init target and luns from config file

pkg/config/config.go

@@ -0,0 +1,114 @@
+/*
+Copyright 2016 The GoStor Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package config
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/gostor/gotgt/pkg/homedir"
+)
+
+const (
+	// ConfigFileName is the name of config file
+	ConfigFileName = "config.json"
+)
+
+var (
+	configDir = os.Getenv("GOSTOR_CONFIG")
+)
+
+type Target struct {
+	Name    string   `json:"name"`
+	Portals []string `json:"portals"`
+	LUNs    []string `json:"luns"`
+}
+
+type Config struct {
+	Storage string            `json:"storage"`
+	Targets map[string]Target `json:"targets"`
+}
+
+func init() {
+	if configDir == "" {
+		configDir = filepath.Join(homedir.Get(), ".gotgt")
+	}
+}
+
+// ConfigDir returns the directory the configuration file is stored in
+func ConfigDir() string {
+	return configDir
+}
+
+// Load reads the configuration files in the given directory and return values.
+func Load(configDir string) (*Config, error) {
+	if configDir == "" {
+		configDir = ConfigDir()
+	}
+
+	filename := filepath.Join(configDir, ConfigFileName)
+	config := &Config{
+		Storage: "file",
+		Targets: make(map[string]Target),
+	}
+
+	// Try happy path first - latest config file
+	if _, err := os.Stat(filename); err != nil {
+		if os.IsNotExist(err) {
+			return config, nil
+		}
+		// if file is there but we can't stat it for any reason other
+		// than it doesn't exist then stop
+		return config, fmt.Errorf("%s - %v", filename, err)
+	}
+	file, err := os.Open(filename)
+	if err != nil {
+		return config, fmt.Errorf("%s - %v", filename, err)
+	}
+	defer file.Close()
+	if err = json.NewDecoder(file).Decode(config); err != nil {
+		return config, err
+	}
+	if err != nil {
+		err = fmt.Errorf("%s - %v", filename, err)
+	}
+	return config, err
+}
+
+// Save encodes and writes out all the authorization information
+func (config *Config) Save(filename string) error {
+	if filename == "" {
+		return fmt.Errorf("Can't save config with empty filename")
+	}
+
+	if err := os.MkdirAll(filepath.Dir(filename), 0700); err != nil {
+		return err
+	}
+	f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	data, err := json.MarshalIndent(config, "", "\t")
+	if err != nil {
+		return err
+	}
+	_, err = f.Write(data)
+	return err
+}