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node.go
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package app
import (
"bytes"
"html"
"io"
"reflect"
"strconv"
"time"
"github.com/maxence-charriere/go-app/v10/pkg/errors"
)
// UI is the interface that describes a user interface element such as
// components and HTML elements.
type UI interface {
// JSValue returns the javascript value linked to the element.
JSValue() Value
// Reports whether the element is mounted.
Mounted() bool
parent() UI
setParent(UI) UI
}
// FilterUIElems processes and returns a filtered list of the provided UI
// elements.
//
// Specifically, it:
// - Interprets and removes selector elements such as Condition and RangeLoop.
// - Eliminates nil elements and nil pointers.
// - Flattens and includes the children of recognized selector elements.
//
// This function is primarily intended for components that accept ui elements as
// variadic arguments or slice, such as the Body method of HTML elements.
func FilterUIElems(v ...UI) []UI {
if len(v) == 0 {
return nil
}
removeELemAt := func(i int) {
copy(v[i:], v[i+1:])
v[len(v)-1] = nil
v = v[:len(v)-1]
}
var trailing []UI
replaceElemAt := func(i int, elems ...UI) {
trailing = append(trailing, v[i+1:]...)
v = append(v[:i], elems...)
v = append(v, trailing...)
trailing = trailing[:0]
}
for i := len(v) - 1; i >= 0; i-- {
elem := v[i]
if elem == nil {
removeELemAt(i)
}
if elemValue := reflect.ValueOf(elem); elemValue.Kind() == reflect.Pointer && elemValue.IsNil() {
removeELemAt(i)
}
switch elem := elem.(type) {
case Condition:
replaceElemAt(i, elem.body()...)
case RangeLoop:
replaceElemAt(i, elem.body()...)
}
}
return v
}
// HTMLString returns a string that represents the HTML markup for the provided
// UI element.
func HTMLString(ui UI) string {
engine := NewTestEngine().(*engineX)
var b bytes.Buffer
engine.nodes.Encode(engine.baseContext(), &b, ui)
return b.String()
}
// PrintHTML writes the HTML representation of the given UI element into the
// specified writer.
func PrintHTML(w io.Writer, ui UI) {
w.Write([]byte(HTMLString(ui)))
}
// Component events.
type nav struct{}
type appUpdate struct{}
type appInstallChange struct{}
type resize struct{}
// nodeManager orchestrates the lifecycle of UI elements, providing specialized
// mechanisms for mounting, dismounting, and updating nodes.
type nodeManager struct {
}
// Mount mounts a UI element based on its type and the specified depth. It
// returns the mounted UI element and any potential error during the process.
func (m nodeManager) Mount(ctx Context, depth uint, v UI) (UI, error) {
ctx = m.context(ctx, v)
switch v := v.(type) {
case *text:
return m.mountText(depth, v)
case HTML:
return m.mountHTML(ctx, depth, v)
case Composer:
return m.mountComponent(ctx, depth, v)
case *raw:
return m.mountRawHTML(depth, v)
default:
return nil, errors.New("unsupported element").
WithTag("type", reflect.TypeOf(v)).
WithTag("depth", depth)
}
}
func (m nodeManager) mountText(depth uint, v *text) (UI, error) {
if v.Mounted() {
return nil, errors.New("text is already mounted").
WithTag("parent-type", reflect.TypeOf(v.parent())).
WithTag("preview-value", previewText(v.value))
}
v.jsvalue = Window().createTextNode(v.value)
return v, nil
}
func (m nodeManager) mountHTML(ctx Context, depth uint, v HTML) (UI, error) {
if v.Mounted() {
return nil, errors.New("html element is already mounted").
WithTag("parent-type", reflect.TypeOf(v.parent())).
WithTag("type", reflect.TypeOf(v)).
WithTag("tag", v.Tag()).
WithTag("depth", v.depth())
}
jsElement, _ := Window().createElement(v.Tag(), v.XMLNamespace())
v = v.setJSElement(jsElement)
m.mountHTMLAttributes(ctx, v)
m.mountHTMLEventHandlers(ctx, v)
v = v.setDepth(depth).(HTML)
children := v.body()
for i, child := range children {
var err error
if child, err = m.Mount(ctx, depth+1, child); err != nil {
return nil, errors.New("mounting child failed").
WithTag("type", reflect.TypeOf(v)).
