// src/lib/logger.ts
// ─────────────────────────────────────────────────────────────────────────────
// Minimal structured logger — JSON lines per event so `docker logs flux-app`
// can be piped through `jq` and shipped to Loki/Sentry/CloudWatch without code
// changes. Zero deps. Replace console.error/log with log.error/log.info.
// ─────────────────────────────────────────────────────────────────────────────

type LogContext = Record<string, unknown>;

function serialiseError(err: unknown) {
  if (err instanceof Error) {
    return { name: err.name, message: err.message, stack: err.stack };
  }
  return { value: String(err) };
}

function emit(level: "info" | "warn" | "error", event: string, ctx?: LogContext, err?: unknown) {
  const line = JSON.stringify({
    lvl: level,
    event,
    ts: new Date().toISOString(),
    ...(err !== undefined ? { err: serialiseError(err) } : {}),
    ...ctx,
  });
  if (level === "error") console.error(line);
  else if (level === "warn") console.warn(line);
  else console.log(line);
}

export const log = {
  info: (event: string, ctx?: LogContext) => emit("info", event, ctx),
  warn: (event: string, ctx?: LogContext) => emit("warn", event, ctx),
  error: (event: string, err: unknown, ctx?: LogContext) => emit("error", event, ctx, err),
};