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|
package jsonpath
import (
"fmt"
"strconv"
"strings"
"src.userspace.com.au/lexer"
base "src.userspace.com.au/query"
)
type Parser struct {
l *lexer.Lexer
pos int
tok *lexer.Token
}
func NewParser() (*Parser, error) {
return &Parser{}, nil
}
func (p *Parser) next() (done bool) {
p.tok, done = p.l.NextToken()
if p.tok != nil {
p.pos = p.tok.Position
}
return p.tok != nil && !done
}
func (p *Parser) Parse(input string) (Selector, error) {
var sel, nr Selector
var err error
p.l = lexer.New(input, pathState)
p.l.Start()
// First token
p.next()
if p.tok.Type != TAbsolute {
// TODO does jsonpath have relative searches
return nil, fmt.Errorf("expected root, got %s", p.tok.Value)
}
p.next()
if p.tok.Type == lexer.EOFToken {
return rootSelector, nil
}
sel = rootSelector
for {
switch p.tok.Type {
case TRecursive:
p.next()
p.next()
if nr, err = p.parseStepSelector(); err != nil {
return nil, err
}
sel = recursiveSelector(nr)
case TChildDot:
p.next()
if nr, err = p.parseStepSelector(); err != nil {
return nil, err
}
sel = childSelector(sel, nr)
default:
return sel, nil
}
}
panic("unreachable")
}
func (p *Parser) parseStepSelector() (Selector, error) {
var sel, nr Selector
var err error
sel = p.parseNodeTestSelector()
p.next()
switch p.tok.Type {
case TPredicateStart:
p.next()
if nr, err = p.parsePredicateExprSelector(); err != nil {
return nil, err
}
sel = childSelector(sel, nr)
case lexer.EOFToken:
return sel, nil
default:
}
return sel, nil
}
func (p *Parser) parseNodeTestSelector() (sel Selector) {
switch p.tok.Type {
case TName:
/*
switch p.tok.Value {
case "object", "array", "string", "number", "boolean", "null":
// TODO
//sel = typeSelector(p.tok.Value)
default:
}
*/
sel = nameSelector(p.tok.Value)
case TQuotedName:
sel = nameSelector(strings.Trim(p.tok.Value, `"'`))
case TWildcard:
sel = wildcardSelector
default:
}
return sel
}
func (p *Parser) parsePredicateExprSelector() (Selector, error) {
var err error
if p.tok.Type != TNumber {
return nil, fmt.Errorf("expecting number")
}
num, err := strconv.ParseInt(p.tok.Value, 10, 64)
if err != nil {
return nil, err
}
return arrayIndexSelector(num), nil
/* TODO
var els []int64
if p.tok.Type == TPredicateEnd {
return arrayIndexSelector(num), nil
}
els = append(els, num)
p.next()
if p.tok.Type == TRange {
// FIXME
p.next()
num, err := strconv.ParseInt(p.tok.Value, 10, 64)
if err != nil {
return nil, err
}
els = append(els, num)
// We have start and finish range
}
if p.tok.Type == TUnion {
// FIXME
}
}
return childSelector(rootSelector, arrayIndexSelector(idx)), nil
return sel, nil
*/
}
// rootSelector checks node is root
func rootSelector(n base.Node) bool {
result := false
parent := n.Parent()
if parent != nil && parent.Type() == base.DocumentNode {
result = true
} else {
result = (n.Type() == base.DocumentNode)
}
return result
}
// wildcardSelector returns true
func wildcardSelector(n base.Node) bool {
return true
}
// childSelector creates a selector for c being a child of p
func childSelector(p, c Selector) Selector {
return func(n base.Node) bool {
parent := n.Parent()
result := (c(n) && parent != nil && p(parent))
return result
}
}
// nameSelector generates selector for object key == k
func nameSelector(k string) Selector {
return func(n base.Node) bool {
result := (n.Type() == base.ElementNode && n.Data() == k)
return result
}
}
// recursiveSelector matches any node below which matches a
func recursiveSelector(a Selector) Selector {
return func(n base.Node) bool {
if n.Type() != base.ElementNode {
return false
}
return hasRecursiveMatch(n, a)
}
}
func hasRecursiveMatch(n base.Node, a Selector) bool {
for c := n.FirstChild(); c != nil; c = c.NextSibling() {
if a(c) || (c.Type() == base.ElementNode && hasRecursiveMatch(c, a)) {
return true
}
}
return false
}
// arrayIndexSelector generates selector for node being idx index of parent
func arrayIndexSelector(idx int64) Selector {
return func(n base.Node) bool {
if n.DataType() != "arrayitem" {
return false
}
parent := n.Parent()
if parent == nil {
return false
}
i := int64(0)
for c := parent.FirstChild(); c != nil && i <= idx; c = c.NextSibling() {
if i == idx && c == n {
return true
}
i++
}
return false
}
}
// typeSelector matches a node with type t
func typeSelector(t string) Selector {
return func(n base.Node) bool {
// FIXME
if n.DataType() == t {
return true
}
return false
}
}
|
