doodle/pkg/scripting/events.go

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package scripting
import (
"github.com/robertkrimen/otto"
)
// Event name constants.
const (
CollideEvent = "OnCollide" // another doodad collides with us
EnterEvent = "OnEnter" // a doodad is fully inside us
LeaveEvent = "OnLeave" // a doodad no longer collides with us
// Controllable (player character) doodad events
KeypressEvent = "OnKeypress" // i.e. arrow keys
)
// Events API for Doodad scripts.
type Events struct {
registry map[string][]otto.Value
}
// NewEvents initializes the Events API.
func NewEvents() *Events {
return &Events{
registry: map[string][]otto.Value{},
}
}
// OnCollide fires when another actor collides with yours.
func (e *Events) OnCollide(call otto.FunctionCall) otto.Value {
return e.register(CollideEvent, call.Argument(0))
}
// RunCollide invokes the OnCollide handler function.
func (e *Events) RunCollide() error {
return e.run(CollideEvent)
}
// register a named event.
func (e *Events) register(name string, callback otto.Value) otto.Value {
if !callback.IsFunction() {
return otto.Value{} // TODO
}
if _, ok := e.registry[name]; !ok {
e.registry[name] = []otto.Value{}
}
e.registry[name] = append(e.registry[name], callback)
return otto.Value{}
}
// Run an event handler. Returns an error only if there was a JavaScript error
// inside the function. If there are no event handlers, just returns nil.
func (e *Events) run(name string, args ...interface{}) error {
if _, ok := e.registry[name]; !ok {
return nil
}
for _, callback := range e.registry[name] {
_, err := callback.Call(otto.Value{}, args...)
if err != nil {
return err
}
}
return nil
}