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|
package query
import (
"fmt"
"strings"
"unicode"
)
type token struct {
qualifier string
value string
}
// TODO: this lexer implementation behave badly with unmatched quotes.
// A hand written one would be better instead of relying on strings.FieldsFunc()
// 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 := splitQuery(query)
var tokens []token
for _, field := range fields {
split := strings.Split(field, ":")
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, token{
qualifier: split[0],
value: removeQuote(split[1]),
})
}
return tokens, nil
}
func splitQuery(query string) []string {
lastQuote := rune(0)
f := func(c rune) bool {
switch {
case c == lastQuote:
lastQuote = rune(0)
return false
case lastQuote != rune(0):
return false
case unicode.In(c, unicode.Quotation_Mark):
lastQuote = c
return false
default:
return unicode.IsSpace(c)
}
}
return strings.FieldsFunc(query, f)
}
func removeQuote(field string) string {
if len(field) >= 2 {
if field[0] == '"' && field[len(field)-1] == '"' {
return field[1 : len(field)-1]
}
}
return field
}
|
