// src/server.mjs
import { createServer } from 'node:http';

const readBody = async (request) => {
  // One decoder for the whole body: a character whose bytes arrive in two chunks is read whole.
  request.setEncoding('utf8');
  let text = '';
  for await (const chunk of request) text += chunk;
  return text;
};

export function createAppServer(db) {
  return createServer(async (request, response) => {
    // The deployed runtime's abort signal: end the response when it fires.
    request.signal?.addEventListener('abort', () => response.destroy(), { once: true });
    const send = (status, body) => {
      if (response.destroyed) return;
      response.writeHead(status, { 'content-type': 'application/json' });
      response.end(JSON.stringify(body));
    };
    try {
      // A target that does not parse as a URL names no route, so it is answered 404 below.
      let pathname = null;
      try {
        pathname = new URL(request.url, 'http://localhost').pathname;
      } catch {}
      if (request.method === 'GET' && pathname === '/health') {
        return (await db.reachable()) ? send(200, { ok: true }) : send(503, { ok: false });
      }
      if (request.method === 'GET' && pathname === '/notes') return send(200, await db.listNotes());
      if (request.method === 'POST' && pathname === '/notes') {
        const posted = JSON.parse(await readBody(request));
        return send(201, await db.addNote(String(posted?.title ?? '')));
      }
      send(404, { error: 'not_found' });
    } catch (error) {
      const refused = error instanceof SyntaxError ? 'invalid_json' : error?.code === '23514' ? 'invalid_note' : null;
      if (refused === null) console.error(error);
      send(refused === null ? 500 : 400, { error: refused ?? 'internal' });
    }
  });
}