const fs = require("fs");
const fsp = require("fs/promises");
const path = require("path");
const crypto = require("crypto");
const { ObjectId } = require("mongodb");
const dayjs = require("dayjs");
const axios = require("axios");
const puppeteer = require("puppeteer-core");
const { decryptDiagnosticRecordFields } = require("../diagnostic-record/format");

let browserPromise;
let activeJobs = 0;
const waiters = [];
const cachedPdfJobs = new Map();
const PDF_TEMPLATE_VERSION = "v5";
const MAX_SIGNATURE_IMAGE_BYTES = 1024 * 1024;
const SIGNATURE_DOWNLOAD_TIMEOUT_MS = 5000;

const signatureMimeTypes = {
  ".png": "image/png",
  ".jpg": "image/jpeg",
  ".jpeg": "image/jpeg",
  ".webp": "image/webp",
};

function resolveDefaultPdfRoot(
  moduleDirectory = __dirname,
  isBuilt = process.env.IS_BUILDED === "YES"
) {
  const serviceRoot = isBuilt
    ? moduleDirectory
    : path.resolve(moduleDirectory, "../..");
  return path.resolve(serviceRoot, "../private-files/prescriptions");
}

function getPdfRoot() {
  return path.resolve(
    process.env.CONFIG_PRESCRIPTION_PDF_ROOT || resolveDefaultPdfRoot()
  );
}

async function initializeStorage() {
  const pdfRoot = getPdfRoot();
  await fsp.mkdir(pdfRoot, { recursive: true });
  await fsp.access(pdfRoot, fs.constants.R_OK | fs.constants.W_OK);
  return pdfRoot;
}

function maxConcurrency() {
  const value = Number.parseInt(process.env.PRESCRIPTION_PDF_MAX_CONCURRENCY, 10);
  return Number.isInteger(value) && value > 0 ? value : 2;
}

async function acquireSlot() {
  if (activeJobs < maxConcurrency()) {
    activeJobs += 1;
    return;
  }
  await new Promise((resolve) => waiters.push(resolve));
  activeJobs += 1;
}

function releaseSlot() {
  activeJobs -= 1;
  const next = waiters.shift();
  if (next) next();
}

function getExecutablePath() {
  const platformCandidates = process.platform === "linux"
    ? [
      "/usr/bin/google-chrome",
      "/usr/bin/google-chrome-stable",
      "/usr/bin/chromium",
      "/usr/bin/chromium-browser",
    ]
    : [
      "C:\\Program Files\\Google\\Chrome\\Application\\chrome.exe",
      "C:\\Program Files (x86)\\Google\\Chrome\\Application\\chrome.exe",
    ];
  const candidates = [process.env.PUPPETEER_EXECUTABLE_PATH, ...platformCandidates]
    .filter(Boolean);
  const executablePath = candidates.find((candidate) => fs.existsSync(candidate));
  if (!executablePath) {
    throw new Error(
      `未找到 Chrome/Chromium，请配置 PUPPETEER_EXECUTABLE_PATH。已检查：${candidates.join(", ")}`
    );
  }
  return executablePath;
}

async function getBrowser() {
  if (!browserPromise) {
    browserPromise = puppeteer.launch({
      executablePath: getExecutablePath(),
      headless: true,
      args: ["--no-sandbox", "--disable-setuid-sandbox", "--disable-dev-shm-usage"],
    });
    const browser = await browserPromise;
    browser.on("disconnected", () => {
      browserPromise = undefined;
    });
  }
  return browserPromise;
}

function escapeHtml(value) {
  return String(value ?? "")
    .replace(/&/g, "&amp;")
    .replace(/</g, "&lt;")
    .replace(/>/g, "&gt;")
    .replace(/\"/g, "&quot;")
    .replace(/'/g, "&#39;");
}

function safeDataImage(value) {
  if (typeof value !== "string" || value.length > 1024 * 1024) return "";
  return /^data:image\/(png|jpeg|webp);base64,[a-z0-9+/=\s]+$/i.test(value)
    ? value
    : "";
}

function getUploadRoot() {
  // 与 upload.js 使用相同的共享上传目录，拒绝任意文件系统路径。
  return path.resolve(__dirname, "../../../upload-files");
}

function getImageMimeType(buffer, contentType = "") {
  const normalizedContentType = String(contentType).split(";", 1)[0].trim().toLowerCase();
  if (["image/png", "image/jpeg", "image/webp"].includes(normalizedContentType)) {
    return normalizedContentType;
  }
  if (buffer.length >= 8 && buffer.subarray(0, 8).equals(Buffer.from("89504e470d0a1a0a", "hex"))) return "image/png";
  if (buffer.length >= 3 && buffer.subarray(0, 3).equals(Buffer.from([0xff, 0xd8, 0xff]))) return "image/jpeg";
  if (buffer.length >= 12 && buffer.subarray(0, 4).toString() === "RIFF" && buffer.subarray(8, 12).toString() === "WEBP") return "image/webp";
  return "";
}

