Implement config loading

internal/config/config.go

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2020 Cr@ns <roots@crans.org>
+ * Authors : Alexandre Iooss <erdnaxe@crans.org>
+ * SPDX-License-Identifier: MIT
+ */
+
+package config
+
+import (
+	"log"
+	"strings"
+
+	"github.com/spf13/viper"
+)
+
+// Config holds app configuration
+type Config struct {
+	AuthBackend string
+	LDAP        struct {
+		URI    string
+		UserDn string
+	}
+	Site struct {
+		ListenAdress string
+		Name         string
+		Hostname     string
+		Favicon      string
+		WidgetURL    string
+	}
+}
+
+// New configuration
+func New() (*Config, error) {
+	// Load configuration from environnement variables
+	// Replace "." to "_" for nested structs
+	// e.g. GHOSTREAM_LDAP_URI will apply to Config.LDAP.URI
+	viper.SetEnvPrefix("ghostream")
+	replacer := strings.NewReplacer(".", "_")
+	viper.SetEnvKeyReplacer(replacer)
+	viper.AutomaticEnv()
+
+	// Load configuration file if exists
+	viper.SetConfigName("ghostream")
+	viper.SetConfigType("yaml")
+	viper.AddConfigPath("$HOME/.ghostream")
+	viper.AddConfigPath("/etc/ghostream")
+	viper.AddConfigPath(".")
+	if err := viper.ReadInConfig(); err != nil {
+		if _, ok := err.(viper.ConfigFileNotFoundError); ok {
+			// Config file not found, ignore and use defaults
+			log.Print(err)
+		} else {
+			// Config file was found but another error was produced
+			log.Fatal(err)
+		}
+	} else {
+		// Config loaded
+		log.Printf("Using config file: %s", viper.ConfigFileUsed())
+	}
+
+	// Define configuration default values
+	viper.SetDefault("AuthBackend", "LDAP")
+	viper.SetDefault("LDAP.URI", "ldap://127.0.0.1:389")
+	viper.SetDefault("LDAP.UserDn", "cn=users,dc=example,dc=com")
+	viper.SetDefault("Site.ListenAdress", "127.0.0.1:8080")
+	viper.SetDefault("Site.Name", "Ghostream")
+	viper.SetDefault("Site.Hostname", "localhost")
+	viper.SetDefault("Site.Favicon", "/favicon.ico")
+
+	config := &Config{}
+	err := viper.Unmarshal(config)
+	return config, err
+}