hostname-service/config/config.go

// Copyright 2024 Florian Beisel
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package config

import (
	"encoding/json"
	"errors"
	"flag"
	"os"
	"reflect"
	"strings"
	// You might need additional imports for file handling, etc.
)

type AppConfig struct {
	JwtKey       string
	DatabaseFile string
}

var GlobalConfig *AppConfig

func LoadConfig() error {
	GlobalConfig = &AppConfig{}

	// Check command line arguments
	configFile := flag.String("c", "", "path to config file")
	flag.Parse()

	if *configFile != "" {
		return loadConfigFromFile(*configFile, GlobalConfig)
	}

	// Check environment variable for config file path
	envConfigFile := os.Getenv("HS_CONFIGFILE")
	if envConfigFile != "" {
		return loadConfigFromFile(envConfigFile, GlobalConfig)
	}

	// Try to load from a default config file
	defaultConfigFile := "config.json" // Replace with your default config file name
	if _, err := os.Stat(defaultConfigFile); err == nil {
		return loadConfigFromFile(defaultConfigFile, GlobalConfig)
	}

	// Load config from environment variables or docker secrets
	loadConfigFromEnvOrSecrets(GlobalConfig)

	// Check if the configuration has been loaded successfully
	if GlobalConfig.DatabaseFile == "" {
		// Add more checks as necessary for other required config fields
		return errors.New("failed to load configuration from any source")
	}

	return nil
}

func loadConfigFromFile(filePath string, config *AppConfig) error {
	fileData, err := os.ReadFile(filePath)
	if err != nil {
		return err
	}

	err = json.Unmarshal(fileData, config)
	if err != nil {
		return err
	}

	return nil
}

func loadConfigFromEnvOrSecrets(config *AppConfig) {
	val := reflect.ValueOf(config).Elem()
	typ := val.Type()

	for i := 0; i < val.NumField(); i++ {
		field := typ.Field(i)
		envVar := "HS_CONFIG_" + strings.ToUpper(field.Name)
		if value, exists := os.LookupEnv(envVar); exists {
			val.Field(i).SetString(value)
		}

		// Handling Docker secrets (file-based secrets)
		secretFileEnvVar := envVar + "_FILE"
		if secretFilePath, exists := os.LookupEnv(secretFileEnvVar); exists {
			if secretValue, err := os.ReadFile(secretFilePath); err == nil {
				val.Field(i).SetString(string(secretValue))
			}
		}
	}
}