Refactor error handling logic.

Author: ruwanego

transport/http/controllers/APIController.go

@@ -20,7 +20,7 @@ func NewAPIController(ctr *container.Container) *APIController {
 }
 
 // GetInfo return basic details of the API.
-func (ctl *APIController) GetInfo(w http.ResponseWriter, r *http.Request) {
+func (ctl *APIController) GetInfo(w http.ResponseWriter, r *http.Request) error {
 	// transform
 	tr := transformers.APITransformer{
 		Name:    "StoryBuilder",
@@ -29,4 +29,5 @@ func (ctl *APIController) GetInfo(w http.ResponseWriter, r *http.Request) {
 	}
 	// send response
 	ctl.sendResponse(r.Context(), w, http.StatusOK, tr)
+	return nil
 }

transport/http/controllers/Controller.go

@@ -45,3 +45,17 @@ func (ctl *Controller) sendResponse(_ context.Context, w http.ResponseWriter, co
 func (ctl *Controller) sendError(ctx context.Context, w http.ResponseWriter, err any) {
 	response.Error(ctx, w, err, ctl.logger)
 }
+
+// Action represents an HTTP handler that can return an error.
+type Action func(w http.ResponseWriter, r *http.Request) error
+
+// Wrap takes an Action and converts it to a standard http.HandlerFunc.
+// If the Action returns an error, Wrap will automatically send the error response.
+func (ctl *Controller) Wrap(action Action) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if err := action(w, r); err != nil {
+			// use the request context to ensure tracing works
+			ctl.sendError(r.Context(), w, err)
+		}
+	}
+}

transport/http/controllers/SampleController.go

@@ -13,6 +13,7 @@ import (
 	"github.com/storybuilder/storybuilder/transport/http/request/unpackers"
 	"github.com/storybuilder/storybuilder/transport/http/response"
 	"github.com/storybuilder/storybuilder/transport/http/response/transformers"
+	"github.com/storybuilder/storybuilder/transport/http/errors"
 )
 
 // SampleController contains controller logic for endpoints.
@@ -30,29 +31,28 @@ func NewSampleController(ctr *container.Container) *SampleController {
 }
 
 // Get handles retrieving a list of samples.
-func (ctl *SampleController) Get(w http.ResponseWriter, r *http.Request) {
+func (ctl *SampleController) Get(w http.ResponseWriter, r *http.Request) error {
 	// get the context
 	ctx := r.Context()
 	// add a trace string to the context
 	ctx = ctl.withTrace(ctx, "SampleController.Get")
 	// get data
 	samples, err := ctl.sampleUseCase.Get(ctx)
 	if err != nil {
-		ctl.sendError(ctx, w, err)
-		return
+		return err
 	}
 	// transform
 	tr, err := response.Transform(samples, transformers.NewSampleTransformer(), true)
 	if err != nil {
-		ctl.sendError(ctx, w, err)
-		return
+		return err
 	}
 	// send response
 	ctl.sendResponse(ctx, w, http.StatusOK, tr)
+	return nil
 }
 
 // GetByID handles retrieving a single sample.
-func (ctl *SampleController) GetByID(w http.ResponseWriter, r *http.Request) {
+func (ctl *SampleController) GetByID(w http.ResponseWriter, r *http.Request) error {
 	// get the context
 	ctx := r.Context()
 	// add a trace string to the context
@@ -63,27 +63,25 @@ func (ctl *SampleController) GetByID(w http.ResponseWriter, r *http.Request) {
 	// validate
 	errs := ctl.validator.ValidateField(id, "required,gt=0")
 	if errs != nil {
-		ctl.sendError(ctx, w, errs)
-		return
+		return errors.ValidationMapError(errs)
 	}
 	// get data
 	smpl, err := ctl.sampleUseCase.GetByID(ctx, id)
 	if err != nil {
-		ctl.sendError(ctx, w, err)
-		return
+		return err
 	}
 	// transform
 	tr, err := response.Transform(smpl, transformers.NewSampleTransformer(), false)
 	if err != nil {
-		ctl.sendError(ctx, w, err)
-		return
+		return err
 	}
 	// send response
 	ctl.sendResponse(ctx, w, http.StatusOK, tr)
+	return nil
 }
 
 // Add adds a new sample entry.
-func (ctl *SampleController) Add(w http.ResponseWriter, r *http.Request) {
+func (ctl *SampleController) Add(w http.ResponseWriter, r *http.Request) error {
 	// get the context
 	ctx := r.Context()
 	// add a trace string to the context
@@ -92,14 +90,12 @@ func (ctl *SampleController) Add(w http.ResponseWriter, r *http.Request) {
 	sampleUnpacker := unpackers.NewSampleUnpacker()
 	err := request.Unpack(r, sampleUnpacker)
 	if err != nil {
-		ctl.sendError(ctx, w, err)
-		return
+		return err
 	}
 	// validate unpacked data
 	errs := ctl.validator.Validate(sampleUnpacker)
 	if errs != nil {
-		ctl.sendError(ctx, w, errs)
-		return
+		return errors.ValidationMapError(errs)
 	}
 	// bind unpacked data to entities
 	smpl := entities.Sample{
@@ -109,17 +105,17 @@ func (ctl *SampleController) Add(w http.ResponseWriter, r *http.Request) {
 	// add
 	err = ctl.sampleUseCase.Add(ctx, smpl)
 	if err != nil {
-		ctl.sendError(ctx, w, err)
-		return
+		return err
 	}
 	// transform
 	// tr := response.Transform(sample, transformers.NewSampleTransformer(), false)
 	// send response
 	ctl.sendResponse(ctx, w, http.StatusCreated)
+	return nil
 }
 
