fix: add nil checks, fix naming

internal/validation/csv_strategy.go → internal/validation/csv_writer.go

@@ -2,16 +2,23 @@ package validation
 
 import (
 	"encoding/csv"
+	"errors"
 	"os"
 	"strings"
 
 	"github.com/ChargePi/chargeflow/pkg/report"
 )
 
-// csvStrategy implements OutputStrategy for CSV output.
-type csvStrategy struct{}
+var headers = []string{"message_id", "type", "errors"}
+
+// csvWriter implements ReportWriter for CSV output.
+type csvWriter struct{}
+
+func (csvWriter) Write(path string, r *report.Report) error {
+	if r == nil {
+		return errors.New("report is nil")
+	}
 
-func (csvStrategy) Write(path string, r *report.Report) error {
 	f, err := os.Create(path)
 	if err != nil {
 		return err
@@ -22,7 +29,7 @@ func (csvStrategy) Write(path string, r *report.Report) error {
 	defer w.Flush()
 
 	// Header
-	if err = w.Write([]string{"message_id", "type", "errors"}); err != nil {
+	if err = w.Write(headers); err != nil {
 		return err
 	}
 

internal/validation/csv_strategy_test.go → internal/validation/csv_writer_test.go

@@ -28,7 +28,7 @@ func TestCSVStrategy_Write(t *testing.T) {
 		Statistics:          report.Statistics{},
 	}
 
-	s := csvStrategy{}
+	s := csvWriter{}
 	require.NoError(t, s.Write(path, r))
 
 	b, err := os.ReadFile(path)

internal/validation/json_strategy.go → internal/validation/json_writer.go

@@ -2,15 +2,20 @@ package validation
 
 import (
 	"encoding/json"
+	"errors"
 	"os"
 
 	"github.com/ChargePi/chargeflow/pkg/report"
 )
 
-// jsonStrategy implements OutputStrategy for JSON output.
+// jsonStrategy implements ReportWriter for JSON output.
 type jsonStrategy struct{}
 
 func (jsonStrategy) Write(path string, r *report.Report) error {
+	if r == nil {
+		return errors.New("report is nil")
+	}
+
 	b, err := json.MarshalIndent(r, "", "  ")
 	if err != nil {
 		return err

internal/validation/output_strategy.go → internal/validation/report_writer.go

@@ -9,28 +9,28 @@ import (
 	"github.com/ChargePi/chargeflow/pkg/report"
 )
 
-// OutputStrategy defines how to write a validation report.
-type OutputStrategy interface {
+// ReportWriter defines how to write a validation report.
+type ReportWriter interface {
 	Write(path string, r *report.Report) error
 }
 
-// outputStrategyFactory returns an OutputStrategy based on the file extension.
-func outputStrategyFactory(path string) (OutputStrategy, error) {
+// outputStrategyFactory returns an ReportWriter based on the file extension.
+func outputStrategyFactory(path string) (ReportWriter, error) {
 	ext := strings.ToLower(filepath.Ext(path))
 	switch ext {
 	case ".json":
 		return jsonStrategy{}, nil
 	case ".csv":
-		return csvStrategy{}, nil
+		return csvWriter{}, nil
 	case ".txt":
-		return txtStrategy{}, nil
+		return txtWriter{}, nil
 	default:
 		return nil, errors.Errorf("unsupported output extension: %s", ext)
 	}
 }
 
 // WriteReport is a convenience exported helper that writes the report using the
-// appropriate OutputStrategy based on the provided path extension.
+// appropriate ReportWriter based on the provided path extension.
 func WriteReport(path string, r *report.Report) error {
 	strat, err := outputStrategyFactory(path)
 	if err != nil {

internal/validation/output_strategy_test.go → internal/validation/report_writer_test.go

@@ -34,9 +34,9 @@ func TestOutputStrategyFactory(t *testing.T) {
 			case ".json":
 				require.IsType(t, jsonStrategy{}, strat)
 			case ".csv":
-				require.IsType(t, csvStrategy{}, strat)
+				require.IsType(t, csvWriter{}, strat)
 			case ".txt":
-				require.IsType(t, txtStrategy{}, strat)
+				require.IsType(t, txtWriter{}, strat)
 			}
 		})
 	}

internal/validation/txt_strategy.go

@@ -1,17 +1,21 @@
 package validation
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"strings"
 
 	"github.com/ChargePi/chargeflow/pkg/report"
 )
 
-// txtStrategy implements OutputStrategy for plain text output.
-type txtStrategy struct{}
+// txtWriter implements ReportWriter for plain text output.
+type txtWriter struct{}
 
-func (txtStrategy) Write(path string, r *report.Report) error {
+func (txtWriter) Write(path string, r *report.Report) error {
+	if r == nil {
+		return errors.New("report is nil")
+	}
 	var b strings.Builder
 
 	stats := r.Statistics

internal/validation/txt_strategy_test.go

@@ -27,7 +27,7 @@ func TestTXTStrategy_Write(t *testing.T) {
 		Statistics:          report.Statistics{ValidRequests: 0, InvalidRequests: 0, ValidResponses: 0, InvalidResponses: 1, UnparsableMessages: 1},
 	}
 
-	s := txtStrategy{}
+	s := txtWriter{}
 	require.NoError(t, s.Write(path, r))
 
 	b, err := os.ReadFile(path)