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parser.go
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parser.go
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package jsx
import (
"fmt"
"runtime"
)
type AttrType int
const (
HtmlAttr AttrType = iota
JsAttr
)
type Attr struct {
Payload string
Typ AttrType
}
type Node interface {
Node()
}
type ElementNode struct {
Name string
Children []Node
Attrs map[string]Attr
SpreadAttrs []JsNode
}
func (ElementNode) Node() {}
type TextNode string
func (TextNode) Node() {}
type JsNode string
func (JsNode) Node() {}
type Parser struct {
lexer *lexer
err error
it *item //lookahead
root *ElementNode
lastPos int
}
func (p *Parser) nextItem() (it item) {
if p.it != nil {
it = *p.it
p.it = nil
return it
}
return p.lexer.nextItem()
}
func (p *Parser) peekItem() item {
it := p.nextItem()
p.it = &it
return it
}
func (p *Parser) expectItem(typ itemType) item {
it := p.nextItem()
if it.typ != typ {
pcs := make([]uintptr, 5)
pcs = pcs[:runtime.Callers(1, pcs)]
s := ""
for _, pc := range pcs {
s += " <- " + runtime.FuncForPC(pc).Name()
}
panic(fmt.Errorf("[%s]: expected token of type %v", s, typ))
}
return it
}
func (p *Parser) Parse() (finalErr error) {
defer func() {
if x := recover(); x != nil {
if err, ok := x.(error); ok {
p.err = err
finalErr = err
} else {
panic(x)
}
}
}()
p.root = p.parseElement()
return nil
}
func (p *Parser) parseElement() *ElementNode {
// opening tag
it := p.expectItem(itemOpeningTag)
node := &ElementNode{
Name: it.val,
Attrs: make(map[string]Attr),
}
for {
it = p.peekItem()
switch it.typ {
case itemAttributeName:
// <node attr
// eat token
key, val := p.parseAttribute()
node.Attrs[key] = val
case itemLeftDelim:
// <node {
node.SpreadAttrs = append(node.SpreadAttrs, p.parseSpreadAttributes())
case itemEndOpeningTag:
p.it = nil
return p.parseChildren(node)
case itemSelfClosingTag:
p.lastPos = p.it.lastPos
p.it = nil
return node
default:
panic(fmt.Errorf("parseElement: unexpected token %#v in %q", it, p.lexer.input[p.lexer.start:p.lexer.start+10]))
}
}
}
func (p *Parser) parseChildren(node *ElementNode) *ElementNode {
for {
it := p.peekItem()
switch it.typ {
case itemOpeningTag:
// <node><child>
node.Children = append(node.Children, p.parseElement())
case itemText:
// <node>text
node.Children = append(node.Children, p.parseText())
case itemClosingTag:
p.lastPos = p.it.lastPos
// eat token
p.it = nil
// </node>
// the end
return node
case itemLeftDelim:
// <node>{
js := p.parseJs()
node.Children = append(node.Children, js)
default:
panic(fmt.Errorf("parseChildren: unexpected token %#v in %q", it, p.lexer.input[p.lexer.start:p.lexer.start+10]))
}
}
}
func (p *Parser) parseText() TextNode {
it := p.expectItem(itemText)
return TextNode(it.val)
}
func (p *Parser) parseJs() JsNode {
p.expectItem(itemLeftDelim)
it := p.expectItem(itemJS)
p.expectItem(itemRightDelim)
return JsNode(it.val)
}
func (p *Parser) parseAttribute() (string, Attr) {
it := p.expectItem(itemAttributeName)
key := it.val
switch p.peekItem().typ {
case itemAttributeValue:
return key, p.parseAttributeValue()
case itemLeftDelim:
val := p.parseJs()
return key, Attr{Payload: string(val), Typ: JsAttr}
default:
panic(fmt.Errorf("parseAttribute: unexpected token %#v", *p.it))
}
}
func (p *Parser) parseAttributeValue() Attr {
it := p.expectItem(itemAttributeValue)
return Attr{Payload: string(it.val), Typ: HtmlAttr}
}
func (p *Parser) parseSpreadAttributes() JsNode {
p.expectItem(itemLeftDelim)
p.expectItem(itemEllipsis)
it := p.expectItem(itemJS)
p.expectItem(itemRightDelim)
return JsNode(it.val)
}