gspot/src/components/cache/cache.go

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package cache
import (
"encoding/json"
"fmt"
"log/slog"
"os"
"path/filepath"
"time"
"go.uber.org/fx"
)
type CacheEntry struct {
Expire time.Time `json:"e"`
Value string `json:"v"`
}
type CacheResult struct {
fx.Out
Cache *Cache
}
type Cache struct {
Root string
Log *slog.Logger
}
type CacheParams struct {
fx.In
Log *slog.Logger
}
func NewCache(p CacheParams) CacheResult {
c := &Cache{
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Root: filepath.Join(os.TempDir(), "gspot.cache"),
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Log: p.Log,
}
return CacheResult{
Cache: c,
}
}
func (c *Cache) load() (map[string]CacheEntry, error) {
out := map[string]CacheEntry{}
cache, err := os.Open(c.Root)
if err != nil {
return nil, err
}
if err := json.NewDecoder(cache).Decode(&out); err != nil {
return nil, err
}
return out, nil
}
func (c *Cache) save(m map[string]CacheEntry) error {
payload, err := json.Marshal(m)
if err != nil {
return err
}
slog.Debug("CACHE", "saving", string(payload))
err = os.WriteFile(c.Root, payload, 0o600)
if err != nil {
return err
}
return nil
}
func (c *Cache) GetOrDo(key string, do func() (string, error), ttl time.Duration) (string, error) {
conf, err := c.load()
if err != nil {
slog.Debug("CACHE", "failed read", err)
return c.Do(key, do, ttl)
}
val, ok := conf[key]
if !ok {
return c.Do(key, do, ttl)
}
if time.Now().After(val.Expire) {
return c.Do(key, do, ttl)
}
return val.Value, nil
}
func (c *Cache) Do(key string, do func() (string, error), ttl time.Duration) (string, error) {
if do == nil {
return "", nil
}
res, err := do()
if err != nil {
return "", err
}
return c.Put(key, res, ttl)
}
func (c *Cache) Put(key string, value string, ttl time.Duration) (string, error) {
conf, err := c.load()
if err != nil {
conf = map[string]CacheEntry{}
}
conf[key] = CacheEntry{
Expire: time.Now().Add(ttl),
Value: value,
}
slog.Debug("CACHE", "new item", fmt.Sprintf("%s: %s", key, value))
err = c.save(conf)
if err != nil {
slog.Debug("CACHE", "failed to save", err)
}
return value, nil
}
func (c *Cache) Clear() error {
return os.Remove(c.Root)
}