<?php
/**
 * Explicit compression recipes. Resizing and editing are not compression.
 *
 * @package AffStackDevImageManager
 */

namespace AffStackDev\ImageManager;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Compression recipes: their choices and defaults, what content a picture holds, the fidelity it gets and the encoder
 * settings for each format.
 */
final class Policy {
	public const VERSION = 'compression-v2';
	/**
	 * The recipe at the start: lossless, content auto, balanced effort, formats auto, metadata kept.
	 *
	 * @return array The recipe.
	 */
	public static function defaults(): array {
		return array(
			'mode'     => 'lossless',
			'content'  => 'auto',
			'effort'   => 'balanced',
			'formats'  => 'auto',
			'metadata' => 'preserve',
		);
	}
	/**
	 * A recipe kept to its allowed choices.
	 *
	 * @param array $input The recipe asked for.
	 * @return array The recipe.
	 * @throws \RuntimeException With invalid_compression_policy when a choice is not allowed, lossless_avif_not_supported
	 *          when a lossless recipe asks for AVIF.
	 */
	public static function clean( array $input ): array {
		$out     = self::defaults();
		$choices = array(
			'mode'     => array( 'lossless', 'high', 'maximum' ),
			'content'  => array( 'auto', 'photo', 'graphics' ),
			'effort'   => array( 'fast', 'balanced' ),
			'formats'  => array( 'auto', 'native', 'webp', 'avif' ),
			'metadata' => array( 'preserve', 'remove_gps', 'remove_all' ),
		);
		foreach ( $choices as  $k => $list ) {
			if ( isset( $input[ $k ] ) ) {
				if ( ! is_string( $input[ $k ] ) || ! in_array( $input[ $k ], $list, true ) ) {
					throw new \RuntimeException( 'invalid_compression_policy' );
				}
				$out[ $k ] = $input[ $k ];
			}
		}
		if ( 'lossless' === $out['mode'] && 'avif' === $out['formats'] ) {
			throw new \RuntimeException( 'lossless_avif_not_supported' );
		}
		return $out;
	}
	/**
	 * The recipe of a picture (its own saved one, or the settings' recipe).
	 *
	 * @param array|null $row The source row, or null for the settings' recipe.
	 * @return array The recipe.
	 */
	public static function current( ?array $row = null ): array {
		return self::clean( (array) ( $row['details']['compression'] ?? Settings::get()['compression'] ?? array() ) );
	}
	/**
	 * A key for a recipe, so copies made with another recipe are told apart.
	 *
	 * @param array $recipe The recipe.
	 * @return string SHA-256 of the policy version and the cleaned recipe.
	 */
	public static function key( array $recipe ): string {
		return hash( 'sha256', self::VERSION . '|' . wp_json_encode( self::clean( $recipe ) ) );
	}
	/**
	 * The name of a recipe mode.
	 *
	 * @param string $mode lossless, high or maximum.
	 * @return string The translated name (Lossless for an unknown mode).
	 */
	public static function label( string $mode ): string {
		return array(
			'lossless' => __( 'Lossless', 'affstackdev-image-manager' ),
			'high'     => __( 'High Quality', 'affstackdev-image-manager' ),
			'maximum'  => __( 'Maximum Savings', 'affstackdev-image-manager' ),
		)[ $mode ] ?? __( 'Lossless', 'affstackdev-image-manager' );
	}
	/**
	 * Conservative content hints, not a claim to understand the subject of a photograph.
	 *
	 * @param array  $info   The picture's input record (ImageInput).
	 * @param array  $recipe The recipe.
	 * @param string $source The source's address or name.
	 * @return string photo or graphics.
	 */
	public static function content( array $info, array $recipe, string $source ): string {
		if ( 'auto' !== $recipe['content'] ) {
			return $recipe['content'];
		}
		if ( ! empty( $info['alpha'] ) || in_array( $info['mime'], array( 'image/png', 'image/gif' ), true ) || preg_match( '/(?:logo|screen|artwork|diagram|chart|icon|banner|catalog|interface)/i', basename( $source ) ) ) {
			return 'graphics';
		}
		return 'photo';
	}
	/**
	 * The fidelity a copy gets: lossless for the Lossless mode, graphics and transparent pictures, otherwise the recipe's
	 * mode.
	 *
	 * @param array  $recipe  The recipe.
	 * @param string $content photo or graphics.
	 * @param bool   $alpha   Whether the picture is transparent.
	 * @return string lossless, high or maximum.
	 */
	public static function fidelity( array $recipe, string $content, bool $alpha ): string {
		return 'lossless' === $recipe['mode'] || 'graphics' === $content || $alpha ? 'lossless' : $recipe['mode'];
	}
	/**
	 * Format-specific encoder settings; these numbers are not equivalent quality scales.
	 *
	 * @param string $format jpeg, webp or avif.
	 * @param string $mode   high or maximum.
	 * @return int The encoder's quality setting.
	 */
	public static function quality( string $format, string $mode ): int {
		return ( 'maximum' === $mode ? array(
			'jpeg' => 82,
			'webp' => 78,
			'avif' => 58,
		) : array(
			'jpeg' => 92,
			'webp' => 90,
			'avif' => 75,
		) )[ $format ] ?? 100;
	}
	/**
	 * Whether a manifest copy was made under a policy this release still serves.
	 *
	 * @param array $v The copy.
	 * @return bool True when it was.
	 */
	public static function valid_variant( array $v ): bool {
		if ( Codec::POLICY === ( $v['policy'] ?? '' ) ) {
			return 'image/webp' === ( $v['output_mime'] ?? 'image/webp' );
		}
		return self::VERSION === ( $v['policy'] ?? '' ) && isset( $v['recipe_key'], $v['verification'], $v['output_mime'] ) && in_array( $v['fidelity'] ?? '', array( 'lossless', 'high', 'maximum' ), true );
	}
}