<?php
/**
 * Fast WebP encoder.
 *
 * Talks to GD / Imagick directly instead of going through WP_Image_Editor for every
 * file, which lets Spinix:
 * - search the right quality in memory (no file written until the final result),
 * - predict the quality needed instead of stepping down 7 points at a time.
 * WordPress' own editor stays the fallback for anything unusual (CMYK, errors).
 *
 * @package Spinix_Image_Optimization
 */

defined( 'ABSPATH' ) || exit;

/**
 * Class Spinix_Image_Optimization_Encoder
 */
class Spinix_Image_Optimization_Encoder {

	/**
	 * Which engine to use: 'gd', 'imagick' or '' (fallback to WP_Image_Editor).
	 *
	 * @return string
	 */
	public static function engine() {
		static $engine = null;
		if ( null !== $engine ) {
			return $engine;
		}
		$engine = '';
		if ( ! apply_filters( 'spinix_io_fast_encoder', true ) ) {
			return $engine;
		}
		$class = _wp_image_editor_choose( array( 'mime_type' => 'image/webp' ) );
		if ( $class && false !== stripos( $class, 'imagick' ) && class_exists( 'Imagick' ) ) {
			$engine = 'imagick';
		} elseif ( $class && false !== stripos( $class, 'gd' ) && function_exists( 'imagewebp' ) && function_exists( 'imagecreatefromstring' ) ) {
			$engine = 'gd';
		}
		return $engine;
	}

	/**
	 * Open an image.
	 *
	 * @param string $path File.
	 * @return array|WP_Error Handle: [engine, resource, width, height, alpha].
	 */
	public static function open( $path ) {
		$engine = self::engine();
		if ( '' === $engine || ! is_readable( $path ) ) {
			return new WP_Error( 'spinix_io_no_engine', 'fallback' );
		}
		try {
			if ( 'imagick' === $engine ) {
				$im = new Imagick();
				$im->readImage( $path );
				if ( $im->getNumberImages() > 1 ) {
					$im = $im->coalesceImages();
					$im->setIteratorIndex( 0 );
					$first = $im->getImage();
					$im->clear();
					$im = $first;
				}
				if ( Imagick::COLORSPACE_CMYK === $im->getImageColorspace() ) {
					$im->clear();
					return new WP_Error( 'spinix_io_cmyk', 'fallback' );
				}
				// Prepare once: drop metadata (keep the colour profile), set WebP output.
				$profiles = $im->getImageProfiles( 'icc', true );
				$im->stripImage();
				if ( ! empty( $profiles['icc'] ) ) {
					$im->profileImage( 'icc', $profiles['icc'] );
				}
				$im->setImageFormat( 'webp' );
				$im->setOption( 'webp:method', '4' );
				return array(
					'engine' => 'imagick',
					'im'     => $im,
					'w'      => $im->getImageWidth(),
					'h'      => $im->getImageHeight(),
				);
			}
			wp_raise_memory_limit( 'image' );
			$data = Spinix_Image_Optimization_Filesystem::read( $path );
			$im   = false === $data ? false : @imagecreatefromstring( $data ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- a broken upload must fail quietly; the error is reported in the Images list.
			unset( $data );
			if ( ! $im ) {
				return new WP_Error( 'spinix_io_decode', __( 'File is not an image.', 'spinix-image-optimization' ) );
			}
			if ( ! imageistruecolor( $im ) ) {
				imagepalettetotruecolor( $im );
			}
			imagealphablending( $im, false );
			imagesavealpha( $im, true );
			return array(
				'engine' => 'gd',
				'im'     => $im,
				'w'      => imagesx( $im ),
				'h'      => imagesy( $im ),
			);
		} catch ( Exception $e ) {
			return new WP_Error( 'spinix_io_decode', $e->getMessage() );
		}
	}

	/**
	 * Free a handle.
	 *
	 * @param array $h Handle.
	 */
	public static function close( $h ) {
		if ( ! is_array( $h ) || empty( $h['im'] ) ) {
			return;
		}
		if ( 'imagick' === $h['engine'] ) {
			$h['im']->clear();
		} elseif ( PHP_VERSION_ID < 80000 ) {
			imagedestroy( $h['im'] ); // GD images are freed automatically on PHP 8+.
		}
	}

	/**
	 * Encode to WebP in memory.
	 *
	 * @param array $h Handle.
	 * @param int   $q Quality.
	 * @return string|false
	 */
	private static function webp( $h, $q ) {
		if ( 'imagick' === $h['engine'] ) {
			$h['im']->setImageCompressionQuality( (int) $q );
			return $h['im']->getImageBlob();
		}
		// GD can only write WebP to a file or to the output: capture it in our own
		// buffer, which is always closed again, even if encoding fails.
		$level = ob_get_level();
		$ok    = false;
		$blob  = '';
		ob_start();
		try {
			$ok = imagewebp( $h['im'], null, $q );
		} finally {
			while ( ob_get_level() > $level ) {
				$blob = (string) ob_get_clean() . $blob;
			}
		}
		return $ok ? $blob : false;
	}

	/**
	 * Encode a handle to a WebP file, searching the quality in memory.
	 *
	 * @param array  $h       Handle.
	 * @param string $dest    Destination path.
	 * @param int    $quality Starting quality.
	 * @param int    $floor   Lowest quality allowed (0 = no search).
	 * @param float  $target  Target bytes per pixel.
	 * @return array|WP_Error {path, width, height, quality, bytes}
	 */
	public static function save( $h, $dest, $quality, $floor, $target ) {
		try {
			$pixels = max( 1, $h['w'] * $h['h'] );
			$q      = (int) $quality;
			$blob   = self::webp( $h, $q );
			if ( false === $blob || '' === $blob ) {
				return new WP_Error( 'spinix_io_encode', __( 'WebP file could not be written.', 'spinix-image-optimization' ) );
			}
			// Quality search: predict the step from how far we are from the target
			// (WebP size grows roughly exponentially with quality), max 3 extra encodes.
			$tries = 0;
			while ( $floor > 0 && $q > $floor && $tries < 3 ) {
				$bytes = strlen( $blob );
				$limit = $pixels * $target;
				if ( $bytes <= $limit || ( $bytes - $limit ) <= 2048 ) {
					break;
				}
				$step = (int) ceil( log( $bytes / $limit ) / 0.022 );
				$q    = max( $floor, $q - max( 4, min( 30, $step ) ) );
				$next = self::webp( $h, $q );
				if ( false === $next || '' === $next ) {
					break;
				}
				$blob = $next;
				++$tries;
			}
			if ( ! Spinix_Image_Optimization_Filesystem::write( $dest, $blob ) ) {
				return new WP_Error( 'spinix_io_write', __( 'WebP file could not be written.', 'spinix-image-optimization' ) );
			}
			return array(
				'path'    => $dest,
				'width'   => $h['w'],
				'height'  => $h['h'],
				'quality' => $q,
				'bytes'   => strlen( $blob ),
			);
		} catch ( Exception $e ) {
			return new WP_Error( 'spinix_io_encode', $e->getMessage() );
		}
	}
}