WithTag("tag", v.Tag()).
WithTag("depth", depth).
WithTag("index", i).
Wrap(err)
}
child = child.setParent(v)
children[i] = child
v.JSValue().appendChild(child)
}
return v, nil
}
func (m nodeManager) mountHTMLAttributes(ctx Context, v HTML) {
for name, value := range v.attrs() {
setJSAttribute(v.JSValue(), name, resolveAttributeURLValue(
name,
value,
ctx.ResolveStaticResource,
))
}
}
func (m nodeManager) mountHTMLEventHandlers(ctx Context, v HTML) {
events := v.events()
for event, handler := range events {
events[event] = m.mountHTMLEventHandler(ctx, v, handler)
}
}
func (m nodeManager) mountHTMLEventHandler(ctx Context, v HTML, handler eventHandler) eventHandler {
event := handler.event
jsHandler := FuncOf(func(this Value, args []Value) any {
if len(args) != 0 {
ctx.Dispatch(func(ctx Context) {
event := Event{Value: args[0]}
trackMousePosition(event)
handler.goHandler(ctx, event)
})
}
return nil
})
v.JSValue().addEventListener(event, jsHandler, handler.options())
return eventHandler{
event: event,
scope: handler.scope,
goHandler: handler.goHandler,
jsHandler: jsHandler,
close: func() {
v.JSValue().removeEventListener(event, jsHandler)
jsHandler.Release()
},
}
}
func (m nodeManager) mountComponent(ctx Context, depth uint, v Composer) (UI, error) {
if v.Mounted() {
return nil, errors.New("component is already mounted").
WithTag("parent-type", reflect.TypeOf(v.parent())).
WithTag("type", reflect.TypeOf(v)).
WithTag("depth", v.depth())
}
v = v.setRef(v)
v = v.setDepth(depth)
if initializer, ok := v.(Initializer); ok {
initializer.OnInit()
}
if preRenderer, ok := v.(PreRenderer); ok && IsServer {
ctx.Dispatch(preRenderer.OnPreRender)
}
if mounter, ok := v.(Mounter); ok && IsClient {
ctx.Dispatch(mounter.OnMount)
}
root, err := m.renderComponent(v)
if err != nil {
return nil, errors.New("rendering component failed").
WithTag("type", reflect.TypeOf(v)).
WithTag("depth", v.depth()).
Wrap(err)
}
if root, err = m.Mount(ctx, depth+1, root); err != nil {
return nil, errors.New("mounting component root failed").
WithTag("type", reflect.TypeOf(v)).
WithTag("depth", v.depth()).
Wrap(err)
}
root = root.setParent(v)
v = v.setRoot(root)
return v, nil
}
func (m nodeManager) renderComponent(v Composer) (UI, error) {
rendering := FilterUIElems(v.Render())
if len(rendering) == 0 {
return nil, errors.New("render method does not returns a text, html element, or component")
}
return rendering[0], nil
}
func (m nodeManager) mountRawHTML(depth uint, v *raw) (UI, error) {
if v.Mounted() {
return nil, errors.New("raw html is already mounted").
WithTag("parent-type", reflect.TypeOf(v.parent())).
WithTag("type", reflect.TypeOf(v)).
WithTag("depth", v.depth()).
WithTag("raw-preview", previewText(v.value))
}
wrapper, _ := Window().createElement("div", "")
wrapper.setInnerHTML(v.value)
v.jsElement = wrapper.firstChild()
wrapper.removeChild(v.jsElement)
return v, nil
}
// Dismount removes a UI element based on its type.
func (m nodeManager) Dismount(v UI) {
switch v := v.(type) {
case *text:
case HTML:
m.dismountHTML(v)
case Composer:
m.dismountComponent(v)
case *raw:
m.dismountRawHTML(v)
}
}
func (m nodeManager) dismountHTML(v HTML) {
for _, child := range v.body() {
m.Dismount(child)
}
for _, handler := range v.events() {
m.dismountHTMLEventHandler(handler)
}
v.setJSElement(nil)
}
func (m nodeManager) dismountHTMLEventHandler(handler eventHandler) {
if handler.close != nil {
handler.close()
}
}
func (m nodeManager) dismountComponent(v Composer) {
m.Dismount(v.root())
v.setRef(nil)
if dismounter, ok := v.(Dismounter); ok {
dismounter.OnDismount()
}
}
func (m nodeManager) dismountRawHTML(v *raw) {
v.jsElement = nil
}
// CanUpdate determines whether a given UI element 'v' can be updated with a new
// UI element 'new'. It returns false if the types of the two elements are
// different.
