fix (tableexporter): add inline documentation

src/Keboola/StorageApi/TableExporter.php

@@ -2,7 +2,8 @@
 /**
  * Storage API Client - Table Exporter
  *
- *
+ * Downloads a table from Storage API and saves it to destination path. Merges all parts of a sliced file and adds
+ * header if missing.
  *
  * @author Ondrej Hlavacek <ondrej.hlavacek@keboola.com>
  * @date: 5.6.14
@@ -43,16 +44,19 @@ public function exportTable($tableId, $destination, $exportOptions)
 			$exportOptions['gzip'] = false;
 		}
 
+		// Export table from Storage API to S3
 		$table = $this->client->getTable($tableId);
 		$fileId = $this->client->exportTableAsync($tableId, $exportOptions);
-
 		$fileInfo = $this->client->getFile($fileId["file"]["id"], (new \Keboola\StorageApi\Options\GetFileOptions())->setFederationToken(true));
+
+		// Initialize S3Client with credentials from Storage API
 		$s3Client = S3Client::factory(array(
 			"key" => $fileInfo["credentials"]["AccessKeyId"],
 			"secret" => $fileInfo["credentials"]["SecretAccessKey"],
 			"token" => $fileInfo["credentials"]["SessionToken"]
 		));
 
+		// Temporary folder to save downloaded files from S3
 		$tmpFilePath = sys_get_temp_dir() . '/sapi-php-client' . '/' . uniqid('sapi-export-');
 
 		$fs = new Filesystem();
@@ -61,8 +65,12 @@ public function exportTable($tableId, $destination, $exportOptions)
 			/**
 			 * sliced file - combine files together
 			 */
+
+			// Download manifest with all sliced files
 			$manifest = json_decode(file_get_contents($fileInfo["url"]), true);
 			$files = array();
+
+			// Download all sliced files
 			foreach($manifest["entries"] as $part) {
 				$fileKey = substr($part["url"], strpos($part["url"], '/', 5) + 1);
 				$filePath = $tmpFilePath . '_' . md5(str_replace('/', '_', $fileKey));
@@ -74,13 +82,15 @@ public function exportTable($tableId, $destination, $exportOptions)
 				));
 			}
 
+			// Create file with header
 			$header = '"' . join($table["columns"], '","') . '"' . "\n";
 			if ($exportOptions["gzip"] === true) {
 				$fs->dumpFile($destination . '.tmp', $header);
 			} else {
 				$fs->dumpFile($destination, $header);
 			}
 
+			// Concat all files into one, compressed files need to be decompressed first
 			foreach($files as $file) {
 				if ($exportOptions["gzip"]) {
 					$catCmd = "gunzip " . escapeshellarg($file) . " --to-stdout >> " . escapeshellarg($destination) . ".tmp";
@@ -90,6 +100,8 @@ public function exportTable($tableId, $destination, $exportOptions)
 				(new Process($catCmd))->mustRun();
 				$fs->remove($file);
 			}
+
+			// Compress the file afterwards if required
 			if ($exportOptions["gzip"]) {
 				$gZipCmd = "gzip " . escapeshellarg($destination) . ".tmp --fast";
 				(new Process($gZipCmd))->mustRun();
@@ -98,7 +110,7 @@ public function exportTable($tableId, $destination, $exportOptions)
 
 		} else {
 			/**
-			 * NonSliced file, just move
+			 * NonSliced file, just move from temp to destination file
 			 */
 			$s3Client->getObject(array(
 				'Bucket' => $fileInfo["s3Path"]["bucket"],