blob: 25a75d88baa3e40247a43cf2b78bf29f226667a8 [file] [log] [blame]
// Copyright 2016 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package query
import (
"log"
"regexp/syntax"
)
var _ = log.Println
func LowerRegexp(r *syntax.Regexp) *syntax.Regexp {
newRE := *r
switch r.Op {
case syntax.OpLiteral, syntax.OpCharClass:
newRE.Rune = make([]rune, len(r.Rune))
for i, c := range r.Rune {
if c >= 'A' && c <= 'Z' {
newRE.Rune[i] = c + 'a' - 'A'
} else {
newRE.Rune[i] = c
}
}
default:
newRE.Sub = make([]*syntax.Regexp, len(newRE.Sub))
for i, s := range r.Sub {
newRE.Sub[i] = LowerRegexp(s)
}
}
return &newRE
}
// RegexpToQuery tries to distill a substring search query that
// matches a superset of the regexp.
func RegexpToQuery(r *syntax.Regexp, minTextSize int) Q {
q := regexpToQueryRecursive(r, minTextSize)
q = Simplify(q)
return q
}
func regexpToQueryRecursive(r *syntax.Regexp, minTextSize int) Q {
// TODO - we could perhaps transform Begin/EndText in '\n'?
// TODO - we could perhaps transform CharClass in (OrQuery )
// if there are just a few runes, and part of a OpConcat?
switch r.Op {
case syntax.OpLiteral:
s := string(r.Rune)
if len(s) >= minTextSize {
return &Substring{Pattern: s}
}
case syntax.OpCapture:
return regexpToQueryRecursive(r.Sub[0], minTextSize)
case syntax.OpPlus:
return regexpToQueryRecursive(r.Sub[0], minTextSize)
case syntax.OpRepeat:
if r.Min >= 1 {
return regexpToQueryRecursive(r.Sub[0], minTextSize)
}
case syntax.OpConcat, syntax.OpAlternate:
var qs []Q
for _, sr := range r.Sub {
if sq := regexpToQueryRecursive(sr, minTextSize); sq != nil {
qs = append(qs, sq)
}
}
if r.Op == syntax.OpConcat {
return &And{qs}
}
return &Or{qs}
}
return &Const{true}
}