feat: *api.Context is required as first handler argument

builder_test.go

@@ -72,7 +72,7 @@ func TestBind(t *testing.T) {
 			Config:        "[]",
 			HandlerMethod: "",
 			HandlerPath:   "",
-			HandlerFn:     func() (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			HandlerFn:     func(*api.Context) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			BindErr:       errUnknownService,
 			BuildErr:      nil,
 		},
@@ -108,7 +108,7 @@ func TestBind(t *testing.T) {
 			]`,
 			HandlerMethod: http.MethodPost,
 			HandlerPath:   "/path",
-			HandlerFn:     func() (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			HandlerFn:     func(*api.Context) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			BindErr:       errUnknownService,
 			BuildErr:      errMissingHandler,
 		},
@@ -126,7 +126,7 @@ func TestBind(t *testing.T) {
 			]`,
 			HandlerMethod: http.MethodGet,
 			HandlerPath:   "/paths",
-			HandlerFn:     func() (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			HandlerFn:     func(*api.Context) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			BindErr:       errUnknownService,
 			BuildErr:      errMissingHandler,
 		},
@@ -144,7 +144,7 @@ func TestBind(t *testing.T) {
 			]`,
 			HandlerMethod: http.MethodGet,
 			HandlerPath:   "/path",
-			HandlerFn:     func() (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			HandlerFn:     func(*api.Context) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			BindErr:       nil,
 			BuildErr:      nil,
 		},
@@ -164,7 +164,7 @@ func TestBind(t *testing.T) {
 			]`,
 			HandlerMethod: http.MethodGet,
 			HandlerPath:   "/path",
-			HandlerFn:     func(struct{ Name int }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			HandlerFn:     func(*api.Context, struct{ Name int }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			BindErr:       nil,
 			BuildErr:      nil,
 		},
@@ -184,7 +184,7 @@ func TestBind(t *testing.T) {
 			]`,
 			HandlerMethod: http.MethodGet,
 			HandlerPath:   "/path",
-			HandlerFn:     func(struct{ Name uint }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			HandlerFn:     func(*api.Context, struct{ Name uint }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			BindErr:       nil,
 			BuildErr:      nil,
 		},
@@ -204,7 +204,7 @@ func TestBind(t *testing.T) {
 			]`,
 			HandlerMethod: http.MethodGet,
 			HandlerPath:   "/path",
-			HandlerFn:     func(struct{ Name string }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			HandlerFn:     func(*api.Context, struct{ Name string }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			BindErr:       nil,
 			BuildErr:      nil,
 		},
@@ -224,7 +224,7 @@ func TestBind(t *testing.T) {
 			]`,
 			HandlerMethod: http.MethodGet,
 			HandlerPath:   "/path",
-			HandlerFn:     func(struct{ Name bool }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			HandlerFn:     func(*api.Context, struct{ Name bool }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			BindErr:       nil,
 			BuildErr:      nil,
 		},

handler.go

@@ -1,12 +1,14 @@
 package aicra
 
 import (
+	"context"
 	"fmt"
 	"net/http"
 	"strings"
 
 	"git.xdrm.io/go/aicra/api"
 	"git.xdrm.io/go/aicra/internal/config"
+	"git.xdrm.io/go/aicra/internal/ctx"
 	"git.xdrm.io/go/aicra/internal/reqdata"
 )
 
@@ -94,11 +96,17 @@ func (s Handler) resolve(w http.ResponseWriter, r *http.Request) {
 }
 
 func (s *Handler) handle(input *reqdata.T, handler *apiHandler, service *config.Service, w http.ResponseWriter, r *http.Request) {
-	// 5. pass execution to the handler
+	// build context with builtin data
-	ctx := api.Context{Res: w, Req: r}
+	c := r.Context()
-	var outData, outErr = handler.dyn.Handle(ctx, input.Data)
+	c = context.WithValue(c, ctx.Request, r)
+	c = context.WithValue(c, ctx.Response, w)
+	c = context.WithValue(c, ctx.Auth, w)
+	apictx := &api.Context{Context: c}
 
