<?php namespace System\Classes;

use Url;
use Crypt;
use Cache;
use Event;
use Config;
use Storage;
use Exception;
use SystemException;
use File as FileHelper;
use System\Models\File as SystemFileModel;
use October\Rain\Database\Attach\File as FileModel;
use October\Rain\Database\Attach\Resizer as DefaultResizer;

/**
 * Image Resizing class used for resizing any image resources accessible
 * to the application.
 *
 * This works by accepting a variety of image sources and normalizing the
 * pipeline for storing the desired resizing configuration and then
 * deferring the actual resizing of the images until requested by the browser.
 *
 * When the resizer route is hit, the configuration is retrieved from the cache
 * and used to generate the desired image and then redirect to the generated images
 * static path to minimize the load on the server. Future loads of the image are
 * automatically pointed to the static URL of the resized image without even hitting
 * the resizer route.
 *
 * The functionality of this class is controlled by these config items:
 *
 * - cms.resized.disk - The disk to store resized images on
 * - cms.resized.folder - The folder on the disk to store resized images in
 * - cms.resized.path - The public path to the resized images as returned
 *                      by the storage disk's URL method, used to identify
 *                      already resized images
 *
 * @see System\Classes\SystemController System controller
 * @see System\Twig\Extension Twig filters for this class defined
 * @package october\system
 * @author Luke Towers
 */
class ImageResizer
{
    /**
     * @var string The cache key prefix for resizer configs
     */
    public const CACHE_PREFIX = 'system.resizer.';

    /**
     * @var array Available sources to get images from
     */
    protected static $availableSources = [];

    /**
     * @var string Unique identifier for the current configuration
     */
    protected $identifier = null;

    /**
     * @var array Image source data ['disk' => string, 'path' => string, 'source' => string]
     */
    protected $image = [];

    /**
     * @var FileModel The instance of the FileModel for the source image
     */
    protected $fileModel = null;

    /**
     * @var integer Desired width
     */
    protected $width = 0;

    /**
     * @var integer Desired height
     */
    protected $height = 0;

    /**
     * @var array Image resizing configuration data
     */
    protected $options = [];

    /**
     * Prepare the resizer instance
     *
     * @param mixed $image Supported values below:
     *              ['disk' => Illuminate\Filesystem\FilesystemAdapter, 'path' => string, 'source' => string, 'fileModel' => FileModel|void],
     *              instance of October\Rain\Database\Attach\File,
     *              string containing URL or path accessible to the application's filesystem manager
     * @param integer|string|bool|null $width Desired width of the resized image
     * @param integer|string|bool|null $height Desired height of the resized image
     * @param array|null $options Array of options to pass to the resizer
     */
    public function __construct($image, $width = 0, $height = 0, $options = [])
    {
        $this->image = static::normalizeImage($image);
        $this->width = (int) (($width === 'auto') ? 0 : $width);
        $this->height = (int) (($height === 'auto') ? 0 : $height);
        $this->options = array_merge($this->getDefaultOptions(), $options);
    }

    /**
     * Get the default options for the resizer
     *
     * @return array
     */
    public function getDefaultOptions()
    {
        // Default options for the built in resizing processor
        $defaultOptions = [
            'mode'      => 'auto',
            'offset'    => [0, 0],
            'sharpen'   => 0,
            'interlace' => false,
            'quality'   => 90,
            'extension' => $this->getExtension(),
        ];

        /**
         * @event system.resizer.getDefaultOptions
         * Provides an opportunity to modify the default options used when generating image resize requests
         *
         * Example usage:
         *
         *     Event::listen('system.resizer.getDefaultOptions', function ((array) &$defaultOptions)) {
         *         $defaultOptions['background'] = '#f2f2f2';
         *     });
         *
         */
        Event::fire('system.resizer.getDefaultOptions', [&$defaultOptions]);

        return $defaultOptions;
    }

    /**
     * Get the available sources for processing image resize requests from
     *
     * @return array
     */
    public static function getAvailableSources()
    {
        if (!empty(static::$availableSources)) {
            return static::$availableSources;
        }

