<?php
/**
 * FAQ schema generator.
 *
 * Auto-generates FAQ structured data from product data:
 * - Custom FAQ meta fields (_aicommerce_faq)
 * - Product attributes as Q&A pairs
 * - Short description patterns
 *
 * @package AICommerce\Schema
 */

declare(strict_types=1);

namespace AICommerce\Schema;

/**
 * Generates FAQPage schema for product pages.
 */
class FaqSchema {

	/**
	 * Generate FAQ schema for a product.
	 *
	 * @param \WC_Product $product The WooCommerce product.
	 *
	 * @return array<string, mixed> FAQPage schema or empty array.
	 */
	public function generate( \WC_Product $product ): array {
		$questions = $this->collect_questions( $product );

		if ( empty( $questions ) ) {
			return array();
		}

		$main_entity = array();
		foreach ( $questions as $qa ) {
			$main_entity[] = array(
				'@type'          => 'Question',
				'name'           => $qa['question'],
				'acceptedAnswer' => array(
					'@type' => 'Answer',
					'text'  => $qa['answer'],
				),
			);
		}

		$schema = array(
			'@context'   => 'https://schema.org',
			'@type'      => 'FAQPage',
			'mainEntity' => $main_entity,
		);

		/**
		 * Filters the FAQPage schema.
		 *
		 * @param array<string, mixed> $schema    The FAQPage data.
		 * @param \WC_Product          $product   The product.
		 * @param array<int, array>    $questions Raw Q&A pairs.
		 */
		return apply_filters( 'aicommerce_faq_schema', $schema, $product, $questions );
	}

	/**
	 * Collect all FAQ items from available sources.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return array<int, array{question: string, answer: string}> Q&A pairs.
	 */
	private function collect_questions( \WC_Product $product ): array {
		$questions = array();

		// 1. Custom FAQ meta field (stored as JSON array).
		$custom_faq = $product->get_meta( '_aicommerce_faq' );
		if ( ! empty( $custom_faq ) ) {
			$parsed = is_string( $custom_faq ) ? json_decode( $custom_faq, true ) : $custom_faq;
			if ( is_array( $parsed ) ) {
				foreach ( $parsed as $item ) {
					if ( ! empty( $item['question'] ) && ! empty( $item['answer'] ) ) {
						$questions[] = array(
							'question' => sanitize_text_field( $item['question'] ),
							'answer'   => wp_strip_all_tags( $item['answer'] ),
						);
					}
				}
			}
		}

		// 2. Auto-generate from product attributes (if no custom FAQs).
		if ( empty( $questions ) ) {
			$questions = array_merge( $questions, $this->generate_from_attributes( $product ) );
		}

		// 3. Auto-generate from product data.
		$questions = array_merge( $questions, $this->generate_from_product_data( $product ) );

		// Deduplicate by question text.
		$seen  = array();
		$dedup = array();
		foreach ( $questions as $qa ) {
			$key = strtolower( $qa['question'] );
			if ( ! isset( $seen[ $key ] ) ) {
				$seen[ $key ] = true;
				$dedup[]      = $qa;
			}
		}

		// Limit to 6 Q&A pairs per product.
		return array_slice( $dedup, 0, 6 );
	}

	/**
	 * Generate Q&A pairs from product attributes.
	 *
	 * E.g., "What color is this product?" → "Available in Red, Blue, Green."
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return array<int, array{question: string, answer: string}>
	 */
	private function generate_from_attributes( \WC_Product $product ): array {
		$questions  = array();
		$attributes = $product->get_attributes();

		if ( empty( $attributes ) ) {
			return $questions;
		}

		foreach ( $attributes as $attribute ) {
			if ( ! $attribute->get_visible() ) {
				continue;
			}

			$name = wc_attribute_label( $attribute->get_name(), $product );

			if ( $attribute->is_taxonomy() ) {
				$terms  = wc_get_product_terms( $product->get_id(), $attribute->get_name(), array( 'fields' => 'names' ) );
				$values = implode( ', ', $terms );
			} else {
				$values = implode( ', ', $attribute->get_options() );
			}

			if ( empty( $values ) ) {
				continue;
			}

			$questions[] = array(
				'question' => sprintf(
					/* translators: 1: Attribute name 2: Product name */
					__( 'What %1$s options are available for %2$s?', 'ai-discoverability-kit' ),
					strtolower( $name ),
					$product->get_name()
				),
				'answer'   => sprintf(
					/* translators: 1: Product name 2: Attribute name 3: Values list */
					__( '%1$s is available in the following %2$s options: %3$s.', 'ai-discoverability-kit' ),
					$product->get_name(),
					strtolower( $name ),
					$values
				),
			);
		}

		return $questions;
	}

	/**
	 * Generate Q&A pairs from core product data.
	 *
	 * Shipping, returns, availability questions that apply broadly.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return array<int, array{question: string, answer: string}>
	 */
	private function generate_from_product_data( \WC_Product $product ): array {
		$questions = array();
		$name      = $product->get_name();

		// Availability question.
		$stock_status = $product->get_stock_status();
		if ( 'instock' === $stock_status ) {
			$questions[] = array(
				'question' => sprintf(
					/* translators: %s: Product name */
					__( 'Is %s currently in stock?', 'ai-discoverability-kit' ),
					$name
				),
				'answer'   => sprintf(
					/* translators: %s: Product name */
					__( 'Yes, %s is currently in stock and available for purchase.', 'ai-discoverability-kit' ),
					$name
				),
			);
		}

		// Weight/dimensions question (if set).
		$weight = $product->get_weight();
		if ( ! empty( $weight ) ) {
			$weight_unit = get_option( 'woocommerce_weight_unit', 'kg' );
			$questions[] = array(
				'question' => sprintf(
					/* translators: %s: Product name */
					__( 'How much does %s weigh?', 'ai-discoverability-kit' ),
					$name
				),
				'answer'   => sprintf(
					/* translators: 1: Product name 2: Weight 3: Unit */
					__( '%1$s weighs %2$s %3$s.', 'ai-discoverability-kit' ),
					$name,
					$weight,
					$weight_unit
				),
			);
		}

		return $questions;
	}
}