model selector

src/server/dbschema/schema.ts

@@ -175,6 +175,7 @@ export const chatMessageRelations = relations(chatMessage, ({ one }) => ({
 export const systemSettings = createTable(
 	"systemSetting",
 	(d) => ({
-		systemPropmt: d.text()
+		systemPropmt: d.text(),
+		model: d.text()
 	})
 )

src/server/routers/chat.ts

@@ -7,6 +7,26 @@ import { isAdmin } from '~/app/actions';
 import { z } from 'zod';
 import { eq } from 'drizzle-orm';
 import { clerkClient, auth } from '@clerk/nextjs/server'
+import { env } from '~/env'
+
+export const DEFAULT_MODEL = 'gpt-5-mini'
+
+// Models returned by the OpenAI API that aren't usable for chat completions.
+const NON_CHAT_MODEL = /embedding|image|audio|realtime|transcribe|tts|whisper|moderation|dall-e|search|codex|instruct/
+
+async function readSettings() {
+	return db.select().from(systemSettings).limit(1).then((r) => r[0])
+}
+
+async function writeSettings(values: { systemPropmt?: string | null; model?: string | null }) {
+	const current = await readSettings()
+	await db.delete(systemSettings)
+	await db.insert(systemSettings).values({
+		systemPropmt: values.systemPropmt ?? current?.systemPropmt ?? null,
+		model: values.model ?? current?.model ?? null,
+	})
+}
+
 export const chatRouter = router({
   getSession: publicProcedure.query(async () => {
     const { userId } = await auth();
@@ -66,13 +86,34 @@ export const chatRouter = router({
 
   }),
   getSystemPrompt: publicProcedure.query(async () => {
-    const row = await db.select().from(systemSettings).limit(1).then((r) => r[0])
+    const row = await readSettings()
     return row?.systemPropmt ?? ''
   }),
   updateSystemPrompt: publicProcedure.input(z.object({ prompt: z.string() })).mutation(async ({ input }) => {
     if (!(await isAdmin())) throw new TRPCError({ code: 'FORBIDDEN' })
-    await db.delete(systemSettings)
-    await db.insert(systemSettings).values({ systemPropmt: input.prompt })
+    await writeSettings({ systemPropmt: input.prompt })
+  }),
+  getModel: publicProcedure.query(async () => {
+    const row = await readSettings()
+    return row?.model ?? DEFAULT_MODEL
+  }),
+  listModels: publicProcedure.query(async () => {
+    if (!(await isAdmin())) throw new TRPCError({ code: 'FORBIDDEN' })
+    const res = await fetch('https://api.openai.com/v1/models', {
+      headers: { Authorization: `Bearer ${env.OPENAI_API_KEY}` },
+    })
+    if (!res.ok) {
+      throw new TRPCError({ code: 'INTERNAL_SERVER_ERROR', message: `failed to fetch models (${res.status})` })
+    }
+    const json = (await res.json()) as { data: { id: string }[] }
+    return json.data
+      .map((m) => m.id)
+      .filter((id) => (id.startsWith('gpt') || /^o\d/.test(id) || id.startsWith('chatgpt')) && !NON_CHAT_MODEL.test(id))
+      .sort()
+  }),
+  updateModel: publicProcedure.input(z.object({ model: z.string() })).mutation(async ({ input }) => {
+    if (!(await isAdmin())) throw new TRPCError({ code: 'FORBIDDEN' })
+    await writeSettings({ model: input.model })
   }),
 })