background.js

// Background service worker (MV3)
// - Handles long-running tasks: summarization, translation
// - Stores/retrieves options from chrome.storage

const DEFAULT_SETTINGS = {
  provider: "deepseek",
  apiBaseUrl: "https://api.deepseek.com/",
  apiKey: "sk-a6e9d09e1e6f402b8e37391c68d07114",
  model: "deepseek-chat",
  targetLang: "zh-CN"
};

async function getSettings() {
  const data = await chrome.storage.sync.get({ settings: DEFAULT_SETTINGS });
  return { ...DEFAULT_SETTINGS, ...(data.settings || {}) };
}

async function setSettings(settings) {
  await chrome.storage.sync.set({ settings });
}

chrome.runtime.onInstalled.addListener(() => {
  // Initialize defaults on install if empty
  chrome.storage.sync.get(["settings"], ({ settings }) => {
    if (!settings) {
      chrome.storage.sync.set({ settings: DEFAULT_SETTINGS });
    }
  });
});

chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  (async () => {
    try {
      if (message?.type === "VCP_GET_SETTINGS") {
        const settings = await getSettings();
        sendResponse({ ok: true, settings });
        return;
      }
      if (message?.type === "VCP_SET_SETTINGS") {
        await setSettings(message.settings);
        sendResponse({ ok: true });
        return;
      }
      if (message?.type === "VCP_SUMMARIZE") {
        const { transcript, title, url } = message;
        const settings = await getSettings();
        const summary = await summarizeTranscript({ transcript, title, url }, settings);
        sendResponse({ ok: true, summary });
        return;
      }
      if (message?.type === "VCP_TRANSLATE") {
        const { lines, targetLang } = message;
        const settings = await getSettings();
        const translated = await translateLines(lines, targetLang || settings.targetLang, settings);
        sendResponse({ ok: true, translated });
        return;
      }
    } catch (error) {
      sendResponse({ ok: false, error: error?.message || String(error) });
    }
  })();
  return true; // keep port open for async
});

async function summarizeTranscript(payload, settings) {
  const system = "你是一个资深视频内容助理，基于字幕生成中文内容概要。输出要点列表与简短摘要。";
  const user = [
    `标题: ${payload.title || "(未知)"}`,
    `URL: ${payload.url || ""}`,
    "字幕: \n" + payload.transcript.slice(0, 15000)
  ].join("\n\n");
  const response = await callChatCompletions({ system, user, model: settings.model }, settings);
  return response;
}

async function translateLines(lines, targetLang, settings) {
  const system = `你是专业翻译，请将输入逐行翻译成${targetLang}，保留时间戳。`;
  const user = lines
    .slice(0, 500) // bound cost: translate first 500 lines per request
    .map(l => `${l.start} --> ${l.end}\n${l.text}`)
    .join("\n\n");
  const response = await callChatCompletions({ system, user, model: settings.model }, settings);
  return response;
}

async function callChatCompletions({ system, user, model }, settings) {
  const url = `${settings.apiBaseUrl}/chat/completions`;
  const res = await fetch(url, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: settings.apiKey ? `Bearer ${settings.apiKey}` : ""
    },
    body: JSON.stringify({
      model: model || settings.model,
      messages: [
        { role: "system", content: system },
        { role: "user", content: user }
      ],
      temperature: 0.3
    })
  });
  if (!res.ok) {
    const text = await res.text();
    throw new Error(`LLM API error: ${res.status} ${text}`);
  }
  const data = await res.json();
  return data?.choices?.[0]?.message?.content || "";
}