pezkuwi-telemetry/packages/common/src/feed.ts

import { Opaque, Maybe } from './helpers';
import { stringify, parse, Stringified } from './stringify';
import {
  FeedVersion,
  Address,
  Latitude,
  Longitude,
  City,
  NodeId,
  NodeCount,
  NodeDetails,
  NodeStats,
  NodeHardware,
  NodeLocation,
  BlockNumber,
  BlockDetails,
  Timestamp,
  Milliseconds,
  ChainLabel
} from './types';

export const Actions = {
  FeedVersion      : 0x00 as 0x00,
  BestBlock        : 0x01 as 0x01,
  AddedNode        : 0x02 as 0x02,
  RemovedNode      : 0x03 as 0x03,
  LocatedNode      : 0x04 as 0x04,
  ImportedBlock    : 0x05 as 0x05,
  NodeStats        : 0x06 as 0x06,
  NodeHardware     : 0x07 as 0x07,
  TimeSync         : 0x08 as 0x08,
  AddedChain       : 0x09 as 0x09,
  RemovedChain     : 0x0A as 0x0A,
  SubscribedTo     : 0x0B as 0x0B,
  UnsubscribedFrom : 0x0C as 0x0C,
  Pong             : 0x0D as 0x0D,
};

export type Action = typeof Actions[keyof typeof Actions];
export type Payload = Message['payload'];

export namespace Variants {
  export interface MessageBase {
    action: Action;
  }

  export interface FeedVersionMessage extends MessageBase {
    action: typeof Actions.FeedVersion;
    payload: FeedVersion;
  }

  export interface BestBlockMessage extends MessageBase {
    action: typeof Actions.BestBlock;
    payload: [BlockNumber, Timestamp, Maybe<Milliseconds>];
  }

  export interface AddedNodeMessage extends MessageBase {
    action: typeof Actions.AddedNode;
    payload: [NodeId, NodeDetails, NodeStats, NodeHardware, BlockDetails, Maybe<NodeLocation>];
  }

  export interface RemovedNodeMessage extends MessageBase {
    action: typeof Actions.RemovedNode;
    payload: NodeId;
  }

  export interface LocatedNodeMessage extends MessageBase {
    action: typeof Actions.LocatedNode;
    payload: [NodeId, Latitude, Longitude, City];
  }

  export interface ImportedBlockMessage extends MessageBase {
    action: typeof Actions.ImportedBlock;
    payload: [NodeId, BlockDetails];
  }

  export interface NodeStatsMessage extends MessageBase {
    action: typeof Actions.NodeStats;
    payload: [NodeId, NodeStats];
  }

  export interface NodeHardwareMessage extends MessageBase {
    action: typeof Actions.NodeHardware;
    payload: [NodeId, NodeHardware];
  }

  export interface TimeSyncMessage extends MessageBase {
    action: typeof Actions.TimeSync;
    payload: Timestamp;
  }

  export interface AddedChainMessage extends MessageBase {
    action: typeof Actions.AddedChain;
    payload: [ChainLabel, NodeCount];
  }

  export interface RemovedChainMessage extends MessageBase {
    action: typeof Actions.RemovedChain;
    payload: ChainLabel;
  }

  export interface SubscribedToMessage extends MessageBase {
    action: typeof Actions.SubscribedTo;
    payload: ChainLabel;
  }

  export interface UnsubscribedFromMessage extends MessageBase {
    action: typeof Actions.UnsubscribedFrom;
    payload: ChainLabel;
  }

  export interface PongMessage extends MessageBase {
    action: typeof Actions.Pong;
    payload: string; // just echo whatever `ping` sent
  }
}

export type Message =
  | Variants.FeedVersionMessage
  | Variants.BestBlockMessage
  | Variants.AddedNodeMessage
  | Variants.RemovedNodeMessage
  | Variants.LocatedNodeMessage
  | Variants.ImportedBlockMessage
  | Variants.NodeStatsMessage
  | Variants.NodeHardwareMessage
  | Variants.TimeSyncMessage
  | Variants.AddedChainMessage
  | Variants.RemovedChainMessage
  | Variants.SubscribedToMessage
  | Variants.UnsubscribedFromMessage
  | Variants.PongMessage;

/**
 * Data type to be sent to the feed. Passing through strings means we can only serialize once,
 * no matter how many feed clients are listening in.
 */
export interface SquashedMessages extends Array<Action | Payload> {};
export type Data = Stringified<SquashedMessages>;

/**
 * Serialize an array of `Message`s to a single JSON string.
 *
 * All messages are squashed into a single array of alternating opcodes and payloads.
 *
 * Action `string`s are converted to opcodes using the `actionToCode` mapping.
 */
export function serialize(messages: Array<Message>): Data {
  const squashed: SquashedMessages = new Array(messages.length * 2);
  let index = 0;

  messages.forEach((message) => {
    const { action, payload } = message;

    squashed[index++] = action;
    squashed[index++] = payload;
  })

  return stringify(squashed);
}

/**
 * Deserialize data to an array of `Message`s.
 */
export function deserialize(data: Data): Array<Message> {
  const json = parse(data);

  if (!Array.isArray(json) || json.length === 0 || json.length % 2 !== 0) {
    throw new Error('Invalid FeedMessage.Data');
  }

  const messages = new Array<Message>(json.length / 2);

  for (const index of messages.keys()) {
    const [ action, payload ] = json.slice(index * 2);

    messages[index] = { action, payload } as Message;
  }

  return messages;
}