api: allow configuration files

Closes https://gitlab.com/commento/commento-ce/issues/55

api/config.go

@@ -14,6 +14,8 @@ func parseConfig() error {
 	}
 
 	defaults := map[string]string{
+		"CONFIG_FILE": "",
+
 		"POSTGRES": "postgres://postgres:postgres@localhost/commento?sslmode=disable",
 
 		"BIND_ADDRESS": "127.0.0.1",
@@ -36,6 +38,12 @@ func parseConfig() error {
 		"GOOGLE_SECRET": "",
 	}
 
+	if os.Getenv("COMMENTO_CONFIG_FILE") != "" {
+		if err := configFileLoad(os.Getenv("COMMENTO_CONFIG_FILE")); err != nil {
+			return err
+		}
+	}
+
 	for key, value := range defaults {
 		if os.Getenv("COMMENTO_"+key) == "" {
 			os.Setenv(key, value)

api/config_file.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"bufio"
+	"os"
+	"strings"
+)
+
+func configFileLoad(filepath string) error {
+	file, err := os.Open(filepath)
+	if err != nil {
+		return err
+	}
+
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		i := strings.Index(line, "=")
+		if i == -1 {
+			continue
+		}
+
+		key := line[:i]
+		value := line[i+1:]
+
+		if !strings.HasPrefix(key, "COMMENTO_") {
+			continue
+		}
+
+		os.Setenv(key[9:], value)
+	}
+
+	return nil
+}