@web5/agent Adding DwnServerInfo to RPC Clients (#489)

- Added a `DwnServerInfo` HTTP client to get info from the `dwn-server`'s `/info` endpoint

```
export type ServerInfo = {
  /** the maximum file size the user can request to store */
  maxFileSize: number,
  /**
   * an array of strings representing the server's registration requirements.
   *
   * ie. ['proof-of-work-sha256-v0', 'terms-of-service']
   * */
  registrationRequirements: string[],
  /** whether web socket support is enabled on this server */
  webSocketSupport: boolean,
}
```

This is helpful for retrieving registration requirements and whether the server supports sockets.

It uses a `TTLCache` memory cache as the currently implemented and default, however additional caches can be easily added if necessary. 

Author: LiranCohen

.changeset/old-hotels-yawn.md

@@ -0,0 +1,14 @@
+---
+"@web5/agent": patch
+"@web5/identity-agent": patch
+"@web5/proxy-agent": patch
+"@web5/user-agent": patch
+---
+
+Add `DwnServerInfoRpc` to `Web5Rpc` for retrieving server specific info.
+
+Server Info includes:
+ - maxFileSize
+ - registrationRequirements
+ - webSocketSupport
+

packages/agent/.c8rc.json

@@ -10,7 +10,8 @@
   "exclude": [
     "tests/compiled/**/src/index.js",
     "tests/compiled/**/src/types.js",
-    "tests/compiled/**/src/types/**"
+    "tests/compiled/**/src/types/**",
+    "tests/compiled/**/src/prototyping/clients/*-types.js"
   ],
   "reporter": [
     "cobertura",

packages/agent/src/prototyping/clients/dwn-server-info-cache-memory.ts

@@ -0,0 +1,79 @@
+
+import ms from 'ms';
+import { TtlCache } from '@web5/common';
+import { DwnServerInfoCache, ServerInfo } from './server-info-types.js';
+
+/**
+ * Configuration parameters for creating an in-memory cache for DWN ServerInfo entries.
+ *
+ * Allows customization of the cache time-to-live (TTL) setting.
+ */
+export type DwnServerInfoCacheMemoryParams = {
+  /**
+   * Optional. The time-to-live for cache entries, expressed as a string (e.g., '1h', '15m').
+   * Determines how long a cache entry should remain valid before being considered expired.
+   *
+   * Defaults to '15m' if not specified.
+   */
+  ttl?: string;
+}
+
+export class DwnServerInfoCacheMemory implements DwnServerInfoCache {
+  private cache: TtlCache<string, ServerInfo>;
+
+  constructor({ ttl = '15m' }: DwnServerInfoCacheMemoryParams= {}) {
+    this.cache = new TtlCache({ ttl: ms(ttl) });
+  }
+
+  /**
+   * Retrieves a DWN ServerInfo entry from the cache.
+   *
+   * If the cached item has exceeded its TTL, it's scheduled for deletion and undefined is returned.
+   *
+   * @param dwnUrl - The DWN URL endpoint string used as the key for getting the entry.
+   * @returns The cached DWN ServerInfo entry or undefined if not found or expired.
+   */
+  public async get(dwnUrl: string): Promise<ServerInfo| undefined> {
+    return this.cache.get(dwnUrl);
+  }
+
+  /**
+   * Stores a DWN ServerInfo entry in the cache with a TTL.
+   *
+   * @param dwnUrl - The DWN URL endpoint string used as the key for storing the entry.
+   * @param value - The DWN ServerInfo entry to be cached.
+   * @returns A promise that resolves when the operation is complete.
+   */
+  public async set(dwnUrl: string, value: ServerInfo): Promise<void> {
+    this.cache.set(dwnUrl, value);
+  }
+
+  /**
+   * Deletes a DWN ServerInfo entry from the cache.
+   *
+   * @param dwnUrl - The DWN URL endpoint string used as the key for deletion.
+   * @returns A promise that resolves when the operation is complete.
+   */
+  public async delete(dwnUrl: string): Promise<void> {
+    this.cache.delete(dwnUrl);
+  }
+
+  /**
+   * Clears all entries from the cache.
+   *
+   * @returns A promise that resolves when the operation is complete.
+   */
+  public async clear(): Promise<void> {
+    this.cache.clear();
+  }
+
+  /**
+   * This method is a no-op but exists to be consistent with other DWN ServerInfo Cache
+   * implementations.
+   *
+   * @returns A promise that resolves immediately.
+   */
+  public async close(): Promise<void> {
+    // No-op since there is no underlying store to close.
+  }
+}

packages/agent/src/prototyping/clients/http-dwn-rpc-client.ts

@@ -3,11 +3,18 @@ import type { DwnRpc, DwnRpcRequest, DwnRpcResponse } from './dwn-rpc-types.js';
 
 import { createJsonRpcRequest, parseJson } from './json-rpc.js';
 import { utils as cryptoUtils } from '@web5/crypto';
+import { DwnServerInfoCache, ServerInfo } from './server-info-types.js';
+import { DwnServerInfoCacheMemory } from './dwn-server-info-cache-memory.js';
 