        $sources = [
            'themes' => [
                'disk' => 'system',
                'folder' => config('cms.themesPathLocal', base_path('themes')),
                'path' => config('cms.themesPath', '/themes'),
            ],
            'plugins' => [
                'disk' => 'system',
                'folder' => config('cms.pluginsPathLocal', base_path('plugins')),
                'path' => config('cms.pluginsPath', '/plugins'),
            ],
            'resized' => [
                'disk' => config('cms.storage.resized.disk', 'local'),
                'folder' => config('cms.storage.resized.folder', 'resized'),
                'path' => config('cms.storage.resized.path', '/storage/app/resized'),
            ],
            'media' => [
                'disk' => config('cms.storage.media.disk', 'local'),
                'folder' => config('cms.storage.media.folder', 'media'),
                'path' => config('cms.storage.media.path', '/storage/app/media'),
            ],
            'modules' => [
                'disk' => 'system',
                'folder' => base_path('modules'),
                'path' => '/modules',
            ],
            'filemodel' => [
                'disk' => config('cms.storage.uploads.disk', 'local'),
                'folder' => config('cms.storage.uploads.folder', 'uploads'),
                'path' => config('cms.storage.uploads.path', '/storage/app/uploads'),
            ],
        ];

        /**
         * @event system.resizer.getAvailableSources
         * Provides an opportunity to modify the sources available for processing resize requests from
         *
         * Example usage:
         *
         *     Event::listen('system.resizer.getAvailableSources', function ((array) &$sources)) {
         *         $sources['custom'] = [
         *              'disk' => 'custom',
         *              'folder' => 'relative/path/on/disk',
         *              'path' => 'publicly/accessible/path',
         *         ];
         *     });
         *
         */
        Event::fire('system.resizer.getAvailableSources', [&$sources]);

        return static::$availableSources = $sources;
    }

    /**
     * Flushes the local sources cache.
     *
     * @return void
     */
    public static function flushAvailableSources()
    {
        if (empty(static::$availableSources)) {
            return;
        }

        static::$availableSources = [];
    }

    /**
     * Get the current config
     *
     * @return array
     */
    public function getConfig()
    {
        $config = [
            'image' => [
                'disk' => $this->image['disk'],
                'path' => $this->image['path'],
                'source' => $this->image['source'],
            ],
            'width' => $this->width,
            'height' => $this->height,
            'options' => $this->options,
        ];

        if ($fileModel = $this->getFileModel()) {
            $config['image']['fileModel'] = [
                'class' => get_class($fileModel),
                'key' => $fileModel->getKey(),
            ];
        }

        return $config;
    }

    /**
     * Process the resize request
     */
    public function resize()
    {
        if ($this->isResized()) {
            return;
        }

        // Get the details for the target image
        list($disk, $path) = $this->getTargetDetails();

        // Copy the image to be resized to the temp directory
        $tempPath = $this->getLocalTempPath();

        try {
            /**
             * @event system.resizer.processResize
             * Halting event that enables replacement of the resizing process. There should only ever be
             * one listener handling this event per project at most, as other listeners would be ignored.
             *
             * > **NOTE:** The `$sourceDisk` and `$sourcePath` variables are only provided for informational
             * purposes, i.e. logging errors. They should never be interacted with directly, only interact
             * with the `$localTempPath` variable.
             *
             * Example usage:
             *
             *     Event::listen('system.resizer.processResize', function ((\System\Classes\ImageResizer) $resizer, (string) $localTempPath, (\Illuminate\Filesystem\FilesystemAdapter) $sourceDisk, (string) $sourcePath) {
             *          // Get the resizing configuration
             *          $config = $resizer->getConfig();
             *
             *          // Resize the image
             *          $resizedImageContents = My\Custom\Resizer::resize($localTempPath, $config['width], $config['height'], $config['options']);
             *
             *          // Place the resized image in the correct location for the resizer to finish processing it
             *          file_put_contents($localTempPath, $resizedImageContents);
             *
             *          // Prevent any other resizing replacer logic from running
             *          return true;
             *     });
             *
             */
            $processed = Event::fire('system.resizer.processResize', [$this, $tempPath, $disk, $path], true);
            if (!$processed) {
                // Process the resize with the default image resizer
                DefaultResizer::open($tempPath)
                    ->resize($this->width, $this->height, $this->options)
                    ->save($tempPath);
            }

