import test from 'node:test';
import assert from 'node:assert/strict';
import fs from 'node:fs';
import os from 'node:os';
import path from 'node:path';
import { readJSON, writeJSON } from '../src/atomicJson.js';

function tmpFile(name) {
    const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'atomicjson-'));
    return path.join(dir, name);
}

test('writeJSON persists and readJSON reads it back', async () => {
    const file = tmpFile('a.json');
    await writeJSON(file, { hello: 'world', n: 1 });
    assert.deepEqual(readJSON(file), { hello: 'world', n: 1 });
});

test('concurrent writeJSON calls all land, none corrupt the target', async () => {
    const file = tmpFile('b.json');
    const writers = [];
    for (let i = 0; i < 25; i++) {
        writers.push(writeJSON(file, { i, at: Date.now() }));
    }
    await Promise.all(writers);
    // File must be valid JSON with one of the written objects.
    const parsed = readJSON(file);
    assert.equal(typeof parsed.i, 'number');
    assert.ok(parsed.i >= 0 && parsed.i < 25);
});

test('writeJSON removes tmp files on rename failure', async () => {
    const file = tmpFile('c.json');
    await writeJSON(file, { ok: true });

    // Force a rename failure by pointing at a path whose parent does not exist.
    const bad = path.join(file, 'nested', 'not', 'there.json');
    await assert.rejects(writeJSON(bad, { x: 1 }));

    // No tmp files should be left in the parent dir of `file`.
    const dir = path.dirname(file);
    const stray = fs.readdirSync(dir).filter(n => n.endsWith('.tmp'));
    assert.deepEqual(stray, []);
});

test('writes to different paths do not block each other', async () => {
    const f1 = tmpFile('d.json');
    const f2 = tmpFile('e.json');
    await Promise.all([writeJSON(f1, { a: 1 }), writeJSON(f2, { b: 2 })]);
    assert.deepEqual(readJSON(f1), { a: 1 });
    assert.deepEqual(readJSON(f2), { b: 2 });
});