<?php

use Aws\S3\S3Client;

class Amazon_S3StorageBackend extends StorageBackend
{
    
    private $s3Client;
    private $proxyHost;

    public function __construct($securityCredentials)
    {
        $this->setBucket($securityCredentials['bucket']);
        $this->setAccessKey($securityCredentials['api_key']);
        $this->setSecretKey($securityCredentials['api_key_secret']);

        $s3Options = array(
            'key' => $securityCredentials['api_key'],
            'secret' => $securityCredentials['api_key_secret'],
            'region' => $securityCredentials['region']
        );
        if (array_key_exists("proxy_host", $securityCredentials)) {
            $s3Options = array_merge($s3Options, array(
                //'base_url' => "http://" . $securityCredentials['proxy_host'],
                'base_url' => "http://s3.amazonaws.com",
                'scheme' => "http",
                //'force_path_style'  => true,
                'signature' => 'v4'
            ));
            $this->proxyHost = $securityCredentials['proxy_host'];
        }
    
        $this->s3Client = S3Client::factory($s3Options);
    }

    public function getAbsoluteFilePath($resourceId)
    {
        return $this->s3Client->getObjectUrl($this->getBucket(), $resourceId);
    }

    /** Returns a signed download URL from Amazon S3, expiring in 60 minutes */
    public function getDownloadURLs($resourceId, $contentDispositionFilename)
    {
        $urls = array();

        $s3args = array('ResponseContentDisposition' => 'attachment; filename="' . urlencode($contentDispositionFilename) . '"');
        $signedS3Url = $this->s3Client->getObjectUrl($this->getBucket(), $resourceId, '+60 minutes', $s3args);

        //If we're using the proxy cache, we need to modify the request URL after it has
        //been generated by the above. (The request signature must be for the amazonaws.com,
        //not our proxy, since the proxy translates the host back to amazonaws.com)
        if ($this->proxyHost) {
            $p = parse_url($signedS3Url);
            $p["host"] = $this->getBucket() . "." . $this->proxyHost;
            $p["scheme"] = "http";
            //If the path contains the bucket name (which is the case with HTTPS requests to Amazon),
            //we need to strip that part out, since we're forcing everything to HTTP. The Amazon S3
            //URL convention for HTTP is to prepend the bucket name to the hostname instead of having
            //it in the path.
            //eg. http://bucket.s3.amazonaws.com/ instead of https://s3.amazonaws.com/bucket/
            if (strpos($p["path"], $this->getBucket()) == 1) {
                $p["path"] = substr($p["path"], 1 + strlen($this->getBucket()));
            }
            $proxyUrl = $p["scheme"] . "://" . $p["host"] . $p["path"] . "?" . $p["query"];
            //Add this proxy cache URL to the list of download URLs.s
            array_push($urls, $proxyUrl);
        }

        //Add the direct S3 URL to the list (as a fallback)
        array_push($urls, $signedS3Url);

        //http_build_url() would be nice to use but it requires pecl_http :-(

        //Logging::info($url);

        return $urls;
    }

    public function deletePhysicalFile($resourceId)
    {
        $bucket = $this->getBucket();

        if ($this->s3Client->doesObjectExist($bucket, $resourceId)) {

            $result = $this->s3Client->deleteObject(array(
                'Bucket' => $bucket,
                'Key' => $resourceId,
            ));
        } else {
            throw new Exception("ERROR: Could not locate file to delete.");
        }
    }
    
    // This should only be called for station termination.
    // We are only deleting the file objects from Amazon S3.
    // Records in the database will remain in case we have to restore the files.
    public function deleteAllCloudFileObjects()
    {
        $bucket = $this->getBucket();
        $prefix = $this->getFilePrefix();

        //Add a trailing slash in for safety
        //(so that deleting /13/413 doesn't delete /13/41313 !)
        $prefix = $prefix . "/";

        //Do a bunch of safety checks to ensure we don't delete more than we intended.
        //An valid prefix is like "12/4312" for instance 4312.
        $slashPos = strpos($prefix, "/");
        if (($slashPos === FALSE) || //Slash must exist
            ($slashPos != 2) ||      //Slash must be the third character
            (strlen($prefix) <= $slashPos) ||    //String must have something after the first slash
            (substr_count($prefix, "/") != 2))  //String must have two slashes
        {
            throw new Exception("Invalid file prefix in " . __FUNCTION__);
    }
        $this->s3Client->deleteMatchingObjects($bucket, $prefix);
    }

    public function getFilePrefix()
    {
        $filePrefix = '';
        // only prefix files on S3 when billing is active since saas customers share a s3 bucket
        // I'm not sure why the choice was made to put everything into one bucket
        // We might refactor this to use a bucket per customer if we revisit S3
        if (LIBRETIME_ENABLE_BILLING === true) {
            $hostingId = Billing::getClientInstanceId();
            $filePrefix = substr($hostingId, -2)."/".$hostingId;
        }
        return $filePrefix;
    }
}