Extract persistence code into own class

pkg/persistence/persistence.go

@@ -0,0 +1,90 @@
+package persistence
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path"
+)
+
+// dataPath global path for persistence
+var dataPath = os.TempDir()
+
+// SetPath sets the persistent path for the data storage
+func SetPath(path string) error {
+	if info, err := os.Stat(path); err != nil {
+		return err
+	} else if !info.IsDir() {
+		return fmt.Errorf("path for persistence is not directory")
+	}
+	dataPath = path
+	return nil
+}
+
+// Converts name to a full path
+func jsonPath(name string) string {
+	return path.Join(dataPath, fmt.Sprintf("rove-%s.json", name))
+}
+
+// Save will serialise the interface into a json file
+func Save(name string, data interface{}) error {
+	if b, err := json.MarshalIndent(data, "", "\t"); err != nil {
+		return err
+	} else {
+		if err := ioutil.WriteFile(jsonPath(name), b, os.ModePerm); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Load will load the interface from the json file
+func Load(name string, data interface{}) error {
+	path := jsonPath(name)
+	// Don't load anything if the file doesn't exist
+	_, err := os.Stat(path)
+	if os.IsNotExist(err) {
+		fmt.Printf("File %s didn't exist, loading with fresh data\n", path)
+		return nil
+	}
+
+	// Read and unmarshal the json
+	if b, err := ioutil.ReadFile(path); err != nil {
+		return err
+	} else if err := json.Unmarshal(b, data); err != nil {
+		return err
+	}
+	return nil
+}
+
+// saveLoadFunc defines a type of function to save or load an interface
+type saveLoadFunc func(string, interface{}) error
+
+func doAll(f saveLoadFunc, args ...interface{}) error {
+	var name string
+	for i, a := range args {
+		if i%2 == 0 {
+			var ok bool
+			name, ok = a.(string)
+			if !ok {
+				return fmt.Errorf("Incorrect args")
+			}
+		} else {
+			if err := f(name, a); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+// SaveAll allows for saving multiple structures in a single call
+func SaveAll(args ...interface{}) error {
+	return doAll(Save, args...)
+}
+
+// LoadAll allows for loading multiple structures in a single call
+func LoadAll(args ...interface{}) error {
+	return doAll(Load, args...)
+}