/functions/api/index.js

const corsHeaders = {
  "access-control-allow-methods": "GET,POST,OPTIONS",
  "access-control-allow-headers": "content-type",
  "access-control-max-age": "86400"
};
const jsonHeaders = { ...corsHeaders, "content-type": "application/json; charset=utf-8" };

const SYSTEM_PROMPT =
  "你是「夜航员」，一座沿海灯塔的值班助手。回答准确、克制、有温度，像在雾夜里把航道说清楚。直接回答用户的问题，不要自我介绍，不要使用markdown标题堆砌。";

function hasValue(value) {
  return typeof value === "string" && value.trim().length > 0;
}

function requiredEnv(name) {
  const value = process.env[name];
  if (!hasValue(value)) {
    throw new Error(`${name} is not configured`);
  }
  return value;
}

function json(statusCode, body) {
  return { statusCode, headers: jsonHeaders, body: JSON.stringify(body) };
}

function requestPath(event) {
  return (event && (event.path || event.rawPath)) || "/api/cloud/health";
}

function requestMethod(event) {
  return (event && (event.method || event.httpMethod)) || "GET";
}

function parseBody(event) {
  if (!event || !event.body) {
    return {};
  }
  const raw = event.isBase64Encoded ? Buffer.from(event.body, "base64").toString("utf8") : event.body;
  try {
    return JSON.parse(raw);
  } catch (error) {
    const detail = error instanceof Error ? error.message : String(error);
    throw new Error(`invalid JSON body: ${detail}`);
  }
}

function modelConfigured() {
  return (
    hasValue(process.env.OPENAI_BASE_URL) &&
    hasValue(process.env.OPENAI_API_KEY) &&
    !process.env.OPENAI_API_KEY.includes("replace-with") &&
    hasValue(process.env.OPENAI_MODEL)
  );
}

function health() {
  return json(200, {
    ok: true,
    service: "beacon-watch",
    keeper: "夜航员",
    bindings: {
      model: modelConfigured()
    }
  });
}

function normalizeMessages(body) {
  const messages = [];
  if (Array.isArray(body.messages)) {
    for (const item of body.messages) {
      if (!item || (item.role !== "user" && item.role !== "assistant")) {
        continue;
      }
      if (typeof item.content !== "string" || !item.content.trim()) {
        continue;
      }
      messages.push({
        role: item.role,
        content: item.content.trim().slice(0, 4000)
      });
      if (messages.length >= 24) {
        break;
      }
    }
  }
  if (typeof body.question === "string" && body.question.trim()) {
    messages.push({ role: "user", content: body.question.trim().slice(0, 4000) });
  }
  return messages;
}

async function chat(event) {
  const body = parseBody(event);
  const messages = normalizeMessages(body);
  if (!messages.length || messages[messages.length - 1].role !== "user") {
    return json(400, { ok: false, error: "请先写下要问的话" });
  }
  if (!modelConfigured()) {
    return json(503, {
      ok: false,
      error: "值班室还没有接通模型令牌。用带 write:model 权限的 PAT 执行 wehub model token create 后写入函数 env。"
    });
  }

  const baseURL = requiredEnv("OPENAI_BASE_URL").replace(/\/+$/, "");
  const apiKey = requiredEnv("OPENAI_API_KEY");
  const model = requiredEnv("OPENAI_MODEL");
  const chatURL = baseURL.endsWith("/v1") ? `${baseURL}/chat/completions` : `${baseURL}/v1/chat/completions`;

  let response;
  try {
    response = await fetch(chatURL, {
      method: "POST",
      headers: { authorization: `Bearer ${apiKey}`, "content-type": "application/json" },
      body: JSON.stringify({
        model,
        messages: [{ role: "system", content: SYSTEM_PROMPT }, ...messages],
        thinking: { type: "disabled" }
      }),
      signal: AbortSignal.timeout(60_000)
    });
  } catch (error) {
    const detail = error instanceof Error ? error.message : String(error);
    return json(502, { ok: false, error: `灯塔链路中断：${detail}` });
  }

  let payload;
  try {
    payload = await response.json();
  } catch (error) {
    return json(502, { ok: false, error: `模型返回了无法阅读的报文（${response.status}）` });
  }
  if (!response.ok) {
    const detail = payload && payload.error && payload.error.message;
    return json(502, { ok: false, error: detail || `模型请求失败：${response.status}` });
  }

  const answer =
    payload &&
    payload.choices &&
    payload.choices[0] &&
    payload.choices[0].message &&
    payload.choices[0].message.content;
  if (typeof answer !== "string" || !answer.trim()) {
    return json(502, { ok: false, error: "值班室沉默了，没有带回答复" });
  }
  return json(200, { ok: true, answer: answer.trim() });
}

exports.handler = async function handler(event) {
  const path = requestPath(event);
  const method = requestMethod(event).toUpperCase();

  try {
    if (method === "OPTIONS") {
      return { statusCode: 204, headers: corsHeaders, body: "" };
    }
    if (method === "GET" && path.endsWith("/health")) {
      return health();
    }
    if (method === "POST" && path.endsWith("/chat")) {
      return await chat(event);
    }
    return json(200, {
      ok: true,
      routes: ["GET /api/cloud/health", "POST /api/cloud/chat"]
    });
  } catch (error) {
    return json(500, { ok: false, error: error instanceof Error ? error.message : String(error) });
  }
};