function getLocalSignaturePath(value) {
  if (typeof value !== "string") return "";
  let pathname = value;
  if (/^https?:\/\//i.test(value)) {
    try {
      pathname = new URL(value).pathname;
    } catch (_error) {
      return "";
    }
  }
  if (!pathname.startsWith("/upload-files/")) return "";

  const uploadRoot = getUploadRoot();
  let relativePath;
  try {
    relativePath = decodeURIComponent(pathname.slice("/upload-files/".length));
  } catch (_error) {
    return "";
  }
  const filePath = path.resolve(uploadRoot, relativePath);
  return filePath.startsWith(`${uploadRoot}${path.sep}`) ? filePath : "";
}

async function loadLocalSignatureDataImage(value) {
  const filePath = getLocalSignaturePath(value);
  if (!filePath) return "";
  const mimeType = signatureMimeTypes[path.extname(filePath).toLowerCase()];
  if (!mimeType) return "";
  try {
    const file = await fsp.readFile(filePath);
    if (file.length === 0 || file.length > MAX_SIGNATURE_IMAGE_BYTES) return "";
    return `data:${mimeType};base64,${file.toString("base64")}`;
  } catch (_error) {
    return "";
  }
}

async function downloadSignatureDataImage(value) {
  if (typeof value !== "string" || !/^https?:\/\//i.test(value)) return "";
  try {
    const url = new URL(value);
    if (url.protocol !== "http:" && url.protocol !== "https:") return "";
    const response = await axios.get(url.toString(), {
      responseType: "arraybuffer",
      timeout: SIGNATURE_DOWNLOAD_TIMEOUT_MS,
      maxContentLength: MAX_SIGNATURE_IMAGE_BYTES,
      maxBodyLength: MAX_SIGNATURE_IMAGE_BYTES,
      maxRedirects: 2,
      validateStatus: (status) => status >= 200 && status < 300,
    });
    const image = Buffer.from(response.data);
    if (image.length === 0 || image.length > MAX_SIGNATURE_IMAGE_BYTES) return "";
    const mimeType = getImageMimeType(image, response.headers["content-type"]);
    return mimeType ? `data:${mimeType};base64,${image.toString("base64")}` : "";
  } catch (_error) {
    return "";
  }
}

async function loadSignatureDataImage(value) {
  const embeddedImage = safeDataImage(value);
  if (embeddedImage) return embeddedImage;
  const localImage = await loadLocalSignatureDataImage(value);
  if (localImage) return localImage;
  return downloadSignatureDataImage(value);
}

function getAge(record) {
  if (Number.isFinite(Number(record.age)) && Number(record.age) >= 0) {
    return `${Number(record.age)}岁`;
  }
  const idCard = String(record.idCard || "");
  if (!/^\d{17}[\dXx]$/.test(idCard)) return "";
  const birth = dayjs(`${idCard.slice(6, 10)}-${idCard.slice(10, 12)}-${idCard.slice(12, 14)}`);
  const reference = dayjs(record.prescriptionEndTime || record.createTime);
  return birth.isValid() && reference.isValid() ? `${reference.diff(birth, "year")}岁` : "";
}

function getSex(record) {
  if (record.sex === "男" || record.sex === "女") return record.sex;
  const idCard = String(record.idCard || "");
  return /^\d{17}[\dXx]$/.test(idCard) ? (Number(idCard[16]) % 2 ? "男" : "女") : "";
}

function medicineUsage(drug) {
  return [
    drug.usageName,
    drug.frequencyName,
    drug.dosage ? `每次${drug.dosage}${drug.dosage_unit || ""}` : "",
  ].filter(Boolean).join(" ");
}

function signature(value, fallback) {
  const image = safeDataImage(value);
  return image
    ? `<img class="signature-image" src="${image}" alt="签名" />`
    : `<span>${escapeHtml(fallback)}</span>`;
}

function buildPrescriptionHtml(record, paperSize = "A5", signatureImages = {}) {
  const size = paperSize === "A4" ? "A4" : "A5";
  const diagnosis = Array.isArray(record.diagnosisList) ? record.diagnosisList : [];
  const drugs = Array.isArray(record.drugs) ? record.drugs : [];
  const prescriptionTime = dayjs(record.prescriptionEndTime || record.createTime);
  const diagnosisHtml = diagnosis.length
    ? diagnosis.map((item, index) => `<div>${index + 1}. ${escapeHtml(item.name)}</div>`).join("")
    : "<div>—</div>";
  const drugHtml = drugs.length
    ? drugs.map((drug, index) => `
      <section class="medicine-item">
        <div class="medicine-name">${index + 1}. ${escapeHtml(drug.drugName)} x ${escapeHtml(drug.quantity)} ${escapeHtml(drug.unit)}</div>
        <div class="medicine-detail">规格：${escapeHtml(drug.specification)}</div>
        <div class="medicine-detail">用法：${escapeHtml(medicineUsage(drug))}</div>
      </section>`).join("")
    : "<section class=\"medicine-item\">暂无药品</section>";

