<?php
/**
 * The try-on prompt for a product type.
 *
 * @package Fitzaro
 */

namespace Fitzaro\Prompt;

defined( 'ABSPATH' ) || exit;

/**
 * Fixed text, plus at most one line naming the selected variant (VariantText: cleaned catalogue
 * text, never shopper input).
 *
 * Image 1 is always the shopper and image 2 the product (ProductInputBuilder keeps that order).
 *
 * Carried over from boutique-ai prompt v3: lock face, body weight and framing, because the model
 * otherwise redraws faces and slims people down. Bump VERSION whenever the text changes; it is
 * stored with every request so results can be compared.
 *
 * Versions: fz1 first per-type prompts; fz2 adds the selected variant (colour, pattern…) for
 * stores whose variations share one photo.
 */
final class PromptBuilder {

	public const VERSION = 'fz2';

	private const START = array(
		'Virtual try-on for an online store. This is an edit of image 1, not a new photo.',
		'Image 1 is the shopper. Keep their face, identity, hair, skin tone, body shape, pose and the background exactly as they are.',
		'Do not redraw, beautify, slim, age or retouch the face or head: same facial features, expression, make-up and beard, same head size and position.',
		'Keep their real body weight and figure exactly: same belly, chest, shoulder width, waist and cheek fullness. Do not slim, flatter or idealise them.',
		'Keep the exact framing, camera angle, crop and scale of image 1. Keep arms, hands and legs in the same positions.',
	);

	private const PRODUCT = array(
		ProductType::TOP     => array(
			'Image 2 is the product: a top. Replace only the garment on the upper body with it.',
			'Keep the trousers, skirt, shoes and accessories from image 1 unchanged.',
			'The top must fit their actual figure the way it really would, including around the stomach, with natural drape and creases.',
			'Reproduce the product faithfully: colour, pattern, fabric texture, neckline, sleeves, buttons and length.',
		),
		ProductType::DRESS   => array(
			'Image 2 is the product: a dress. Replace their clothes with this dress.',
			'Keep their shoes and accessories unless the dress covers them.',
			'The dress must fit their actual figure the way it really would, including around the stomach and hips, with natural drape and folds.',
			'Reproduce the product faithfully: colour, pattern, fabric texture, neckline, sleeves, waistline and length.',
		),
		ProductType::EYEWEAR => array(
			'Image 2 is the product: a pair of glasses. Put these glasses on their face, sitting naturally on the nose and ears, sized realistically for their face.',
			'Keep their clothes and everything else in image 1 unchanged. If they already wear glasses, replace them with these.',
			'Reproduce the frame faithfully: shape, colour, thickness, bridge and lens tint. Keep the eyes visible through clear lenses.',
		),
	);

	private const END = 'Photorealistic, same lighting, colours and image quality as image 1. Do not add text, logos or watermarks.';

	/**
	 * Prompt text for a product type.
	 *
	 * @param string $type    ProductType constant.
	 * @param string $variant Line from VariantText::line(), or ''.
	 * @throws \InvalidArgumentException When the type is unknown.
	 */
	public static function build( string $type, string $variant = '' ): string {
		if ( ! isset( self::PRODUCT[ $type ] ) ) {
			throw new \InvalidArgumentException( 'Unknown product type.' );
		}

		$lines = array_merge( self::START, self::PRODUCT[ $type ] );
		if ( '' !== $variant ) {
			$lines[] = $variant;
		}
		$lines[] = self::END;

		return implode( "\n", $lines );
	}
}