//
// For HTML elements, it ensures that the tag names match. Otherwise, it returns
// true indicating that an update is feasible.
func (m nodeManager) CanUpdate(v, new UI) bool {
if vType, newType := reflect.TypeOf(v), reflect.TypeOf(new); vType != newType {
return false
}
switch v.(type) {
case *htmlElem, *htmlElemSelfClosing:
return v.(HTML).Tag() == new.(HTML).Tag()
default:
return true
}
}
// Update updates the existing UI element 'v' with a new UI element 'new'. It
// returns the updated UI element and any error encountered during the update
// process.
func (m nodeManager) Update(ctx Context, v, new UI) (UI, error) {
if !v.Mounted() {
return nil, errors.New("element not mounted").WithTag("type", reflect.TypeOf(v))
}
ctx = m.context(ctx, v)
switch v := v.(type) {
case *text:
return m.updateText(v, new.(*text))
case HTML:
return m.updateHTML(ctx, v, new.(HTML))
case Composer:
return m.updateComponent(ctx, v, new.(Composer))
case *raw:
return m.updateRawHTML(ctx, v, new.(*raw))
default:
return nil, errors.New("unsupported element").WithTag("type", reflect.TypeOf(v))
}
}
func (m nodeManager) updateText(v, new *text) (UI, error) {
if v.value == new.value {
return v, nil
}
v.value = new.value
v.JSValue().setNodeValue(v.value)
return v, nil
}
func (m nodeManager) updateHTML(ctx Context, v, new HTML) (UI, error) {
attrs := v.attrs()
newAttrs := new.attrs()
if attrs == nil && len(newAttrs) != 0 {
v = v.setAttrs(newAttrs)
m.mountHTMLAttributes(ctx, v)
} else if attrs != nil {
m.updateHTMLAttributes(ctx, v, newAttrs)
}
events := v.events()
newEvents := new.events()
if events == nil && len(newEvents) != 0 {
v = v.setEvents(newEvents)
m.mountHTMLEventHandlers(ctx, v)
} else if events != nil {
m.updateHTMLEventHandlers(ctx, v, newEvents)
}
children := v.body()
newChildren := new.body()
sharedLen := min(len(children), len(newChildren))
for i := 0; i < min(len(children), len(newChildren)); i++ {
child := children[i]
newChild := newChildren[i]
if m.CanUpdate(child, newChild) {
child, err := m.Update(ctx, child, newChild)
if err != nil {
return nil, errors.New("updating child failed").
WithTag("type", reflect.TypeOf(v)).
WithTag("tag", v.Tag()).
WithTag("depth", v.depth()).
WithTag("index", i).
Wrap(err)
}
children[i] = child
continue
}
newChild, err := m.Mount(ctx, v.depth()+1, newChildren[i])
if err != nil {
return nil, errors.New("mounting child failed").
WithTag("type", reflect.TypeOf(v)).
WithTag("tag", v.Tag()).
WithTag("depth", v.depth()).
WithTag("index", i).
Wrap(err)
}
v.JSValue().replaceChild(newChild, child)
newChild = newChild.setParent(v)
children[i] = newChild
m.Dismount(child)
}
for i := sharedLen; i < len(children); i++ {
child := children[i]
v.JSValue().removeChild(child)
m.Dismount(child)
children[i] = nil
}
children = children[:sharedLen]
for i := sharedLen; i < len(newChildren); i++ {
newChild, err := m.Mount(ctx, v.depth()+1, newChildren[i])
if err != nil {
return nil, errors.New("mounting child failed").
WithTag("type", reflect.TypeOf(v)).
WithTag("tag", v.Tag()).
WithTag("depth", v.depth()).
WithTag("index", i).
