/**
 * @personal-blog/server — EPPP public server application.
 *
 * [E00-S02-T03] minimal serving process: a small HTTP server built on Node's
 * `node:http` that answers the application health endpoint. `GET /health`
 * reports the application readiness — HTTP 200 with `{"status":"ok"}` — so
 * the Compose stack's `app` service stays up and the health endpoint
 * succeeds once the stack is running.
 *
 * [E00-S03-T06] readiness gate: the app does **not** report ready before
 * migrations complete. When a `DATABASE_URL` is configured, the server runs
 * the startup migrations (the `MigrationRunner` from
 * `@personal-blog/database-postgres` over the migration ledger, E00-S03-T03)
 * before it reports ready: `GET /health` answers HTTP 503 with
 * `{"status":"not ready"}` while the migration run is in flight, and flips to
 * HTTP 200 `{"status":"ok"}` only after the run finishes. When no
 * `DATABASE_URL` is configured (e.g. the local non-container developer path,
 * E00-S01-T06) there are no migrations to run, so the app reports ready
 * immediately.
 *
 * [E00-S04-T02] field-specific startup error: the required settings are
 * validated before the server binds, so a deployment missing a required
 * setting (the admin-session secret `EPPP_SESSION_SECRET` — the schema's
 * required field, Security-and-Operations §32/§26) fails fast at startup
 * with an error naming the missing field instead of booting with an invalid
 * configuration.
 *
 * [E00-S04-T04] environment adapter: ALL settings flow through the config
 * package's environment adapter (`loadConfigFromEnv` from
 * `@personal-blog/config`) — the workspace's single owner of `process.env`
 * reads — so this module (and every other module outside the config package)
 * never reads `process.env` directly. The adapter maps the environment
 * (`HOST`/`PORT`/`DATABASE_URL`/`EPPP_SESSION_SECRET`) onto the validated
 * config shape and validates it with `assertValidConfig` (E00-S04-T02) before
 * the server binds, so a missing required setting is still a startup error
 * naming the missing field. `HOST` is validated at the adapter boundary as a
 * hostname or IP address and the server passes `config.host` to
 * `server.listen`, so a configured `HOST` binds exactly that interface and
 * the startup log reflects the actual bind — it never claims a bind the
 * process does not enforce, and never echoes unvalidated env content.
 *
 * [E00-S04-T03] secret redaction: ALL log output goes through the redacting
 * logger (`createLogger`, defined below — every line is scrubbed of the
 * config's secret values before it reaches stdout/stderr), so secret values —
 * the admin-session secret and the password in a `DATABASE_URL` connection
 * string — automatically redact from logs. The server logs its resolved
 * configuration at startup through `redactConfig` (the issue's test plan:
 * "log configuration and confirm secret values are redacted"), so operators
 * see the effective settings with every secret value replaced by
 * `[REDACTED]` and no secret value reaches the log output.
 *
 * The Fastify 5 application shell (and the real HTTP API) lands in a later
 * story; this bootstrap keeps the application health-checkable until then.
 */

import { createServer, type IncomingMessage, type ServerResponse } from 'node:http';
import { loadConfigFromEnv } from '@personal-blog/config';
import { redactConfig, redactText, type Config } from '@personal-blog/config';
import { Pool } from '@personal-blog/database-postgres';
import { MigrationLedger, MigrationRunner } from '@personal-blog/database-postgres';
import type { Migration } from '@personal-blog/database-postgres';

// [E00-S04-T04] environment adapter: ALL settings flow through the config
// package's adapter — the workspace's single owner of process.env reads — so
// the server never reads process.env directly. The adapter maps the
// environment onto the validated config shape and validates it with
// assertValidConfig (E00-S04-T02) before the server binds, so a missing
// required setting (e.g. EPPP_SESSION_SECRET) still crashes the process at
// startup with an error naming the missing field — never boots with an
// invalid configuration.
const config = loadConfigFromEnv();

// [E00-S04-T03] secret redaction: every log line goes through the redacting
// logger, seeded with the validated config's secrets — and the resolved
// configuration is logged redacted, so operators see the effective settings
// while secret values stay out of the log output.
const logger = createLogger(config);
logger.log('[config] resolved configuration:', JSON.stringify(redactConfig(config)));

/** Health payload — reported once the startup migration run completes. */
const HEALTH_PAYLOAD = JSON.stringify({ status: 'ok' });

/** Payload while the startup migration run is still in flight — the app is up but NOT ready. */
const NOT_READY_PAYLOAD = JSON.stringify({ status: 'not ready' });

/** Payload for any route that is not the health endpoint. */
const NOT_FOUND_PAYLOAD = JSON.stringify({ error: 'not found' });