-	// 6. build res from returned data
+	// pass execution to the handler
+	var outData, outErr = handler.dyn.Handle(apictx, input.Data)
+
+	// build response from returned arguments
 	var res = api.EmptyResponse().WithError(outErr)
 	for key, value := range outData {
 

handler_test.go

@@ -82,9 +82,9 @@ func TestWith(t *testing.T) {
 		t.Fatalf("setup: unexpected error <%v>", err)
 	}
 
-	pathHandler := func(ctx api.Context) (*struct{}, api.Err) {
+	pathHandler := func(ctx *api.Context) (*struct{}, api.Err) {
 		// write value from middlewares into response
-		value := ctx.Req.Context().Value(key)
+		value := ctx.Value(key)
 		if value == nil {
 			t.Fatalf("nothing found in context")
 		}
@@ -93,7 +93,7 @@ func TestWith(t *testing.T) {
 			t.Fatalf("cannot cast context data to int")
 		}
 		// write to response
-		ctx.Res.Write([]byte(fmt.Sprintf("#%d#", cast)))
+		ctx.ResponseWriter().Write([]byte(fmt.Sprintf("#%d#", cast)))
 
 		return nil, api.ErrSuccess
 	}
@@ -237,7 +237,7 @@ func TestWithAuth(t *testing.T) {
 				t.Fatalf("setup: unexpected error <%v>", err)
 			}
 
-			pathHandler := func(ctx api.Context) (*struct{}, api.Err) {
+			pathHandler := func(ctx *api.Context) (*struct{}, api.Err) {
 				return nil, api.ErrNotImplemented
 			}
 
@@ -290,7 +290,7 @@ func TestDynamicScope(t *testing.T) {
 				}
 			]`,
 			path:        "/path/{id}",
-			handler:     func(struct{ Input1 uint }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			handler:     func(*api.Context, struct{ Input1 uint }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			url:         "/path/123",
 			body:        ``,
 			permissions: []string{"user[123]"},
@@ -311,7 +311,7 @@ func TestDynamicScope(t *testing.T) {
 				}
 			]`,
 			path:        "/path/{id}",
-			handler:     func(struct{ Input1 uint }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			handler:     func(*api.Context, struct{ Input1 uint }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			url:         "/path/666",
 			body:        ``,
 			permissions: []string{"user[123]"},
@@ -332,7 +332,7 @@ func TestDynamicScope(t *testing.T) {
 				}
 			]`,
 			path:        "/path/{id}",
-			handler:     func(struct{ User uint }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			handler:     func(*api.Context, struct{ User uint }) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			url:         "/path/123",
 			body:        ``,
 			permissions: []string{"prefix.user[123].suffix"},
@@ -354,7 +354,7 @@ func TestDynamicScope(t *testing.T) {
 				}
 			]`,
 			path: "/prefix/{pid}/user/{uid}",
-			handler: func(struct {
+			handler: func(*api.Context, struct {
 				Prefix uint
 				User   uint
 			}) (*struct{}, api.Err) {
@@ -381,7 +381,7 @@ func TestDynamicScope(t *testing.T) {
 				}
 			]`,
 			path: "/prefix/{pid}/user/{uid}",
-			handler: func(struct {
+			handler: func(*api.Context, struct {
 				Prefix uint
 				User   uint
 			}) (*struct{}, api.Err) {
@@ -409,7 +409,7 @@ func TestDynamicScope(t *testing.T) {
 				}
 			]`,
 			path: "/prefix/{pid}/user/{uid}/suffix/{sid}",
-			handler: func(struct {
+			handler: func(*api.Context, struct {
 				Prefix uint
 				User   uint
 				Suffix uint
@@ -438,7 +438,7 @@ func TestDynamicScope(t *testing.T) {
 				}
 			]`,
 			path: "/prefix/{pid}/user/{uid}/suffix/{sid}",
-			handler: func(struct {
+			handler: func(*api.Context, struct {
 				Prefix uint
 				User   uint
 				Suffix uint

internal/dynfunc/errors.go

@@ -14,16 +14,19 @@ const errHandlerNotFunc = cerr("handler must be a func")
 const errNoServiceForHandler = cerr("no service found for this handler")
 
