package cache

import (
	"strings"
	"sync"
	"time"
)

// memoryFallback Redis 不可用时的内存备用缓存，保证服务可用
var (
	memoryMu   sync.RWMutex
	memoryData = make(map[string]*memoryEntry)
)

type memoryEntry struct {
	Data   []byte
	Expiry time.Time
}

func memoryGet(key string) ([]byte, bool) {
	memoryMu.RLock()
	defer memoryMu.RUnlock()
	e, ok := memoryData[key]
	if !ok || e == nil || time.Now().After(e.Expiry) {
		return nil, false
	}
	return e.Data, true
}

func memorySet(key string, data []byte, ttl time.Duration) {
	memoryMu.Lock()
	defer memoryMu.Unlock()
	memoryData[key] = &memoryEntry{Data: data, Expiry: time.Now().Add(ttl)}
}

func memoryDel(key string) {
	memoryMu.Lock()
	defer memoryMu.Unlock()
	delete(memoryData, key)
}

// memoryDelPattern 按前缀删除（pattern 如 soul:book:chapters-by-part:* 转为前缀 soul:book:chapters-by-part:）
func memoryDelPattern(pattern string) {
	prefix := strings.TrimSuffix(pattern, "*")
	memoryMu.Lock()
	defer memoryMu.Unlock()
	for k := range memoryData {
		if strings.HasPrefix(k, prefix) {
			delete(memoryData, k)
		}
	}
}