            /**
             * @event system.resizer.afterResize
             * Enables post processing of resized images after they've been resized before the
             * resizing process is finalized (ex. adding watermarks, further optimizing, etc)
             *
             * > **NOTE:** The `$sourceDisk` and `$sourcePath` variables are only provided for informational
             * purposes, i.e. logging errors. They should never be interacted with directly, only interact
             * with the `$localTempPath` variable.
             *
             * Example usage:
             *
             *     Event::listen('system.resizer.afterResize', function ((\System\Classes\ImageResizer) $resizer, (string) $localTempPath, (\Illuminate\Filesystem\FilesystemAdapter) $disk, (string) $path)) {
             *          // Get the resized image data
             *          $resizedImageContents = file_get_contents($localTempPath);
             *
             *          // Post process the image
             *          $processedContents = TinyPNG::optimize($resizedImageContents);
             *
             *          // Place the processed image in the correct location for the resizer to finish processing it
             *          file_put_contents($localTempPath, $processedContents);
             *     });
             *
             */
            Event::fire('system.resizer.afterResize', [$this, $tempPath, $disk, $path]);

            // Store the resized image
            $disk->put($path, file_get_contents($tempPath));

            // Clean up
            unlink($tempPath);
        } catch (Exception $ex) {
            // Clean up in case of any issues
            unlink($tempPath);

            // Pass the exception up
            throw $ex;
        }
    }

    /**
     * Define the internal working path, override this method to define.
     */
    public function getTempPath()
    {
        $path = temp_path() . '/resizer';

        if (!FileHelper::isDirectory($path)) {
            FileHelper::makeDirectory($path, 0777, true, true);
        }

        return $path;
    }

    /**
     * Stores the current source image in the temp directory and returns the path to it
     *
     * @param string $path The path to suffix the temp directory path with, defaults to $identifier.$ext
     * @return string $tempPath
     */
    protected function getLocalTempPath($path = null)
    {
        if (!is_null($path) && is_string($path)) {
            $tempPath = $this->getTempPath() . '/' . $path;
        } else {
            $tempPath = $this->getTempPath() . '/' . $this->getIdentifier() . '.' . $this->getExtension();
        }

        if (!file_exists($tempPath)) {
            FileHelper::put($tempPath, $this->getSourceFileContents());
        }

        return $tempPath;
    }

    /**
     * Returns the file extension.
     */
    public function getExtension()
    {
        return FileHelper::extension($this->image['path']);
    }

    /**
     * Get the contents of the image file to be resized
     *
     * @return string
     */
    public function getSourceFileContents()
    {
        return $this->image['disk']->get($this->image['path']);
    }

    /**
     * Gets the current fileModel associated with the source image if one exists
     *
     * @return FileModel|null
     */
    public function getFileModel()
    {
        if ($this->fileModel) {
            return $this->fileModel;
        }

        if ($this->image['source'] === 'filemodel') {
            if ($this->image['fileModel'] instanceof FileModel) {
                $this->fileModel = $this->image['fileModel'];
            } else {
                $this->fileModel = $this->image['fileModel']['class']::findOrFail($this->image['fileModel']['key']);
            }
        }

        return $this->fileModel;
    }

    /**
     * Get the details for the target image
     *
     * @return array [Illuminate\Filesystem\FilesystemAdapter $disk, (string) $path]
     */
    protected function getTargetDetails()
    {
        if ($this->image['source'] === 'filemodel' && $fileModel = $this->getFileModel()) {
            $disk = $fileModel->getDisk();
            $path = $fileModel->getDiskPath($fileModel->getThumbFilename($this->width, $this->height, $this->options));
        } else {
            $disk = Storage::disk(Config::get('cms.resized.disk', 'local'));
            $path = $this->getPathToResizedImage();
        }

        return [$disk, $path];
    }

    /**
     * Get the reference to the resized image if the requested resize exists
     *
     * @param string $identifier The Resizer Identifier that references the source image and desired resizing configuration
     * @return bool|string
     */
    public function isResized()
    {
        // Get the details for the target image
        list($disk, $path) = $this->getTargetDetails();

