import { createServer } from "node:http";
import { createHash } from "node:crypto";
import { readFileSync, mkdtempSync, rmSync } from "node:fs";
import { tmpdir } from "node:os";
import { join } from "node:path";
import { academicStartYear, todayIso } from "../../shared/weeks.js";

// A stand-in for the university's Nextcloud that serves the fixtures as a small catalog, and the
// real API server started against it with a temporary data folder.
export const SHARE = "/public.php/dav/files/no5zKbMrns6j5jQ/";
export const fixture = (name) => readFileSync(new URL(`../fixtures/${name}`, import.meta.url));
const year = academicStartYear(todayIso());
const YEAR = `${year}-${year + 1}`;
const FOLDER = `${SHARE}${YEAR}/Финансово-экономический факультет/Дневная форма/`;
const MODIFIED = "Mon, 14 Sep 2026 13:05:15 GMT";
const files = {
  [`${SHARE}Расписание белых и зеленых недель.docx`]: fixture("weeks.docx"),
  [`${SHARE}Расписание звонков.docx`]: fixture("bells.docx"),
  [`${FOLDER}23-ЛГ_23-БА.docx`]: fixture("fef-23-ba.docx"),
  [`${FOLDER}24-ИТ.docx`]: fixture("fit-daily.docx"),
  // The university fails on one document and is too slow on another.
  [`${FOLDER}Сломанный.docx`]: 500,
  [`${FOLDER}Медленный.docx`]: "slow",
};
const folders = [SHARE, `${SHARE}${YEAR}/`, `${SHARE}${YEAR}/Финансово-экономический факультет/`, FOLDER];
// Dates of files changed during a test; the others keep MODIFIED.
const dates = {};
const dateOf = (path) => dates[path] || MODIFIED;
// As in Nextcloud, a folder's ETag changes whenever anything below it does.
const etagOf = (folder) =>
  `"${createHash("sha1").update(Object.keys(files).filter((f) => f.startsWith(folder)).sort().map((f) => f + dateOf(f)).join("|")).digest("hex").slice(0, 13)}"`;

const encode = (path) => path.split("/").map(encodeURIComponent).join("/");
const listing = (folder) => {
  const children = [...folders.filter((f) => f !== folder && f.startsWith(folder) && !f.slice(folder.length, -1).includes("/")),
    ...Object.keys(files).filter((f) => f.startsWith(folder) && !f.slice(folder.length).includes("/"))];
  const entry = (path) => {
    const folder = path.endsWith("/");
    const size = Buffer.isBuffer(files[path]) ? files[path].length : 1000;
    return `<d:response><d:href>${encode(path)}</d:href><d:propstat><d:prop>${
      folder ? "<d:resourcetype><d:collection/></d:resourcetype>" : `<d:resourcetype/><d:getcontentlength>${size}</d:getcontentlength>`
    }<d:getlastmodified>${dateOf(path)}</d:getlastmodified><d:getetag>${folder ? etagOf(path) : `"${dateOf(path)}"`}</d:getetag></d:prop><d:status>HTTP/1.1 200 OK</d:status></d:propstat></d:response>`;
  };
  return `<?xml version="1.0"?><d:multistatus xmlns:d="DAV:">${[folder, ...children].map(entry).join("")}</d:multistatus>`;
};

/**
 * Starts the stand-in and the API server; `env` adds settings such as lower limits.
 * Returns the server's base URL, request statistics of the stand-in, `catalog` to change the
 * stand-in's documents during a test, and `stop()`.
 */
export async function startApi(env = {}) {
  const stats = { requests: 0, connections: 0, listings: 0 };
  let down = false;
  const source = createServer((req, res) => {
    stats.requests++;
    if (req.method === "PROPFIND") stats.listings++;
    if (down) return res.writeHead(503).end();
    const path = decodeURIComponent(req.url);
    if (req.method === "PROPFIND" && folders.includes(path)) {
      res.writeHead(207, { "Content-Type": "application/xml" });
      return res.end(listing(path));
    }
    const body = files[path];
    if (body === "slow") return setTimeout(() => res.end("late"), 2000);
    if (typeof body === "number" || !body) return res.writeHead(body || 404).end();
    res.end(body);
  });
  source.on("connection", () => stats.connections++);
  await new Promise((resolve) => source.listen(0, "127.0.0.1", resolve));
  const data = mkdtempSync(join(tmpdir(), "psu-api-"));
  Object.assign(process.env, {
    PSU_SOURCE_ORIGIN: `http://127.0.0.1:${source.address().port}`,
    PSU_DATA_DIR: data,
    PSU_SOURCE_TIMEOUT_MS: "500",
    // The request log would drown the test output; the metrics test turns it on.
    PSU_REQUEST_LOG: "off",
    ...env,
  });
  const { app } = await import("../../server/index.js");
  const server = app.listen(0, "127.0.0.1");
  await new Promise((resolve) => server.on("listening", resolve));
  let tick = 0;
  return {
    base: `http://127.0.0.1:${server.address().port}`,
    stats,
    catalog: {
      /** Publishes a document in the faculty folder (or republishes it) with a new date. */
      put(name, body) {
        const path = FOLDER + name;
        files[path] = body;
        dates[path] = new Date(Date.parse(MODIFIED) + ++tick * 60_000).toUTCString();
      },
      /** The university stops (true) or starts again (false) answering. */
      down(on) {
        down = on;
      },
    },
    stop() {
      server.close();
      server.closeAllConnections();
      source.closeAllConnections();
      source.close();
      rmSync(data, { recursive: true, force: true });
    },
  };
}