<?php
/**
 * Writes catalog price revisions (TSG-015).
 *
 * @package Kayvandra\MarginBeacon
 */

declare(strict_types=1);

namespace Kayvandra\MarginBeacon\Application\Provenance;

use Kayvandra\MarginBeacon\Infrastructure\Persistence\PriceRevisionRepository;

/**
 * Observes product price state and appends immutable revision intervals.
 */
final class PriceRevisionWriter {

	const DETECTOR_VERSION = '1.0.0';

	/**
	 * @var PriceRevisionRepository
	 */
	private $repo;

	/**
	 * @param PriceRevisionRepository|null $repo Repository.
	 */
	public function __construct( $repo = null ) {
		$this->repo = $repo ? $repo : new PriceRevisionRepository();
	}

	/**
	 * Observe a WC product or variation.
	 *
	 * @param \WC_Product $product Product.
	 * @param string      $source  capture_source.
	 * @param string      $continuity continuous|gap_detected.
	 * @return array{changed:bool,id?:int}
	 */
	public function observe_product( $product, $source = 'admin', $continuity = 'continuous' ) {
		if ( ! $product || ! is_object( $product ) ) {
			return array( 'changed' => false );
		}

		$is_variation = method_exists( $product, 'is_type' ) && $product->is_type( 'variation' );
		$variation_id = $is_variation ? (int) $product->get_id() : 0;
		$product_id   = $is_variation ? (int) $product->get_parent_id() : (int) $product->get_id();
		if ( $product_id <= 0 ) {
			return array( 'changed' => false );
		}

		$snapshot = $this->snapshot_from_product( $product );
		$hash     = $this->revision_hash( $product_id, $variation_id, $snapshot );
		$input    = hash(
			'sha256',
			wp_json_encode(
				array(
					'product_id'   => $product_id,
					'variation_id' => $variation_id,
					'hash'         => $hash,
					'source'       => $source,
					'at'           => gmdate( 'Y-m-d H:i:s' ),
				)
			)
		);

		$open = $this->repo->get_open( $product_id, $variation_id );
		if ( $open && $open['price_revision_hash'] === $hash ) {
			return array(
				'changed' => false,
				'id'      => (int) $open['id'],
			);
		}

		$now     = gmdate( 'Y-m-d H:i:s' );
		$user_id = function_exists( 'get_current_user_id' ) ? (int) get_current_user_id() : 0;

		$row = array(
			'product_id'          => $product_id,
			'variation_id'        => $variation_id,
			'regular_price'       => $snapshot['regular_price'],
			'sale_price'          => $snapshot['sale_price'],
			'sale_from_gmt'       => $snapshot['sale_from_gmt'],
			'sale_to_gmt'         => $snapshot['sale_to_gmt'],
			'price_revision_hash' => $hash,
			'valid_from_gmt'      => $now,
			'valid_to_gmt'        => null,
			'captured_at_gmt'     => $now,
			'capture_source'      => $source,
			'continuity_state'    => $continuity,
			'detector_version'    => self::DETECTOR_VERSION,
			'input_hash'          => $input,
		);
		if ( $user_id > 0 ) {
			$row['captured_by_user_id'] = $user_id;
		}

		$id = $this->repo->replace_open(
			$row,
			$open ? (int) $open['id'] : null,
			$now
		);

		return array(
			'changed' => false !== $id && $id > 0,
			'id'      => $id ? (int) $id : 0,
		);
	}

	/**
	 * Observe by product/variation IDs.
	 *
	 * @param int    $product_id   Product ID.
	 * @param int    $variation_id Variation ID.
	 * @param string $source       Source.
	 * @param string $continuity   Continuity.
	 * @return array{changed:bool,id?:int}
	 */
	public function observe_ids( $product_id, $variation_id = 0, $source = 'admin', $continuity = 'continuous' ) {
		if ( ! function_exists( 'wc_get_product' ) ) {
			return array( 'changed' => false );
		}
		$id      = $variation_id > 0 ? (int) $variation_id : (int) $product_id;
		$product = wc_get_product( $id );
		if ( ! $product ) {
			return array( 'changed' => false );
		}
		return $this->observe_product( $product, $source, $continuity );
	}

	/**
	 * @param \WC_Product $product Product.
	 * @return array{regular_price:?string,sale_price:?string,sale_from_gmt:?string,sale_to_gmt:?string}
	 */
	public function snapshot_from_product( $product ) {
		$regular = $product->get_regular_price();
		$sale    = $product->get_sale_price();
		$from    = $product->get_date_on_sale_from( 'edit' );
		$to      = $product->get_date_on_sale_to( 'edit' );

		return array(
			'regular_price' => ( '' === $regular || null === $regular ) ? null : (string) $regular,
			'sale_price'    => ( '' === $sale || null === $sale ) ? null : (string) $sale,
			'sale_from_gmt' => $from ? gmdate( 'Y-m-d H:i:s', $from->getTimestamp() ) : null,
			'sale_to_gmt'   => $to ? gmdate( 'Y-m-d H:i:s', $to->getTimestamp() ) : null,
		);
	}

	/**
	 * Deterministic material hash.
	 *
	 * @param int   $product_id   Product ID.
	 * @param int   $variation_id Variation ID.
	 * @param array $snapshot     Snapshot.
	 * @return string
	 */
	public function revision_hash( $product_id, $variation_id, array $snapshot ) {
		return hash(
			'sha256',
			wp_json_encode(
				array(
					'product_id'    => (int) $product_id,
					'variation_id'  => (int) $variation_id,
					'regular_price' => $snapshot['regular_price'],
					'sale_price'    => $snapshot['sale_price'],
					'sale_from_gmt' => $snapshot['sale_from_gmt'],
					'sale_to_gmt'   => $snapshot['sale_to_gmt'],
					'detector'      => self::DETECTOR_VERSION,
				)
			)
		);
	}

	/**
	 * Whether a revision proves an active sale at order time.
	 *
	 * @param array  $revision Revision row.
	 * @param string $at_gmt   Order created GMT.
	 * @return bool
	 */
	public static function revision_proves_sale( array $revision, $at_gmt ) {
		if ( empty( $revision['sale_price'] ) && '0' !== (string) $revision['sale_price'] ) {
			return false;
		}
		if ( 'continuous' !== $revision['continuity_state'] ) {
			return false;
		}
		if ( ! empty( $revision['sale_from_gmt'] ) && $at_gmt < $revision['sale_from_gmt'] ) {
			return false;
		}
		if ( ! empty( $revision['sale_to_gmt'] ) && $at_gmt >= $revision['sale_to_gmt'] ) {
			return false;
		}
		return true;
	}
}