/**
 * @file Which npm-distributed AI tools are npm-MANAGED (their binary resolves
 * under `npm prefix -g`, so an npm update actually replaces what runs) and
 * whether a newer version is published. A tool installed another way — Codex's
 * standalone build, say — is never offered an npm update: it would install a
 * second copy that the PATH order shadows. npm is the LOGIN SHELL's (its PATH
 * first), not the pinned Node's beside the server. Cached for a day.
 * A system-wide Node (`/usr/local`, root's) leaves npm's global prefix
 * unwritable to the dashboard's account, so there a global install goes to the
 * account's own `~/.local` (`--prefix`, bin in `~/.local/bin`) instead, and a
 * tool found under `~/.local/lib/node_modules` counts as npm-managed there.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const fs = require("node:fs");
const os = require("node:os");
const path = require("node:path");
const { execFile } = require("node:child_process");
const aiTools = require("./ai-tools");
const { shellPath } = require("./shell-path");
const { compareVersions } = require("./update-check");

const CACHE_MS = 24 * 60 * 60 * 1000;
const TIMEOUT_MS = 5000;

let cache = null; // { at, data }

const defaultExec = (file, args, opts) =>
  new Promise((resolve, reject) =>
    execFile(file, args, { ...opts, encoding: "utf8" }, (err, stdout) =>
      err ? reject(err) : resolve({ stdout })
    )
  );
let exec = defaultExec;
let userPrefixImpl = () =>
  process.platform === "win32" ? null : path.join(os.homedir(), ".local");

/** The PATH a job runs with: the shell's own order first, then the server's. */
const jobPath = () => [shellPath(), process.env.PATH].filter(Boolean).join(path.delimiter);

/** The login shell's npm, else the server's; null when there is none. */
function npmBin() {
  const sp = shellPath();
  return (sp && aiTools.which("npm", sp)) || aiTools.which("npm");
}

const run = (bin, args) => {
  const { file, shell } = aiTools.spawnTarget(bin);
  return exec(file, args, { shell, timeout: TIMEOUT_MS, env: { ...process.env, PATH: jobPath() } });
};

const parseVersion = (out) => (String(out || "").match(/\d+\.\d+\.\d+/) || [null])[0];

async function npmPrefix(npm) {
  try {
    return (await run(npm, ["prefix", "-g"])).stdout.trim() || null;
  } catch {
    return null;
  }
}

function under(prefix, file) {
  try {
    const real = fs.realpathSync(file);
    const base = fs.realpathSync(prefix);
    return real.startsWith(base + path.sep);
  } catch {
    return false;
  }
}

/** The account's own npm prefix (`~/.local`), or null where npm has none (Windows). */
const userPrefix = () => userPrefixImpl();

/** Whether npm can write `dir` — or, when it is not there yet, its nearest existing parent. */
function writable(dir) {
  let d = dir;
  for (;;) {
    try {
      fs.accessSync(d, fs.constants.W_OK);
      return true;
    } catch (err) {
      if (err.code !== "ENOENT") return false;
    }
    const up = path.dirname(d);
    if (up === d) return false;
    d = up;
  }
}

/** Whether a global install into `prefix` would succeed: its package and bin folders. */
const prefixWritable = (prefix) =>
  process.platform === "win32"
    ? writable(prefix)
    : writable(path.join(prefix, "lib", "node_modules")) && writable(path.join(prefix, "bin"));

/**
 * The `--prefix` a global install needs: none while npm's own global prefix is
 * writable, else the account's `~/.local` (a system-wide Node: EACCES otherwise).
 */
async function installPrefixArgs() {
  const npm = npmBin();
  const prefix = npm ? await npmPrefix(npm) : null;
  const up = userPrefix();
  if (!prefix || !up || prefixWritable(prefix)) return [];
  return ["--prefix", up];
}

/**
 * Which npm prefix holds tool `id`: `"global"` (npm's own), `"user"` (the
 * account's `~/.local/lib/node_modules`), or null — not installed, or not by npm.
 */
async function managedBy(id, prefix) {
  const d = aiTools.detect(id);
  if (!d.installed) return null;
  if (prefix === undefined) {
    const npm = npmBin();
    prefix = npm ? await npmPrefix(npm) : null;
  }
  if (prefix && under(prefix, d.path)) return "global";
  const up = userPrefix();
  if (up && under(path.join(up, "lib", "node_modules"), d.path)) return "user";
  return null;
}

/** Whether tool `id` is installed AND lives under npm's global or the account's prefix. */
const npmManaged = async (id, prefix) => !!(await managedBy(id, prefix));

async function compute() {
  const npm = npmBin();
  const prefix = npm ? await npmPrefix(npm) : null;
  const tools = aiTools
    .list()
    .filter((t) => t.update?.kind === "npm" && aiTools.detect(t.id).installed);
  const rows = await Promise.all(
    tools.map(async (t) => {
      const managed = await npmManaged(t.id, prefix);
      if (!managed) {
        return [t.id, { npmManaged: false, installed: null, latest: null, updateAvailable: false }];
      }
      const [inst, latest] = await Promise.all([
        run(aiTools.detect(t.id).path, ["--version"]).then(
          (r) => parseVersion(r.stdout),
          () => null
        ),
        run(npm, ["view", t.install.package, "version"]).then(
          (r) => parseVersion(r.stdout),
          () => null
        ),
      ]);
      const updateAvailable = !!(inst && latest && compareVersions(latest, inst) > 0);
      return [t.id, { npmManaged: true, installed: inst, latest, updateAvailable }];
    })
  );
  return Object.fromEntries(rows);
}

/** `{[id]: {npmManaged, installed, latest, updateAvailable}}`, cached a day. */
async function versions({ fresh = false } = {}) {
  if (!fresh && cache && Date.now() - cache.at < CACHE_MS) return cache.data;
  const data = await compute();
  cache = { at: Date.now(), data };
  return data;
}

function invalidate() {
  cache = null;
}

/** Test seam: the account's npm prefix (a path, or null for none); undefined restores it. */
function __setUserPrefix(p) {
  userPrefixImpl =
    p === undefined
      ? () => (process.platform === "win32" ? null : path.join(os.homedir(), ".local"))
      : () => p;
}

/** Test seam: `fn(file, args, opts) → Promise<{stdout}>`, or null for execFile. */
function __setExec(fn) {
  exec = fn || defaultExec;
  cache = null;
}

module.exports = {
  versions,
  invalidate,
  npmManaged,
  managedBy,
  installPrefixArgs,
  userPrefix,
  npmBin,
  jobPath,
  parseVersion,
  __setExec,
  __setUserPrefix,
};