[Event Hubs] Define classes and interfaces for EPH as per API design

sdk/eventhub/event-hubs/src/checkpointManager.ts

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+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+// import { PartitionContext } from "./partitionContext";
+import { EventData } from "./eventData";
+// import { PartitionManager } from "./eventProcessor";
+
+/**
+ * Used by createCheckpoint in PartitionManager
+ **/
+export interface Checkpoint {
+  eventHubName: string;
+  consumerGroupName: string;
+  instanceId: string;
+  partitionId: string;
+  sequenceNumber: number;
+  offset: number;
+}
+
+/**
+ * CheckPointManager is created by the library & passed to user's code to let them create a checkpoint
+ */
+export class CheckpointManager {
+  // private _partitionContext: PartitionContext; // for internal use by createCheckpoint
+  // private _partitionManager: PartitionManager; // for internal use by createCheckpoint
+
+  // constructor(partitionContext: PartitionContext, partitionManager: PartitionManager) {
+  //   this._partitionContext = partitionContext;
+  //   this._partitionManager = partitionManager;
+  // }
+
+  public async updateCheckpoint(eventData: EventData): Promise<void>;
+
+  public async updateCheckpoint(offset: string, sequenceNumber: number): Promise<void>;
+
+  public async updateCheckpoint(
+    eventDataOrOffset: EventData | string,
+    sequenceNumber?: number
+  ): Promise<void> {}
+}

sdk/eventhub/event-hubs/src/eventProcessor.ts

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+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+import { EventHubClient } from "./eventHubClient";
+import { EventPosition } from "./eventPosition";
+import { PartitionContext } from "./partitionContext";
+import { CheckpointManager, Checkpoint } from "./checkpointManager";
+import { EventData } from "./eventData";
+
+export interface PartitionProcessor {
+  /**
+   * Optional. Called when EPH begins processing a partition.
+   */
+  initialize?(): Promise<void>;
+  /**
+   * Optional. Called when EPH stops processing a partition.
+   * This may occur when control of the partition switches to another EPH or when user stops EPH
+   * TODO: update string -> CloseReason
+   */
+  close?(reason: string): Promise<void>;
+  /**
+   * Called when a batch of events have been received.
+   */
+  processEvents(events: EventData[]): Promise<void>;
+  /**
+   * Called when the underlying client experiences an error while receiving.
+   */
+  processError(error: Error): Promise<void>;
+}
+
+/**
+ * used by PartitionManager to claim ownership.
+ * returned by listOwnerships
+ */
+export interface PartitionOwnership {
+  eventHubName: string;
+  consumerGroupName: string;
+  instanceId: string;
+  partitionId: string;
+  ownerLevel: number;
+  offset?: number;
+  sequenceNumber?: number;
+  lastModifiedTime?: number;
+  ETag?: string;
+}
+
+/**
+ * The PartitionProcessorFactory is called by EPH whenever a new partition is about to be processed.
+ */
+export interface PartitionProcessorFactory {
+  (context: PartitionContext, checkpointManager: CheckpointManager): PartitionProcessor;
+}
+
+/**
+ * Interface for the plugin to be passed when creating the EventProcessorHost
+ * to manage partition ownership and checkpoint creation.
+ * Deals mainly with read/write to the chosen storage service
+ */
+export interface PartitionManager {
+  listOwnerships(eventHubName: string, consumerGroupName: string): Promise<PartitionOwnership[]>;
+  claimOwnerships(partitionOwnerships: PartitionOwnership[]): Promise<PartitionOwnership[]>;
+  createCheckpoint(checkpoint: Checkpoint): Promise<void>;
+}
+
+// Options passed when creating EventProcessor, everything is optional
+export interface EventProcessorOptions {
+  initialEventPosition?: EventPosition;
+  maxBatchSize?: number;
+  maxWaitTime?: number;
+}
+
+/**
+ * Describes the Event Processor Host to process events from an EventHub.
+ * @class EventProcessorHost
+ */
+export class EventProcessor {
+  constructor(
+    consumerGroupName: string,
+    eventHubClient: EventHubClient,
+    partitionProcessorFactory: PartitionProcessorFactory,
+    partitionManager: PartitionManager,
+    options?: EventProcessorOptions
+  ) {}
+
+  /**
+   * Starts the event processor, fetching the list of partitions, and attempting to grab leases
+   * For each successful lease, it will get the details from the blob and start a receiver at the
+   * point where it left off previously.
+   *
+   * @return {Promise<void>}
+   */
+  async start(): Promise<void> {}
+
+  /**
+   * Stops the EventProcessor from processing messages.
+   * @return {Promise<void>}
+   */
+  async stop(): Promise<void> {}
+}

sdk/eventhub/event-hubs/src/partitionContext.ts

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+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+/**
+ * PartitionContext is passed into an EventProrcessor's initialization handler and contains information
+ * about the partition, the EventProcessor will be processing events from.
+ */
+export interface PartitionContext {
+  readonly partitionId: string;
+  readonly eventHubName: string;
+  readonly consumerGroupName: string;
+}