTENT_TYPE, $value);
        } else {
            $this->addExactMatchCondition(self::$CONTENT_TYPE, $value);
        }
    }

    public function setSecurityToken($token)
    {
        $this->addExactMatchCondition('x-amz-security-token', $token);
    }

    protected function addExactMatchCondition($name, $value)
    {
        $this->conditions[] = array(
            'eq',
            $this->getPrefixedFieldName($name),
            $value,
        );
    }

    protected function addStartsWithCondition($name, $prefix = '')
    {
        $this->conditions[] = array(
            'starts-with',
            $this->getPrefixedFieldName($name),
            $prefix,
        );
    }

    protected function addRangeCondition($name, $low, $high)
    {
        $this->conditions[] = array(
            $name,
            $low,
            $high,
        );
    }

    public function __toString()
    {
        return base64_encode(json_encode(array(
            'expiration' => substr_replace($this->expiry->format('c'), 'Z', -6),
            'conditions' => $this->conditions,
        )));
    }

    private function getPrefixedFieldName($name)
    {
        return '$' . $name;
    }

    public function jsonSerialize()
    {
        return $this->__toString();
    }
}