 /**
  * HTTP client that can be used to communicate with Dwn Servers
  */
 export class HttpDwnRpcClient implements DwnRpc {
+  private serverInfoCache: DwnServerInfoCache;
+  constructor(serverInfoCache?: DwnServerInfoCache) {
+    this.serverInfoCache = serverInfoCache ?? new DwnServerInfoCacheMemory();
+  }
+
   get transportProtocols() { return ['http:', 'https:']; }
 
   async sendDwnRequest(request: DwnRpcRequest): Promise<DwnRpcResponse> {
@@ -65,4 +72,37 @@ export class HttpDwnRpcClient implements DwnRpc {
 
     return reply as DwnRpcResponse;
   }
+
+  async getServerInfo(dwnUrl: string): Promise<ServerInfo> {
+    const serverInfo = await this.serverInfoCache.get(dwnUrl);
+    if (serverInfo) {
+      return serverInfo;
+    }
+
+    const url = new URL(dwnUrl);
+
+    // add `/info` to the dwn server url path
+    url.pathname.endsWith('/') ? url.pathname += 'info' : url.pathname += '/info';
+
+    try {
+      const response = await fetch(url.toString());
+      if(response.ok) {
+        const results = await response.json() as ServerInfo;
+
+        // explicitly return and cache only the desired properties.
+        const serverInfo = {
+          registrationRequirements : results.registrationRequirements,
+          maxFileSize              : results.maxFileSize,
+          webSocketSupport         : results.webSocketSupport,
+        };
+        this.serverInfoCache.set(dwnUrl, serverInfo);
+
+        return serverInfo;
+      } else {
+        throw new Error(`HTTP (${response.status}) - ${response.statusText}`);
+      }
+    } catch(error: any) {
+      throw new Error(`Error encountered while processing response from ${url.toString()}: ${error.message}`);
+    }
+  }
 }

packages/agent/src/prototyping/clients/server-info-types.ts

@@ -0,0 +1,21 @@
+import { KeyValueStore } from '@web5/common';
+
+export type ServerInfo = {
+  /** the maximum file size the user can request to store */
+  maxFileSize: number,
+  /**
+   * an array of strings representing the server's registration requirements.
+   *
+   * ie. ['proof-of-work-sha256-v0', 'terms-of-service']
+   * */
+  registrationRequirements: string[],
+  /** whether web socket support is enabled on this server */
+  webSocketSupport: boolean,
+}
+
+export interface DwnServerInfoCache extends KeyValueStore<string, ServerInfo| undefined> {}
+
+export interface DwnServerInfoRpc {
+  /** retrieves the DWN Sever info, used to detect features such as WebSocket Subscriptions */
+  getServerInfo(url: string): Promise<ServerInfo>;
+}

packages/agent/src/rpc-client.ts

@@ -2,6 +2,7 @@ import { utils as cryptoUtils } from '@web5/crypto';
 
 
 import type { DwnRpc, DwnRpcRequest, DwnRpcResponse } from './prototyping/clients/dwn-rpc-types.js';
+import type { DwnServerInfoRpc, ServerInfo } from './prototyping/clients/server-info-types.js';
 import type { JsonRpcResponse } from './prototyping/clients/json-rpc.js';
 
 import { createJsonRpcRequest } from './prototyping/clients/json-rpc.js';
@@ -39,7 +40,7 @@ export type RpcStatus = {
   message: string;
 };
 
-export interface Web5Rpc extends DwnRpc, DidRpc {}
+export interface Web5Rpc extends DwnRpc, DidRpc, DwnServerInfoRpc {}
 
 /**
  * Client used to communicate with Dwn Servers
@@ -94,6 +95,21 @@ export class Web5RpcClient implements Web5Rpc {
 
     return transportClient.sendDwnRequest(request);
   }
+
+  async getServerInfo(dwnUrl: string): Promise<ServerInfo> {
+    // will throw if url is invalid
+    const url = new URL(dwnUrl);
+
+    const transportClient = this.transportClients.get(url.protocol);
+    if(!transportClient) {
+      const error = new Error(`no ${url.protocol} transport client available`);
+      error.name = 'NO_TRANSPORT_CLIENT';
+
+      throw error;
+    }
+
+    return transportClient.getServerInfo(dwnUrl);
+  }
 }
 