        // Return true if the path is a file and it exists on the target disk
        return !empty(FileHelper::extension($path)) && $disk->exists($path);
    }

    /**
     * Get the path of the resized image
     */
    public function getPathToResizedImage()
    {
        // Generate the unique file identifier for the resized image
        $fileIdentifier = hash_hmac('sha1', serialize($this->getConfig()), Crypt::getKey());

        // Generate the filename for the resized image
        $name = pathinfo($this->image['path'], PATHINFO_FILENAME) . "_resized_$fileIdentifier.{$this->options['extension']}";

        // Generate the path to the containing folder for the resized image
        $folder = implode('/', array_slice(str_split(str_limit($fileIdentifier, 9), 3), 0, 3));

        // Generate and return the full path
        return Config::get('cms.resized.folder', 'resized') . '/' . $folder . '/' . $name;
    }

    /**
     * Gets the current useful URL to the resized image
     * (resizer if not resized, resized image directly if resized)
     *
     * @return string
     */
    public function getUrl()
    {
        if ($this->isResized()) {
            return $this->getResizedUrl();
        } else {
            return $this->getResizerUrl();
        }
    }

    /**
     * Get the URL to the system resizer route for this instance's configuration
     *
     * @return string $url
     */
    public function getResizerUrl()
    {
        // Slashes in URL params have to be double encoded to survive Laravel's router
        // @see https://github.com/octobercms/october/issues/3592#issuecomment-671017380
        $resizedUrl = urlencode(urlencode($this->getResizedUrl()));

        // Get the current configuration's identifier
        $identifier = $this->getIdentifier();

        // Store the current configuration
        $this->storeConfig();

        return Url::to("/resizer/$identifier/$resizedUrl");
    }

    /**
     * Get the URL to the resized image
     *
     * @return string
     */
    public function getResizedUrl()
    {
        $url = '';

        if ($this->image['source'] === 'filemodel') {
            $model = $this->getFileModel();
            $thumbFile = $model->getThumbFilename($this->width, $this->height, $this->options);
            $url = $model->getPath($thumbFile);
        } else {
            $resizedDisk = Storage::disk(Config::get('cms.resized.disk', 'local'));
            $url = $resizedDisk->url($this->getPathToResizedImage());
        }

        return $url;
    }

    /**
     * Normalize the provided input into information that the resizer can work with
     *
     * @param mixed $image Supported values below:
     *              ['disk' => Illuminate\Filesystem\FilesystemAdapter, 'path' => string, 'source' => string, 'fileModel' => FileModel|void],
     *              instance of October\Rain\Database\Attach\File,
     *              string containing URL or path accessible to the application's filesystem manager
     * @throws SystemException If the image was unable to be identified
     * @return array Array containing the disk, path, source, and fileModel if applicable
     *               ['disk' => Illuminate\Filesystem\FilesystemAdapter, 'path' => string, 'source' => string, 'fileModel' => FileModel|void]
     */
    public static function normalizeImage($image)
    {
        $disk = null;
        $path = null;
        $selectedSource = null;
        $fileModel = null;

        // Process an array
        if (is_array($image) && !empty($image['disk']) && !empty($image['path']) && !empty($image['source'])) {
            $disk = $image['disk'];
            $path = $image['path'];
            $selectedSource = $image['source'];

            // Verify that the source file exists
            if (empty(FileHelper::extension($path)) || !$disk->exists($path)) {
                $disk = null;
                $path = null;
                $selectedSource = null;
            }

            if (!empty($image['fileModel'])) {
                $fileModel = $image['fileModel'];
            }