 // Edit updates an existing sample entry.
-func (ctl *SampleController) Edit(w http.ResponseWriter, r *http.Request) {
+func (ctl *SampleController) Edit(w http.ResponseWriter, r *http.Request) error {
 	// get the context
 	ctx := r.Context()
 	// add a trace string to the context
@@ -128,23 +124,20 @@ func (ctl *SampleController) Edit(w http.ResponseWriter, r *http.Request) {
 	sampleUnpacker := unpackers.NewSampleUnpacker()
 	err := request.Unpack(r, sampleUnpacker)
 	if err != nil {
-		ctl.sendError(ctx, w, err)
-		return
+		return err
 	}
 	// get id from request
-	idVal := ctx.Value("id").(string)
+	idVal := chi.URLParam(r, "id")
 	id, _ := strconv.Atoi(idVal)
 	// validate request parameters
 	errs := ctl.validator.ValidateField(id, "required,gt=0")
 	if errs != nil {
-		ctl.sendError(ctx, w, errs)
-		return
+		return errors.ValidationMapError(errs)
 	}
 	// validate unpacked data
 	errs = ctl.validator.Validate(sampleUnpacker)
 	if errs != nil {
-		ctl.sendError(ctx, w, errs)
-		return
+		return errors.ValidationMapError(errs)
 	}
 	// bind unpacked data to entities
 	smpl := entities.Sample{
@@ -155,34 +148,33 @@ func (ctl *SampleController) Edit(w http.ResponseWriter, r *http.Request) {
 	// edit
 	err = ctl.sampleUseCase.Edit(ctx, smpl)
 	if err != nil {
-		ctl.sendError(ctx, w, err)
-		return
+		return err
 	}
 	// send response
 	ctl.sendResponse(ctx, w, http.StatusNoContent)
+	return nil
 }
 
 // Delete deletes an existing sample entry.
-func (ctl *SampleController) Delete(w http.ResponseWriter, r *http.Request) {
+func (ctl *SampleController) Delete(w http.ResponseWriter, r *http.Request) error {
 	// get the context
 	ctx := r.Context()
 	// add a trace string to the context
 	ctx = ctl.withTrace(ctx, "SampleController.Delete")
 	// get id from request
-	idVal := ctx.Value("id").(string)
+	idVal := chi.URLParam(r, "id")
 	id, _ := strconv.Atoi(idVal)
 	// validate request parameters
 	errs := ctl.validator.ValidateField(id, "required,gt=0")
 	if errs != nil {
-		ctl.sendError(ctx, w, errs)
-		return
+		return errors.ValidationMapError(errs)
 	}
 	// delete
 	err := ctl.sampleUseCase.Delete(ctx, id)
 	if err != nil {
-		ctl.sendError(ctx, w, err)
-		return
+		return err
 	}
 	// send response
 	ctl.sendResponse(ctx, w, http.StatusNoContent)
+	return nil
 }

transport/http/errors/ValidationMapError.go

@@ -0,0 +1,9 @@
+package errors
+
+// ValidationMapError is the type of errors thrown by the field wise validator.
+type ValidationMapError map[string]string
+
+// Error returns a generic validation failed message.
+func (e ValidationMapError) Error() string {
+	return "validation failed"
+}

transport/http/response/responder.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 
 	errHandler "github.com/storybuilder/storybuilder/transport/http/error"
+	httpErrs "github.com/storybuilder/storybuilder/transport/http/errors"
 	"github.com/storybuilder/storybuilder/transport/http/response/mappers"
 )
 
@@ -37,12 +38,11 @@ func Error(ctx context.Context, w http.ResponseWriter, err any, logger *slog.Log
 	code := http.StatusInternalServerError
 	// check whether err is a general error or a validation error
 	errG, isG := err.(error)
-	errV, isV := err.(map[string]string)
-	if isG {
-		msg, code = errHandler.Handle(ctx, errG, logger)
-	}
+	errV, isV := err.(httpErrs.ValidationMapError)
 	if isV {
-		msg, code = errHandler.HandleValidationErrors(ctx, errV, logger)
+		msg, code = errHandler.HandleValidationErrors(ctx, map[string]string(errV), logger)
+	} else if isG {
+		msg, code = errHandler.Handle(ctx, errG, logger)
 	}
 	Send(w, msg, code)
 }

transport/http/router/router.go

@@ -19,12 +19,12 @@ func Init(ctr *container.Container) *chi.Mux {
 	sampleController := controllers.NewSampleController(ctr)
 	// bind controller functions to routes
 	// api info
-	r.Get("/", apiController.GetInfo)
+	r.Get("/", apiController.Wrap(apiController.GetInfo))
 	// sample
-	r.Get("/samples", sampleController.Get)
-	r.Get("/samples/{id:[0-9]+}", sampleController.GetByID)
-	r.Post("/samples", sampleController.Add)
-	r.Put("/samples/{id:[0-9]+}", sampleController.Edit)
-	r.Delete("/samples/{id:[0-9]+}", sampleController.Delete)
+	r.Get("/samples", sampleController.Wrap(sampleController.Get))
+	r.Get("/samples/{id:[0-9]+}", sampleController.Wrap(sampleController.GetByID))
+	r.Post("/samples", sampleController.Wrap(sampleController.Add))
+	r.Put("/samples/{id:[0-9]+}", sampleController.Wrap(sampleController.Edit))
+	r.Delete("/samples/{id:[0-9]+}", sampleController.Wrap(sampleController.Delete))
 	return r
 }