129 lines
3.1 KiB
Go
129 lines
3.1 KiB
Go
// Package event is the event handler
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package event
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import (
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"errors"
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"fmt"
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"log/slog"
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"reflect"
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"strings"
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)
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type Loop struct {
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handlerFunctions map[reflect.Type][]reflect.Value
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Handlers []any
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}
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type Unhandled struct {
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Val any
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}
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type Anything struct {
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Val any
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}
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type (
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Start struct{}
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Tick struct{}
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)
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// HandlerDoneErr will stop the event loop and return the error if provided.
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type HandlerDoneErr struct {
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Return error
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}
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// Close is fired when the loop shuts down.
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type Close struct {
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Reason error
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}
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func (e HandlerDoneErr) Error() string {
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return "HandlerDoneErr"
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}
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func (e HandlerDoneErr) Unwrap() error {
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return e.Return
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}
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// ErrDontForward will stop the event from being forwarded to other handlers, including anything handlers.
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var ErrDontForward = errors.New("dont forward")
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var WhileClosingErr = errors.New("error while closing")
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// UpdateHandlerFunctions initializes and populates the handlerFunctions map by reflecting over methods of registered handlers.
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func (l *Loop) UpdateHandlerFunctions() {
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l.handlerFunctions = make(map[reflect.Type][]reflect.Value)
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for _, inst := range l.Handlers {
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t := reflect.TypeOf(inst)
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v := reflect.ValueOf(inst)
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for i := 0; i < t.NumMethod(); i++ {
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method := t.Method(i)
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if strings.HasPrefix(method.Name, "On") {
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if method.Type.NumIn() != 2 || method.Type.NumOut() != 1 || method.Type.Out(0) != reflect.TypeFor[error]() {
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slog.Warn("Invalid event handler signature", "at", t.String()+"."+method.Name)
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continue
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}
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} else {
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continue
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}
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eventType := method.Type.In(1)
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l.handlerFunctions[eventType] = append(l.handlerFunctions[eventType], v.Method(i))
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slog.Debug("Registered Handler", "at", t.String()+"."+method.Name, "for", eventType.String())
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}
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}
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}
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// FireFound triggers all handlers registered for the specified event type and returns if handlers were found or an error occurred.
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func (l *Loop) FireFound(event any) (found bool, err error) {
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var handlers []reflect.Value
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if handlers, found = l.handlerFunctions[reflect.TypeOf(event)]; found {
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for _, handler := range handlers {
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errV := handler.Call([]reflect.Value{reflect.ValueOf(event)})[0]
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if !errV.IsNil() {
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err = errV.Interface().(error)
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err = errors.Join(fmt.Errorf("event handler failed at: %s(%T)", handler.Type().In(0), event), err)
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return
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}
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}
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}
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return
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}
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// Fire dispatches the provided event to all appropriate handlers and invokes fallback handlers if the event is unhandled.
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func (l *Loop) Fire(event any) (err error) {
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found, err := l.FireFound(event)
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if err != nil {
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if errors.Is(err, ErrDontForward) {
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err = nil
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}
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return
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}
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if !found {
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_, err = l.FireFound(Unhandled{event})
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if err != nil {
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return
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}
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}
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_, err = l.FireFound(Anything{event})
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return
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}
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func (l *Loop) Start() (err error) {
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_ = *l // exit early on nil loop
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l.UpdateHandlerFunctions()
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err = l.Fire(Start{})
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for err == nil {
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err = l.Fire(Tick{})
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if err != nil {
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break
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}
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}
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if errors.Is(err, HandlerDoneErr{}) {
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err = errors.Unwrap(err)
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}
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closeErr := l.Fire(Close{err})
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if closeErr != nil {
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err = errors.Join(err, errors.Join(WhileClosingErr, closeErr))
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}
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return
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}
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