<?php

namespace Rubix\ML\Transformers;

use Rubix\ML\DataType;
use Rubix\ML\Specifications\ExtensionIsLoaded;
use Rubix\ML\Exceptions\InvalidArgumentException;
use Rubix\ML\Exceptions\RuntimeException;

/**
 * Image Resizer
 *
 * Image Resizer fits (scales and crops) images in a dataset to a user-specified width and height.
 *
 * > **Note**: The GD extension is required to use this transformer.
 *
 * @category    Machine Learning
 * @package     Rubix/ML
 * @author      Andrew DalPino
 */
class ImageResizer implements Transformer
{
    /**
     * The width to fit the image to.
     *
     * @var int
     */
    protected int $width;

    /**
     * The height to fit the image to.
     *
     * @var int
     */
    protected int $height;

    /**
     * The ratio of width to height.
     *
     * @var float
     */
    protected float $ratio;

    /**
     * @param int $width
     * @param int $height
     * @throws \Rubix\ML\Exceptions\InvalidArgumentException
     */
    public function __construct(int $width = 32, int $height = 32)
    {
        ExtensionIsLoaded::with('gd')->check();

        if ($width < 1 or $height < 1) {
            throw new InvalidArgumentException('Width and height must be'
                . " greater than 0, $width and $height given.");
        }

        $this->width = $width;
        $this->height = $height;
        $this->ratio = $width / $height;
    }

    /**
     * Return the data types that this transformer is compatible with.
     *
     * @internal
     *
     * @return list<\Rubix\ML\DataType>
     */
    public function compatibility() : array
    {
        return DataType::all();
    }

    /**
     * Transform the dataset in place.
     *
     * @param array<mixed[]> $samples
     */
    public function transform(array &$samples) : void
    {
        array_walk($samples, [$this, 'resize']);
    }

    /**
     * resize the images in a sample.
     *
     * @param list<mixed> $sample
     * @throws \Rubix\ML\Exceptions\RuntimeException
     */
    public function resize(array &$sample) : void
    {
        foreach ($sample as &$value) {
            if (DataType::detect($value)->isImage()) {
                $width = imagesx($value);
                $height = imagesy($value);

                if ($width === $this->width and $height === $this->height) {
                    continue;
                }

                if ($width / $height < $this->ratio) {
                    $w = $width;
                    $h = (int) ceil(($width * $this->height) / $this->width);

                    $x = 0;
                    $y = (int) ceil(0.5 * ($height - $h));
                } else {
                    $w = (int) ceil(($height * $this->width) / $this->height);
                    $h = $height;

                    $x = (int) ceil(0.5 * ($width - $w));
                    $y = 0;
                }

                $resized = imagecreatetruecolor($this->width, $this->height);

                if (!$resized) {
                    throw new RuntimeException('Could not create placeholder image.');
                }

                $success = imagecopyresampled($resized, $value, 0, 0, $x, $y, $this->width, $this->height, $w, $h);

                if (!$success) {
                    throw new RuntimeException('Failed to resize image.');
                }

                $value = $resized;
            }
        }
    }

    /**
     * Return the string representation of the object.
     *
     * @internal
     *
     * @return string
     */
    public function __toString() : string
    {
        return "Image Resizer (width: {$this->width}, height: {$this->height})";
    }
}
