feat: Implement chat completions and caching

Author: ericc-ch

package.json

@@ -1,7 +1,7 @@
 {
   "name": "copilot-api",
   "scripts": {
-    "dev": "bun run ./src/main.ts",
+    "dev": "bun run --hot ./src/main.ts",
     "start": "bun run ./src/main.ts"
   },
   "dependencies": {

src/lib/cache.ts

@@ -0,0 +1,40 @@
+import { PATHS } from "./paths"
+
+interface CacheEntry {
+  value: string
+  createdAt: number
+}
+
+type Cache = Record<string, CacheEntry>
+
+const readCache = async () => {
+  const content = await Bun.file(PATHS.PATH_CACHE_FILE).text()
+  return JSON.parse(content) as Cache
+}
+
+const writeCache = (cache: Cache) =>
+  Bun.write(PATHS.PATH_CACHE_FILE, JSON.stringify(cache))
+
+const setCache = async (key: string, value: string) => {
+  const cache = await readCache()
+  cache[key] = {
+    value,
+    createdAt: Date.now(),
+  }
+
+  return writeCache(cache)
+}
+
+const getCache = async (key: string): Promise<CacheEntry | undefined> => {
+  const cache = await readCache()
+  return cache[key]
+}
+
+export const CACHE = {
+  get: getCache,
+  set: setCache,
+
+  // Lower level methods
+  _read: readCache,
+  _write: writeCache,
+}

src/lib/paths.ts

@@ -3,9 +3,9 @@ import path from "pathe"
 
 const DIR_CACHE = path.join(os.homedir(), ".cache", "copilot-api")
 
-const PATH_TOKEN_CACHE = path.join(DIR_CACHE, "token")
+const PATH_CACHE_FILE = path.join(DIR_CACHE, "cache.json")
 
 export const PATHS = {
   DIR_CACHE,
-  PATH_TOKEN_CACHE,
+  PATH_CACHE_FILE,
 }

src/main.ts

@@ -1,11 +1,36 @@
 import consola from "consola"
+import fs from "node:fs"
 
+import { CACHE } from "./lib/cache"
+import { PATHS } from "./lib/paths"
 import { TOKENS } from "./lib/tokens"
-import { chatCompletions } from "./services/copilot-vscode/chat-completions/service"
+import { server } from "./server"
+import { getModels } from "./services/copilot-vscode/get-models/service"
 import { getCopilotToken } from "./services/copilot-vscode/get-token/copilot-token"
 import { getGitHubToken } from "./services/copilot-vscode/get-token/github-token"
 
-const githubToken = await getGitHubToken()
+if (!fs.existsSync(PATHS.PATH_CACHE_FILE)) {
+  fs.mkdirSync(PATHS.DIR_CACHE, { recursive: true })
+  await CACHE._write({})
+}
+
+let githubToken: string
+
+const cachedGithubToken = await CACHE.get("github-token")
+
+const FOUR_HOURS = 4 * 60 * 60 * 1000
+
+// If exists and at most 4 hours old
+if (
+  cachedGithubToken &&
+  Date.now() - cachedGithubToken.createdAt < FOUR_HOURS
+) {
+  githubToken = cachedGithubToken.value
+} else {
+  githubToken = await getGitHubToken()
+  await CACHE.set("github-token", githubToken)
+}
+
 TOKENS.GITHUB_TOKEN = githubToken
 
 const { token: copilotToken, refresh_in } = await getCopilotToken()
@@ -21,17 +46,10 @@ setInterval(async () => {
   TOKENS.COPILOT_TOKEN = copilotToken
 }, refreshInterval)
 
-const response = await chatCompletions({
-  messages: [
-    {
-      role: "user",
-      content: "Write a function that returns the sum of two numbers",
-    },
-  ],
-  model: "gpt-4o-mini",
-  stream: false,
-})
+const models = await getModels()
 
-console.log(response)
+consola.info(
+  `Available models: ${models.data.map((model) => model.id).join("\n")}`,
+)
 
-await Bun.write("response.json", JSON.stringify(response, null, 2))
+export default server

src/routes/chat-completions/route.ts

@@ -0,0 +1,51 @@
+import { Hono } from "hono"
+import { streamSSE } from "hono/streaming"
+
+import type { ChatCompletionsPayload } from "~/services/copilot-vscode/chat-completions/types"
+import type { ChatCompletionsChunk } from "~/services/copilot-vscode/chat-completions/types.streaming"
+
+import { chatCompletions } from "~/services/copilot-vscode/chat-completions/service"
+
+export const chatCompletionsRoutes = new Hono()
+
+chatCompletionsRoutes.post("/chat/completions", async (c) => {
+  const payload = await c.req.json<ChatCompletionsPayload>()
+
+  payload.stream = false
+
+  await Bun.write("payload.json", JSON.stringify(payload))
+
+  const response = await chatCompletions(payload)
+  await Bun.write("response.json", JSON.stringify(response))
+
+  const chunks: Array<ChatCompletionsChunk> = [
+    {
+      data: {
+        choices: [
+          {
+            delta: {
+              content: response.choices[0].message.content,
+              role: response.choices[0].message.role,
+            },
+            finish_reason: response.choices[0].finish_reason,
+            index: 0,
+          },
+        ],
+        created: response.created,
+        id: response.id,
+        model: response.model,
+      },
+    },
+    {
+      data: "[DONE]",
+    },
+  ]
+
+  return streamSSE(c, async (stream) => {
+    for (const chunk of chunks) {
+      await stream.writeSSE({
+        data: JSON.stringify(chunk.data),
+      })
+    }
+  })
+})

src/server.ts

@@ -0,0 +1,11 @@
+import { Hono } from "hono"
+import { logger } from "hono/logger"
+
+import { chatCompletionsRoutes } from "./routes/chat-completions/route"
+
+export const server = new Hono()
+
+server.use(logger())
+
+server.get("/", (c) => c.text("Server running"))
+server.route("/", chatCompletionsRoutes)

src/services/copilot-vscode/api-instance.ts

@@ -1,3 +1,4 @@
+import consola from "consola"
 import { ofetch } from "ofetch"
 
 import { TOKENS } from "~/lib/tokens"
@@ -11,6 +12,12 @@ export const copilotVSCode = ofetch.create({
   onRequest({ options }) {
     options.headers.set("authorization", `Bearer ${TOKENS.COPILOT_TOKEN}`)
   },
+  onRequestError({ error }) {
+    consola.error("request error", error)
+  },
+  onResponseError({ error, response }) {
+    consola.error("response error", error, response)
+  },
 })
 
 export const github = ofetch.create({

src/services/copilot-vscode/chat-completions/types.streaming.ts

@@ -52,7 +52,7 @@ interface Usage {
 }
 
 interface ChatCompletionResponse {
-  choices: Array<Choice>
+  choices: [Choice]
   created: number
   id: string
   model: string

src/services/copilot-vscode/chat-completions/types.ts

@@ -57,7 +57,7 @@ interface Usage {
 }
 
 export interface ChatCompletionResponse {
-  choices: Array<Choice>
+  choices: [Choice]
   created: number
   id: string
   model: string