<?php

/**
 * @package KantPHP
 * @author  Zhenqiang Zhang <zhenqiang.zhang@hotmail.com>
 * @copyright (c) KantPHP Studio, All rights reserved.
 * @license http://www.opensource.org/licenses/BSD-3-Clause  The BSD 3-Clause License
 */
namespace Kant\I18n;

use Kant\Kant;

/**
 * PhpMessageSource represents a message source that stores translated messages in PHP scripts.
 *
 * PhpMessageSource uses PHP arrays to keep message translations.
 *
 * - Each PHP script contains one array which stores the message translations in one particular
 * language and for a single message category;
 * - Each PHP script is saved as a file named as `[[basePath]]/LanguageID/CategoryName.php`;
 * - Within each PHP script, the message translations are returned as an array like the following:
 *
 * ```php
 * return [
 * 'original message 1' => 'translated message 1',
 * 'original message 2' => 'translated message 2',
 * ];
 * ```
 *
 * You may use [[fileMap]] to customize the association between category names and the file names.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class PhpMessageSource extends MessageSource
{

    /**
     *
     * @var string the base path for all translated messages. Defaults to '@app/messages'.
     */
    public $basePath = KANT_PATH . '/Messages/';

    /**
     *
     * @var array mapping between message categories and the corresponding message file paths.
     *      The file paths are relative to [[basePath]]. For example,
     *     
     *      ```php
     *      [
     *      'core' => 'core.php',
     *      'ext' => 'extensions.php',
     *      ]
     *      ```
     */
    public $fileMap;

    /**
     * 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`. When both are present, the `en-US` messages will be merged
     * over `en`. See [[loadFallbackMessages]] for details.
     * If the $language is less specific than [[sourceLanguage]], the method will try to
     * load the messages for [[sourceLanguage]]. For example: [[sourceLanguage]] is `en-GB`,
     * $language is `en`. The method will load the messages for `en` and merge them over `en-GB`.
     *
     * @param string $category
     *            the message category
     * @param string $language
     *            the target language
     * @return array the loaded messages. The keys are original messages, and the values are the translated messages.
     * @see loadFallbackMessages
     * @see sourceLanguage
     */
    protected function loadMessages($category, $language)
    {
        $messageFile = $this->getMessageFilePath($category, $language);
        $messages = $this->loadMessagesFromFile($messageFile);
        
        $fallbackLanguage = substr($language, 0, 2);
        $fallbackSourceLanguage = substr($this->sourceLanguage, 0, 2);
        
        if ($language !== $fallbackLanguage) {
            $messages = $this->loadFallbackMessages($category, $fallbackLanguage, $messages, $messageFile);
        } elseif ($language === $fallbackSourceLanguage) {
            $messages = $this->loadFallbackMessages($category, $this->sourceLanguage, $messages, $messageFile);
        } else {
            if ($messages === null) {
                Kant::error("The message file for category '$category' does not exist: $messageFile", __METHOD__);
            }
        }
        
        return (array) $messages;
    }

    /**
     * The method is normally called by [[loadMessages]] to load the fallback messages for the language.
     * Method tries to load the $category messages for the $fallbackLanguage and adds them to the $messages array.
     *
     * @param string $category
     *            the message category
     * @param string $fallbackLanguage
     *            the target fallback language
     * @param array $messages
     *            the array of previously loaded translation messages.
     *            The keys are original messages, and the values are the translated messages.
     * @param string $originalMessageFile
     *            the path to the file with messages. Used to log an error message
     *            in case when no translations were found.
     * @return array the loaded messages. The keys are original messages, and the values are the translated messages.
     * @since 2.0.7
     */
    protected function loadFallbackMessages($category, $fallbackLanguage, $messages, $originalMessageFile)
    {
        $fallbackMessageFile = $this->getMessageFilePath($category, $fallbackLanguage);
        $fallbackMessages = $this->loadMessagesFromFile($fallbackMessageFile);
        
        if ($messages === null && $fallbackMessages === null && $fallbackLanguage !== $this->sourceLanguage && $fallbackLanguage !== substr($this->sourceLanguage, 0, 2)) {
            "The message file for category '$category' does not exist: $originalMessageFile " . "Fallback file does not exist as well: $fallbackMessageFile";
            // Kant::error("The message file for category '$category' does not exist: $originalMessageFile "
            // . "Fallback file does not exist as well: $fallbackMessageFile", __METHOD__);
        } elseif (empty($messages)) {
            return $fallbackMessages;
        } elseif (!empty($fallbackMessages)) {
            foreach ($fallbackMessages as $key => $value) {
                if (!empty($value) && empty($messages[$key])) {
                    $messages[$key] = $fallbackMessages[$key];
                }
            }
        }
        
        return (array) $messages;
    }

    /**
     * Returns message file path for the specified language and category.
     *
     * @param string $category
     *            the message category
     * @param string $language
     *            the target language
     * @return string path to message file
     */
    protected function getMessageFilePath($category, $language)
    {
        $messageFile = $this->basePath . "$language/";
        if (isset($this->fileMap[$category])) {
            $messageFile .= $this->fileMap[$category];
        } else {
            $messageFile .= str_replace('\\', '/', $category) . '.php';
        }
        return $messageFile;
    }

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