  return `<!doctype html>
<html lang="zh-CN"><head><meta charset="utf-8" />
<style>
  @page { size: ${size} portrait; margin: 6mm; }
  * { box-sizing: border-box; }
  html, body { margin: 0; padding: 0; color: #111; font-family: "Noto Sans CJK SC", "Noto Sans SC", SimSun, "Songti SC", serif; font-size: 12px; }
  body { -webkit-print-color-adjust: exact; print-color-adjust: exact; }
  .prescription { min-height: ${size === "A5" ? "198mm" : "285mm"}; display: flex; flex-direction: column; line-height: 1.5; }
  .header { position: relative; border-bottom: 1px solid #111; padding: 1px 0 5px; }
  .title { font-weight: 700; font-size: 16px; text-align: center; line-height: 1.75; }
  .rx-type { position: absolute; top: 0; right: 0; width: 38px; border: 1px solid #555; text-align: center; color: #555; line-height: 1.55; }
  .rx-number { margin-top: 4px; font-size: 12px; }
  .patient-info { padding-top: 5px; }
  .info-row { display: flex; padding: 2px 0; gap: 5px; }
  .info-cell { flex: 1; min-width: 0; overflow-wrap: anywhere; }
  .info-half { width: 50%; overflow-wrap: anywhere; }
  .diagnosis { margin-top: 5px; }
  .diagnosis-head { display: flex; justify-content: space-between; gap: 8px; }
  .diagnosis-list { padding-top: 2px; min-height: 18px; }
  .date { white-space: nowrap; color: #555; }
  .medicine { margin-top: 4px; }
  .rp { font-size: 16px; font-weight: 700; margin-bottom: 3px; }
  .medicine-item { break-inside: avoid; margin: 0 0 11px; padding-left: 2px; }
  .medicine-name { font-weight: 700; font-size: 13px; }
  .medicine-detail { color: #444; margin-top: 2px; }
  .footer { margin-top: auto; border-top: 1px dashed #999; padding-top: 6px; break-inside: avoid; }
  .signature-row, .action-row { display: flex; padding: 2px 0; }
  .signature-cell, .action-cell { width: 33.333%; min-height: 20px; }
  .signature-image { display: inline-block; width: 82px; height: 28px; object-fit: contain; vertical-align: middle; }
  .notice { margin-top: 4px; color: #b33; font-size: 10px; line-height: 1.4; }
  .blank-line { display: inline-block; width: 35px; border-bottom: 1px solid currentColor; }
  @media print { .medicine-item, .footer { page-break-inside: avoid; } }
</style></head><body>
  <main class="prescription">
    <header class="header">
      <div class="rx-type">普通<br>处方</div>
      <div class="title">海宁康华医院互联网医院<br>处方笺</div>
      <div class="rx-number">NO:${escapeHtml(record.medOrgOrderNo || record._id)}</div>
    </header>
    <section class="patient-info">
      <div class="info-row"><div class="info-cell">姓名：${escapeHtml(record.name)}</div><div class="info-cell">性别：${escapeHtml(getSex(record))}</div><div class="info-cell">费别：${record.feeType === "YB" ? "医保" : "自费"}</div><div class="info-cell">年龄：${escapeHtml(getAge(record))}</div></div>
      <div class="info-row"><div class="info-half">门诊病历号：${escapeHtml(record.blhno)}</div><div class="info-half">科别：${escapeHtml(record.deptName)}</div></div>
      <div class="info-row"><div class="info-cell">地址：${escapeHtml(record.address)}</div></div>
      <div class="info-row"><div class="info-cell">电话号：${escapeHtml(record.mobile)}</div></div>
    </section>
    <section class="diagnosis"><div class="diagnosis-head"><div>诊断：</div><div class="date">开方日期：${prescriptionTime.isValid() ? prescriptionTime.format("YYYY-MM-DD HH:mm") : ""}</div></div><div class="diagnosis-list">${diagnosisHtml}</div></section>
    <section class="medicine"><div class="rp">Rp</div>${drugHtml}</section>
    <footer class="footer"><div class="signature-row"><div class="signature-cell">医生：${signature(signatureImages.doctor || record.doctorSignImg, record.doctorName)}</div><div class="signature-cell">审方药师：${signature(signatureImages.pharmacist || record.pharmacistSignImg, record.pharmacist)}</div></div><div class="action-row"><div class="action-cell">调配：</div><div class="action-cell">核对：</div><div class="action-cell">发药：</div></div><div class="notice">注意：请勿丢失，处方当日有效，因特殊情况，该处方有效为<span class="blank-line"></span>天（签名：<span class="blank-line"></span>）</div></footer>
  </main>
</body></html>`;
}

