src/cache/cache.go

@@ -0,0 +1,85 @@
+package cache
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+type Cache struct {
+	Root string
+}
+
+type CacheEntry struct {
+	Expire time.Time `json:"e"`
+	Value  string    `json:"v"`
+}
+
+func DefaultCache() *Cache {
+	return &Cache{
+		Root: filepath.Join(os.TempDir(), "gospt.cache"),
+	}
+}
+
+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(map[string]CacheEntry) error {
+	out := map[string]CacheEntry{}
+	payload, err := json.Marshal(out)
+	if err != nil {
+		return err
+	}
+	err = os.WriteFile(c.Root, payload, 0640)
+	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 {
+		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,
+	}
+	return value, nil
+}