Wrap(err)
}
v.JSValue().appendChild(newChild)
newChild = newChild.setParent(v)
children = append(children, newChild)
}
v = v.setBody(children)
return v, nil
}
func (m nodeManager) updateHTMLAttributes(ctx Context, v HTML, newAttrs attributes) {
attrs := v.attrs()
for name := range attrs {
if _, remains := newAttrs[name]; !remains {
deleteJSAttribute(v.JSValue(), name)
delete(attrs, name)
}
}
for name, value := range newAttrs {
if attrs[name] == value {
continue
}
attrs[name] = value
setJSAttribute(v.JSValue(), name, resolveAttributeURLValue(
name,
value,
ctx.ResolveStaticResource,
))
}
}
func (m nodeManager) updateHTMLEventHandlers(ctx Context, v HTML, newEvents eventHandlers) {
events := v.events()
for event, handler := range events {
if _, remains := newEvents[event]; !remains {
m.dismountHTMLEventHandler(handler)
delete(events, event)
}
}
for event, newHandler := range newEvents {
handler, exists := events[event]
if !exists {
events[event] = m.mountHTMLEventHandler(ctx, v, newHandler)
continue
}
if handler.Equal(newHandler) {
continue
}
m.dismountHTMLEventHandler(handler)
events[event] = m.mountHTMLEventHandler(ctx, v, newHandler)
}
}
func (m nodeManager) updateComponent(ctx Context, v, new Composer) (UI, error) {
value := reflect.Indirect(reflect.ValueOf(v))
newValue := reflect.Indirect(reflect.ValueOf(new))
var modifiedFields bool
for i := 0; i < value.NumField(); i++ {
field := value.Field(i)
newField := newValue.Field(i)
if !field.CanSet() {
continue
}
if _, compoStruct := field.Interface().(Compo); compoStruct {
continue
}
if !canUpdateValue(field, newField) {
continue
}
field.Set(newField)
modifiedFields = true
}
if !modifiedFields {
return v, nil
}
if updater, ok := v.(Updater); ok {
updater.OnUpdate(ctx)
}
ctx.removeComponentUpdate(v)
return m.UpdateComponentRoot(ctx, v)
}
// UpdateComponentRoot updates the root element of the given component.
func (m nodeManager) UpdateComponentRoot(ctx Context, v Composer) (UI, error) {
ctx = m.context(ctx, v)
root := v.root()
newRoot, err := m.renderComponent(v)
if err != nil {
return nil, errors.New("rendering component failed").
WithTag("type", reflect.TypeOf(v)).
WithTag("depth", v.depth()).
Wrap(err)
}
if m.CanUpdate(root, newRoot) {
if root, err = m.Update(ctx, root, newRoot); err != nil {
return nil, errors.New("updating component root failed").
WithTag("type", reflect.TypeOf(v)).
WithTag("depth", v.depth()).
Wrap(err)
}
v.setRoot(root)
} else {
if newRoot, err = m.Mount(ctx, v.depth()+1, newRoot); err != nil {
return nil, errors.New("mounting component root failed").
WithTag("type", reflect.TypeOf(v)).
WithTag("depth", v.depth()).
Wrap(err)
}
for parent := v.parent(); parent != nil; parent = parent.parent() {
if parent, isHTML := parent.(HTML); isHTML {
parent.JSValue().replaceChild(newRoot, root)
break
}
}
newRoot.setParent(v)
v.setRoot(newRoot)
m.Dismount(root)
}
return v, nil
}
func (m nodeManager) updateRawHTML(ctx Context, v, new *raw) (UI, error) {
if v.value == new.value {
return v, nil
}
newMount, err := m.Mount(ctx, v.depth(), new)
if err != nil {
return nil, errors.New("mounting updated raw html failed").
WithTag("type", reflect.TypeOf(v)).
WithTag("depth", v.depth()).
WithTag("raw-preview", previewText(v.value)).
Wrap(err)
}
for parent := v.parent(); parent != nil; parent = parent.parent() {
if parent, isHTML := parent.(HTML); isHTML {
parent.JSValue().replaceChild(newMount, v)
break
}
}
m.Dismount(v)
return newMount, nil
}
func (m nodeManager) context(ctx Context, v UI) Context {
ctx.sourceElement = v
ctx.notifyComponentEvent = m.NotifyComponentEvent
return ctx
}
// NotifyComponentEvent traverses a UI element tree to propagate a component
// event, activating pertinent component handlers and potentially enqueuing
// component updates as needed.
