feat: Improve error handling with custom error types and detailed messages

config/config.go

@@ -39,13 +39,21 @@ func (c *Config) String() string {
 var CONFIG Config
 
 // parsePositiveInt parses and validates positive integer values
-func parsePositiveInt(value string) (int, error) {
+func parsePositiveInt(param, value string) (int, error) {
 	val, err := strconv.Atoi(value)
 	if err != nil {
-		return 0, err
+		return 0, &ValidationError{
+			Param:  param,
+			Value:  value,
+			Reason: "must be a valid integer",
+		}
 	}
 	if val <= 0 {
-		return 0, fmt.Errorf("value must be positive")
+		return 0, &ValidationError{
+			Param:  param,
+			Value:  value,
+			Reason: "must be positive",
+		}
 	}
 	return val, nil
 }
@@ -59,46 +67,53 @@ func GetConfig() *Config {
 		EnvLogLevel: func(v string) error {
 			level, err := zerolog.ParseLevel(v)
 			if err != nil {
-				return fmt.Errorf("invalid log level: %w", err)
+				return &ValidationError{
+					Param:  EnvLogLevel,
+					Value:  v,
+					Reason: "must be one of: debug, info, warn, error",
+				}
 			}
 			config.LogLevel = level
 			return nil
 		},
 		EnvRootPath: func(v string) error {
 			if _, err := os.Stat(v); err != nil {
-				return fmt.Errorf("invalid root path: %w", err)
+				return &ConfigError{
+					Param: EnvRootPath,
+					Err:   err,
+				}
 			}
 			config.RootPath = v
 			return nil
 		},
 		EnvNumWorkers: func(v string) error {
-			val, err := parsePositiveInt(v)
+			val, err := parsePositiveInt(EnvNumWorkers, v)
 			if err != nil {
-				return fmt.Errorf("invalid number of workers: %w", err)
+				return err
 			}
 			config.NumOfWorkers = val
 			return nil
 		},
 		EnvWorkerBatchSize: func(v string) error {
-			val, err := parsePositiveInt(v)
+			val, err := parsePositiveInt(EnvWorkerBatchSize, v)
 			if err != nil {
-				return fmt.Errorf("invalid worker batch size: %w", err)
+				return err
 			}
 			config.WorkerBatchSize = val
 			return nil
 		},
 		EnvMaxResponseSize: func(v string) error {
-			val, err := parsePositiveInt(v)
+			val, err := parsePositiveInt(EnvMaxResponseSize, v)
 			if err != nil {
-				return fmt.Errorf("invalid max response size: %w", err)
+				return err
 			}
 			config.MaxResponseSize = val
 			return nil
 		},
 		EnvResponseTimeout: func(v string) error {
-			val, err := parsePositiveInt(v)
+			val, err := parsePositiveInt(EnvResponseTimeout, v)
 			if err != nil {
-				return fmt.Errorf("invalid response timeout: %w", err)
+				return err
 			}
 			config.ResponseTimeout = val
 			return nil