BallModuleHandler class abstract

Contract for a ball base-module handler.

BallEngine routes every isBase function call through its registered moduleHandlers, delegating to the first one whose handles returns true. Implement this class to add entirely new modules or to replace the built-in StdModuleHandler:

class DbHandler extends BallModuleHandler {
  @override bool handles(String module) => module == 'db';
  @override Object? call(String fn, Object? input, BallCallable engine) {
    return switch (fn) {
      'query' => _runQuery(input),
      _ => throw BallRuntimeError('Unknown db function: "$fn"'),
    };
  }
}

Composition-only ball modules

If a ball program module contains only user-defined (non-isBase) functions that delegate to other modules, no handler is needed at all. The engine evaluates their bodies and resolves cross-module calls automatically:

// ball program (proto/JSON)
module math_utils:
  function hypotenuse(a, b):   // isBase: false, has a body
    std.math_sqrt(std.add(std.math_pow(a,2), std.math_pow(b,2)))

Handler composition (handler calling handler)

If your handler needs to call another ball function (user-defined or from another module), use the BallCallable passed to call:

class MathFacade extends BallModuleHandler {
  @override bool handles(String m) => m == 'myfacade';
  @override Object? call(String fn, Object? input, BallCallable engine) {
    if (fn == 'taxed_total')
      return engine('myfacade', 'subtotal', input)
             + engine('tax', 'compute', input);
    throw BallRuntimeError('unknown: $fn');
  }
}