events-dom.go

package vugu

import (
	"sync"

	"github.com/vugu/vugu/js"
)

// NewDOMEvent returns a new initialized DOMEvent.
func NewDOMEvent(eventEnv EventEnv, eventSummary map[string]interface{}) DOMEvent {
	return &domEvent{
		eventSummary: eventSummary,
		eventEnv:     eventEnv,
		window:       js.Global().Get("window"),
	}
}

// DOMEvent is an event originated in the browser.  It wraps the JS event that comes in.
// It is meant to be used in WebAssembly but some methods exist here so code can compile
// server-side as well (although DOMEvents should not ever be generated server-side).
type DOMEvent interface {

	// Prop returns a value from the EventSummary using the keys you specify.
	// The keys is a list of map keys to be looked up. For example:
	// e.Prop("target", "name") will return the same value as e.EventSummary()["target"]["name"],
	// except that Prop helps with some edge cases and if a value is missing
	// of the wrong type, nil will be returned, instead of panicing.
	Prop(keys ...string) interface{}

	// PropString is like Prop but returns it's value as a string.
	// No type conversion is done, if the requested value is not
	// already a string then an empty string will be returned.
	PropString(keys ...string) string

	// PropFloat64 is like Prop but returns it's value as a float64.
	// No type conversion is done, if the requested value is not
	// already a float64 then float64(0) will be returned.
	PropFloat64(keys ...string) float64

	// PropBool is like Prop but returns it's value as a bool.
	// No type conversion is done, if the requested value is not
	// already a bool then false will be returned.
	PropBool(keys ...string) bool

	// EventSummary returns a map with simple properties (primitive types) from the event.
	// Accessing values returns by EventSummary incurs no additional performance or memory
	// penalty, whereas calls to JSEvent, JSEventTarget, etc. require a call into the browser
	// JS engine and the attendant resource usage.  So if you can get the information you
	// need from the EventSummary, that's better.
	EventSummary() map[string]interface{}

	// JSEvent returns a js.Value in wasm that corresponds to the event object.
	// Non-wasm implementation returns nil.
	JSEvent() js.Value

	// JSEventTarget returns the value of the "target" property of the event, the element
	// that the event was originally fired/registered on.
	JSEventTarget() js.Value

	// JSEventCurrentTarget returns the value of the "currentTarget" property of the event, the element
	// that is currently processing the event.
	JSEventCurrentTarget() js.Value

	// EventEnv returns the EventEnv for the current environment and allows locking and unlocking around modifications.
	// See EventEnv struct.
	EventEnv() EventEnv

	// PreventDefault calls preventDefault() on the underlying DOM event.
	// May only be used within event handler in same goroutine.
	PreventDefault()

	// StopPropagation calls stopPropagation() on the underlying DOM event.
	// May only be used within event handler in same goroutine.
	StopPropagation()
}

// domEvent implements the DOMEvent interface.
// This way DOMEvent can be passed around without a pointer this helps make
// DOM events and component events similar and consistent.
// It might actually makes sense to move this into the domrender package at some point.
type domEvent struct {
	eventSummary map[string]interface{}

	eventEnv EventEnv // from the renderer

	// TODO: yeah but why? this does not need to be here
	window js.Value // sure, why not
}

var _ DOMEvent = &domEvent{} // assert domEvent implements DOMEvent

// Prop returns a value from the EventSummary using the keys you specify.
// The keys is a list of map keys to be looked up. For example:
// e.Prop("target", "name") will return the same value as e.EventSummary()["target"]["name"],
// except that Prop helps with some edge cases and if a value is missing
// of the wrong type, nil will be returned, instead of panicing.
func (e *domEvent) Prop(keys ...string) interface{} {

	var ret interface{}
	ret = e.eventSummary

	for _, key := range keys {

		// see if ret is a map
		m, _ := ret.(map[string]interface{})
		if m == nil {
			return nil
		}

		// and index into the map if so, replacing ret
		ret = m[key]

	}

	return ret
}

// PropString is like Prop but returns it's value as a string.
// No type conversion is done, if the requested value is not
// already a string then an empty string will be returned.
func (e *domEvent) PropString(keys ...string) string {
	ret, _ := e.Prop(keys...).(string)
	return ret
}

// PropFloat64 is like Prop but returns it's value as a float64.
// No type conversion is done, if the requested value is not
// already a float64 then float64(0) will be returned.
func (e *domEvent) PropFloat64(keys ...string) float64 {
	ret, _ := e.Prop(keys...).(float64)
	return ret
}

// PropBool is like Prop but returns it's value as a bool.
// No type conversion is done, if the requested value is not
// already a bool then false will be returned.
func (e *domEvent) PropBool(keys ...string) bool {
	ret, _ := e.Prop(keys...).(bool)
	return ret
}

// EventSummary returns a map with simple properties (primitive types) from the event.
// Accessing values returns by EventSummary incurs no additional performance or memory
// penalty, whereas calls to JSEvent, JSEventTarget, etc. require a call into the browser
// JS engine and the attendant resource usage.  So if you can get the information you
// need from the EventSummary, that's better.
func (e *domEvent) EventSummary() map[string]interface{} {
	return e.eventSummary
}

