<?php
namespace Vichan\Service\Media;

use Vichan\Data\ThumbGenerationResult;

use function Vichan\Functions\Fs\link_or_copy;

class GdThumbGenerator implements ThumbGenerator {
	private const PHP81 = PHP_MAJOR_VERSION >= 8 && PHP_MINOR_VERSION >= 1;

	private const MIME_TO_EXT = [
		'image/jpeg' => 'jpg',
		'image/png' => 'png',
		'image/gif' => 'gif',
		'image/webp' => 'webp',
		'image/bmp' => 'bmp',
		'image/avif' => 'avif'
	];


	private static function imageCreateFrom(string $file, string $mime): mixed {
		switch ($mime) {
			case 'image/jpeg':
				return imagecreatefromjpeg($file);
			case 'image/png':
				return imagecreatefrompng($file);
			case 'image/gif':
				return imagecreatefromgif($file);
			case 'image/webp':
				return imagecreatefromwbmp($file);
			case 'image/bmp':
				return imagecreatefrombmp($file);
			case 'image/avif':
				return self::PHP81 ? imagecreatefromavif($file) : false;
		}
		return false;
	}

	public static function imageSaveTo(mixed $gd, string $file, string $mime) {
		// Somebody should tune the quality and speed values...
		switch ($mime) {
			case 'image/jpeg':
				return imagejpeg($gd, $file, 50);
			case 'image/png':
				return imagepng($gd, $file, 7);
			case 'image/gif':
				return imagegif($gd, $file);
			case 'image/webp':
				return imagewbmp($gd, $file, 50);
			case 'image/bmp':
				return imagebmp($gd, $file, true);
			case 'image/avif':
				return self::PHP81 ? imageavif($gd, $file, 30, 6) : false;
		}
		return false;
	}

	private static function createCanvas(string $mime, int $width, int $height) {
		$gd = \imagecreatetruecolor($width, $height);
		switch ($mime) {
			case 'image/png':
				imagecolortransparent($gd, imagecolorallocatealpha($gd, 0, 0, 0, 0));
				imagesavealpha($gd, true);
				imagealphablending($gd, false);
				break;
			case 'image/gif':
				\imagecolortransparent($gd, \imagecolorallocatealpha($gd, 0, 0, 0, 0));
				\imagesavealpha($gd, true);
				break;
		}
		return $gd;
	}

	public function supportsMime(string $mime): bool {
		$info = \gd_info();
		return ($mime === 'image/jpeg' && $info['JPEG Support'])
			|| ($mime === 'image/png' && $info['PNG Support'])
			|| ($mime === 'image/gif' && $info['GIF Read Support'] && $info['GIF Create Support'])
			|| ($mime === 'image/webp' && $info['WebP Support'])
			|| $mime === 'image/bmp'
			|| ($mime === 'image/avif' && self::PHP81 && $info['AVIF Support']);
	}

	public function generateThumb(
		string $source_file_path,
		string $source_file_mime,
		string $preferred_out_file_path,
		string $preferred_out_mime,
		int $max_width,
		int $max_height
	): ThumbGenerationResult {
		$gd = self::imageCreateFrom($source_file_path, $source_file_mime);
		if ($gd === false) {
			throw new \RuntimeException("Could not open '$source_file_path'");
		}

		$width = \imagesx($gd);
		$height = \imagesy($gd);

		if ($width <= $max_width && $height <= $max_height) {
			$out_path = $preferred_out_file_path . '.' . self::MIME_TO_EXT[$source_file_mime];

			if (!link_or_copy($source_file_path, $out_path)) {
				throw new \RuntimeException("Could not link or copy '$source_file_path' to '$out_path'");
			}

			return new ThumbGenerationResult(
				$out_path,
				$source_file_mime,
				false,
				$width,
				$height
			);
		} else {
			$out_path = $preferred_out_file_path . '.' . self::MIME_TO_EXT[$preferred_out_mime];

			$gd_other = self::createCanvas($preferred_out_mime, $max_width, $max_height);
			\imagecopyresampled($gd_other, $gd, 0, 0, 0, 0, $max_width, $max_height, $width, $height);

			if (!self::imageSaveTo($gd_other, $out_path, $preferred_out_mime)) {
				throw new \RuntimeException("Could not create thumbnail file at '$out_path'");
			}

			return new ThumbGenerationResult(
				$out_path,
				$preferred_out_mime,
				false,
				$max_width,
				$max_height
			);
		}
	}
}