async function generatePrescriptionPdf(record, options = {}) {
  await acquireSlot();
  let page;
  try {
    const browser = await getBrowser();
    page = await browser.newPage();
    const [doctor, pharmacist] = await Promise.all([
      loadSignatureDataImage(record.doctorSignImg),
      loadSignatureDataImage(record.pharmacistSignImg),
    ]);
    await page.setContent(
      buildPrescriptionHtml(record, options.paperSize, { doctor, pharmacist }),
      { waitUntil: "load" }
    );
    await page.evaluate(() => document.fonts && document.fonts.ready);
    return Buffer.from(await page.pdf({
      format: options.paperSize === "A4" ? "A4" : "A5",
      preferCSSPageSize: true,
      printBackground: true,
      margin: { top: 0, right: 0, bottom: 0, left: 0 },
    }));
  } finally {
    if (page) await page.close().catch(() => {});
    releaseSlot();
  }
}

async function createPrescriptionPdf(db, id, options) {
  if (typeof id !== "string" || !ObjectId.isValid(id)) {
    const error = new Error("处方 id 格式错误");
    error.statusCode = 400;
    throw error;
  }
  const record = await db.collection("diagnostic-record").findOne({ _id: new ObjectId(id) });
  if (!record) {
    const error = new Error("处方不存在");
    error.statusCode = 404;
    throw error;
  }
  return generatePrescriptionPdf(decryptDiagnosticRecordFields(record), options);
}

function getPdfPath(id, paperSize) {
  const size = paperSize === "A4" ? "A4" : "A5";
  // MongoDB ObjectId 的前四字节是创建时间戳；用 UTC 日期分目录，避免因服务器时区不同写入不同路径。
  const createdAt = new ObjectId(id).getTimestamp();
  const year = String(createdAt.getUTCFullYear());
  const month = String(createdAt.getUTCMonth() + 1).padStart(2, "0");
  const day = String(createdAt.getUTCDate()).padStart(2, "0");
  return path.join(
    getPdfRoot(),
    year,
    month,
    day,
    `${id}-${size}-${PDF_TEMPLATE_VERSION}.pdf`
  );
}

async function getOrCreatePrescriptionPdf(db, id, options = {}) {
  if (typeof id !== "string" || !ObjectId.isValid(id)) {
    const error = new Error("处方 id 格式错误");
    error.statusCode = 400;
    throw error;
  }
  const paperSize = options.paperSize === "A4" ? "A4" : "A5";
  const pdfPath = getPdfPath(id, paperSize);
  try {
    await fsp.access(pdfPath, fs.constants.R_OK);
    return { pdfPath, cached: true };
  } catch (_error) {
    // 文件尚未生成，继续生成；不要将 access 错误泄漏给客户端。
  }

  const key = `${id}:${paperSize}`;
  if (!cachedPdfJobs.has(key)) {
    cachedPdfJobs.set(key, (async () => {
      await initializeStorage();
      await fsp.mkdir(path.dirname(pdfPath), { recursive: true });
      try {
        await fsp.access(pdfPath, fs.constants.R_OK);
        return;
      } catch (_error) {
        // 仍不存在，当前请求负责生成。
      }
      const record = await db.collection("diagnostic-record").findOne({ _id: new ObjectId(id) });
      if (!record) {
        const error = new Error("处方不存在");
        error.statusCode = 404;
        throw error;
      }
      const pdf = await generatePrescriptionPdf(decryptDiagnosticRecordFields(record), { paperSize });
      const temporaryPath = `${pdfPath}.${crypto.randomUUID()}.tmp`;
      try {
        await fsp.writeFile(temporaryPath, pdf, { flag: "wx" });
        await fsp.rename(temporaryPath, pdfPath);
      } catch (error) {
        await fsp.unlink(temporaryPath).catch(() => {});
        throw error;
      }
    })().finally(() => cachedPdfJobs.delete(key)));
  }
  await cachedPdfJobs.get(key);
  return { pdfPath, cached: false };
}

async function closeBrowser() {
  if (!browserPromise) return;
  const browser = await browserPromise;
  browserPromise = undefined;
  await browser.close();
}

module.exports = {
  buildPrescriptionHtml,
  createPrescriptionPdf,
  generatePrescriptionPdf,
  getOrCreatePrescriptionPdf,
  initializeStorage,
  loadSignatureDataImage,
  loadLocalSignatureDataImage,
  downloadSignatureDataImage,
  getPdfPath,
  closeBrowser,
};