"use strict";

// Swapoff safety rule of the fixed remote swap helper, run locally with a fake /proc (no swap is touched).
const test = require("node:test");
const assert = require("node:assert/strict");
const fs = require("node:fs");
const os = require("node:os");
const path = require("node:path");
const { spawnSync } = require("node:child_process");

const SCRIPT = path.join(__dirname, "../src/main/system/remoteSwap.sh");
const MiB = 1024;
// The helper is a POSIX shell script; Windows hosts have no /bin/sh.
const skip = process.platform === "win32" ? "POSIX sh is not available on Windows." : false;

function check({ totalMiB, availableMiB, areas }) {
  const proc = fs.mkdtempSync(path.join(os.tmpdir(), "chj-swap-proc-"));
  try {
    fs.writeFileSync(path.join(proc, "meminfo"), `MemTotal: ${totalMiB * MiB} kB\nMemAvailable: ${availableMiB * MiB} kB\n`);
    fs.writeFileSync(path.join(proc, "swaps"), "Filename\tType\tSize\tUsed\tPriority\n" + areas.map(([name, sizeMiB, usedMiB]) => `${name}\tfile\t${sizeMiB * MiB}\t${usedMiB * MiB}\t-2`).join("\n") + "\n");
    const result = spawnSync("sh", [SCRIPT, "safety-check", areas[0][0]], { encoding: "utf8", env: { ...process.env, CHJ_SWAP_TEST_PROC: proc } });
    return result.stdout.includes("safe\n") ? "safe" : (result.stdout.match(/CHJ_ERR=(\w+)/) || [])[1];
  } finally { fs.rmSync(proc, { recursive: true, force: true }); }
}

test("swapoff is refused when the used swap cannot fit into RAM minus the reserve", { skip }, () => {
  assert.equal(check({ totalMiB: 4096, availableMiB: 1024, areas: [["/swapfile", 2048, 900]] }), "SWAPOFF_UNSAFE");
  assert.equal(check({ totalMiB: 4096, availableMiB: 1024, areas: [["/swapfile", 2048, 400]] }), "safe");
});

test("free space in other active swap areas counts towards the room", { skip }, () => {
  assert.equal(check({ totalMiB: 4096, availableMiB: 1024, areas: [["/swapfile", 2048, 900], ["/swap/b", 1024, 0]] }), "safe");
});

test("an unused swap area can always be deactivated, even on a small server", { skip }, () => {
  assert.equal(check({ totalMiB: 468, availableMiB: 408, areas: [["/swapfile", 128, 0]] }), "safe");
});

test("the reserve never exceeds a quarter of RAM on small servers", { skip }, () => {
  // 468 MiB RAM: reserve 117 MiB instead of 512 MiB.
  assert.equal(check({ totalMiB: 468, availableMiB: 400, areas: [["/swapfile", 256, 200]] }), "safe");
  assert.equal(check({ totalMiB: 468, availableMiB: 300, areas: [["/swapfile", 256, 200]] }), "SWAPOFF_UNSAFE");
});

test("the test-only operation is unavailable without the test /proc override", { skip }, () => {
  const result = spawnSync("sh", [SCRIPT, "safety-check", "/swapfile"], { encoding: "utf8", env: { PATH: process.env.PATH } });
  assert.match(result.stdout, /CHJ_ERR=ACTION_INVALID/);
});