Add OpenRouter support as fallback to Gemini in chatActions

Co-authored-by: na-trium-144 <100704180+na-trium-144@users.noreply.github.com>

Author: Copilot

app/actions/chatActions.ts

@@ -1,12 +1,20 @@
 "use server";
 
 // import { z } from "zod";
-import { generateContent } from "./gemini";
+import { generateContent as generateContentGemini } from "./gemini";
+import { generateContent as generateContentOpenRouter } from "./openrouter";
 import { DynamicMarkdownSection } from "../[lang]/[pageId]/pageContent";
 import { ReplCommand, ReplOutput } from "@my-code/runtime/interface";
 import { addChat, ChatWithMessages } from "@/lib/chatHistory";
 import { getPagesList, introSectionId, PagePath, SectionId } from "@/lib/docs";
 
+function generateContent(prompt: string, systemInstruction?: string) {
+  if (process.env.OPENROUTER_API_KEY && process.env.OPENROUTER_MODEL) {
+    return generateContentOpenRouter(prompt, systemInstruction);
+  }
+  return generateContentGemini(prompt, systemInstruction);
+}
+
 type ChatResult =
   | {
       error: string;

app/actions/openrouter.ts

@@ -0,0 +1,47 @@
+"use server";
+
+export async function generateContent(
+  prompt: string,
+  systemInstruction?: string
+): Promise<{ text: string }> {
+  const apiKey = process.env.OPENROUTER_API_KEY;
+  const model = process.env.OPENROUTER_MODEL;
+
+  if (!apiKey || !model) {
+    throw new Error(
+      "OPENROUTER_API_KEY and OPENROUTER_MODEL environment variables must be set"
+    );
+  }
+
+  const messages: { role: string; content: string }[] = [];
+  if (systemInstruction) {
+    messages.push({ role: "system", content: systemInstruction });
+  }
+  messages.push({ role: "user", content: prompt });
+
+  const response = await fetch("https://openrouter.ai/api/v1/chat/completions", {
+    method: "POST",
+    headers: {
+      Authorization: `Bearer ${apiKey}`,
+      "Content-Type": "application/json",
+    },
+    body: JSON.stringify({ model, messages }),
+  });
+
+  if (!response.ok) {
+    const errorText = await response.text();
+    throw new Error(
+      `OpenRouter API error: ${response.status} ${response.statusText} - ${errorText}`
+    );
+  }
+
+  const data = (await response.json()) as {
+    choices: { message: { content: string } }[];
+  };
+
+  const text = data.choices[0]?.message?.content;
+  if (!text) {
+    throw new Error("OpenRouterからの応答が空でした");
+  }
+  return { text };
+}