<?php
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Fetches and parses a GPX file from a URL to extract track points and elevation profile.
 *
 * @param string $gpx_url The URL of the GPX file.
 * @return array An array containing 'points' for the map and 'elevation_profile'.
 */
function statpress_parse_gpx_data( $gpx_url ) {
	if ( empty( $gpx_url ) ) {
		return array();
	}

	$response = wp_remote_get( $gpx_url, array( 'timeout' => 20 ) );

	if ( is_wp_error( $response ) || wp_remote_retrieve_response_code( $response ) !== 200 ) {
		return array();
	}

	$gpx_content = wp_remote_retrieve_body( $response );
	if ( empty( $gpx_content ) ) {
		return array();
	}

	// --- Privacy Zone ---
	$privacy_options    = get_option( 'statpress_privacy_options' );
	$privacy_enabled    = ! empty( $privacy_options['latitude'] ) && ! empty( $privacy_options['longitude'] ) && ! empty( $privacy_options['radius'] );
	$privacy_center_lat = $privacy_enabled ? (float) $privacy_options['latitude'] : 0;
	$privacy_center_lon = $privacy_enabled ? (float) $privacy_options['longitude'] : 0;
	$privacy_radius_km  = $privacy_enabled ? ( (int) $privacy_options['radius'] ) / 1000 : 0; // Convert meters to km

	libxml_use_internal_errors( true );
	$gpx = simplexml_load_string( $gpx_content );
	libxml_clear_errors();

	if ( false === $gpx ) {
		return array();
	}

	// Use XPath to be more robust against different GPX structures/namespaces
	$gpx->registerXPathNamespace( 'gpx', 'http://www.topografix.com/GPX/1/1' );
	$trackpoints = $gpx->xpath( '//gpx:trkpt' );
	if ( empty( $trackpoints ) ) {
		$trackpoints = $gpx->xpath( '//trkpt' ); // Fallback for files without namespace
	}

	$raw_points = array();
	$start_time = null;

	foreach ( $trackpoints as $trkpt ) {
		if ( isset( $trkpt['lat'], $trkpt['lon'] ) ) {
			$extensions = $trkpt->extensions ? $trkpt->extensions->children( 'gpxtpx', true ) : null;
			$time       = isset( $trkpt->time ) ? strtotime( (string) $trkpt->time ) : null;
			if ( $time && is_null( $start_time ) ) {
				$start_time = $time;
			}

			$hr_val  = ( $extensions && isset( $extensions->TrackPointExtension->hr ) ) ? (int) $extensions->TrackPointExtension->hr : null;
			$cad_val = ( $extensions && isset( $extensions->TrackPointExtension->cad ) ) ? (int) $extensions->TrackPointExtension->cad : null;

			$raw_points[] = array(
				'lat'         => (float) $trkpt['lat'],
				'lon'         => (float) $trkpt['lon'],
				'ele'         => isset( $trkpt->ele ) ? (float) $trkpt->ele : null,
				'time_offset' => $start_time && $time ? $time - $start_time : null,
				'hr'          => $hr_val,
				'cad'         => $cad_val,
			);
		}
	}

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

	// Process raw points to calculate profiles
	$map_points          = array();
	$profiles            = array(
		'distance'  => array(),
		'time'      => array(),
		'elevation' => array(),
		'speed'     => array(),
		'hr'        => array(),
		'cadence'   => array(),
	);
	$cumulative_distance = 0;

	$haversine = function( $lat1, $lon1, $lat2, $lon2 ) {
		$earth_radius = 6371; // in km
		$dLat         = deg2rad( $lat2 - $lat1 );
		$dLon         = deg2rad( $lon2 - $lon1 );
		$a            = sin( $dLat / 2 ) * sin( $dLat / 2 ) + cos( deg2rad( $lat1 ) ) * cos( deg2rad( $lat2 ) ) * sin( $dLon / 2 ) * sin( $dLon / 2 );
		$c            = 2 * atan2( sqrt( $a ), sqrt( 1 - $a ) );
		return $earth_radius * $c;
	};

	foreach ( $raw_points as $i => $point ) {
		$is_in_privacy_zone = false;
		if ( $privacy_enabled ) {
			$distance_from_center = $haversine( $privacy_center_lat, $privacy_center_lon, $point['lat'], $point['lon'] );
			if ( $distance_from_center <= $privacy_radius_km ) {
				$is_in_privacy_zone = true;
			}
		}

		if ( ! $is_in_privacy_zone ) {
			$map_points[] = array( $point['lat'], $point['lon'] );
			$speed        = null;

			if ( $i > 0 ) {
				$prev_point     = $raw_points[ $i - 1 ];
				$distance_delta = $haversine( $prev_point['lat'], $prev_point['lon'], $point['lat'], $point['lon'] ); // km
				$cumulative_distance += $distance_delta;

				if ( ! is_null( $point['time_offset'] ) && ! is_null( $prev_point['time_offset'] ) ) {
					$time_delta = $point['time_offset'] - $prev_point['time_offset']; // seconds
					if ( $time_delta > 0 ) {
						$speed = ( $distance_delta * 3600 ) / $time_delta; // km/h
					}
				}
			}

			$profiles['distance'][]  = round( $cumulative_distance, 3 );
			$profiles['time'][]      = $point['time_offset'];
			$profiles['elevation'][] = ! is_null( $point['ele'] ) ? round( $point['ele'], 2 ) : null;
			$profiles['speed'][]     = ! is_null( $speed ) ? round( $speed, 1 ) : null;
			$profiles['hr'][]        = $point['hr'];
			$profiles['cadence'][]   = $point['cad'];
		}
	}

	return array(
		'points'   => $map_points,
		'profiles' => $profiles,
	);
}