1 files changed, 120 insertions, 0 deletions
diff --git a/lib/xdsconfig/fileconfig.go b/lib/xdsconfig/fileconfig.go
new file mode 100644
index 0000000..0c4828c
--- /dev/null
+++ b/lib/xdsconfig/fileconfig.go
@@ -0,0 +1,120 @@
+package xdsconfig
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/user"
+	"path"
+	"path/filepath"
+	"regexp"
+)
+
+type SyncThingConf struct {
+	BinDir     string `json:"binDir"`
+	Home       string `json:"home"`
+	GuiAddress string `json:"gui-address"`
+	GuiAPIKey  string `json:"gui-apikey"`
+}
+
+type FileConfig struct {
+	HTTPPort string         `json:"httpPort"`
+	SThgConf *SyncThingConf `json:"syncthing"`
+}
+
+// getConfigFromFile reads configuration from a config file.
+// Order to determine which config file is used:
+//  1/ from command line option: "--config myConfig.json"
+//  2/ $HOME/.xds/agent-config.json file
+//  3/ <current_dir>/agent-config.json file
+//  4/ <executable dir>/agent-config.json file
+
+func updateConfigFromFile(c *Config, confFile string) (*FileConfig, error) {
+
+	searchIn := make([]string, 0, 3)
+	if confFile != "" {
+		searchIn = append(searchIn, confFile)
+	}
+	if usr, err := user.Current(); err == nil {
+		searchIn = append(searchIn, path.Join(usr.HomeDir, ".xds", "agent-config.json"))
+	}
+	cwd, err := os.Getwd()
+	if err == nil {
+		searchIn = append(searchIn, path.Join(cwd, "agent-config.json"))
+	}
+	exePath, err := filepath.Abs(filepath.Dir(os.Args[0]))
+	if err == nil {
+		searchIn = append(searchIn, path.Join(exePath, "agent-config.json"))
+	}
+
+	var cFile *string
+	for _, p := range searchIn {
+		if _, err := os.Stat(p); err == nil {
+			cFile = &p
+			break
+		}
+	}
+	fCfg := FileConfig{}
+	if cFile == nil {
+		// No config file found
+		return &fCfg, nil
+	}
+
+	c.log.Infof("Use config file: %s", *cFile)
+
+	// TODO move on viper package to support comments in JSON and also
+	// bind with flags (command line options)
+	// see https://github.com/spf13/viper#working-with-flags
+
+	fd, _ := os.Open(*cFile)
+	defer fd.Close()
+	if err := json.NewDecoder(fd).Decode(&fCfg); err != nil {
+		return nil, err
+	}
+
+	// Support environment variables (IOW ${MY_ENV_VAR} syntax) in agent-config.json
+	// TODO: better to use reflect package to iterate on fields and be more generic
+	var rep string
+
+	if rep, err = resolveEnvVar(fCfg.SThgConf.BinDir); err != nil {
+		return nil, err
+	}
+	fCfg.SThgConf.BinDir = path.Clean(rep)
+
+	if rep, err = resolveEnvVar(fCfg.SThgConf.Home); err != nil {
+		return nil, err
+	}
+	fCfg.SThgConf.Home = path.Clean(rep)
+
+	return &fCfg, nil
+}
+
+// resolveEnvVar Resolved environment variable regarding the syntax ${MYVAR}
+func resolveEnvVar(s string) (string, error) {
+	re := regexp.MustCompile("\\${(.*)}")
+	vars := re.FindAllStringSubmatch(s, -1)
+	res := s
+	for _, v := range vars {
+		val := os.Getenv(v[1])
+		if val == "" {
+			return res, fmt.Errorf("ERROR: %s env variable not defined", v[1])
+		}
+
+		rer := regexp.MustCompile("\\${" + v[1] + "}")
+		res = rer.ReplaceAllString(res, val)
+	}
+
+	return res, nil
+}
+
+// exists returns whether the given file or directory exists or not
+func exists(path string) bool {
+	_, err := os.Stat(path)
+	if err == nil {
+		return true
+	}
+	if os.IsNotExist(err) {
+		return false
+	}
+	return true
+}