<?php
/**
 * Handler for the Gimp's native file format (XCF)
 *
 * Overview:
 *   https://en.wikipedia.org/wiki/XCF_(file_format)
 * Specification in Gnome repository:
 *   http://svn.gnome.org/viewvc/gimp/trunk/devel-docs/xcf.txt?view=markup
 *
 * @license GPL-2.0-or-later
 * @file
 * @ingroup Media
 */

use MediaWiki\FileRepo\File\File;
use Wikimedia\StringUtils\StringUtils;
use Wikimedia\UnpackFailedException;

/**
 * Handler for the Gimp's native file format; getimagesize() doesn't
 * support these files
 *
 * @ingroup Media
 */
class XCFHandler extends BitmapHandler {
	/**
	 * @param File $file
	 * @return bool
	 */
	public function mustRender( $file ) {
		return true;
	}

	/**
	 * Render files as PNG
	 *
	 * @param string $ext
	 * @param string $mime
	 * @param array|null $params
	 * @return array
	 */
	public function getThumbType( $ext, $mime, $params = null ) {
		return [ 'png', 'image/png' ];
	}

	/**
	 * Metadata for a given XCF file
	 *
	 * Will return false if file magic signature is not recognized
	 * @author Hexmode
	 * @author Hashar
	 *
	 * @param string $filename Full path to a XCF file
	 * @return array|null Metadata Array just like PHP getimagesize()
	 */
	private static function getXCFMetaData( $filename ) {
		# Decode master structure
		$f = fopen( $filename, 'rb' );
		if ( !$f ) {
			return null;
		}
		# The image structure always starts at offset 0 in the XCF file.
		# So we just read it :-)
		$binaryHeader = fread( $f, 26 );
		fclose( $f );

		/**
		 * Master image structure:
		 *
		 * byte[9] "gimp xcf "  File type magic
		 * byte[4] version      XCF version
		 *                        "file" - version 0
		 *                        "v001" - version 1
		 *                        "v002" - version 2
		 * byte    0            Zero-terminator for version tag
		 * uint32  width        With of canvas
		 * uint32  height       Height of canvas
		 * uint32  base_type    Color mode of the image; one of
		 *                         0: RGB color
		 *                         1: Grayscale
		 *                         2: Indexed color
		 *        (enum GimpImageBaseType in libgimpbase/gimpbaseenums.h)
		 */
		try {
			$header = StringUtils::unpack(
				"A9magic" . # A: space padded
					"/a5version" . # a: zero padded
					"/Nwidth" . # \
					"/Nheight" . # N: unsigned long 32bit big endian
					"/Nbase_type", # /
				$binaryHeader
			);
		} catch ( UnpackFailedException ) {
			return null;
		}

		# Check values
		if ( $header['magic'] !== 'gimp xcf' ) {
			wfDebug( __METHOD__ . " '$filename' has invalid magic signature." );

			return null;
		}
		# TODO: we might want to check for correct values of width and height

		wfDebug( __METHOD__ .
			": canvas size of '$filename' is {$header['width']} x {$header['height']} px" );

		return $header;
	}

	/** @inheritDoc */
	public function getSizeAndMetadata( $state, $filename ) {
		$header = self::getXCFMetaData( $filename );
		$metadata = [];
		if ( $header ) {
			// Try to be consistent with the names used by PNG files.
			// Unclear from base media type if it has an alpha layer,
			// so just assume that it does since it "potentially" could.
			switch ( $header['base_type'] ) {
				case 0:
					$metadata['colorType'] = 'truecolour-alpha';
					break;
				case 1:
					$metadata['colorType'] = 'greyscale-alpha';
					break;
				case 2:
					$metadata['colorType'] = 'index-coloured';
					break;
				default:
					$metadata['colorType'] = 'unknown';
			}
		} else {
			// Marker to prevent repeated attempted extraction
			$metadata['error'] = true;
		}
		return [
			'width' => $header['width'] ?? 0,
			'height' => $header['height'] ?? 0,
			'bits' => 8,
			'metadata' => $metadata
		];
	}

	/**
	 * Should we refresh the metadata
	 *
	 * @param File $file The file object for the file in question
	 * @return bool|int One of the self::METADATA_(BAD|GOOD|COMPATIBLE) constants
	 */
	public function isFileMetadataValid( $file ) {
		if ( !$file->getMetadataArray() ) {
			// Old metadata when we just put an empty string in there
			return self::METADATA_BAD;
		}

		return self::METADATA_GOOD;
	}

	/** @inheritDoc */
	protected function hasGDSupport() {
		return false;
	}

	/**
	 * Can we render this file?
	 *
	 * Image magick doesn't support indexed xcf files as of current
	 * writing (as of 6.8.9-3)
	 * @param File $file
	 * @return bool
	 */
	public function canRender( $file ) {
		$xcfMeta = $file->getMetadataArray();
		if ( isset( $xcfMeta['colorType'] ) && $xcfMeta['colorType'] === 'index-coloured' ) {
			return false;
		}
		return parent::canRender( $file );
	}
}
