package wasm

import (
	"strconv"
	"syscall/js"
)

type Node struct {
	tag       string
	id        string
	attrs     []*Attribute
	children  []*Node
	jsElement js.Value
	innerText string
}

type Attribute struct {
	Name  string
	Value string
}

func document(document js.Value) *Node {
	return &Node{jsElement: document}
}

func (n *Node) createElement(document js.Value) {
	var el = document.Call("createElement", n.tag)
	el.Call("setAttribute", "id", n.id)
	for _, attr := range n.attrs {
		el.Call("setAttribute", attr.Name, attr.Value)
	}
	n.jsElement = el
}

func (n *Node) AppendChild(child *Node) {
	if child.tag != "" {
		n.children = append(n.children, child)
		n.jsElement.Call("appendChild", child.jsElement)
	} else {
		n.jsElement.Set("innerText", child.innerText)
	}
}

func (n *Node) GetChildren() []*Node {
	return n.children
}

func (n *Node) ReplaceChildren(newChildren []*Node) {
	n.children = newChildren
	for {
		child := n.jsElement.Get("firstChild")
		if child.IsNull() {
			break
		}
		n.jsElement.Call("removeChild", child)
	}
	for _, child := range n.children {
		n.AppendChild(child)
	}
}

type NodeFactory struct {
	document  *Node
	idCounter int64
	root      *Node
}

func NewNodeFactory(jsDocument js.Value) *NodeFactory {
	var f = &NodeFactory{document: document(jsDocument), idCounter: 0}
	f.setRoot()
	return f
}

func (f *NodeFactory) setRoot() {
	var rootElement = f.document.jsElement.Get("firstElementChild")
	if rootElement.IsNull() {
		f.root = f.NewNode("html")
	} else {
		f.root = &Node{tag: "html", jsElement: rootElement}
		f.document.AppendChild(f.root)
	}
}

func (f *NodeFactory) Root() *Node {
	return f.root
}

func (f *NodeFactory) NewBody() *Node {
	var body = f.NewNode("body")
	f.root.AppendChild(body)
	return body
}

func (f *NodeFactory) NewNode(tag string, attributes ...*Attribute) *Node {
	var id = f.idCounter
	f.idCounter++
	var n = &Node{tag: tag, id: strconv.FormatInt(id, 10), attrs: attributes}
	n.createElement(f.document.jsElement)
	return n
}

func (f *NodeFactory) NewTextNode(text string) *Node {
	return &Node{innerText: text}
}