doodle/pkg/scripting/events.go
Noah Petherbridge 4d08bf1d85 Switch JavaScript engine to goja
* Switch from otto to goja for JavaScript engine.
* goja supports many ES6 syntax features like arrow functions,
  const/let, for-of with more coming soon.
* Same great features as otto, more modern environment for doodads!
2022-01-16 20:09:27 -08:00

131 lines
3.3 KiB
Go

package scripting
import (
"errors"
"fmt"
"sync"
"git.kirsle.net/apps/doodle/pkg/keybind"
"github.com/dop251/goja"
)
// 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
UseEvent = "OnUse" // player pressed the Use key while touching 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 {
runtime *goja.Runtime
registry map[string][]goja.Value
lock sync.RWMutex
}
// NewEvents initializes the Events API.
func NewEvents(runtime *goja.Runtime) *Events {
return &Events{
runtime: runtime,
registry: map[string][]goja.Value{},
}
}
// OnCollide fires when another actor collides with yours.
func (e *Events) OnCollide(call goja.FunctionCall) goja.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)
}
// OnUse fires when another actor collides with yours.
func (e *Events) OnUse(call goja.FunctionCall) goja.Value {
return e.register(UseEvent, call.Argument(0))
}
// RunUse invokes the OnUse handler function.
func (e *Events) RunUse(v interface{}) error {
return e.run(UseEvent, v)
}
// OnLeave fires when another actor stops colliding with yours.
func (e *Events) OnLeave(call goja.FunctionCall) goja.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 goja.FunctionCall) goja.Value {
return e.register(KeypressEvent, call.Argument(0))
}
// RunKeypress invokes the OnCollide handler function.
func (e *Events) RunKeypress(ev keybind.State) error {
return e.run(KeypressEvent, e.runtime.ToValue(ev))
}
// register a named event.
func (e *Events) register(name string, callback goja.Value) goja.Value {
e.lock.Lock()
defer e.lock.Unlock()
if _, ok := e.registry[name]; !ok {
e.registry[name] = []goja.Value{}
}
e.registry[name] = append(e.registry[name], callback)
return goja.Undefined()
}
// 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 {
e.lock.RLock()
defer e.lock.RUnlock()
if _, ok := e.registry[name]; !ok {
return nil
}
var params = make([]goja.Value, len(args))
for i, v := range args {
params[i] = e.runtime.ToValue(v)
}
for _, callback := range e.registry[name] {
function, ok := goja.AssertFunction(callback)
if !ok {
return fmt.Errorf("failed to callback %s: %s", name, callback)
}
value, err := function(goja.Undefined(), params...)
if err != nil {
return err
}
// If the event handler returned a boolean false, stop all other
// callbacks and return the boolean.
if b, ok := value.Export().(bool); ok && !b {
return ErrReturnFalse
}
}
return nil
}