refactor: enhance database configuration handling with individual parameters and URL resolution methods

.env.example

@@ -1,6 +1,23 @@
 SOURCE_DB_URL=sqlserver://sa:password@localhost:1433?database=master&packet+size=32767&loc=UTC&dial+timeout=120&connection+timeout=120&KeepAlive=30
+
+# used only when SOURCE_DB_URL is not set
+# SOURCE_DB_HOST=localhost
+# SOURCE_DB_PORT=1433
+# SOURCE_DB_NAME=master
+# SOURCE_DB_USER=sa
+# SOURCE_DB_PWD=secure_password!123
+# SOURCE_DB_OPTIONS="packet+size=32767&loc=UTC&dial+timeout=120&connection+timeout=120&KeepAlive=30"
+
 TARGET_DB_URL=postgresql://postgres:password@localhost:5432/db
 
+# used only when TARGET_DB_URL is not set
+# TARGET_DB_HOST=localhost
+# TARGET_DB_PORT=5432
+# TARGET_DB_NAME=db
+# TARGET_DB_USER=postgres
+# TARGET_DB_PWD=secure_password!123
+# TARGET_DB_OPTIONS=""
+
 LOG_LEVEL=INFO
 
 AZ_STORAGE_ENABLED=false

cmd/go_migrate/main.go

@@ -43,6 +43,15 @@ func main() {
 
 	startTime := time.Now()
 
+	sourceDbUrl, err := config.App.ResolveSourceDbUrl(migrationConfig.SourceDbType)
+	if err != nil {
+		log.Fatalf("source DB config error: %v", err)
+	}
+	targetDbUrl, err := config.App.ResolveTargetDbUrl(migrationConfig.TargetDbType)
+	if err != nil {
+		log.Fatalf("target DB config error: %v", err)
+	}
+
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
@@ -51,7 +60,7 @@ func main() {
 
 	wgConnect.Go(func() error {
 		var err error
-		sourceDb, err = connectWithTimeout(ctx, migrationConfig.SourceDbType, config.App.SourceDbUrl, 20*time.Second)
+		sourceDb, err = connectWithTimeout(ctx, migrationConfig.SourceDbType, sourceDbUrl, 20*time.Second)
 		if err != nil {
 			return err
 		}
@@ -62,7 +71,7 @@ func main() {
 
 	wgConnect.Go(func() error {
 		var err error
-		targetDb, err = connectWithTimeout(ctx, migrationConfig.TargetDbType, config.App.TargetDbUrl, 20*time.Second)
+		targetDb, err = connectWithTimeout(ctx, migrationConfig.TargetDbType, targetDbUrl, 20*time.Second)
 		if err != nil {
 			return err
 		}

internal/app/config/main.go

@@ -1,6 +1,10 @@
 package config
 
 import (
+	"fmt"
+	"maps"
+	"net/url"
+
 	"github.com/ilyakaznacheev/cleanenv"
 	log "github.com/sirupsen/logrus"
 )
@@ -16,10 +20,95 @@ type AzureStorageConfig struct {
 }
 
 type appConfig struct {
-	SourceDbUrl  string `env:"SOURCE_DB_URL" env-required:"true"`
-	TargetDbUrl  string `env:"TARGET_DB_URL" env-required:"true"`
-	LogLevel     string `env:"LOG_LEVEL" env-default:"INFO"`
-	AzureStorage AzureStorageConfig
+	SourceDbUrl     string `env:"SOURCE_DB_URL"`
+	SourceDbHost    string `env:"SOURCE_DB_HOST"`
+	SourceDbPort    string `env:"SOURCE_DB_PORT"`
+	SourceDbName    string `env:"SOURCE_DB_NAME"`
+	SourceDbUser    string `env:"SOURCE_DB_USER"`
+	SourceDbPwd     string `env:"SOURCE_DB_PWD"`
+	SourceDbOptions string `env:"SOURCE_DB_OPTIONS"`
+	TargetDbUrl     string `env:"TARGET_DB_URL"`
+	TargetDbHost    string `env:"TARGET_DB_HOST"`
+	TargetDbPort    string `env:"TARGET_DB_PORT"`
+	TargetDbName    string `env:"TARGET_DB_NAME"`
+	TargetDbUser    string `env:"TARGET_DB_USER"`
+	TargetDbPwd     string `env:"TARGET_DB_PWD"`
+	TargetDbOptions string `env:"TARGET_DB_OPTIONS"`
+	LogLevel        string `env:"LOG_LEVEL" env-default:"INFO"`
+	AzureStorage    AzureStorageConfig
+}
+
+func (c *appConfig) ResolveSourceDbUrl(dbType string) (string, error) {
+	if c.SourceDbUrl != "" {
+		return c.SourceDbUrl, nil
+	}
+	u, err := buildDbUrl(dbType, c.SourceDbHost, c.SourceDbPort, c.SourceDbName, c.SourceDbUser, c.SourceDbPwd, c.SourceDbOptions)
+	if err != nil {
+		return "", fmt.Errorf("source DB: %w", err)
+	}
+	return u, nil
+}
+
+func (c *appConfig) ResolveTargetDbUrl(dbType string) (string, error) {
+	if c.TargetDbUrl != "" {
+		return c.TargetDbUrl, nil
+	}
+	u, err := buildDbUrl(dbType, c.TargetDbHost, c.TargetDbPort, c.TargetDbName, c.TargetDbUser, c.TargetDbPwd, c.TargetDbOptions)
+	if err != nil {
+		return "", fmt.Errorf("target DB: %w", err)
+	}
+	return u, nil
+}
+
+func buildDbUrl(dbType, host, port, name, user, pwd, options string) (string, error) {
+	if host == "" {
+		return "", fmt.Errorf("DB_HOST is required when DB_URL is not set")
+	}
+	if name == "" {
+		return "", fmt.Errorf("DB_NAME is required when DB_URL is not set")
+	}
+	if user == "" {
+		return "", fmt.Errorf("DB_USER is required when DB_URL is not set")
+	}
+
+	switch dbType {
+	case "sqlserver":
+		if port == "" {
+			port = "1433"
+		}
+		q := url.Values{}
+		if options != "" {
+			extra, err := url.ParseQuery(options)
+			if err != nil {
+				return "", fmt.Errorf("invalid DB_OPTIONS: %w", err)
+			}
+			maps.Copy(q, extra)
+		}
+		q.Set("database", name)
+		u := &url.URL{
+			Scheme:   "sqlserver",
+			Host:     host + ":" + port,
+			User:     url.UserPassword(user, pwd),
+			RawQuery: q.Encode(),
+		}
+		return u.String(), nil
+
+	case "postgres":
+		if port == "" {
+			port = "5432"
+		}
+		u := &url.URL{
+			Scheme:   "postgres",
+			Host:     host + ":" + port,
+			User:     url.UserPassword(user, pwd),
+			Path:     "/" + name,
+			RawQuery: options,
+		}
+		return u.String(), nil
+
+	default:
+		return "", fmt.Errorf("unknown db type %q — cannot build URL from individual components", dbType)
+	}
 }
 
 func getAppConfig() appConfig {