viney-shih/go-cache

package cache

import (
    "strings"
    "sync"
)

const (
    packageKey = "ca"
    topicKey   = "tp"

    // delimiters
    cacheDelim = ":"
    topicDelim = "#"
)

var (
    regPkgKey = packageKey
    // regKeyOnce limits key registeration happening once
    regKeyOnce = sync.Once{}
)

func registerKey(pkgKey string) {
    regKeyOnce.Do(func() {
        regPkgKey = pkgKey
    })
}

func customKey(delimiter string, components ...string) string {
    return strings.Join(components, delimiter)
}

func getTopic(topic string) string {
    return customKey(topicDelim, regPkgKey, topicKey, topic)
}

func getCacheKey(pfx, key string) string {
    if regPkgKey == "" {
        return customKey(cacheDelim, pfx, key)
    }

    return customKey(cacheDelim, regPkgKey, pfx, key)
}

func getCacheKeys(pfx string, keys []string) []string {
    cacheKeys := make([]string, len(keys))
    for i, k := range keys {
        cacheKeys[i] = getCacheKey(pfx, k)
    }

    return cacheKeys
}

func getPrefixAndKey(cacheKey string) (string, string) {
    // 1) cacheKey = regPkgKey + prefix + key (normal case)
    // 2) cacheKey = prefix + key (if customized package key is empty)
    idx := strings.Index(cacheKey, cacheDelim)
    if idx < 0 {
        return cacheKey, "" // should not happen
    }

    if regPkgKey == "" {
        return cacheKey[:idx], cacheKey[idx+len(cacheDelim):]
    }

    // mixedKey = prefix + key
    mixedKey := cacheKey[idx+len(cacheDelim):]
    idx = strings.Index(mixedKey, cacheDelim)
    if idx < 0 {
        return mixedKey, ""
    }

    return mixedKey[:idx], mixedKey[idx+len(cacheDelim):]
}