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|
package query
import (
"fmt"
"strings"
"unicode"
)
type tokenKind int
const (
_ tokenKind = iota
tokenKindKV
tokenKindKVV
tokenKindSearch
)
type token struct {
kind tokenKind
// KV and KVV
qualifier string
value string
// KVV only
subQualifier string
// Search
term string
}
func newTokenKV(qualifier, value string) token {
return token{
kind: tokenKindKV,
qualifier: qualifier,
value: value,
}
}
func newTokenKVV(qualifier, subQualifier, value string) token {
return token{
kind: tokenKindKVV,
qualifier: qualifier,
subQualifier: subQualifier,
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 := splitFunc(query, unicode.IsSpace)
if err != nil {
return nil, err
}
var tokens []token
for _, field := range fields {
chunks, err := splitFunc(field, func(r rune) bool { return r == ':' })
if err != nil {
return nil, err
}
if strings.HasPrefix(field, ":") || strings.HasSuffix(field, ":") {
return nil, fmt.Errorf("empty qualifier or value")
}
// pre-process chunks
for i, chunk := range chunks {
if len(chunk) == 0 {
return nil, fmt.Errorf("empty qualifier or value")
}
chunks[i] = removeQuote(chunk)
}
switch len(chunks) {
case 1: // full text search
tokens = append(tokens, newTokenSearch(chunks[0]))
case 2: // KV
tokens = append(tokens, newTokenKV(chunks[0], chunks[1]))
case 3: // KVV
tokens = append(tokens, newTokenKVV(chunks[0], chunks[1], chunks[2]))
default:
return nil, fmt.Errorf("can't tokenize \"%s\": too many separators", field)
}
}
return tokens, nil
}
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
}
// split the input into chunks by splitting according to separatorFunc but respecting
// quotes
func splitFunc(input string, separatorFunc func(r rune) bool) ([]string, error) {
lastQuote := rune(0)
inQuote := false
// return true if it's part of a chunk, or false if it's a rune that delimit one, as determined by the separatorFunc.
isChunk := 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 !separatorFunc(r)
}
}
var result []string
var chunk strings.Builder
for _, r := range input {
if isChunk(r) {
chunk.WriteRune(r)
} else {
if chunk.Len() > 0 {
result = append(result, chunk.String())
chunk.Reset()
}
}
}
if inQuote {
return nil, fmt.Errorf("unmatched quote")
}
if chunk.Len() > 0 {
result = append(result, chunk.String())
}
return result, nil
}
func isQuote(r rune) bool {
return r == '"' || r == '\''
}
|
