Frontend stuff

packages/common/src/feed.ts

@@ -0,0 +1,100 @@
+import { Opaque } from './helpers';
+import { NodeId, NodeDetails, NodeStats, BlockNumber, BlockDetails } from './types';
+
+export const Actions = {
+    BestBlock: 0 as 0,
+    AddedNode: 1 as 1,
+    RemovedNode: 2 as 2,
+    ImportedBlock: 3 as 3,
+    NodeStats: 4 as 4,
+};
+
+export type Action = typeof Actions[keyof typeof Actions];
+export type Payload = Message['payload'];
+
+export namespace Variants {
+    export interface MessageBase {
+        action: Action;
+    }
+
+    export interface BestBlockMessage extends MessageBase {
+        action: typeof Actions.BestBlock;
+        payload: BlockNumber;
+    }
+
+    export interface AddedNodeMessage extends MessageBase {
+        action: typeof Actions.AddedNode;
+        payload: [NodeId, NodeDetails, NodeStats, BlockDetails];
+    }
+
+    export interface RemovedNodeMessage extends MessageBase {
+        action: typeof Actions.RemovedNode;
+        payload: NodeId;
+    }
+
+    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 type Message =
+    | Variants.BestBlockMessage
+    | Variants.AddedNodeMessage
+    | Variants.RemovedNodeMessage
+    | Variants.ImportedBlockMessage
+    | Variants.NodeStatsMessage;
+
+/**
+ * Opaque 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 type Data = Opaque<string, 'FeedMessage.Data'>;
+
+/**
+ * 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 = new Array(messages.length * 2);
+    let index = 0;
+
+    messages.forEach((message) => {
+        const { action, payload } = message;
+
+        squashed[index++] = action;
+        squashed[index++] = payload;
+    })
+
+    return JSON.stringify(squashed) as Data;
+}
+
+/**
+ * Deserialize data to an array of `Message`s.
+ */
+export function deserialize(data: Data): Array<Message> {
+    const json: Array<Action | Payload> = JSON.parse(data);
+
+    if (!Array.isArray(json) || json.length === 0 || json.length % 2 !== 0) {
+        throw new Error('Invalid FeedMessage.Data');
+    }
+
+    const messages: Array<Message> = new Array(json.length / 2);
+
+    for (const index of messages.keys()) {
+        const [ action, payload ] = json.slice(index * 2);
+
+        messages[index] = { action, payload } as Message;
+    }
+
+    return messages;
+}