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

config/config_test.go

@@ -39,21 +39,55 @@ func TestGetConfig(t *testing.T) {
 func TestParsePositiveInt(t *testing.T) {
 	tests := []struct {
 		name       string
+		param      string
 		input      string
 		want       int
 		wantErr    bool
+		errType    interface{}
+		errMessage string
 	}{
-		{"valid positive", "42", 42, false},
-		{"zero", "0", 0, true},
-		{"negative", "-1", 0, true},
-		{"invalid", "abc", 0, true},
+		{
+			name:    "valid positive",
+			param:   "TEST_PARAM",
+			input:   "42",
+			want:    42,
+			wantErr: false,
+		},
+		{
+			name:       "zero",
+			param:      "TEST_PARAM",
+			input:      "0",
+			wantErr:    true,
+			errType:    &ValidationError{},
+			errMessage: "invalid value '0' for TEST_PARAM: must be positive",
+		},
+		{
+			name:       "negative",
+			param:      "TEST_PARAM",
+			input:      "-1",
+			wantErr:    true,
+			errType:    &ValidationError{},
+			errMessage: "invalid value '-1' for TEST_PARAM: must be positive",
+		},
+		{
+			name:       "invalid",
+			param:      "TEST_PARAM",
+			input:      "abc",
+			wantErr:    true,
+			errType:    &ValidationError{},
+			errMessage: "invalid value 'abc' for TEST_PARAM: must be a valid integer",
+		},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			got, err := parsePositiveInt(tt.input)
+			got, err := parsePositiveInt(tt.param, tt.input)
 			if tt.wantErr {
 				assert.Error(t, err)
+				assert.IsType(t, tt.errType, err)
+				if tt.errMessage != "" {
+					assert.Equal(t, tt.errMessage, err.Error())
+				}
 			} else {
 				assert.NoError(t, err)
 				assert.Equal(t, tt.want, got)
@@ -61,3 +95,52 @@ func TestParsePositiveInt(t *testing.T) {
 		})
 	}
 }
+
+func TestConfigValidation(t *testing.T) {
+	tests := []struct {
+		name       string
+		envVars    map[string]string
+		wantErr    bool
+		errMessage string
+	}{
+		{
+			name: "invalid log level",
+			envVars: map[string]string{
+				EnvLogLevel: "invalid",
+			},
+			wantErr:    true,
+			errMessage: "invalid value 'invalid' for LOG_LEVEL: must be one of: debug, info, warn, error",
+		},
+		{
+			name: "invalid worker count",
+			envVars: map[string]string{
+				EnvLogLevel:   "debug",
+				EnvRootPath:   ".",
+				EnvNumWorkers: "-1",
+			},
+			wantErr:    true,
+			errMessage: "invalid value '-1' for NUM_OF_WORKERS: must be positive",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Clear environment
+			os.Clearenv()
+
+			// Set required environment variables
+			for k, v := range tt.envVars {
+				os.Setenv(k, v)
+			}
+
+			// Defer cleanup
+			defer os.Clearenv()
+
+			if tt.wantErr {
+				assert.PanicsWithError(t, tt.errMessage, func() {
+					GetConfig()
+				})
+			}
+		})
+	}
+}

config/errors.go

@@ -0,0 +1,28 @@
+package config
+
+import "fmt"
+
+// ConfigError represents a configuration error
+type ConfigError struct {
+	Param string
+	Err   error
+}
+
+func (e *ConfigError) Error() string {
+	return fmt.Sprintf("configuration error for %s: %v", e.Param, e.Err)
+}
+
+func (e *ConfigError) Unwrap() error {
+	return e.Err
+}
+
+// ValidationError represents a validation error
+type ValidationError struct {
+	Param  string
+	Value  string
+	Reason string
+}
+
+func (e *ValidationError) Error() string {
+	return fmt.Sprintf("invalid value '%s' for %s: %s", e.Value, e.Param, e.Reason)
+}