feat: Cache flags and components for one hour (#114)

This PR adds a caching layer to the background service worker for the
flags and components fetchers. The cache just uses localstorage and will
start with a one hour TTL.

Closes #110

Author: spalmurray-codecov

src/constants.ts

@@ -1,11 +1,13 @@
-export const codecovApiTokenStorageKey = "self_hosted_codecov_api_token"; // Keeping this key to not break existing installs.
+export const codecovApiTokenStorageKey = "self_hosted_codecov_api_token";
 export const selfHostedCodecovURLStorageKey = "self_hosted_codecov_url";
 export const selfHostedGitHubURLStorageKey = "self_hosted_github_url";
 export const dynamicContentScriptRegistrationId = "dynamic-content-script";
 
 export const codecovCloudApiUrl = "https://api.codecov.io";
 export const githubCloudUrl = "https://github.com";
 
+export const cacheTtlMs = 1000 * 60 * 60; // 1 hour
+
 export const providers = {
   github: "github",
   githubEnterprise: "github_enterprise",

src/service.ts

@@ -8,6 +8,7 @@ import {
   selfHostedCodecovURLStorageKey,
   selfHostedGitHubURLStorageKey,
   providers,
+  cacheTtlMs,
 } from "src/constants";
 
 export class Codecov {
@@ -137,10 +138,65 @@ export class Codecov {
     };
   }
 
+  async getCached(
+    type: "flags" | "components",
+    owner: string,
+    repo: string
+  ): Promise<any> {
+    const cacheKey = `${owner}/${repo}/${type}`;
+    const cacheExpiryKey = `${owner}/${repo}/${type}/expiry`;
+
+    const storage = await browser.storage.local.get([cacheKey, cacheExpiryKey]);
+
+    if (!storage[cacheKey] || !storage[cacheExpiryKey]) {
+      // Cache is not set
+      return null;
+    }
+
+    const value = JSON.parse(storage[cacheKey]);
+    const expiry = storage[cacheExpiryKey];
+
+    if (Date.now() <= expiry) {
+      // Cache is valid, return cached value
+      return value;
+    }
+
+    // Cache is expired, clear cache
+    await browser.storage.local.remove([cacheKey, cacheExpiryKey]);
+
+    return null;
+  }
+
+  async setCached(
+    type: "flags" | "components",
+    owner: string,
+    repo: string,
+    data: any
+  ): Promise<void> {
+    const cacheKey = `${owner}/${repo}/${type}`;
+    const cacheExpiryKey = `${owner}/${repo}/${type}/expiry`;
+
+    await browser.storage.local.set({
+      [cacheKey]: JSON.stringify(data),
+      [cacheExpiryKey]: Date.now() + cacheTtlMs,
+    });
+
+    return;
+  }
+
   async listFlags(payload: any, referrer: string): Promise<any> {
     await this.init();
     const { owner, repo } = payload;
 
+    const cachedFlags = await this.getCached("flags", owner, repo);
+
+    if (cachedFlags != null) {
+      return {
+        ok: true,
+        data: cachedFlags,
+      };
+    }
+
     const url = new URL(
       `/api/v2/${this.provider}/${owner}/repos/${repo}/flags`,
       this.apiUrl
@@ -153,6 +209,8 @@ export class Codecov {
     });
     const data = await response.json();
 
+    await this.setCached("flags", owner, repo, data);
+
     return {
       ok: response.ok,
       data,
@@ -163,6 +221,15 @@ export class Codecov {
     await this.init();
     const { owner, repo } = payload;
 
+    const cachedComponents = await this.getCached("components", owner, repo);
+
+    if (cachedComponents != null) {
+      return {
+        ok: true,
+        data: cachedComponents,
+      };
+    }
+
     const url = new URL(
       `/api/v2/${this.provider}/${owner}/repos/${repo}/components`,
       this.apiUrl
@@ -175,6 +242,8 @@ export class Codecov {
     });
     const data = await response.json();
 
+    await this.setCached("components", owner, repo, data);
+
     return {
       ok: response.ok,
       data,