/*
 * Copyright 2022 The Backstage Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { FilterPredicate } from '@backstage/filter-predicates';

export interface Config {
  events?: {
    modules?: {
      /**
       * events-backend-module-google-pubsub configuration.
       */
      googlePubSub?: {
        /**
         * Configuration for `GooglePubSubConsumingEventPublisher`, which
         * consumes messages from a Google Pub/Sub subscription and forwards
         * them into the Backstage events system.
         */
        googlePubSubConsumingEventPublisher?: {
          /**
           * Generally contains a record per subscription to consume.
           */
          subscriptions: {
            /**
             * The name can be anything, but it is recommended to use only
             * letters, numbers, and hyphens for this identifier since it will
             * appear in logs and metric names etc.
             */
            [name: string]: {
              /**
               * The complete name of the Pub/Sub subscription to be used, on the
               * form
               * `projects/PROJECT_ID/subscriptions/SUBSCRIPTION_ID`.
               */
              subscriptionName: string;

              /**
               * The name of the events backend topic to which the messages are
               * to be forwarded.
               *
               * @remarks
               *
               * The value can contain placeholders on the form `{{ message.attributes.foo }}`,
               * to mirror attribute `foo` as the whole or part of the topic name.
               *
               * @example
               *
               * This example expects the Pub/Sub topic to contain GitHub
               * webhook events where the HTTP headers were mapped into
               * message attributes. The outcome should be that messages
               * end up on event topics such as `github.push`,
               * `github.repository` etc which matches the [`@backstage/plugin-events-backend-module-github`](https://github.com/backstage/backstage/tree/master/plugins/events-backend-module-github) structure.
               *
               * ```yaml
               * targetTopic: 'github.{{ message.attributes.x-github-event }}'
               * ```
               */
              targetTopic: string;

              /**
               * Message filter predicate expression.
               *
               * @remarks
               *
               * The value should be a JSON object that represents a filter predicate expression.
               * The object being passed to the filter is on the following form:
               *
               * ```js
               * {
               *   message: {
               *     // The raw JSON parsed message data
               *     data: { ... },
               *     // The message attributes as key-value pairs
               *     attributes: { key: 'value', ... },
               *   }
               * }
               * ```
               *
               * @example
               *
               * ```yaml
               * filter:
               *   $any:
               *     - 'message.attributes.x-github-event': 'push'
               *     - 'message.attributes.x-github-event': 'repository'
               *       'message.data.action': { $in: ['created', 'deleted'] }
               * ```
               */
              filter?: FilterPredicate;

              /**
               * Pub/Sub message attributes are by default copied to the event
               * metadata field. This setting allows you to override or amend
               * that metadata.
               *
               * @remarks
               *
               * The values can contain placeholders on the form `{{ message.attributes.foo }}`,
               * to mirror attribute `foo` as the whole or part of a metadata value.
               *
               * @example
               *
               * ```yaml
               * eventMetadata:
               *   x-gitHub-event: '{{ message.attributes.event }}'
               * ```
               */
              eventMetadata?: {
                [key: string]: string;
              };
            };
          };
        };

        /**
         * Configuration for `EventConsumingGooglePubSubPublisher`, which
         * consumes messages from the Backstage events system and forwards them
         * into Google Pub/Sub topics.
         */
        eventConsumingGooglePubSubPublisher?: {
          subscriptions: {
            [name: string]: {
              /**
               * The name of the events backend topic(s) that messages are
               * consumed from.
               */
              sourceTopic: string | string[];

              /**
               * The complete name of the Google Pub/Sub subscription to forward
               * events to, on the form
               * `projects/PROJECT_ID/topics/TOPIC_ID`.
               *
               * The value can contain placeholders on the form `{{
               * message.attributes.foo }}`, to mirror attribute `foo` as the
               * whole or part of the topic name.
               *
               * @example
               *
               * This example expects the events topic to contain GitHub
               * webhook events where the HTTP headers were mapped into
               * event metadata fields. The outcome should be that messages
               * end up on event topics such as `github.push`,
               * `github.repository` etc which matches the [`@backstage/plugin-events-backend-module-github`](https://github.com/backstage/backstage/tree/master/plugins/events-backend-module-github) structure.
               *
               * ```yaml
               * targetTopic: 'projects/my-project/topics/github.{{ event.metadata.x-github-event }}'
               * ```
               */
              targetTopicName: string;

              /**
               * Event filter predicate expression.
               *
               * @remarks
               *
               * The value should be a JSON object that represents a filter predicate expression.
               * The object being passed to the filter is on the following form:
               *
               * ```js
               * {
               *   event: {
               *     // The event topic
               *     topic: '...',
               *     // The raw event payload
               *     eventPayload: { ... },
               *     // The event metadata as key-value pairs
               *     metadata: { key: 'value', ... },
               *   }
               * }
               * ```
               *
               * @example
               *
               * ```yaml
               * filter:
               *   $any:
               *     - 'event.topic': 'github.push'
               *     - 'event.topic': 'github.repository'
               *       'event.eventPayload.action': { $in: ['created', 'deleted'] }
               * ```
               */
              filter?: FilterPredicate;

              /**
               * Event metadata fields are by default copied to the Pub/Sub
               * message attribute. This setting allows you to override or amend
               * those attributes.
               *
               * @remarks
               *
               * The values can contain placeholders on the form `{{ event.metadata.foo }}`,
               * to mirror metadata field `foo` as the whole or part of a
               * message attribute value.
               *
               * @example
               *
               * ```yaml
               * messageAttributes:
               *   x-gitHub-event: '{{ event.metadata.event }}'
               * ```
               */
              messageAttributes?: {
                [key: string]: string;
              };
            };
          };
        };
      };
    };
  };
}