func (m nodeManager) NotifyComponentEvent(ctx Context, root UI, event any) {
ctx = m.context(ctx, root)
switch element := root.(type) {
case HTML:
for _, child := range element.body() {
m.NotifyComponentEvent(ctx, child, event)
}
case Composer:
switch event.(type) {
case nav:
if navigator, ok := element.(Navigator); ok {
ctx.Dispatch(navigator.OnNav)
}
case appUpdate:
if appUpdater, ok := element.(AppUpdater); ok {
ctx.Dispatch(appUpdater.OnAppUpdate)
}
case appInstallChange:
if appInstaller, ok := element.(AppInstaller); ok {
ctx.Dispatch(appInstaller.OnAppInstallChange)
}
case resize:
if resizer, ok := element.(Resizer); ok {
ctx.Dispatch(resizer.OnResize)
}
}
m.NotifyComponentEvent(ctx, element.root(), event)
}
}
// Encode transforms the provided UI element into its HTML byte slice
// representation. This allows for the conversion of in-memory UI structures
// into a format suitable for server rendering.
func (m nodeManager) Encode(ctx Context, w *bytes.Buffer, v UI) {
m.encode(ctx, w, 0, v)
}
func (m nodeManager) encode(ctx Context, w *bytes.Buffer, depth int, v UI) {
switch v := v.(type) {
case *text:
m.encodeText(w, depth, v)
case HTML:
m.encodeHTML(ctx, w, depth, v)
case Composer:
m.encodeComponent(ctx, w, depth, v)
case *raw:
m.encodeRawHTML(w, depth, v)
}
}
func (m nodeManager) encodeText(w *bytes.Buffer, depth int, v *text) {
if v.value != "" {
m.encodeIndent(w, depth)
w.WriteString(html.EscapeString(v.value))
}
}
func (m nodeManager) encodeIndent(w *bytes.Buffer, depth int) {
for i := 0; i < depth*2; i++ {
w.WriteByte(' ')
}
}
func (m nodeManager) encodeHTML(ctx Context, w *bytes.Buffer, depth int, v HTML) {
m.encodeIndent(w, depth)
w.WriteByte('<')
w.WriteString(v.Tag())
for name, value := range v.attrs() {
m.encodeHTMLAttribute(ctx, w, name, value)
}
w.WriteByte('>')
if v.SelfClosing() {
return
}
children := v.body()
switch {
case len(children) > 1:
w.WriteByte('\n')
for _, child := range children {
m.encode(ctx, w, depth+1, child)
w.WriteByte('\n')
}
m.encodeIndent(w, depth)
case len(children) == 1:
child := children[0]
if text, ok := child.(*text); ok {
m.encodeText(w, 0, text)
} else {
w.WriteByte('\n')
m.encode(ctx, w, depth+1, child)
w.WriteByte('\n')
m.encodeIndent(w, depth)
}
}
w.WriteString("</")
w.WriteString(v.Tag())
w.WriteByte('>')
}
func (m nodeManager) encodeHTMLAttribute(ctx Context, w *bytes.Buffer, name, value string) {
if value == "" {
switch name {
case "id", "class", "title":
return
}
}
w.WriteString(" ")
w.WriteString(name)
if value != "" && value != "true" {
w.WriteString("=")
w.WriteString(strconv.Quote(resolveAttributeURLValue(name, value, ctx.ResolveStaticResource)))
}
}
func (m nodeManager) encodeComponent(ctx Context, w *bytes.Buffer, depth int, v Composer) {
root := v.root()
if root == nil {
root, _ = m.renderComponent(v)
}
if root != nil {
m.encode(ctx, w, depth, root)
}
}
func (m nodeManager) encodeRawHTML(w *bytes.Buffer, depth int, v *raw) {
if v.value != "" {
m.encodeIndent(w, depth)
w.WriteString(v.value)
}
}
func canUpdateValue(v, new reflect.Value) bool {
switch v.Kind() {
case reflect.String,
reflect.Bool,
reflect.Int,
reflect.Int64,
reflect.Int32,
reflect.Int16,
reflect.Int8,
reflect.Uint,
reflect.Uint64,
reflect.Uint32,
reflect.Uint16,
reflect.Uint8,
reflect.Float64,
reflect.Float32:
return !v.Equal(new)
default:
switch v.Interface().(type) {
case time.Time:
return !v.Equal(new)
default:
return !reflect.DeepEqual(v.Interface(), new.Interface())
}
}
}
func component(v UI) (Composer, bool) {
for element := v; element != nil; element = element.parent() {
if component, ok := element.(Composer); ok {
return component, true
}
}
return nil, false
}