 // errMissingHandlerArgumentParam - missing params arguments for handler
-const errMissingHandlerArgumentParam = cerr("missing handler argument : parameter struct")
+const errMissingHandlerContextArgument = cerr("missing handler first argument of type *api.Context")
+
+// errMissingHandlerInputArgument - missing params arguments for handler
+const errMissingHandlerInputArgument = cerr("missing handler argument: input struct")
 
 // errUnexpectedInput - input argument is not expected
 const errUnexpectedInput = cerr("unexpected input struct")
 
-// errMissingHandlerOutput - missing output for handler
+// errMissingHandlerOutputArgument - missing output for handler
-const errMissingHandlerOutput = cerr("handler must have at least 1 output")
+const errMissingHandlerOutputArgument = cerr("missing handler first output argument: output struct")
 
 // errMissingHandlerOutputError - missing error output for handler
-const errMissingHandlerOutputError = cerr("handler must have its last output of type api.Err")
+const errMissingHandlerOutputError = cerr("missing handler last output argument of type api.Err")
 
 // errMissingRequestArgument - missing request argument for handler
 const errMissingRequestArgument = cerr("handler first argument must be of type api.Request")
@@ -34,17 +37,14 @@ const errMissingParamArgument = cerr("handler second argument must be a struct")
 // errUnexportedName - argument is unexported in struct
 const errUnexportedName = cerr("unexported name")
 
-// errMissingParamOutput - missing output argument for handler
+// errWrongOutputArgumentType - wrong type for output first argument
-const errMissingParamOutput = cerr("handler first output must be a *struct")
+const errWrongOutputArgumentType = cerr("handler first output argument must be a *struct")
 
-// errMissingParamFromConfig - missing a parameter in handler struct
+// errMissingConfigArgument - missing an input/output argument in handler struct
-const errMissingParamFromConfig = cerr("missing a parameter from configuration")
+const errMissingConfigArgument = cerr("missing an argument from the configuration")
-
-// errMissingOutputFromConfig - missing a parameter in handler struct
-const errMissingOutputFromConfig = cerr("missing a parameter from configuration")
 
 // errWrongParamTypeFromConfig - a configuration parameter type is invalid in the handler param struct
 const errWrongParamTypeFromConfig = cerr("invalid struct field type")
 
-// errMissingHandlerErrorOutput - missing handler output error
+// errMissingHandlerErrorArgument - missing handler output error
-const errMissingHandlerErrorOutput = cerr("last output must be of type api.Err")
+const errMissingHandlerErrorArgument = cerr("last output must be of type api.Err")

internal/dynfunc/handler.go

@@ -9,73 +9,69 @@ import (
 	"git.xdrm.io/go/aicra/internal/config"
 )
 
-// Handler represents a dynamic api handler
+// Handler represents a dynamic aicra service handler
 type Handler struct {
-	spec *signature
+	// signature defined from the service configuration
-	fn   interface{}
+	signature *Signature
-	// whether fn uses api.Ctx as 1st argument
+	// fn provided function that will be the service's handler
-	hasContext bool
+	fn interface{}
-	// index in input arguments where the data struct must be
-	dataIndex int
 }
 
-// Build a handler from a service configuration and a dynamic function
+// Build a handler from a dynamic function and checks its signature against a
-//
+// service configuration
-// @fn must have as a signature : `func(inputStruct) (*outputStruct, api.Err)`
+//e
-//  - `inputStruct` is a struct{} containing a field for each service input (with valid reflect.Type)
+// `fn` must have as a signature : `func(*api.Context, in) (*out, api.Err)`
-//  - `outputStruct` is a struct{} containing a field for each service output (with valid reflect.Type)
+//  - `in` is a struct{} containing a field for each service input (with valid reflect.Type)
+//  - `out` is a struct{} containing a field for each service output (with valid reflect.Type)
 //
 // Special cases:
-//  - a first optional input parameter of type `api.Ctx` can be added
+//  - it there is no input, `in` MUST be omitted
-//  - it there is no input, `inputStruct` must be omitted
+//  - it there is no output, `out` MUST be omitted
-//  - it there is no output, `outputStruct` must be omitted
 func Build(fn interface{}, service config.Service) (*Handler, error) {
-	h := &Handler{
+	var (
-		spec: signatureFromService(service),
+		h = &Handler{
-		fn:   fn,
+			signature: BuildSignature(service),
-	}
+			fn:        fn,
+		}
+		fnType = reflect.TypeOf(fn)
+	)
 