/**
 * The migrations the server applies at startup, oldest first. Empty until the
 * first schema migration lands (E00-S03 is the migration-runner foundation;
 * real schema migrations arrive with the domain stories). The runner still
 * ensures the migration ledger (E00-S03-T03) exists and reads the applied
 * versions, so even an empty run is a real, observable migration step that
 * readiness waits for.
 */
const MIGRATIONS: readonly Migration[] = [];

/**
 * Readiness state — false until the startup migration run completes. The app
 * is "up" (the HTTP server is listening) but reports not-ready (E00-S03-T06)
 * while migrations are pending.
 */
let migrationsComplete = false;

/** Writes a JSON response with an explicit content-length. */
function sendJson(res: ServerResponse, statusCode: number, body: string): void {
  res.writeHead(statusCode, {
    'Content-Type': 'application/json; charset=utf-8',
    'Content-Length': Buffer.byteLength(body),
  });
  res.end(body);
}

/** The server's logger: `log` writes to stdout, `error` writes to stderr — both redacted. */
interface ServerLogger {
  log(...args: unknown[]): void;
  error(...args: unknown[]): void;
}

/**
 * Creates the redacting logger for the validated configuration (E00-S04-T03):
 * each argument is serialized (strings verbatim, errors by message, other
 * values as JSON) and the joined line is scrubbed of the config's secret
 * values — the admin-session secret and the password embedded in a
 * `DATABASE_URL` connection string — before it is written, so no secret value
 * can reach the log output. The server uses this logger for ALL of its
 * output; a bare `console.log`/`console.error` would bypass the redaction and
 * is rejected by the test suite.
 */
function createLogger(config: Config): ServerLogger {
  const write = (stream: NodeJS.WriteStream, args: unknown[]): void => {
    stream.write(`${redactText(args.map(serialize).join(' '), config)}\n`);
  };
  return {
    log: (...args) => write(process.stdout, args),
    error: (...args) => write(process.stderr, args),
  };
}

/** Serializes one log argument: strings verbatim, errors by message, objects as JSON. */
function serialize(value: unknown): string {
  if (typeof value === 'string') return value;
  if (value instanceof Error) return String(value);
  if (typeof value === 'undefined') return 'undefined';
  if (typeof value === 'object' && value !== null) {
    try {
      return JSON.stringify(value);
    } catch {
      return String(value);
    }
  }
  return String(value);
}

/**
 * Routes one request. The application only serves the health endpoint at this
 * stage; anything else is a 404 so misconfiguration is loud. The health route
 * is the readiness probe (E00-S03-T06): it answers 200 only after the startup
 * migration run completes, and 503 while the run is still pending.
 */
function handleRequest(req: IncomingMessage, res: ServerResponse): void {
  if (req.method === 'GET' && (req.url ?? '/') === '/health') {
    if (migrationsComplete) {
      sendJson(res, 200, HEALTH_PAYLOAD);
    } else {
      sendJson(res, 503, NOT_READY_PAYLOAD);
    }
    return;
  }
  sendJson(res, 404, NOT_FOUND_PAYLOAD);
}

const server = createServer(handleRequest);

const databaseUrl = config.databaseUrl;

if (databaseUrl === undefined) {
  // No DATABASE_URL configured (e.g. local non-container dev): there are no
  // migrations to run, so the app reports ready from the start.
  migrationsComplete = true;
  logger.log('[migrate] no DATABASE_URL configured; reporting ready without a migration run');
} else {
  // E00-S03-T06: run the startup migrations; readiness follows completion.
  const pool = new Pool({ connectionString: databaseUrl });
  const runner = new MigrationRunner(pool, MIGRATIONS, new MigrationLedger(pool));
  runner
    .run()
    .then((result) => {
      migrationsComplete = true;
      logger.log(
        `[migrate] startup migration run complete (applied ${result.applied.length}, skipped ${result.skipped.length}); reporting ready`,
      );
    })
    .catch((error) => {
      // Failure diagnostics are E00-S03-T05 (out of scope for T06): the
      // runner already throws a serializable MigrationFailedError. The app
      // logs the failure and stays not-ready, so a deployment with failed
      // migrations is surfaced by the readiness probe instead of
      // crash-looping. The redacting logger scrubs any secret value (e.g.
      // the database password) the error text may embed.
      logger.error('[migrate] startup migration run failed; app stays not-ready:', error);
    });
}

// The server binds the validated bind interface: `config.host` (default
// `0.0.0.0`, validated as a hostname/IP by the adapter) is passed to
// `server.listen`, so a configured `HOST` binds exactly that interface and
// the startup log reflects the actual bind.
server.listen(config.port, config.host, () => {
  logger.log(`@personal-blog/server listening on http://${config.host}:${config.port} (health: GET /health)`);
});

// `docker stop` (Compose down) and Ctrl-C send SIGTERM/SIGINT — close the
// server and exit cleanly instead of being killed mid-request.
for (const signal of ['SIGTERM', 'SIGINT'] as const) {
  process.on(signal, () => {
    server.close(() => process.exit(0));
  });
}