import { spawn } from "node:child_process";
import fs from "node:fs/promises";
import path from "node:path";

const workingDirectory = process.cwd();
const vitestCliPath = path.join(workingDirectory, "node_modules", "vitest", "vitest.mjs");
const unitTestsRoot = path.join(workingDirectory, "tests", "unit");
const args = parseArgs(process.argv.slice(2));
const batchSize = normalizePositiveInt(args.batchSize ?? process.env.VITEST_BATCH_SIZE, 5);

let activeChild = null;
let isShuttingDown = false;

for (const signal of ["SIGINT", "SIGTERM"]) {
  process.on(signal, () => {
    void shutdown(signal).finally(() => {
      process.exit(130);
    });
  });
}

function parseArgs(rawArgs) {
  const parsed = {
    help: false,
    batchSize: null,
    specFilters: [],
    forwardedArgs: [],
  };

  for (let index = 0; index < rawArgs.length; index += 1) {
    const value = rawArgs[index];

    if (value === "--") {
      parsed.forwardedArgs.push(...rawArgs.slice(index + 1));
      break;
    }

    if (value === "--help" || value === "-h") {
      parsed.help = true;
      continue;
    }

    if (value === "--batch-size" && rawArgs[index + 1]) {
      parsed.batchSize = rawArgs[index + 1];
      index += 1;
      continue;
    }

    if (value.startsWith("--batch-size=")) {
      parsed.batchSize = value.slice("--batch-size=".length);
      continue;
    }

    if (value.startsWith("-")) {
      parsed.forwardedArgs.push(...rawArgs.slice(index));
      break;
    }

    parsed.specFilters.push(value);
  }

  return parsed;
}

function normalizePositiveInt(value, fallback) {
  const parsed = Number(value);
  return Number.isFinite(parsed) && parsed > 0 ? parsed : fallback;
}

function normalizePathSegments(value) {
  return value.replace(/\\/g, "/");
}

function printUsage() {
  console.log(`
Vitest unit batch runner

Usage:
  node scripts/run-vitest-unit-batches.mjs [spec-filter ...] [options] [-- <vitest args>]

Options:
  --batch-size <n>   Spec files per batch. Default: 5
  -h, --help         Show help

Examples:
  npm run test:unit
  npm run test:unit -- tests/unit/select-vehicle-form-pos.spec.js
  npm run test:unit -- tests/unit/select-vehicle-form-pos.spec.js -- --reporter=verbose
`);
}

async function collectSpecFiles(targetDirectory) {
  const directoryEntries = await fs.readdir(targetDirectory, { withFileTypes: true });
  const files = [];

  for (const entry of directoryEntries) {
    const absolutePath = path.join(targetDirectory, entry.name);

    if (entry.isDirectory()) {
      files.push(...(await collectSpecFiles(absolutePath)));
      continue;
    }

    if (entry.isFile() && entry.name.endsWith(".spec.js")) {
      files.push(absolutePath);
    }
  }

  return files.sort((left, right) => left.localeCompare(right));
}

function matchesFilter(relativePath, rawFilter) {
  const normalizedRelativePath = normalizePathSegments(relativePath);
  const normalizedFilter = normalizePathSegments(rawFilter.trim());

  if (!normalizedFilter) {
    return false;
  }

  return (
    normalizedRelativePath === normalizedFilter ||
    normalizedRelativePath.endsWith(normalizedFilter) ||
    normalizedRelativePath.includes(normalizedFilter)
  );
}

function applyFilters(files, specFilters) {
  if (specFilters.length === 0) {
    return files;
  }

  return files.filter((absolutePath) => {
    const relativePath = path.relative(workingDirectory, absolutePath);
    return specFilters.some((filter) => matchesFilter(relativePath, filter));
  });
}

function chunkFiles(files, size) {
  const chunks = [];

  for (let index = 0; index < files.length; index += size) {
    chunks.push({
      batch: Math.floor(index / size) + 1,
      files: files.slice(index, index + size),
    });
  }

  return chunks;
}

function formatDuration(durationMs) {
  return `${(durationMs / 1000).toFixed(1)}s`;
}

function hasForwardedArg(name) {
  return args.forwardedArgs.some((value) => value === name || value.startsWith(`${name}=`));
}

async function runBatch(chunk, totalBatches) {
  console.log(`[vitest-batch] Running batch ${chunk.batch}/${totalBatches} with ${chunk.files.length} spec file(s).`);

  const startedAt = Date.now();
  const enforcedArgs = [];

  if (!hasForwardedArg("--maxWorkers")) {
    enforcedArgs.push("--maxWorkers=1");
  }

  if (!hasForwardedArg("--fileParallelism") && !hasForwardedArg("--no-file-parallelism")) {
    enforcedArgs.push("--no-file-parallelism");
  }

  return new Promise((resolve) => {
    activeChild = spawn(
      process.execPath,
      [vitestCliPath, "run", ...chunk.files, ...enforcedArgs, ...args.forwardedArgs],
      {
        cwd: workingDirectory,
        env: process.env,
        stdio: "inherit",
        windowsHide: true,
      }
    );

    activeChild.on("close", (code) => {
      activeChild = null;
      resolve({
        batch: chunk.batch,
        files: chunk.files.length,
        code: code ?? 1,
        durationMs: Date.now() - startedAt,
      });
    });
  });
}

function printSummary(results, totalFiles) {
  console.log("\nVitest batch summary");
  console.log(`Total spec files: ${totalFiles}`);
  console.log("batch\tstatus\tfiles\tduration");

  for (const result of results) {
    const status = result.code === 0 ? "passed" : "failed";
    console.log(`${result.batch}\t${status}\t${result.files}\t${formatDuration(result.durationMs)}`);
  }
}

async function shutdown(signal) {
  if (isShuttingDown) {
    return;
  }

  isShuttingDown = true;
  console.error(`Received ${signal}. Stopping active Vitest batch...`);

  if (activeChild?.pid) {
    if (process.platform === "win32") {
      spawn("taskkill", ["/PID", String(activeChild.pid), "/T", "/F"], {
        stdio: "ignore",
        windowsHide: true,
      });
    } else {
      activeChild.kill("SIGTERM");
    }
  }
}

async function main() {
  if (args.help) {
    printUsage();
    return;
  }

  await fs.access(vitestCliPath);

  const discoveredFiles = await collectSpecFiles(unitTestsRoot);
  const selectedFiles = applyFilters(discoveredFiles, args.specFilters);

  if (selectedFiles.length === 0) {
    throw new Error("No unit spec files matched the provided filters.");
  }

  const chunks = chunkFiles(selectedFiles, batchSize);
  console.log(
    `Running ${selectedFiles.length} unit spec file(s) in ${chunks.length} batch(es) at ${batchSize} file(s) per batch.`
  );

  const results = [];

  for (const chunk of chunks) {
    results.push(await runBatch(chunk, chunks.length));
  }

  printSummary(results, selectedFiles.length);

  const failedBatches = results.filter((result) => result.code !== 0);
  if (failedBatches.length > 0) {
    throw new Error(`Vitest batches failed: ${failedBatches.map((result) => result.batch).join(", ")}`);
  }
}

await main().catch((error) => {
  console.error(error instanceof Error ? error.message : error);
  process.exitCode = 1;
});