<?php
/**
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\i18n;

use Yii;

/**
 * GettextMessageSource represents a message source that is based on GNU Gettext.
 *
 * Each GettextMessageSource instance represents the message tranlations
 * for a single domain. And each message category represents a message context
 * in Gettext. Translated messages are stored as either a MO or PO file,
 * depending on the [[useMoFile]] property value.
 *
 * All translations are saved under the [[basePath]] directory.
 *
 * Translations in one language are kept as MO or PO files under an individual
 * subdirectory whose name is the language ID. The file name is specified via
 * [[catalog]] property, which defaults to 'messages'.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class GettextMessageSource extends MessageSource
{
	const MO_FILE_EXT = '.mo';
	const PO_FILE_EXT = '.po';

	/**
	 * @var string
	 */
	public $basePath = '@app/messages';
	/**
	 * @var string
	 */
	public $catalog = 'messages';
	/**
	 * @var boolean
	 */
	public $useMoFile = true;
	/**
	 * @var boolean
	 */
	public $useBigEndian = false;

	/**
	 * Loads the message translation for the specified language and category.
	 * If translation for specific locale code such as `en-US` isn't found it
	 * tries more generic `en`.
	 *
	 * @param string $category the message category
	 * @param string $language the target language
	 * @return array the loaded messages. The keys are original messages, and the values
	 * are translated messages.
	 */
	protected function loadMessages($category, $language)
	{
		$messageFile = $this->getMessageFilePath($language);
		$messages = $this->loadMessagesFromFile($messageFile, $category);

		$fallbackLanguage = substr($language, 0, 2);
		if ($fallbackLanguage != $language) {
			$fallbackMessageFile = $this->getMessageFilePath($fallbackLanguage);
			$fallbackMessages = $this->loadMessagesFromFile($fallbackMessageFile, $category);

			if ($messages === null && $fallbackMessages === null && $fallbackLanguage != $this->sourceLanguage) {
				Yii::error("The message file for category '$category' does not exist: $messageFile Fallback file does not exist as well: $fallbackMessageFile", __METHOD__);
			} else if (empty($messages)) {
				return $fallbackMessages;
			} else if (!empty($fallbackMessages)) {
				foreach ($fallbackMessages as $key => $value) {
					if (!empty($value) && empty($messages[$key])) {
						$messages[$key] = $fallbackMessages[$key];
					}
				}
			}
		} else {
			if ($messages === null) {
				Yii::error("The message file for category '$category' does not exist: $messageFile", __METHOD__);
			}
		}
		return (array)$messages;
	}

	/**
	 * Returns message file path for the specified language and category.
	 *
	 * @param string $language the target language
	 * @return string path to message file
	 */
	protected function getMessageFilePath($language)
	{
		$messageFile = Yii::getAlias($this->basePath) . '/' . $language . '/' . $this->catalog;
		if ($this->useMoFile) {
			$messageFile .= static::MO_FILE_EXT;
		} else {
			$messageFile .= static::PO_FILE_EXT;
		}
		return $messageFile;
	}

	/**
	 * Loads the message translation for the specified language and category or returns null if file doesn't exist.
	 *
	 * @param string $messageFile path to message file
	 * @param string $category the message category
	 * @return array|null array of messages or null if file not found
	 */
	protected function loadMessagesFromFile($messageFile, $category)
	{
		if (is_file($messageFile)) {
			if ($this->useMoFile) {
				$gettextFile = new GettextMoFile(['useBigEndian' => $this->useBigEndian]);
			} else {
				$gettextFile = new GettextPoFile();
			}
			$messages = $gettextFile->load($messageFile, $category);
			if (!is_array($messages)) {
				$messages = [];
			}
			return $messages;
		} else {
			return null;
		}
	}
}