refactor(api,cli,ssh,pkg): standardize access to environment variables

agent/main.go

@@ -11,6 +11,7 @@ import (
 	"github.com/kelseyhightower/envconfig"
 	"github.com/shellhub-io/shellhub/pkg/agent"
 	"github.com/shellhub-io/shellhub/pkg/agent/pkg/selfupdater"
+	"github.com/shellhub-io/shellhub/pkg/envs"
 	"github.com/shellhub-io/shellhub/pkg/loglevel"
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
@@ -31,13 +32,28 @@ func main() {
 		Run: func(cmd *cobra.Command, args []string) {
 			loglevel.SetLogLevel()
 
-			cfg := agent.Config{}
-
-			// Process unprefixed env vars for backward compatibility
-			envconfig.Process("", &cfg) // nolint:errcheck
-
-			if err := envconfig.Process("shellhub", &cfg); err != nil {
-				// show envconfig usage help users to run agent
+			// NOTE(r): When T, the generic parameter, is a structure with required tag, the fallback for an
+			// "unprefixed" parameter is used.
+			//
+			// For example,
+			//
+			// For the structure below, the parser will parse successfully when the variables exist with or without the
+			// prefixes since the "required" tag is set to true.
+			//
+			//  SHELLHUB_TENANT_ID=00000000-0000-4000-0000-000000000000 SERVER_ADDRESS=http://127.0.0.1
+			//  PRIVATE_KEY=/tmp/shellhub sudo -E ./agent
+			//
+			//  struct {
+			//    ServerAddress string `envconfig:"server_address" required:"true"`
+			//    PrivateKey string `envconfig:"private_key" required:"true"`
+			//    TenantID string `envconfig:"tenant_id" required:"true"`
+			//  }
+			//
+			//  This behavior is driven by the [envconfig] package. Check it out for more information.
+			//
+			// [envconfig]: https://github.com/kelseyhightower/envconfig
+			cfg, err := envs.ParseWithPrefix[agent.Config]("shellhub")
+			if err != nil {
 				envconfig.Usage("shellhub", &cfg) // nolint:errcheck
 				log.Fatal(err)
 			}
@@ -88,7 +104,7 @@ func main() {
 				"mode":    mode,
 			}).Info("Starting ShellHub")
 
-			ag, err := agent.NewAgentWithConfig(&cfg)
+			ag, err := agent.NewAgentWithConfig(cfg)
 			if err != nil {
 				log.WithError(err).WithFields(log.Fields{
 					"version":       AgentVersion,

api/main.go

@@ -3,7 +3,7 @@ package main
 import (
 	"context"
 
-	"github.com/kelseyhightower/envconfig"
+	"github.com/shellhub-io/shellhub/pkg/envs"
 	"github.com/shellhub-io/shellhub/pkg/loglevel"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
@@ -18,13 +18,13 @@ func main() {
 
 	rootCmd.AddCommand(serverCmd)
 
-	// Populates configuration based on environment variables prefixed with 'API_'
-	var cfg config
-	if err := envconfig.Process("api", &cfg); err != nil {
+	// Populates configuration based on environment variables prefixed with 'API_'.
+	cfg, err := envs.ParseWithPrefix[config]("api")
+	if err != nil {
 		logrus.WithError(err).Fatal("Failed to load environment variables")
 	}
 
-	ctx := context.WithValue(context.TODO(), "cfg", &cfg) //nolint:revive
+	ctx := context.WithValue(context.TODO(), "cfg", cfg) //nolint:revive
 
 	if err := rootCmd.ExecuteContext(ctx); err != nil {
 		logrus.Fatal(err)

api/workers/workers.go

@@ -1,8 +1,6 @@
 package workers
 
-import (
-	"github.com/kelseyhightower/envconfig"
-)
+import "github.com/shellhub-io/shellhub/pkg/envs"
 
 type Envs struct {
 	MongoURI                      string `envconfig:"mongo_uri" default:"mongodb://mongo:27017/main"`
@@ -30,10 +28,10 @@ type Envs struct {
 }
 
 func getEnvs() (*Envs, error) {
-	var envs Envs
-	if err := envconfig.Process("api", &envs); err != nil {
+	env, err := envs.ParseWithPrefix[Envs]("api")
+	if err != nil {
 		return nil, err
 	}
 
