<?php
declare(strict_types=1);

namespace Operanse\Agent\Telemetry;

defined( 'ABSPATH' ) || exit;

use Operanse\Agent\Privacy\Redactor;

/** Telemetry event envelope v1 (docs/telemetry/contract.md). */
final class Event {
	public const SCHEMA_VERSION = 1;

	public const PRIORITY_CRITICAL = 'critical';
	public const PRIORITY_NORMAL   = 'normal';
	public const PRIORITY_SAMPLED  = 'sampled';

	/**
	 * @param array<string,mixed> $attributes
	 * @param array<string,float|int> $metrics
	 * @return array<string,mixed>
	 */
	public static function make( string $type, string $source, string $priority, array $attributes = array(), array $metrics = array(), ?string $correlation_id = null, ?float $occurred_at = null ): array {
		$ts = $occurred_at ?? microtime( true );
		$m  = array();
		foreach ( $metrics as $k => $v ) {
			if ( is_int( $v ) || is_float( $v ) ) {
				if ( is_finite( (float) $v ) ) {
					$m[ substr( (string) $k, 0, 64 ) ] = $v;
				}
			}
		}
		$event = array(
			'schema_version' => self::SCHEMA_VERSION,
			'event_id'       => self::uuid7( $ts ),
			'occurred_at'    => gmdate( 'Y-m-d\TH:i:s', (int) floor( $ts ) ) . sprintf( '.%03dZ', (int) ( ( $ts - floor( $ts ) ) * 1000 ) ),
			'event_type'     => $type,
			'source'         => $source,
			'priority'       => $priority,
			'attributes'     => (object) Redactor::attributes( $attributes ),
			'metrics'        => (object) $m,
		);
		if ( $correlation_id !== null ) {
			$event['correlation_id'] = Redactor::text( $correlation_id, 128 );
		}
		return $event;
	}

	/** RFC 9562 UUIDv7 (time-ordered); generated locally so the cloud can deduplicate. */
	public static function uuid7( ?float $ts = null ): string {
		$ms   = (int) floor( ( $ts ?? microtime( true ) ) * 1000 );
		$rand = random_bytes( 10 );
		$hex  = sprintf( '%012x', $ms ) . bin2hex( $rand );
		// version 7 and RFC variant bits
		$hex[12] = '7';
		$hex[16] = dechex( ( hexdec( $hex[16] ) & 0x3 ) | 0x8 );
		return substr( $hex, 0, 8 ) . '-' . substr( $hex, 8, 4 ) . '-' . substr( $hex, 12, 4 ) . '-' . substr( $hex, 16, 4 ) . '-' . substr( $hex, 20, 12 );
	}
}