 export class HttpWeb5RpcClient extends HttpDwnRpcClient implements Web5Rpc {
@@ -139,4 +155,8 @@ export class WebSocketWeb5RpcClient extends WebSocketDwnRpcClient implements Web
   async sendDidRequest(_request: DidRpcRequest): Promise<DidRpcResponse> {
     throw new Error(`not implemented for transports [${this.transportProtocols.join(', ')}]`);
   }
+
+  async getServerInfo(_dwnUrl: string): Promise<ServerInfo> {
+    throw new Error(`not implemented for transports [${this.transportProtocols.join(', ')}]`);
+  }
 }

packages/agent/tests/prototyping/clients/dwn-server-info-cache.spec.ts

@@ -0,0 +1,119 @@
+import sinon from 'sinon';
+
+import { expect } from 'chai';
+
+import { DwnServerInfoCache, ServerInfo } from '../../../src/prototyping/clients/server-info-types.js';
+import { DwnServerInfoCacheMemory } from '../../../src/prototyping/clients/dwn-server-info-cache-memory.js';
+import { isNode } from '../../utils/runtimes.js';
+
+describe('DwnServerInfoCache', () => {
+
+  describe(`DwnServerInfoCacheMemory`, () => {
+    let cache: DwnServerInfoCache;
+    let clock: sinon.SinonFakeTimers;
+
+    const exampleInfo:ServerInfo = {
+      maxFileSize              : 100,
+      webSocketSupport         : true,
+      registrationRequirements : []
+    };
+
+    after(() => {
+      sinon.restore();
+    });
+
+    beforeEach(() => {
+      clock = sinon.useFakeTimers();
+      cache = new DwnServerInfoCacheMemory();
+    });
+
+    afterEach(async () => {
+      await cache.clear();
+      await cache.close();
+      clock.restore();
+    });
+
+    it('sets server info in cache', async () => {
+      const key1 = 'some-key1';
+      const key2 = 'some-key2';
+      await cache.set(key1, { ...exampleInfo });
+      await cache.set(key2, { ...exampleInfo, webSocketSupport: false }); // set to false
+
+      const result1 = await cache.get(key1);
+      expect(result1!.webSocketSupport).to.deep.equal(true);
+      expect(result1).to.deep.equal(exampleInfo);
+
+      const result2 = await cache.get(key2);
+      expect(result2!.webSocketSupport).to.deep.equal(false);
+    });
+
+    it('deletes from cache', async () => {
+      const key1 = 'some-key1';
+      const key2 = 'some-key2';
+      await cache.set(key1, { ...exampleInfo });
+      await cache.set(key2, { ...exampleInfo, webSocketSupport: false }); // set to false
+
+      const result1 = await cache.get(key1);
+      expect(result1!.webSocketSupport).to.deep.equal(true);
+      expect(result1).to.deep.equal(exampleInfo);
+
+      const result2 = await cache.get(key2);
+      expect(result2!.webSocketSupport).to.deep.equal(false);
+
+      // delete one of the keys
+      await cache.delete(key1);
+
+      // check results after delete
+      const resultAfterDelete = await cache.get(key1);
+      expect(resultAfterDelete).to.equal(undefined);
+
+      // key 2 still exists
+      const result2AfterDelete = await cache.get(key2);
+      expect(result2AfterDelete!.webSocketSupport).to.equal(false);
+    });
+
+    it('clears cache', async () => {
+      const key1 = 'some-key1';
+      const key2 = 'some-key2';
+      await cache.set(key1, { ...exampleInfo });
+      await cache.set(key2, { ...exampleInfo, webSocketSupport: false }); // set to false
+
+      const result1 = await cache.get(key1);
+      expect(result1!.webSocketSupport).to.deep.equal(true);
+      expect(result1).to.deep.equal(exampleInfo);
+
+      const result2 = await cache.get(key2);
+      expect(result2!.webSocketSupport).to.deep.equal(false);
+
+      // delete one of the keys
+      await cache.clear();
+
+      // check results after delete
+      const resultAfterDelete = await cache.get(key1);
+      expect(resultAfterDelete).to.equal(undefined);
+      const result2AfterDelete = await cache.get(key2);
+      expect(result2AfterDelete).to.equal(undefined);
+    });
+
+    it('returns undefined after ttl', async function () {
+      // skip this test in the browser, sinon fake timers don't seem to work here
+      // with a an await setTimeout in the test, it passes.
+      if (!isNode) {
+        this.skip();
+      }
+
+      const key = 'some-key1';
+      await cache.set(key, { ...exampleInfo });
+
+      const result = await cache.get(key);
+      expect(result!.webSocketSupport).to.deep.equal(true);
+      expect(result).to.deep.equal(exampleInfo);
+
+      // wait until 15m default ttl is up
+      await clock.tickAsync('15:01');
+
+      const resultAfter = await cache.get(key);
+      expect(resultAfter).to.be.undefined;
+    });
+  });
+});