<?php
namespace Vichan\Data;

class Exif {
	public const EXIF_ORIENTATION_0_UPRIGHT = 1;
	public const EXIF_ORIENTATION_0_FLIPPED = 2;
	public const EXIF_ORIENTATION_180_UPRIGHT = 3;
	public const EXIF_ORIENTATION_180_FLIPPED = 4;
	public const EXIF_ORIENTATION_90_UPRIGHT = 5;
	public const EXIF_ORIENTATION_90_FLIPPED = 6;
	public const EXIF_ORIENTATION_270_UPRIGHT = 7;
	public const EXIF_ORIENTATION_270_FLIPPED = 8;
	public const EXIF_ORIENTATION_UNDEFINED = 9;

	/**
	 * Should you switch width and height since the image is on the side?
	 *
	 * @param int $exif_orientation An EXIF_ORIENTATION_* constant.
	 * @return boolean
	 */
	public static function exifOrientationOnSide(int $exif_orientation): bool {
		return $exif_orientation >= 5 && $exif_orientation <= 8;
	}

	/**
	 * Gives the rotation in degrees of the given exif orientation.
	 *
	 * @param int $exif_orientation One of the EXIF_ORIENTATION_* constants.
	 * @return int Rotation in degrees.
	 */
	public static function exifOrientationDegrees(int $exif_orientation): int {
		switch ($exif_orientation) {
			case self::EXIF_ORIENTATION_UNDEFINED:
			case self::EXIF_ORIENTATION_0_UPRIGHT:
			case self::EXIF_ORIENTATION_0_FLIPPED:
				return 0;
			case self::EXIF_ORIENTATION_180_UPRIGHT:
			case self::EXIF_ORIENTATION_180_FLIPPED:
				return 180;
			case self::EXIF_ORIENTATION_90_UPRIGHT:
			case self::EXIF_ORIENTATION_90_FLIPPED:
				return 90;
			case self::EXIF_ORIENTATION_270_UPRIGHT:
			case self::EXIF_ORIENTATION_270_FLIPPED:
				return 270;
			default:
				throw new \RuntimeException("Invalid exif orientation '$exif_orientation'");
		}
	}

	/**
	 * If the given exif orientation flips the image.
	 *
	 * @param int $exif_orientation One of the EXIF_ORIENTATION_* constants.
	 * @return bool If the image is flipped.
	 */
	public static function exifOrientationIsFlipped(int $exif_orientation): bool {
		return $exif_orientation % 2 == 0;
	}
}