refactor repo-mock package (#408)

Signed-off-by: Brian DeHamer <bdehamer@github.com>

Author: bdehamer

.changeset/fast-coins-laugh.md

@@ -0,0 +1,5 @@
+---
+'@tufjs/repo-mock': minor
+---
+
+Export new helpers: `initializeTUFRepo` and `tufHandlers`

packages/repo-mock/src/__tests__/index.test.ts

@@ -62,6 +62,12 @@ describe('mockRepo', () => {
     await expect(fetch(`${baseURL}/metadata/2.root.json`)).rejects.toThrow(
       /404/
     );
+
+    // No mock should be set-up for the 1.root.json file as this should never be
+    // fetched in a normal TUF flow.
+    await expect(fetch(`${baseURL}/metadata/1.root.json`)).rejects.toThrow(
+      /No match for request/
+    );
   });
 
   it('mocks the targets endpoints', async () => {

packages/repo-mock/src/handler.ts

@@ -0,0 +1,57 @@
+import { Metadata } from '@tufjs/models';
+import { TUFRepo } from './repo';
+import { Handler, HandlerFn } from './shared.types';
+
+export interface TUFHandlerOptions {
+  metadataPathPrefix?: string;
+  targetPathPrefix?: string;
+}
+
+export function tufHandlers(
+  tufRepo: TUFRepo,
+  opts: TUFHandlerOptions
+): Handler[] {
+  const metadataPrefix = opts.metadataPathPrefix ?? '/metadata';
+  const targetPrefix = opts.targetPathPrefix ?? '/targets';
+
+  const handlers: Handler[] = [
+    {
+      path: `${metadataPrefix}/1.root.json`,
+      fn: respondWithMetadata(tufRepo.rootMeta),
+    },
+    {
+      path: `${metadataPrefix}/timestamp.json`,
+      fn: respondWithMetadata(tufRepo.timestampMeta),
+    },
+    {
+      path: `${metadataPrefix}/snapshot.json`,
+      fn: respondWithMetadata(tufRepo.snapshotMeta),
+    },
+    {
+      path: `${metadataPrefix}/targets.json`,
+      fn: respondWithMetadata(tufRepo.targetsMeta),
+    },
+    {
+      path: `${metadataPrefix}/2.root.json`,
+      fn: () => ({ statusCode: 404, response: '' }),
+    },
+  ];
+
+  tufRepo.targets.forEach((target) => {
+    handlers.push({
+      path: `${targetPrefix}/${target.name}`,
+      fn: () => ({ statusCode: 200, response: target.content }),
+    });
+  });
+
+  return handlers;
+}
+
+/* eslint-disable-next-line @typescript-eslint/no-explicit-any */
+function respondWithMetadata(meta: Metadata<any>): HandlerFn {
+  return () => ({
+    statusCode: 200,
+    response: JSON.stringify(meta.toJSON()),
+    contentType: 'application/json',
+  });
+}

packages/repo-mock/src/index.ts

@@ -2,66 +2,39 @@ import fs from 'fs';
 import nock from 'nock';
 import os from 'os';
 import path from 'path';
-import { KeyPair } from './key';
-import {
-  createRootMeta,
-  createSnapshotMeta,
-  createTargetsMeta,
-  createTimestampMeta,
-} from './metadata';
-import { Target, collectTargets } from './target';
+import { TUFHandlerOptions, tufHandlers } from './handler';
+import { mock } from './mock';
+import { initializeTUFRepo } from './repo';
+import { Target } from './shared.types';
 
-export type { Target } from './target';
+export { TUFHandlerOptions, tufHandlers } from './handler';
+export { TUFRepo, initializeTUFRepo } from './repo';
+export type { Target } from './shared.types';
 
-interface MockRepoOptions {
+type MockRepoOptions = {
   baseURL?: string;
-  metadataPathPrefix?: string;
-  targetPathPrefix?: string;
   cachePath?: string;
-  responseCount?: number;
-}
+} & TUFHandlerOptions;
 
