cmd/bitcask: recovery tool (#92)

* cmd/bitcask: recovery tool

* refactor configuration & use it in recover tool

internal/config/config.go

@@ -0,0 +1,36 @@
+package config
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"path/filepath"
+)
+
+// Config contains the bitcask configuration parameters
+type Config struct {
+	MaxDatafileSize int  `json:"max_datafile_size"`
+	MaxKeySize      int  `json:"max_key_size"`
+	MaxValueSize    int  `json:"max_value_size"`
+	Sync            bool `json:"sync"`
+}
+
+// Decode decodes a serialized configuration
+func Decode(path string) (*Config, error) {
+	var cfg Config
+
+	data, err := ioutil.ReadFile(filepath.Join(path, "config.json"))
+	if err != nil {
+		return nil, err
+	}
+
+	if err := json.Unmarshal(data, &cfg); err != nil {
+		return nil, err
+	}
+
+	return &cfg, nil
+}
+
+// Encode encodes the configuration for storage
+func (c *Config) Encode() ([]byte, error) {
+	return json.Marshal(c)
+}