// Copyright 2019 gf Author(https://github.com/gogf/gf). All Rights Reserved.
//
// This Source Code Form is subject to the terms of the MIT License.
// If a copy of the MIT was not distributed with this file,
// You can obtain one at https://github.com/gogf/gf.

package gregex

import (
	"regexp"
	"sync"
)

var (
	regexMu = sync.RWMutex{}
	// Cache for regex object.
	// TODO There's no expiring logic for this map.
	regexMap = make(map[string]*regexp.Regexp)
)

// getRegexp returns *regexp.Regexp object with given <pattern>.
// It uses cache to enhance the performance for compiling regular expression pattern,
// which means, it will return the same *regexp.Regexp object with the same regular
// expression pattern.
func getRegexp(pattern string) (*regexp.Regexp, error) {
	if r := getCache(pattern); r != nil {
		return r, nil
	}
	if r, err := regexp.Compile(pattern); err == nil {
		setCache(pattern, r)
		return r, nil
	} else {
		return nil, err
	}
}

// getCache returns *regexp.Regexp object from cache by given <pattern>, for internal usage.
func getCache(pattern string) (regex *regexp.Regexp) {
	regexMu.RLock()
	regex = regexMap[pattern]
	regexMu.RUnlock()
	return
}

// setCache stores *regexp.Regexp object into cache, for internal usage.
func setCache(pattern string, regex *regexp.Regexp) {
	regexMu.Lock()
	regexMap[pattern] = regex
	regexMu.Unlock()
}