doodle/pkg/scripting/events.go

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package scripting
import (
"errors"
"git.kirsle.net/go/render/event"
"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
)
// Event return errors.
var (
ErrReturnFalse = errors.New("JS callback function returned false")
)
// 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(v interface{}) error {
return e.run(CollideEvent, v)
}
// OnLeave fires when another actor stops colliding with yours.
func (e *Events) OnLeave(call otto.FunctionCall) otto.Value {
return e.register(LeaveEvent, call.Argument(0))
}
// RunLeave invokes the OnLeave handler function.
func (e *Events) RunLeave(v interface{}) error {
return e.run(LeaveEvent, v)
}
// OnKeypress fires when another actor collides with yours.
func (e *Events) OnKeypress(call otto.FunctionCall) otto.Value {
return e.register(KeypressEvent, call.Argument(0))
}
// RunKeypress invokes the OnCollide handler function.
func (e *Events) RunKeypress(ev *event.State) error {
return e.run(KeypressEvent, ev)
}
// 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] {
value, err := callback.Call(otto.Value{}, args...)
if err != nil {
return err
}
// If the event handler returned a boolean false, stop all other
// callbacks and return the boolean.
if value.IsBoolean() {
if b, err := value.ToBoolean(); err == nil && b == false {
return ErrReturnFalse
}
}
}
return nil
}