 export function mockRepo(
   baseURL: string,
   targets: Target[],
-  options: Omit<MockRepoOptions, 'baseURL' | 'cachePath'> = {}
+  options: TUFHandlerOptions = {}
 ): string {
-  const metadataPrefix = options.metadataPathPrefix ?? '/metadata';
-  const targetPrefix = options.targetPathPrefix ?? '/targets';
-  const count = options.responseCount ?? 1;
-  const keyPair = new KeyPair();
-
-  // Translate the input targets into TUF TargetFile objects
-  const targetFiles = collectTargets(targets);
-
-  // Generate all of the TUF metadata objects
-  const targetsMeta = createTargetsMeta(targetFiles, keyPair);
-  const snapshotMeta = createSnapshotMeta(targetsMeta, keyPair);
-  const timestampMeta = createTimestampMeta(snapshotMeta, keyPair);
-  const rootMeta = createRootMeta(keyPair);
-
-  // Calculate paths for all of the metadata files
-  const rootPath = `${metadataPrefix}/2.root.json`;
-  const timestampPath = `${metadataPrefix}/timestamp.json`;
-  const snapshotPath = `${metadataPrefix}/snapshot.json`;
-  const targetsPath = `${metadataPrefix}/targets.json`;
-
-  // Mock the metadata endpoints
-  // Note: the root metadata file request always returns a 404 to indicate that
-  // the client should use the initial root metadata file from the cache
-  nock(baseURL).get(rootPath).times(count).reply(404);
-  nock(baseURL).get(timestampPath).times(count).reply(200, timestampMeta);
-  nock(baseURL).get(snapshotPath).times(count).reply(200, snapshotMeta);
-  nock(baseURL).get(targetsPath).times(count).reply(200, targetsMeta);
+  const tufRepo = initializeTUFRepo(targets);
+  const handlers = tufHandlers(tufRepo, options);
+
+  handlers.forEach((handler) => {
+    // Don't set-up a mock for the 1.root.json file as this should never be
+    // fetched in a normal TUF flow.
+    if (handler.path.endsWith('1.root.json')) {
+      return;
+    }
 
-  // Mock the target endpoints
-  targets.forEach((target) => {
-    nock(baseURL)
-      .get(`${targetPrefix}/${target.name}`)
-      .reply(200, target.content);
+    mock(baseURL, handler);
   });
 
-  return JSON.stringify(rootMeta);
+  return JSON.stringify(tufRepo.rootMeta.toJSON());
 }
 
 export function clearMock() {

packages/repo-mock/src/mock.ts

@@ -0,0 +1,23 @@
+import nock from 'nock';
+import type { Handler, HandlerFn } from './shared.types';
+
+type NockHandler = (uri: string, request: nock.Body) => nock.ReplyFnResult;
+
+// Sets-up nock-based mocking for the given handler
+export function mock(base: string, handler: Handler): void {
+  nock(base).get(handler.path).reply(adapt(handler.fn));
+}
+
+// Adapts our HandlerFn to nock's NockHandler format
+function adapt(handler: HandlerFn): NockHandler {
+  /* istanbul ignore next */
+  return (): nock.ReplyFnResult => {
+    const { statusCode, response, contentType } = handler();
+
+    return [
+      statusCode,
+      response,
+      { 'Content-Type': contentType || 'text/plain' },
+    ];
+  };
+}

packages/repo-mock/src/repo.ts

@@ -0,0 +1,39 @@
+import { Metadata, Root, Snapshot, Targets, Timestamp } from '@tufjs/models';
+import { KeyPair } from './key';
+import {
+  createRootMeta,
+  createSnapshotMeta,
+  createTargetsMeta,
+  createTimestampMeta,
+} from './metadata';
+import { collectTargets } from './target';
+
+import type { Target } from './shared.types';
+
+export interface TUFRepo {
+  rootMeta: Metadata<Root>;
+  timestampMeta: Metadata<Timestamp>;
+  snapshotMeta: Metadata<Snapshot>;
+  targetsMeta: Metadata<Targets>;
+  targets: Target[];
+}
+
+export function initializeTUFRepo(targets: Target[]): TUFRepo {
+  const keyPair = new KeyPair();
+  // Translate the input targets into TUF TargetFile objects
+  const targetFiles = collectTargets(targets);
+
+  // Generate all of the TUF metadata objects
+  const targetsMeta = createTargetsMeta(targetFiles, keyPair);
+  const snapshotMeta = createSnapshotMeta(targetsMeta, keyPair);
+  const timestampMeta = createTimestampMeta(snapshotMeta, keyPair);
+  const rootMeta = createRootMeta(keyPair);
+
+  return {
+    rootMeta,
+    snapshotMeta,
+    timestampMeta,
+    targetsMeta,
+    targets,
+  };
+}

packages/repo-mock/src/shared.types.ts

@@ -0,0 +1,17 @@
+export interface Target {
+  name: string;
+  content: string | Buffer;
+}
+
+export type HandlerFn = () => HandlerFnResult;
+
+export type HandlerFnResult = {
+  statusCode: number;
+  response: string | Buffer;
+  contentType?: string;
+};
+
+export type Handler = {
+  path: string;
+  fn: HandlerFn;
+};

packages/repo-mock/src/target.ts

@@ -1,10 +1,7 @@
 import { TargetFile } from '@tufjs/models';
 import { digestSHA256 } from './crypto';
 
-export interface Target {
-  name: string;
-  content: string | Buffer;
-}
+import type { Target } from './shared.types';
 
 export function collectTargets(targets: Target[]): TargetFile[] {
   return targets.map((target) => {