Add configDir & configFile function

config.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+// configFile returns the config file for pavo. It is
+// configDir/pavo.json by default but can be changed by setting
+// PAVO_CONFIG_FILE environment variable. If you set this then no need
+// to set PAVO_CONFIG_DIR.
+func configFile() (configFile string) {
+	configFile = os.Getenv("PAVO_CONFIG_FILE")
+
+	if len(configFile) == 0 {
+		configFile = fmt.Sprintf("%s/%s",
+			configDir(),
+			"pavo.json")
+	}
+
+	return
+}
+
+// configDir returns the config directory for pavo. First
+// PAVO_CONFIG_DIR environment variable is checked, if it doesn't
+// exist then XDG_CONFIG_HOME & if that is not set either then we
+// assume it to be the default value which is $HOME/.config according
+// to XDG Base Directory Specification.
+func configDir() (configDir string) {
+	configDir = os.Getenv("PAVO_CONFIG_DIR")
+
+	if len(configDir) == 0 {
+		configDir = os.Getenv("XDG_CONFIG_HOME")
+	}
+
+	if len(configDir) == 0 {
+		configDir = fmt.Sprintf("%s/%s",
+			os.Getenv("HOME"),
+			".config")
+	}
+
+	return
+}