        // Process a FileModel
        } elseif ($image instanceof FileModel) {
            $disk = $image->getDisk();
            $path = $image->getDiskPath();
            $selectedSource = 'filemodel';
            $fileModel = $image;

            // Verify that the source file exists
            if (empty(FileHelper::extension($path)) || !$disk->exists($path)) {
                $disk = null;
                $path = null;
                $selectedSource = null;
                $fileModel = null;
            }

        // Process a string
        } elseif (is_string($image)) {
            // Parse the provided image path into a filesystem ready relative path
            $relativePath = static::normalizePath(urldecode(parse_url($image, PHP_URL_PATH)));

            // Loop through the sources available to the application to pull from
            // to identify the source most likely to be holding the image
            $resizeSources = static::getAvailableSources();
            foreach ($resizeSources as $source => $details) {
                // Normalize the source path
                $sourcePath = static::normalizePath(urldecode(parse_url($details['path'], PHP_URL_PATH)));

                // Identify if the current source is a match
                if (starts_with($relativePath, $sourcePath)) {
                    // Attempt to handle FileModel URLs passed as strings
                    if ($source === 'filemodel') {
                        $diskName = pathinfo($relativePath, PATHINFO_BASENAME);
                        $model = SystemFileModel::where('disk_name', $diskName)->first();
                        if ($model && $image = static::normalizeImage($model)) {
                            $disk = $image['disk'];
                            $path = $image['path'];
                            $selectedSource = $image['source'];
                            $fileModel = $image['fileModel'];
                        }
                        // Stop any further path processing from happening on filemodel sources
                        break;
                    }

                    // Generate a path relative to the selected disk
                    $path = static::normalizePath($details['folder']) . '/' . str_after($relativePath, $sourcePath . '/');

                    // Handle disks of type "system" (the local file system the application is running on)
                    if ($details['disk'] === 'system') {
                        Config::set('filesystems.disks.system', [
                            'driver' => 'local',
                            'root' => base_path(),
                        ]);
                        // Regenerate the path relative to the newly defined "system" disk
                        $path = str_after($path, static::normalizePath(base_path()) . '/');
                    }

                    $disk = Storage::disk($details['disk']);

                    // Verify that the file exists before exiting the identification process
                    if (!empty(FileHelper::extension($path)) && $disk->exists($path)) {
                        $selectedSource = $source;
                        break;
                    } else {
                        $disk = null;
                        $path = null;
                        continue;
                    }
                }
            }
        }

        if (!$disk || !$path || !$selectedSource) {
            if (is_object($image)) {
                $image = get_class($image);
            }
            throw new SystemException("Unable to process the provided image: " . e(var_export($image, true)));
        }

        $data = [
            'disk' => $disk,
            'path' => $path,
            'source' => $selectedSource,
        ];

        if ($fileModel) {
            $data['fileModel'] = $fileModel;
        }

        return $data;
    }

    /**
     * Normalize the provided path to Unix style directory seperators to ensure
     * that path manipulation operations succeed regardless of environment
     *
     * NOTE: Can't use October\Rain\FileSystem\PathResolver because it prepends
     * the current working directory to relative paths
     *
     * @param string $path
     * @return string
     */
    protected static function normalizePath($path)
    {
        return str_replace('\\', '/', $path);
    }

    /**
     * Check if the provided identifier looks like a valid identifier
     *
     * @param string $id
     * @return bool
     */
    public static function isValidIdentifier($id)
    {
        return is_string($id) && ctype_alnum($id) && strlen($id) === 40;
    }

    /**
     * Gets the identifier for provided resizing configuration
     *
     * @return string 40 character string used as a unique reference to the provided configuration
     */
    public function getIdentifier()
    {
        if ($this->identifier) {
            return $this->identifier;
        }

        // Generate & return the identifier
        return $this->identifier = hash_hmac('sha1', $this->getResizedUrl(), Crypt::getKey());
    }

