// Post-processes the tsc emit (tsconfig.build.json) into something node can
// run directly:
//
//  1. tsc does not rewrite module specifiers, but node ESM requires explicit
//     file extensions — append ".js" (or "/index.js" for directories) to every
//     extensionless RELATIVE import/export specifier in dist/**/*.js. Bare
//     package specifiers (effect, hono, the pi SDK, ws) are left alone and
//     resolve at runtime through services/node_modules -> frontend/node_modules.
//
//  2. rootDir is the repo root (the sources import ../../shared/agent/*), so
//     the real entry lands at dist/services/agent-runtime/src/server.js. Write
//     a stable dist/server.js shim so "npm start" / systemd ExecStart stay
//     "node dist/server.js" regardless of the emitted layout.

import { readdirSync, readFileSync, statSync, writeFileSync, existsSync } from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";

const packageDir = path.dirname(path.dirname(fileURLToPath(import.meta.url)));
const distDir = path.join(packageDir, "dist");
const realEntry = path.join(distDir, "services", "agent-runtime", "src", "server.js");

if (!existsSync(realEntry)) {
  console.error(`[postbuild] expected tsc output missing: ${realEntry}`);
  process.exit(1);
}

const SPECIFIER_RE = /(from\s+|import\s*\(\s*|export\s+\*\s+from\s+|import\s+)("(\.{1,2}\/[^"]+)"|'(\.{1,2}\/[^']+)')/g;

function* jsFiles(dir) {
  for (const entry of readdirSync(dir, { withFileTypes: true })) {
    const full = path.join(dir, entry.name);
    if (entry.isDirectory()) yield* jsFiles(full);
    else if (entry.isFile() && entry.name.endsWith(".js")) yield full;
  }
}

function resolveSpecifier(fromFile, spec) {
  if (/\.(js|mjs|cjs|json|node)$/.test(spec)) return spec;
  const base = path.resolve(path.dirname(fromFile), spec);
  if (existsSync(`${base}.js`)) return `${spec}.js`;
  if (existsSync(base) && statSync(base).isDirectory() && existsSync(path.join(base, "index.js"))) {
    return `${spec}/index.js`;
  }
  return spec;
}

let rewrites = 0;
for (const file of jsFiles(distDir)) {
  const source = readFileSync(file, "utf8");
  const next = source.replace(SPECIFIER_RE, (match, lead, quoted, dq, sq) => {
    const spec = dq ?? sq;
    const fixed = resolveSpecifier(file, spec);
    if (fixed === spec) return match;
    rewrites += 1;
    const quote = quoted[0];
    return `${lead}${quote}${fixed}${quote}`;
  });
  if (next !== source) writeFileSync(file, next);
}

const shim = `// Generated by scripts/postbuild.mjs — stable entry for "node dist/server.js".
import "./services/agent-runtime/src/server.js";
`;
writeFileSync(path.join(distDir, "server.js"), shim);

console.log(`[postbuild] rewrote ${rewrites} relative specifiers; wrote dist/server.js shim`);