export type HttpErrorDiagnostic = Readonly<{
  name: string;
  code?: string;
  errno?: number;
  sqlState?: string;
  frames: readonly string[];
}>;

/** Extrae datos técnicos sin serializar mensajes, SQL ni propiedades arbitrarias del error. */
export function httpErrorDiagnostics(failure: unknown): readonly HttpErrorDiagnostic[] {
  const diagnostics: HttpErrorDiagnostic[] = [];
  const visited = new Set<Error>();
  let current = failure;

  while (current instanceof Error && !visited.has(current) && diagnostics.length < 5) {
    visited.add(current);
    diagnostics.push(describeError(current));
    current =
      current.cause instanceof Error
        ? current.cause
        : "parent" in current
          ? current.parent
          : undefined;
  }

  return diagnostics.length ? diagnostics : [{ name: "NonErrorThrown", frames: [] }];
}

function describeError(failure: Error): HttpErrorDiagnostic {
  const code = "code" in failure ? failure.code : undefined;
  const errno = "errno" in failure ? failure.errno : undefined;
  const sqlState = "sqlState" in failure ? failure.sqlState : undefined;
  // El prefijo puede contener un mensaje multilínea: se elimina completo antes de leer los frames.
  const prefix = failure.message ? `${failure.name}: ${failure.message}` : failure.name;
  const stack = failure.stack?.startsWith(prefix) ? failure.stack.slice(prefix.length) : "";

  return {
    name: /^[A-Za-z][A-Za-z0-9]*Error$|^Error$/.test(failure.name) ? failure.name : "Error",
    ...(typeof code === "string" && /^(?:ER_[A-Z0-9_]+|E[A-Z0-9_]+)$/.test(code) ? { code } : {}),
    ...(typeof errno === "number" && Number.isSafeInteger(errno) ? { errno } : {}),
    ...(typeof sqlState === "string" && /^[0-9A-Z]{5}$/.test(sqlState) ? { sqlState } : {}),
    frames: stack
      .split("\n")
      .filter((line) => /^\s+at .+:\d+:\d+\)?$/.test(line))
      .slice(0, 20)
      .map((line) => line.trim()),
  };
}