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|
package query
import (
"fmt"
"strings"
"unicode"
)
type tokenKind int
const (
_ tokenKind = iota
tokenKindKV
tokenKindSearch
)
type token struct {
kind tokenKind
// KV
qualifier string
value string
// Search
term string
}
func newTokenKV(qualifier, value string) token {
return token{
kind: tokenKindKV,
qualifier: qualifier,
value: value,
}
}
func newTokenSearch(term string) token {
return token{
kind: tokenKindSearch,
term: term,
}
}
// tokenize parse and break a input into tokens ready to be
// interpreted later by a parser to get the semantic.
func tokenize(query string) ([]token, error) {
fields, err := splitQuery(query)
if err != nil {
return nil, err
}
var tokens []token
for _, field := range fields {
split := strings.Split(field, ":")
// full text search
if len(split) == 1 {
tokens = append(tokens, newTokenSearch(removeQuote(field)))
continue
}
if len(split) != 2 {
return nil, fmt.Errorf("can't tokenize \"%s\"", field)
}
if len(split[0]) == 0 {
return nil, fmt.Errorf("can't tokenize \"%s\": empty qualifier", field)
}
if len(split[1]) == 0 {
return nil, fmt.Errorf("empty value for qualifier \"%s\"", split[0])
}
tokens = append(tokens, newTokenKV(split[0], removeQuote(split[1])))
}
return tokens, nil
}
// split the query into chunks by splitting on whitespaces but respecting
// quotes
func splitQuery(query string) ([]string, error) {
lastQuote := rune(0)
inQuote := false
isToken := func(r rune) bool {
switch {
case !inQuote && isQuote(r):
lastQuote = r
inQuote = true
return true
case inQuote && r == lastQuote:
lastQuote = rune(0)
inQuote = false
return true
case inQuote:
return true
default:
return !unicode.IsSpace(r)
}
}
var result []string
var token strings.Builder
for _, r := range query {
if isToken(r) {
token.WriteRune(r)
} else {
if token.Len() > 0 {
result = append(result, token.String())
token.Reset()
}
}
}
if inQuote {
return nil, fmt.Errorf("unmatched quote")
}
if token.Len() > 0 {
result = append(result, token.String())
}
return result, nil
}
func isQuote(r rune) bool {
return r == '"' || r == '\''
}
func removeQuote(field string) string {
runes := []rune(field)
if len(runes) >= 2 {
r1 := runes[0]
r2 := runes[len(runes)-1]
if r1 == r2 && isQuote(r1) {
return string(runes[1 : len(runes)-1])
}
}
return field
}
|
