<?php
/**
 * \page eande Events and Extensions
 *
 * An event is a little blob of data saying "something happened", possibly
 * "something happened, here's the specific data". Events are sent with the
 * send_event() function. Since events can store data, they can be used to
 * return data to the extension which sent them, for example:
 *
 * \code
 * $tfe = new TextFormattingEvent($original_text);
 * send_event($tfe);
 * $formatted_text = $tfe->formatted;
 * \endcode
 *
 * An extension is something which is capable of reacting to events.
 *
 *
 * \page hello The Hello World Extension
 *
 * \code
 * // ext/hello/main.php
 * public class HelloEvent extends Event {
 *     public function __construct($username) {
 *         $this->username = $username;
 *     }
 * }
 *
 * public class Hello extends Extension {
 *     public function onPageRequest(PageRequestEvent $event) {   // Every time a page request is sent
 *         global $user;                                          // Look at the global "currently logged in user" object
 *         send_event(new HelloEvent($user->name));               // Broadcast a signal saying hello to that user
 *     }
 *     public function onHello(HelloEvent $event) {               // When the "Hello" signal is recieved
 *         $this->theme->display_hello($event->username);         // Display a message on the web page
 *     }
 * }
 *
 * // ext/hello/theme.php
 * public class HelloTheme extends Themelet {
 *     public function display_hello($username) {
 *         global $page;
 *         $h_user = html_escape($username);                     // Escape the data before adding it to the page
 *         $block = new Block("Hello!", "Hello there $h_user");  // HTML-safe variables start with "h_"
 *         $page->add_block($block);                             // Add the block to the page
 *     }
 * }
 *
 * // ext/hello/test.php
 * public class HelloTest extends SCorePHPUnitTestCase {
 *     public function testHello() {
 *         $this->get_page("post/list");                   // View a page, any page
 *         $this->assert_text("Hello there");              // Check that the specified text is in that page
 *     }
 * }
 *
 * // themes/mytheme/hello.theme.php
 * public class CustomHelloTheme extends HelloTheme {     // CustomHelloTheme overrides HelloTheme
 *     public function display_hello($username) {         // the display_hello() function is customised
 *         global $page;
 *         $h_user = html_escape($username);
 *         $page->add_block(new Block(
 *             "Hello!",
 *             "Hello there $h_user, look at my snazzy custom theme!"
 *         );
 *     }
 * }
 * \endcode
 *
 */

/**
 * Class Extension
 *
 * send_event(BlahEvent()) -> onBlah($event)
 *
 * Also loads the theme object into $this->theme if available
 *
 * The original concept came from Artanis's Extension extension
 * --> http://github.com/Artanis/simple-extension/tree/master
 * Then re-implemented by Shish after he broke the forum and couldn't
 * find the thread where the original was posted >_<
 */
abstract class Extension
{
    /** @var array which DBs this ext supports (blank for 'all') */
    protected $db_support = [];

    /** @var Themelet this theme's Themelet object */
    public $theme;

    public function __construct()
    {
        $this->theme = $this->get_theme_object(get_called_class());
    }

    public function is_live(): bool
    {
        global $database;
        return (
            empty($this->db_support) ||
            in_array($database->get_driver_name(), $this->db_support)
        );
    }

    /**
     * Find the theme object for a given extension.
     */
    private function get_theme_object(string $base): ?Themelet
    {
        $custom = 'Custom'.$base.'Theme';
        $normal = $base.'Theme';

        if (class_exists($custom)) {
            return new $custom();
        } elseif (class_exists($normal)) {
            return new $normal();
        } else {
            return null;
        }
    }

    /**
     * Override this to change the priority of the extension,
     * lower numbered ones will receive events first.
     */
    public function get_priority(): int
    {
        return 50;
    }
}

/**
 * Class FormatterExtension
 *
 * Several extensions have this in common, make a common API.
 */
abstract class FormatterExtension extends Extension
{
    public function onTextFormatting(TextFormattingEvent $event)
    {
        $event->formatted = $this->format($event->formatted);
        $event->stripped  = $this->strip($event->stripped);
    }

    abstract public function format(string $text): string;
    abstract public function strip(string $text): string;
}

/**
 * Class DataHandlerExtension
 *
 * This too is a common class of extension with many methods in common,
 * so we have a base class to extend from.
 */
abstract class DataHandlerExtension extends Extension
{
    public function onDataUpload(DataUploadEvent $event)
    {
        $supported_ext = $this->supported_ext($event->type);
        $check_contents = $this->check_contents($event->tmpname);
        if ($supported_ext && $check_contents) {
            move_upload_to_archive($event);
            send_event(new ThumbnailGenerationEvent($event->hash, $event->type));

            /* Check if we are replacing an image */
            if (array_key_exists('replace', $event->metadata) && isset($event->metadata['replace'])) {
                /* hax: This seems like such a dirty way to do this.. */

                /* Validate things */
                $image_id = int_escape($event->metadata['replace']);

                /* Check to make sure the image exists. */
                $existing = Image::by_id($image_id);

                if (is_null($existing)) {
                    throw new UploadException("Image to replace does not exist!");
                }
                if ($existing->hash === $event->metadata['hash']) {
                    throw new UploadException("The uploaded image is the same as the one to replace.");
                }

                // even more hax..
                $event->metadata['tags'] = $existing->get_tag_list();
                $image = $this->create_image_from_data(warehouse_path("images", $event->metadata['hash']), $event->metadata);

                if (is_null($image)) {
                    throw new UploadException("Data handler failed to create image object from data");
                }

                $ire = new ImageReplaceEvent($image_id, $image);
                send_event($ire);
                $event->image_id = $image_id;
            } else {
                $image = $this->create_image_from_data(warehouse_path("images", $event->hash), $event->metadata);
                if (is_null($image)) {
                    throw new UploadException("Data handler failed to create image object from data");
                }
                $iae = new ImageAdditionEvent($image);
                send_event($iae);
                $event->image_id = $iae->image->id;

                // Rating Stuff.
                if (!empty($event->metadata['rating'])) {
                    $rating = $event->metadata['rating'];
                    send_event(new RatingSetEvent($image, $rating));
                }

                // Locked Stuff.
                if (!empty($event->metadata['locked'])) {
                    $locked = $event->metadata['locked'];
                    send_event(new LockSetEvent($image, !empty($locked)));
                }
            }
        } elseif ($supported_ext && !$check_contents) {
            throw new UploadException("Invalid or corrupted file");
        }
    }

    public function onThumbnailGeneration(ThumbnailGenerationEvent $event)
    {
        $result = false;
        if ($this->supported_ext($event->type)) {
            if ($event->force) {
                $result = $this->create_thumb($event->hash, $event->type);
            } else {
                $outname = warehouse_path("thumbs", $event->hash);
                if (file_exists($outname)) {
                    return;
                }
                $result = $this->create_thumb($event->hash, $event->type);
            }
        }
        if ($result) {
            $event->generated = true;
        }
    }

    public function onDisplayingImage(DisplayingImageEvent $event)
    {
        global $page;
        if ($this->supported_ext($event->image->ext)) {
            $this->theme->display_image($page, $event->image);
        }
    }

    /*
    public function onSetupBuilding(SetupBuildingEvent $event) {
        $sb = $this->setup();
        if($sb) $event->panel->add_block($sb);
    }

    protected function setup() {}
    */

    abstract protected function supported_ext(string $ext): bool;
    abstract protected function check_contents(string $tmpname): bool;
    abstract protected function create_image_from_data(string $filename, array $metadata);
    abstract protected function create_thumb(string $hash, string $type): bool;
}