<?php
/**
 * Works out where a shopper is and which zone serves them. Shared by the checker and the checkout rules.
 *
 * Privacy: addresses are only ever passed on to the ReachZone API (licensed shops) to be turned into coordinates. What is
 * kept, in the shopper's WooCommerce session, is coordinates plus a keyed hash of the address as the cache key. No
 * address text is stored.
 *
 * @package ReachZone
 */

namespace ReachZone;

defined( 'ABSPATH' ) || exit;

/**
 * Resolver.
 */
final class Resolver {

	const SESSION_POINT = 'reachzone_point';
	const SESSION_CACHE = 'reachzone_geocache';

	/**
	 * Evaluate a WooCommerce shipping destination.
	 *
	 * @param array $dest Destination with address_1, city, state, postcode, country.
	 * @return array array( status, zone, lat, lon ). status: none|incomplete|in|out|unknown.
	 */
	public static function evaluate_destination( array $dest ) {
		static $memo = array();
		$key = md5( wp_json_encode( array( $dest, Settings::get(), get_option( Settings::OPTION_LOCATIONS ), self::session_point() ) ) );
		if ( isset( $memo[ $key ] ) ) {
			return $memo[ $key ];
		}

		$zones = Settings::flat_zones();
		$d     = wp_parse_args(
			$dest,
			array(
				'address_1' => '',
				'address'   => '',
				'city'      => '',
				'state'     => '',
				'postcode'  => '',
				'country'   => '',
			)
		);
		$result = array(
			'status' => 'none',
			'zone'   => null,
			'lat'    => null,
			'lon'    => null,
		);
		if ( empty( $zones ) ) {
			return $memo[ $key ] = $result; // phpcs:ignore Squiz.PHP.DisallowMultipleAssignments.Found
		}
		$street   = '' !== trim( (string) $d['address_1'] ) ? $d['address_1'] : $d['address'];
		$postcode = trim( (string) $d['postcode'] );
		if ( '' === trim( (string) $street ) && '' === $postcode ) {
			$result['status'] = 'incomplete';
			return $memo[ $key ] = $result; // phpcs:ignore Squiz.PHP.DisallowMultipleAssignments.Found
		}

		$point = null;
		if ( Api_Client::enabled() && '' !== trim( (string) $street ) ) {
			$point = self::geocode_cached( $street, $d['city'], $d['state'], $postcode, $d['country'] );
		}
		if ( null === $point ) {
			$point = self::session_point();
		}
		$decision         = Zones::decide( $zones, $point ? $point['lat'] : null, $point ? $point['lon'] : null, $postcode );
		$result['status'] = $decision['status'];
		$result['zone']   = $decision['zone'];
		if ( $point ) {
			$result['lat'] = $point['lat'];
			$result['lon'] = $point['lon'];
		}
		return $memo[ $key ] = $result; // phpcs:ignore Squiz.PHP.DisallowMultipleAssignments.Found
	}

	/**
	 * Geocode through the API with a per-session cache (coordinates under a keyed hash, never the address).
	 *
	 * @param string $street   Street line.
	 * @param string $city     City.
	 * @param string $state    State.
	 * @param string $postcode Postcode.
	 * @param string $country  Country.
	 * @return array|null array( lat, lon ) or null.
	 */
	public static function geocode_cached( $street, $city, $state, $postcode, $country ) {
		$text = trim( implode( ', ', array_filter( array( trim( (string) $street ), trim( (string) $city ), trim( (string) $state ), trim( (string) $postcode ) ) ) ) );
		if ( strlen( $text ) < 3 ) {
			return null;
		}
		$country = Api_Client::country( $country );
		$hash    = self::address_hash( $text, $country );
		$cache   = self::session_get( self::SESSION_CACHE );
		$cache   = is_array( $cache ) ? $cache : array();
		if ( isset( $cache[ $hash ] ) ) {
			return $cache[ $hash ] ? $cache[ $hash ] : null;
		}
		$res = Api_Client::geocode( $text, $country );
		if ( is_wp_error( $res ) ) {
			// Remember a definite miss (404) so that every cart refresh does not re-call the API; keep transient errors out.
			if ( 'reachzone_not_found' === $res->get_error_code() ) {
				$cache[ $hash ] = false;
				self::session_set( self::SESSION_CACHE, array_slice( $cache, -10, null, true ) );
			}
			return null;
		}
		$point          = array(
			'lat' => round( $res['lat'], 5 ),
			'lon' => round( $res['lon'], 5 ),
		);
		$cache[ $hash ] = $point;
		self::session_set( self::SESSION_CACHE, array_slice( $cache, -10, null, true ) );
		return $point;
	}

	/**
	 * Keyed hash used as the cache key.
	 *
	 * @param string $text    Address text.
	 * @param string $country Country.
	 * @return string
	 */
	public static function address_hash( $text, $country ) {
		$norm = strtolower( preg_replace( '/[^a-z0-9]+/i', ' ', $text ) );
		return hash_hmac( 'sha256', $country . '|' . trim( $norm ), wp_salt( 'auth' ) );
	}

	/**
	 * The position the shopper gave in the checker (browser location or a geocoded address), if any.
	 *
	 * @return array|null
	 */
	public static function session_point() {
		$p = self::session_get( self::SESSION_POINT );
		if ( is_array( $p ) && isset( $p['lat'], $p['lon'] ) && is_numeric( $p['lat'] ) && is_numeric( $p['lon'] ) ) {
			return array(
				'lat' => (float) $p['lat'],
				'lon' => (float) $p['lon'],
			);
		}
		return null;
	}

	/**
	 * Remember the checker position for this shopper's session (coordinates only).
	 *
	 * @param float $lat Latitude.
	 * @param float $lon Longitude.
	 */
	public static function set_session_point( $lat, $lon ) {
		self::session_set(
			self::SESSION_POINT,
			array(
				'lat' => round( (float) $lat, 4 ),
				'lon' => round( (float) $lon, 4 ),
			)
		);
	}

	/**
	 * Read a value from the WooCommerce session.
	 *
	 * @param string $key Key.
	 * @return mixed
	 */
	private static function session_get( $key ) {
		return function_exists( 'WC' ) && WC()->session ? WC()->session->get( $key ) : null;
	}

	/**
	 * Write a value to the WooCommerce session.
	 *
	 * @param string $key   Key.
	 * @param mixed  $value Value.
	 */
	private static function session_set( $key, $value ) {
		if ( function_exists( 'WC' ) && WC()->session ) {
			WC()->session->set( $key, $value );
		}
	}
}