    /**
     * Stores the resizer configuration if the resizing hasn't been completed yet
     */
    public function storeConfig()
    {
        // If the image hasn't been resized yet, then store the config data for the resizer to use
        if (!$this->isResized()) {
            Cache::put(static::CACHE_PREFIX . $this->getIdentifier(), $this->getConfig());
        }
    }

    /**
     * Instantiate a resizer instance from the provided identifier
     *
     * @param string $identifier The 40 character cache identifier for the desired resizer configuration
     * @throws SystemException If the identifier is unable to be loaded
     * @return static
     */
    public static function fromIdentifier(string $identifier)
    {
        // Attempt to retrieve the resizer configuration and remove the data from the cache after retrieval
        $config = Cache::pull(static::CACHE_PREFIX . $identifier, null);

        // Validate that the desired config was able to be loaded
        if (empty($config)) {
            throw new SystemException("Unable to retrieve the configuration for " . e($identifier));
        }

        return new static($config['image'], $config['width'], $config['height'], $config['options']);
    }

    /**
     * Check the provided encoded URL to verify its signature and return the decoded URL
     *
     * @param string $identifier
     * @param string $encodedUrl
     * @return string|null Returns null if the provided value was invalid
     */
    public static function getValidResizedUrl($identifier, $encodedUrl)
    {
        // Slashes in URL params have to be double encoded to survive Laravel's router
        // @see https://github.com/octobercms/october/issues/3592#issuecomment-671017380
        $decodedUrl = urldecode(urldecode($encodedUrl));
        $url = null;

        // The identifier should be the signed version of the decoded URL
        if (static::isValidIdentifier($identifier) && $identifier === hash_hmac('sha1', $decodedUrl, Crypt::getKey())) {
            $url = $decodedUrl;
        }

        return $url;
    }

    /**
     * Converts supplied input into a URL that will return the desired resized image
     *
     * @param mixed $image Supported values below:
     *              ['disk' => Illuminate\Filesystem\FilesystemAdapter, 'path' => string, 'source' => string, 'fileModel' => FileModel|void],
     *              instance of October\Rain\Database\Attach\File,
     *              string containing URL or path accessible to the application's filesystem manager
     * @param integer|bool|null $width Desired width of the resized image
     * @param integer|bool|null $height Desired height of the resized image
     * @param array|null $options Array of options to pass to the resizer
     * @throws Exception If the provided image was unable to be processed
     * @return string
     */
    public static function filterGetUrl($image, $width = null, $height = null, $options = [])
    {
        // Attempt to process the provided image
        try {
            $resizer = new static($image, $width, $height, $options);
        } catch (SystemException $ex) {
            // Ignore processing this URL if the resizer is unable to identify it
            if (is_string($image)) {
                return $image;
            } elseif ($image instanceof FileModel) {
                return $image->getPath();
            } else {
                throw $ex;
            }
        }

        return $resizer->getUrl();
    }

    /**
     * Gets the dimensions of the provided image file
     * NOTE: Doesn't currently support being passed a FileModel image that has already been resized
     *
     * @param mixed $image Supported values below:
     *              ['disk' => Illuminate\Filesystem\FilesystemAdapter, 'path' => string, 'source' => string, 'fileModel' => FileModel|void],
     *              instance of October\Rain\Database\Attach\File,
     *              string containing URL or path accessible to the application's filesystem manager
     * @throws SystemException If the provided input was unable to be processed
     * @return array ['width' => int, 'height' => int]
     */
    public static function filterGetDimensions($image)
    {
        $resizer = new static($image);

        return Cache::rememberForever(static::CACHE_PREFIX . 'dimensions.' . $resizer->getIdentifier(), function () use ($resizer) {
            // Prepare the local file for assessment
            $tempPath = $resizer->getLocalTempPath();
            $dimensions = [];

            // Attempt to get the image size
            try {
                $size = getimagesize($tempPath);
                $dimensions['width'] = $size[0];
                $dimensions['height'] = $size[1];
            } catch (\Exception $ex) {
                @unlink($tempPath);
                throw $ex;
            }

            // Cleanup afterwards
            @unlink($tempPath);

            return $dimensions;
        });
    }
}