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node.go
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node.go
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package app
import (
"fmt"
"io"
"reflect"
)
// Node is the interface that describes an UI node.
type Node interface {
nodeType() reflect.Type
}
// UI is the interface that describes a node that is a user interface element.
// eg. HTML elements and components.
type UI interface {
Node
Wrapper
parent() UI
setParent(p UI)
dismount()
}
type nodeWithChildren interface {
replaceChild(old, new UI)
}
type writableNode interface {
html(w io.Writer)
htmlWithIndent(w io.Writer, indent int)
}
func indirect(nodes ...Node) []UI {
inodes := make([]UI, 0, len(nodes))
for _, n := range nodes {
switch t := n.(type) {
case Condition:
inodes = append(inodes, t.nodes()...)
case RangeLoop:
inodes = append(inodes, t.nodes()...)
case Composer:
t.setCompo(t)
inodes = append(inodes, t)
case UI:
inodes = append(inodes, t)
}
}
return inodes
}
func mount(n Node) error {
switch t := n.(type) {
case textNode:
return t.mount()
case standardNode:
return t.mount()
case rawNode:
return t.mount()
case Composer:
return t.mount(t)
default:
return fmt.Errorf("%T is not mountable", n)
}
}
func update(a, b UI) error {
if a.nodeType() != b.nodeType() {
return replace(a, b)
}
switch t := a.(type) {
case textNode:
t.update(b.(textNode))
case standardNode:
return updateStandardNode(t, b.(standardNode))
case rawNode:
return updateRawNode(t, b.(rawNode))
case Composer:
t.update(b.(Composer))
t.Update()
default:
return fmt.Errorf("%T: node can't be updated", t)
}
return nil
}
func replace(a, b UI) error {
if err := mount(b); err != nil {
return err
}
parent := a.parent()
b.setParent(parent)
parent.(nodeWithChildren).replaceChild(a, b)
for {
parentValue, ok := parent.(standardNode)
if ok {
parentValue.replaceChildValue(a, b)
break
}
parent = parent.parent()
}
a.dismount()
return nil
}
func updateStandardNode(a, b standardNode) error {
a.update(b)
achildren := a.children()
bchildren := b.children()
for len(achildren) != 0 && len(bchildren) != 0 {
if err := update(achildren[0], bchildren[0]); err != nil {
return err
}
achildren = achildren[1:]
bchildren = bchildren[1:]
}
for len(achildren) != 0 {
c := achildren[0]
a.removeChildValue(c)
a.removeChild(c)
c.dismount()
achildren = achildren[:len(achildren)-1]
}
for len(bchildren) != 0 {
c := bchildren[0]
if err := mount(c); err != nil {
return err
}
a.appendChild(c)
a.appendChildValue(c)
bchildren = bchildren[1:]
}
return nil
}
func updateRawNode(a, b rawNode) error {
if a.raw() != b.raw() {
return replace(a, b)
}
return nil
}