Handle config options

internal/config/config.go

@@ -0,0 +1,79 @@
+package config
+
+import (
+	"flag"
+	"log"
+	"os"
+	"path"
+	"strings"
+)
+
+type Config struct {
+	Bind string
+}
+
+// ConsolidateConfig fills an Options struct by reading configuration from
+// config files, environment, then command line.
+//
+// Should be called only one time.
+func ConsolidateConfig() (opts *Config, err error) {
+	// Define defaults options
+	opts = &Config{
+		Bind: ":8080",
+	}
+
+	declareFlags(opts)
+
+	// Establish a list of possible configuration file locations
+	configLocations := []string{
+		"repeater.conf",
+	}
+
+	if home, err := os.UserConfigDir(); err == nil {
+		configLocations = append(configLocations, path.Join(home, "repeater", "repeater.conf"))
+	}
+
+	configLocations = append(configLocations, path.Join("etc", "repeater.conf"))
+
+	// If config file exists, read configuration from it
+	for _, filename := range configLocations {
+		if _, e := os.Stat(filename); !os.IsNotExist(e) {
+			log.Printf("Loading configuration from %s\n", filename)
+			err = parseFile(opts, filename)
+			if err != nil {
+				return
+			}
+			break
+		}
+	}
+
+	// Then, overwrite that by what is present in the environment
+	err = parseEnvironmentVariables(opts)
+	if err != nil {
+		return
+	}
+
+	// Finaly, command line takes precedence
+	err = parseCLI(opts)
+	if err != nil {
+		return
+	}
+
+	return
+}
+
+// parseLine treats a config line and place the read value in the variable
+// declared to the corresponding flag.
+func parseLine(o *Config, line string) (err error) {
+	fields := strings.SplitN(line, "=", 2)
+	orig_key := strings.TrimSpace(fields[0])
+	value := strings.TrimSpace(fields[1])
+
+	key := strings.TrimPrefix(orig_key, "REPEATER_")
+	key = strings.Replace(key, "_", "-", -1)
+	key = strings.ToLower(key)
+
+	err = flag.Set(key, value)
+
+	return
+}