import assert from "node:assert/strict";
import { mkdtemp, mkdir, writeFile, readFile, readdir, rm } from "node:fs/promises";
import { tmpdir } from "node:os";
import path from "node:path";
import test from "node:test";

import { safeReplaceDir } from "../lib/safe-replace-dir.mjs";

// ── Happy path ────────────────────────────────────────────────────────────

test("safeReplaceDir copies source content into the target", async () => {
  const dir = await mkdtemp(path.join(tmpdir(), "safe-replace-copy-"));
  try {
    const safetyRoot = path.join(dir, "root");
    const source = path.join(dir, "source");
    const target = path.join(safetyRoot, "target");

    await mkdir(source, { recursive: true });
    await writeFile(path.join(source, "file.txt"), "hello");
    await mkdir(safetyRoot, { recursive: true });

    await safeReplaceDir(source, target, safetyRoot);

    const content = await readFile(path.join(target, "file.txt"), "utf8");
    assert.equal(content, "hello");
  } finally {
    await rm(dir, { recursive: true, force: true });
  }
});

test("safeReplaceDir removes existing content before replacing", async () => {
  const dir = await mkdtemp(path.join(tmpdir(), "safe-replace-stale-"));
  try {
    const safetyRoot = path.join(dir, "root");
    const source = path.join(dir, "source");
    const target = path.join(safetyRoot, "target");

    await mkdir(target, { recursive: true });
    await writeFile(path.join(target, "old.txt"), "stale");
    await mkdir(source, { recursive: true });
    await writeFile(path.join(source, "new.txt"), "fresh");

    await safeReplaceDir(source, target, safetyRoot);

    const files = await readdir(target);
    assert.deepEqual(files.sort(), ["new.txt"]);
  } finally {
    await rm(dir, { recursive: true, force: true });
  }
});

test("safeReplaceDir creates target parent directories if they do not exist", async () => {
  const dir = await mkdtemp(path.join(tmpdir(), "safe-replace-mkdir-"));
  try {
    const safetyRoot = path.join(dir, "root");
    const source = path.join(dir, "source");
    const target = path.join(safetyRoot, "nested", "target");

    await mkdir(source, { recursive: true });
    await writeFile(path.join(source, "data.txt"), "data");
    await mkdir(safetyRoot, { recursive: true });
    // nested parent does NOT exist yet

    await safeReplaceDir(source, target, safetyRoot);

    const content = await readFile(path.join(target, "data.txt"), "utf8");
    assert.equal(content, "data");
  } finally {
    await rm(dir, { recursive: true, force: true });
  }
});

test("safeReplaceDir creates deeply nested parent directories (2+ levels missing)", async () => {
  const dir = await mkdtemp(path.join(tmpdir(), "safe-replace-deep-"));
  try {
    const safetyRoot = path.join(dir, "root");
    const source = path.join(dir, "source");
    // two parent levels (a/b) do NOT exist under safetyRoot
    const target = path.join(safetyRoot, "a", "b", "target");

    await mkdir(source, { recursive: true });
    await writeFile(path.join(source, "deep.txt"), "deep");
    await mkdir(safetyRoot, { recursive: true });
    // a/ and a/b/ intentionally NOT created

    await safeReplaceDir(source, target, safetyRoot);

    const content = await readFile(path.join(target, "deep.txt"), "utf8");
    assert.equal(content, "deep");
  } finally {
    await rm(dir, { recursive: true, force: true });
  }
});

// ── Safety checks ─────────────────────────────────────────────────────────

test("safeReplaceDir refuses when target is outside the safety root", async () => {
  const dir = await mkdtemp(path.join(tmpdir(), "safe-replace-outside-"));
  try {
    const safetyRoot = path.join(dir, "root");
    const source = path.join(dir, "source");
    const outside = path.join(dir, "outside");

    await mkdir(source, { recursive: true });
    await mkdir(safetyRoot, { recursive: true });

    await assert.rejects(
      () => safeReplaceDir(source, outside, safetyRoot),
      /outside safety root/,
    );
  } finally {
    await rm(dir, { recursive: true, force: true });
  }
});

test("safeReplaceDir refuses when target equals the safety root", async () => {
  const dir = await mkdtemp(path.join(tmpdir(), "safe-replace-same-"));
  try {
    const safetyRoot = path.join(dir, "root");
    const source = path.join(dir, "source");

    await mkdir(source, { recursive: true });
    await mkdir(safetyRoot, { recursive: true });

    await assert.rejects(
      () => safeReplaceDir(source, safetyRoot, safetyRoot),
      /outside safety root/,
    );
  } finally {
    await rm(dir, { recursive: true, force: true });
  }
});

test("safeReplaceDir refuses an empty target string", async () => {
  await assert.rejects(
    () => safeReplaceDir("/any", "", "/root"),
    /unsafe target/,
  );
});