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parser.go
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parser.go
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package cqlparser
import (
"errors"
"strings"
)
func Parse(query string) (Node, error) {
parser, err := newParser(query)
if err != nil {
return nil, err
}
return parser.parse()
}
type parser struct {
query string
lexer *lexer
curToken *token
}
func newParser(query string) (*parser, error) {
lexer, err := newLexerFromString(query)
if err != nil {
return nil, err
}
return &parser{
query: query,
lexer: lexer,
}, nil
}
func (p *parser) nextToken() *token {
p.curToken = p.lexer.NextToken()
return p.curToken
}
func (p *parser) parse() (Node, error) {
p.nextToken()
root, err := p.parseQuery("srw.ServerChoice", CQL_SCR)
if err != nil {
return nil, err
}
if t := p.nextToken(); t != nil && t.Type != CQL_EOF {
return nil, errors.New("junk after end: " + t.Value)
}
return root, nil
}
func (p *parser) parseQuery(qualifier string, relation int) (Node, error) {
term, err := p.parseTerm(qualifier, relation)
if err != nil {
return nil, err
}
for p.curToken != nil && p.curToken.Type != CQL_EOF && p.curToken.Type != CQL_RPAREN {
switch p.curToken.Type {
case CQL_AND:
p.nextToken()
term2, err := p.parseTerm(qualifier, relation)
if err != nil {
return nil, err
}
term = &BooleanNode{
Op: "and",
Left: term,
Right: term2,
}
case CQL_OR:
p.nextToken()
term2, err := p.parseTerm(qualifier, relation)
if err != nil {
return nil, err
}
term = &BooleanNode{
Op: "or",
Left: term,
Right: term2,
}
case CQL_NOT:
p.nextToken()
term2, err := p.parseTerm(qualifier, relation)
if err != nil {
return nil, err
}
term = &BooleanNode{
Op: "not",
Left: term,
Right: term2,
}
default:
return nil, errors.New("expected boolean got " + p.curToken.Value)
}
}
return term, nil
}
func (p *parser) parseTerm(qualifier string, relation int) (Node, error) {
var word string
for p.curToken != nil {
if p.curToken.Type == CQL_LPAREN {
p.nextToken()
expr, err := p.parseQuery(qualifier, relation)
if err != nil {
return nil, err
}
if p.curToken.Type != CQL_RPAREN {
return nil, errors.New("missing )")
}
p.nextToken()
return expr, nil
}
word = p.curToken.Value
p.nextToken()
if !p.isBaseRelation(p.curToken) {
break
}
qualifier = word
relation = p.curToken.Type
p.nextToken()
}
if word == "" {
return nil, errors.New("missing term")
}
return &TermNode{
Index: qualifier,
Relation: relationToStr(relation),
Value: word,
}, nil
}
func (p *parser) isBaseRelation(t *token) bool {
if t == nil {
return false
}
// unknown first class relation
if t.Type == CQL_WORD && !strings.Contains(t.Value, ".") {
return false
}
return p.isProxRelation(t) || t.Type == CQL_ALL || t.Type == CQL_ANY || t.Type == CQL_EXACT ||
t.Type == CQL_SCR || t.Type == CQL_WORD || t.Type == CQL_WITHIN
}
func (p *parser) isProxRelation(t *token) bool {
if t == nil {
return false
}
return t.Type == CQL_LT || t.Type == CQL_GT || t.Type == CQL_EQ ||
t.Type == CQL_LE || t.Type == CQL_GE || t.Type == CQL_NE
}