// Copyright (c) Cratis. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

import { EventType } from './EventType.js';
import { CausationEntry } from './CausationEntry.js';
import { Tag } from './Tag.js';
import type { NamedTag } from './NamedTag.js';
import type { Identity } from '../identity/Identity.js';

/**
 * Represents contextual information about an appended event.
 */
export interface EventContext {
    /** The sequence number of the event in the event sequence. */
    readonly sequenceNumber: bigint;

    /** The unique identifier of the event source. */
    readonly eventSourceId: string;

    /** The event store, when included by the kernel. */
    readonly eventStore?: string;

    /** The namespace, when included by the kernel. */
    readonly namespace?: string;

    /** The source type returned by the kernel. */
    readonly eventSourceType?: string;

    /** The stream type returned by the kernel. */
    readonly eventStreamType?: string;

    /** The stream identifier returned by the kernel. */
    readonly eventStreamId?: string;

    /**
     * The registered event source definition the event was appended through.
     * Undefined for events appended without a definition, including events stored before event sources existed.
     */
    readonly eventSource?: string;

    /** The compliance subject returned by the kernel. */
    readonly subject?: string;

    /** The persisted event hash. */
    readonly hash?: string;

    /** The identity responsible for the event. */
    readonly causedBy?: Identity;

    /** The observation state carried by the delivery. */
    readonly observationState?: number;

    /** The type of the event. */
    readonly eventType: EventType;

    /** The timestamp when the event occurred. */
    readonly occurred: Date;

    /** The correlation identifier for the event. */
    readonly correlationId: string;

    /** The causation chain for the event. */
    readonly causation: ReadonlyArray<CausationEntry>;

    /** The tags the event carries. */
    readonly tags: ReadonlyArray<Tag>;

    /**
     * The structured named tags the event carries, in the order the kernel stored them.
     * Always present on events read from or delivered by the kernel (empty when the event has none);
     * optional so that contexts constructed by hand remain valid.
     */
    readonly namedTags?: ReadonlyArray<NamedTag>;
}