// JSEvent this returns a js.Value in wasm that corresponds to the event object.
// Non-wasm implementation returns nil.
func (e *domEvent) JSEvent() js.Value {
	return e.window.Call("vuguGetActiveEvent")
}

// JSEventTarget returns the value of the "target" property of the event, the element
// that the event was originally fired/registered on.
func (e *domEvent) JSEventTarget() js.Value {
	return e.window.Call("vuguGetActiveEventTarget")
}

// JSEventCurrentTarget returns the value of the "currentTarget" property of the event, the element
// that is currently processing the event.
func (e *domEvent) JSEventCurrentTarget() js.Value {
	return e.window.Call("vuguGetActiveEventCurrentTarget")
}

// EventEnv returns the EventEnv for the current environment and allows locking and unlocking around modifications.
// See EventEnv struct.
func (e *domEvent) EventEnv() EventEnv {
	return e.eventEnv
}

// PreventDefault calls preventDefault() on the underlying DOM event.
// May only be used within event handler in same goroutine.
func (e *domEvent) PreventDefault() {
	e.window.Call("vuguActiveEventPreventDefault")
}

// StopPropagation calls stopPropagation() on the underlying DOM event.
// May only be used within event handler in same goroutine.
func (e *domEvent) StopPropagation() {
	e.window.Call("vuguActiveEventStopPropagation")
}

// DOMEventHandlerSpec describes an event that gets registered with addEventListener.
type DOMEventHandlerSpec struct {
	EventType string // "click", "mouseover", etc.
	Func      func(DOMEvent)
	Capture   bool
	Passive   bool
}

// // DOMEventHandler is created in BuildVDOM to represent a method call that is performed to handle an event.
// type DOMEventHandler struct {
// 	ReceiverAndMethodHash uint64        // hash value corresponding to the method and receiver, so we get a unique value for each combination of method and receiver
// 	Method                reflect.Value // method to be called, with receiver baked into it if needed (see reflect/Value.MethodByName)
// 	Args                  []interface{} // arguments to be passed in when calling (special case for eventStub)
// }

// func (d DOMEventHandler) hashString() string {
// 	return fmt.Sprintf("%x", d.hash())
// }

// func (d DOMEventHandler) hash() (ret uint64) {

// 	// defer func() {
// 	// 	log.Printf("DOMEventHandler.hash for (receiver_and_method_hash=%v, method=%#v, args=%#v) is returning %v", d.ReceiverAndMethodHash, d.Method, d.Args, ret)
// 	// }()

// 	if !d.Method.IsValid() && len(d.Args) == 0 {
// 		return 0
// 	}

// 	b8 := make([]byte, 8)
// 	h := xxhash.New()

// 	// this may end up being an issue but I need to move through this for now -
// 	// this is only unique for the method itself, not the instance it's tied to, although
// 	// it's probably rare to have to distinguish between multiple component types in use in an application
// 	// fmt.Fprintf(h, "%#v", d.Method)

// 	// NOTE: added ReceiverAndMethodHash to deal with the note above, let's see if it solves the problem
// 	binary.BigEndian.PutUint64(b8, d.ReceiverAndMethodHash)
// 	h.Write(b8)

// 	// add the args
// 	for _, a := range d.Args {
// 		binary.BigEndian.PutUint64(b8, ComputeHash(a))
// 		h.Write(b8)
// 	}
// 	return h.Sum64()
// }

// EventEnv provides locking mechanism to for rendering environment to events so
// data access and rendering can be synchronized and avoid race conditions.
type EventEnv interface {
	Lock()         // acquire write lock
	UnlockOnly()   // release write lock
	UnlockRender() // release write lock and request re-render

	RLock()   // acquire read lock
	RUnlock() // release read lock
}

// NewEventEnvImpl creates and returns a new EventEnvImpl.
func NewEventEnvImpl(rwmu *sync.RWMutex, requestRenderCH chan bool) *EventEnvImpl {
	return &EventEnvImpl{
		rwmu:            rwmu,
		requestRenderCH: requestRenderCH,
	}
}

// EventEnvImpl implements EventEnv
type EventEnvImpl struct {
	rwmu            *sync.RWMutex
	requestRenderCH chan bool
}

// Lock will acquire write lock
func (ee *EventEnvImpl) Lock() {
	// if ee.rwmu == nil {
	// 	return
	// }
	ee.rwmu.Lock()
}

// UnlockOnly will release the write lock
func (ee *EventEnvImpl) UnlockOnly() {
	// if ee.rwmu == nil {
	// 	return
	// }
	ee.rwmu.Unlock()
}

// UnlockRender will release write lock and request re-render
func (ee *EventEnvImpl) UnlockRender() {
	// if ee.rwmu != nil {
	ee.rwmu.Unlock()
	// }
	if ee.requestRenderCH != nil {
		// send non-blocking
		select {
		case ee.requestRenderCH <- true:
		default:
		}
	}
}

// RLock will acquire a read lock
func (ee *EventEnvImpl) RLock() {
	// if ee.rwmu == nil {
	// 	return
	// }
	ee.rwmu.RLock()
}

// RUnlock will release the read lock
func (ee *EventEnvImpl) RUnlock() {
	// if ee.rwmu == nil {
	// 	return
	// }
	ee.rwmu.RUnlock()
}