1 files changed, 133 insertions, 0 deletions
diff --git a/lib/xdsconfig/fileconfig.go b/lib/xdsconfig/fileconfig.go
new file mode 100644
index 0000000..262d023
--- /dev/null
+++ b/lib/xdsconfig/fileconfig.go
@@ -0,0 +1,133 @@
+package xdsconfig
+
+import (
+	"encoding/json"
+	"os"
+	"os/user"
+	"path"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+type SyncThingConf struct {
+	Home       string `json:"home"`
+	GuiAddress string `json:"gui-address"`
+	GuiAPIKey  string `json:"gui-apikey"`
+}
+
+type FileConfig struct {
+	WebAppDir    string        `json:"webAppDir"`
+	ShareRootDir string        `json:"shareRootDir"`
+	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/config.json file
+//  3/ <xds-server executable dir>/config.json file
+
+func updateConfigFromFile(c *Config, confFile string) 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", "config.json"))
+	}
+	cwd, err := os.Getwd()
+	if err == nil {
+		searchIn = append(searchIn, path.Join(cwd, "config.json"))
+	}
+	exePath, err := filepath.Abs(filepath.Dir(os.Args[0]))
+	if err == nil {
+		searchIn = append(searchIn, path.Join(exePath, "config.json"))
+	}
+
+	var cFile *string
+	for _, p := range searchIn {
+		if _, err := os.Stat(p); err == nil {
+			cFile = &p
+			break
+		}
+	}
+	if cFile == nil {
+		// No config file found
+		return nil
+	}
+
+	// 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()
+	fCfg := FileConfig{}
+	if err := json.NewDecoder(fd).Decode(&fCfg); err != nil {
+		return err
+	}
+	c.fileConf = fCfg
+
+	// Support environment variables (IOW ${MY_ENV_VAR} syntax) in config.json
+	// TODO: better to use reflect package to iterate on fields and be more generic
+	fCfg.WebAppDir = path.Clean(resolveEnvVar(fCfg.WebAppDir))
+	fCfg.ShareRootDir = path.Clean(resolveEnvVar(fCfg.ShareRootDir))
+	fCfg.SThgConf.Home = path.Clean(resolveEnvVar(fCfg.SThgConf.Home))
+
+	// Config file settings overwrite default config
+
+	if fCfg.WebAppDir != "" {
+		c.WebAppDir = strings.Trim(fCfg.WebAppDir, " ")
+	}
+	// Is it a full path ?
+	if !strings.HasPrefix(c.WebAppDir, "/") && exePath != "" {
+		// Check first from current directory
+		for _, rootD := range []string{cwd, exePath} {
+			ff := path.Join(rootD, c.WebAppDir, "index.html")
+			if exists(ff) {
+				c.WebAppDir = path.Join(rootD, c.WebAppDir)
+				break
+			}
+		}
+	}
+
+	if fCfg.ShareRootDir != "" {
+		c.ShareRootDir = fCfg.ShareRootDir
+	}
+
+	if fCfg.HTTPPort != "" {
+		c.HTTPPort = fCfg.HTTPPort
+	}
+
+	return nil
+}
+
+// resolveEnvVar Resolved environment variable regarding the syntax ${MYVAR}
+func resolveEnvVar(s string) string {
+	re := regexp.MustCompile("\\${(.*)}")
+	vars := re.FindAllStringSubmatch(s, -1)
+	res := s
+	for _, v := range vars {
+		val := os.Getenv(v[1])
+		if val != "" {
+			rer := regexp.MustCompile("\\${" + v[1] + "}")
+			res = rer.ReplaceAllString(res, val)
+		}
+	}
+	return res
+}
+
+// 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
+}