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parser.go
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parser.go
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package airp
import (
"regexp"
"strconv"
)
var keyRegex = regexp.MustCompile(`[[:alpha:]][[:word:]:\-]*`)
// parser is a state machine creating an ast from lex tokens
// the parser is only allowed to cancel it if receives an error from the lexer
type parser struct {
in <-chan token
quitIn func()
init parseFunc
ast *Node
prev token
}
type parseFunc func(p *parser) (parseFunc, error)
// Parse reads tokens from a channel and generates a ast.
// The returned node is the root node of the ast.
func parse(ch <-chan token, quit func()) (*Node, error) {
defer quit()
p := &parser{
in: ch,
quitIn: quit,
init: expektValue,
ast: new(Node),
}
var err error
for f := p.init; f != nil && err == nil; f, err = f(p) {
}
return p.ast, err
}
// parseFunc's
func expektKey(p *parser) (parseFunc, error) {
t := <-p.in
if p.ast.parent == nil || p.ast.parent.jsonType != Object {
panic("invariant violation: expect key while not in object")
}
if t.Type == objectCToken {
if kn, ok := p.ast.parent.value.([]KeyNode); ok && len(kn) == 1 {
p.ast.parent.value = []KeyNode(nil)
p.ast = p.ast.parent
return expektDelim, nil
}
}
if t.Type != stringToken {
return nil, newParseError("key", p.prev, t, p.ast)
}
if t.value != keyRegex.FindString(t.value) {
return nil, newParseError("valid key", p.prev, t, p.ast)
}
pp := p.ast.parent.value.([]KeyNode)
for _, kn := range pp {
if kn.Key == t.value {
return nil, newParseError("unique key", p.prev, t, p.ast)
}
}
if pp[len(pp)-1].Node != p.ast {
panic("not 'this'")
}
pp[len(pp)-1].Key = t.value
p.prev, t = t, <-p.in
defer func() { p.prev = t }()
if t.Type != colonToken {
return nil, newParseError("colon", p.prev, t, p.ast)
}
return expektValue, nil
}
func expektValue(p *parser) (parseFunc, error) {
t := <-p.in
defer func() { p.prev = t }()
if p.ast.parent != nil && t.Type == arrayCToken {
if nn, ok := p.ast.parent.value.([]*Node); ok && len(nn) == 1 {
p.ast.parent.value = []*Node(nil)
p.ast = p.ast.parent
return expektDelim, nil
}
}
switch t.Type {
case numberToken:
p.ast.jsonType = Number
// number check
num, err := strconv.ParseFloat(t.value, 64)
if err != nil {
return nil, newParseError("number", p.prev, t, p.ast)
}
p.ast.value = num
return expektDelim, nil
case stringToken:
p.ast.jsonType = String
p.ast.value = t.value
return expektDelim, nil
case nullToken:
p.ast.jsonType = Null
return expektDelim, nil
case trueToken:
p.ast.jsonType = Bool
p.ast.value = true
return expektDelim, nil
case falseToken:
p.ast.jsonType = Bool
p.ast.value = false
return expektDelim, nil
case arrayOToken:
p.ast.jsonType = Array
nn := make([]*Node, 1, 4)
nn[0] = new(Node)
nn[0].parent = p.ast
p.ast.value = nn
p.ast = nn[0]
return expektValue, nil
case objectOToken:
p.ast.jsonType = Object
kn := make([]KeyNode, 1, 4)
kn[0].Node = new(Node)
kn[0].parent = p.ast
p.ast.value = kn
p.ast = kn[0].Node
return expektKey, nil
default:
return nil, newParseError("value", p.prev, t, p.ast)
}
}
func expektDelim(p *parser) (parseFunc, error) {
t, ok := <-p.in
defer func() { p.prev = t }()
if !ok {
if p.ast.parent == nil {
return nil, nil // all OK!
}
return nil, newParseError("delimiter", p.prev, p.prev, p.ast)
}
switch t.Type {
case commaToken:
if p.ast.parent == nil {
return nil, newParseError("no comma", p.prev, t, p.ast)
}
if p.ast.parent.jsonType == Array {
p.ast.parent.value = append(p.ast.parent.value.([]*Node), &Node{parent: p.ast.parent})
p.ast = p.ast.parent.value.([]*Node)[len(p.ast.parent.value.([]*Node))-1]
return expektValue, nil
}
if p.ast.parent.jsonType == Object {
p.ast.parent.value = append(p.ast.parent.value.([]KeyNode), KeyNode{Node: &Node{parent: p.ast.parent}})
p.ast = p.ast.parent.value.([]KeyNode)[len(p.ast.parent.value.([]KeyNode))-1].Node
return expektKey, nil
}
return nil, newParseError("no comma", p.prev, t, p.ast)
case arrayCToken, objectCToken:
if p.ast.parent == nil {
return nil, newParseError("to be in array or object", p.prev, t, p.ast)
}
switch p.ast.parent.jsonType {
case Array:
if t.Type != arrayCToken {
return nil, newParseError("array closing", p.prev, t, p.ast)
}
p.ast = p.ast.parent
return expektDelim, nil
case Object:
if t.Type != objectCToken {
return nil, newParseError("object closing", p.prev, t, p.ast)
}
p.ast = p.ast.parent
return expektDelim, nil
default:
return nil, newParseError("to be in array or object", p.prev, t, p.ast)
}
default:
return nil, newParseError("delimiter", p.prev, t, p.ast)
}
}