initial commit

lib/cache.go

@@ -0,0 +1,80 @@
+package lib
+
+import (
+	"encoding/json"
+	"os"
+)
+
+const cacheFile = "cache.json"
+
+type CacheItem struct {
+	Fetcher string
+	Value   string
+}
+
+type Cache struct {
+	Items []CacheItem
+}
+
+func (c *Cache) Update(fetcher string, value string) {
+	for i := range c.Items {
+		if c.Items[i].Fetcher == fetcher {
+			c.Items[i].Value = value
+			return
+		}
+	}
+	c.Items = append(c.Items, CacheItem{
+		Fetcher: fetcher,
+		Value:   value,
+	})
+}
+
+func (c *Cache) Get(fetcher string) (string, bool) {
+	for _, item := range c.Items {
+		if item.Fetcher == fetcher {
+			return item.Value, true
+		}
+	}
+	return "", false
+}
+
+func (c *Cache) Has(fetcher string) bool {
+	_, found := c.Get(fetcher)
+	return found
+}
+
+func (c *Cache) IsChanged(fetcher string, value string) bool {
+	cachedValue, found := c.Get(fetcher)
+	if !found || cachedValue != value {
+		return true
+	}
+	return false
+}
+
+func (c *Cache) TryUpdate(fetcher string, value string) bool {
+	if c.IsChanged(fetcher, value) {
+		c.Update(fetcher, value)
+		return true
+	}
+	return false
+}
+
+func (c *Cache) Load() {
+	f, err := os.Open(cacheFile)
+	if err != nil {
+		return
+	}
+	defer f.Close()
+
+	_ = json.NewDecoder(f).Decode(&c.Items)
+}
+
+func (c *Cache) Save() {
+	f, err := os.Create(cacheFile)
+	if err != nil {
+		return
+	}
+	defer f.Close()
+
+	_ = json.NewEncoder(f).Encode(c.Items)
+}