// npm run build - the only writer of dist/.
//
//   node scripts/build.mjs [--out <dir>]      <dir> defaults to dist/ in the package
//
// Two compiler runs over src/: CommonJS with its declarations (cjs/, types/), then ES modules with theirs (esm/).
// TypeScript reads a .d.ts as CommonJS or as an ES module by the package.json above it, so each build needs its own
// set: the one in types/ would tell an ES module consumer that a default import works.
//
// Both runs write to a staging directory that replaces the three directories only after both passed, so a failed
// build leaves the tracked dist/ as it was. Files of sources that no longer exist go with the old directories.
import { spawnSync } from "node:child_process";
import { mkdirSync, renameSync, rmSync, writeFileSync } from "node:fs";
import { createRequire } from "node:module";
import { basename, dirname, join, resolve } from "node:path";
import { fileURLToPath } from "node:url";

const USAGE = "usage: node scripts/build.mjs [--out <dir>]";
const root = resolve(dirname(fileURLToPath(import.meta.url)), "..");

function outputDirectory(args) {
  if (args.length === 0) return join(root, "dist");
  const [flag, dir, ...rest] = args;
  // A misspelt --out must not fall back to the default and replace the tracked dist/
  if (flag !== "--out") throw new Error(`unknown argument ${flag}; ${USAGE}`);
  if (!dir) throw new Error(`--out needs a directory; ${USAGE}`);
  if (rest.length > 0) throw new Error(`unknown argument ${rest[0]}; ${USAGE}`);
  return resolve(dir);
}

function compiler() {
  try {
    return createRequire(import.meta.url).resolve("typescript/bin/tsc");
  } catch (err) {
    if (err.code !== "MODULE_NOT_FOUND") throw err;
    throw new Error("typescript is not installed: run npm install (it is a devDependency)");
  }
}

function build(args) {
  const out = outputDirectory(args);
  const tsc = compiler();
  // Beside the output, not in it: the package ships all of dist/, and a build that is killed cannot remove its
  // staging directory - the next build does. Same parent directory, so the renames below stay on one filesystem.
  const staging = join(dirname(out), `.${basename(out)}-staging`);
  const compile = (project, options) => {
    const run = spawnSync(process.execPath, [tsc, "-p", join(root, project), ...options], { cwd: root, stdio: "inherit" });
    if (run.error) throw run.error;
    if (run.status !== 0) throw new Error(`tsc -p ${project} failed, ${out} is unchanged`);
  };

  rmSync(staging, { recursive: true, force: true });
  try {
    compile("tsconfig.cjs.json", ["--outDir", join(staging, "cjs"), "--declarationDir", join(staging, "types")]);
    compile("tsconfig.esm.json", ["--outDir", join(staging, "esm")]);
    // The package is "type": "commonjs"; this marks the .js files under esm/ as ES modules.
    writeFileSync(join(staging, "esm", "package.json"), JSON.stringify({ type: "module" }, null, 2) + "\n");
    mkdirSync(out, { recursive: true });
    for (const part of ["cjs", "esm", "types"]) {
      rmSync(join(out, part), { recursive: true, force: true });
      renameSync(join(staging, part), join(out, part));
    }
  } finally {
    rmSync(staging, { recursive: true, force: true });
  }
}

try {
  build(process.argv.slice(2));
} catch (err) {
  console.error(`build: ${err.message}`);
  process.exitCode = 1;
}