-	return &envs, nil
+	return env, nil
 }

cli/main.go

@@ -3,11 +3,11 @@ package main
 import (
 	"context"
 
-	"github.com/kelseyhightower/envconfig"
 	"github.com/shellhub-io/shellhub/api/store/mongo"
 	"github.com/shellhub-io/shellhub/cli/cmd"
 	"github.com/shellhub-io/shellhub/cli/services"
 	storecache "github.com/shellhub-io/shellhub/pkg/cache"
+	"github.com/shellhub-io/shellhub/pkg/envs"
 	"github.com/shellhub-io/shellhub/pkg/loglevel"
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
@@ -26,8 +26,8 @@ func init() {
 }
 
 func main() {
-	var cfg config
-	if err := envconfig.Process("cli", &cfg); err != nil {
+	cfg, err := envs.ParseWithPrefix[config]("cli")
+	if err != nil {
 		log.Error(err.Error())
 	}
 

pkg/api/webhook/webhook.go

@@ -11,8 +11,8 @@ import (
 	"path"
 
 	"github.com/go-resty/resty/v2"
-	"github.com/kelseyhightower/envconfig"
 	client "github.com/shellhub-io/shellhub/pkg/api/internalclient"
+	"github.com/shellhub-io/shellhub/pkg/envs"
 	"github.com/shellhub-io/shellhub/pkg/uuid"
 	"github.com/sirupsen/logrus"
 )
@@ -36,8 +36,7 @@ type Options struct {
 func NewClient() Webhook {
 	httpClient := resty.New()
 	httpClient.SetRetryCount(3)
-	opts := Options{}
-	err := envconfig.Process("", &opts)
+	opts, err := envs.ParseWithPrefix[Options]("")
 	if err != nil {
 		return nil
 	}

pkg/envs/backend_env.go

@@ -1,10 +1,18 @@
 package envs
 
-import "os"
+import (
+	"os"
+
+	"github.com/kelseyhightower/envconfig"
+)
 
 type envBackend struct{}
 
 // envBackend is the default key/value store that reads from environment variables.
 func (b *envBackend) Get(name string) string {
 	return os.Getenv(name)
 }
+
+func (b *envBackend) Process(prefix string, spec interface{}) error {
+	return envconfig.Process(prefix, spec)
+}

pkg/envs/envs.go

@@ -1,12 +1,17 @@
 package envs
 
+import (
+	"errors"
+)
+
 const (
 	ENABLED = "true"
 )
 
 // Backend is an interface for any sort of underlying key/value store.
 type Backend interface {
 	Get(key string) string
+	Process(prefix string, spec interface{}) error
 }
 
 // DefaultBackend define the backend to be used to get environment variables.
@@ -36,3 +41,24 @@ func HasBilling() bool {
 func IsCommunity() bool {
 	return (DefaultBackend.Get("SHELLHUB_CLOUD") != ENABLED && DefaultBackend.Get("SHELLHUB_ENTERPRISE") != ENABLED)
 }
+
+var ErrParse = errors.New("failed to parse environment variables for the given prefix")
+
+// ParseWithPrefix parses the environment variables for the a given prefix.
+//
+// This function uses the [envconfig] package as its default backend, so it requires the struct to be annotated with
+// the [envconfig] tags. Check the [envconfig] documentation for more information.
+//
+// The T generic parameter must be a struct with the fields annotated with the [envconfig] tags, that will be returned
+// with the values parsed from the environment variables.
+//
+// [envconfig]: https://github.com/kelseyhightower/envconfig
+func ParseWithPrefix[T any](prefix string) (*T, error) {
+	envs := new(T)
+
+	if err := DefaultBackend.Process(prefix, envs); err != nil {
+		return nil, errors.Join(ErrParse, err)
+	}
+
+	return envs, nil
+}