-	impl := reflect.TypeOf(fn)
+	if fnType.Kind() != reflect.Func {
-
-	if impl.Kind() != reflect.Func {
 		return nil, errHandlerNotFunc
 	}
-
+	if err := h.signature.ValidateInput(fnType); err != nil {
-	h.hasContext = impl.NumIn() >= 1 && reflect.TypeOf(api.Context{}).AssignableTo(impl.In(0))
-	if h.hasContext {
-		h.dataIndex = 1
-	}
-
-	if err := h.spec.checkInput(impl, h.dataIndex); err != nil {
 		return nil, fmt.Errorf("input: %w", err)
 	}
-	if err := h.spec.checkOutput(impl); err != nil {
+	if err := h.signature.ValidateOutput(fnType); err != nil {
 		return nil, fmt.Errorf("output: %w", err)
 	}
 
 	return h, nil
 }
 
-// Handle binds input @data into the dynamic function and returns map output
+// Handle binds input `data` into the dynamic function and returns an output map
-func (h *Handler) Handle(ctx api.Context, data map[string]interface{}) (map[string]interface{}, api.Err) {
+func (h *Handler) Handle(ctx *api.Context, data map[string]interface{}) (map[string]interface{}, api.Err) {
-	var ert = reflect.TypeOf(api.Err{})
+	var (
-	var fnv = reflect.ValueOf(h.fn)
+		ert      = reflect.TypeOf(api.Err{})
+		fnv      = reflect.ValueOf(h.fn)
+		callArgs = make([]reflect.Value, 0)
+	)
 
-	callArgs := []reflect.Value{}
+	// bind context
+	callArgs = append(callArgs, reflect.ValueOf(ctx))
 
-	// bind context if used in handler
+	inputStructRequired := fnv.Type().NumIn() > 1
-	if h.hasContext {
-		callArgs = append(callArgs, reflect.ValueOf(ctx))
-	}
 
-	// bind input data
+	// bind input arguments
-	if fnv.Type().NumIn() > h.dataIndex {
+	if inputStructRequired {
 		// create zero value struct
-		callStructPtr := reflect.New(fnv.Type().In(0))
+		var (
-		callStruct := callStructPtr.Elem()
+			callStructPtr = reflect.New(fnv.Type().In(1))
+			callStruct    = callStructPtr.Elem()
+		)
 
 		// set each field
-		for name := range h.spec.Input {
+		for name := range h.signature.Input {
 			field := callStruct.FieldByName(name)
 			if !field.CanSet() {
 				continue
@@ -115,12 +111,12 @@ func (h *Handler) Handle(ctx api.Context, data map[string]interface{}) (map[stri
 		callArgs = append(callArgs, callStruct)
 	}
 
-	// call the HandlerFn
+	// call the handler
 	output := fnv.Call(callArgs)
 
 	// no output OR pointer to output struct is nil
 	outdata := make(map[string]interface{})
-	if len(h.spec.Output) < 1 || output[0].IsNil() {
+	if len(h.signature.Output) < 1 || output[0].IsNil() {
 		var structerr = output[len(output)-1].Convert(ert)
 		return outdata, api.Err{
 			Code:   int(structerr.FieldByName("Code").Int()),
@@ -132,7 +128,7 @@ func (h *Handler) Handle(ctx api.Context, data map[string]interface{}) (map[stri
 	// extract struct from pointer
 	returnStruct := output[0].Elem()
 
-	for name := range h.spec.Output {
+	for name := range h.signature.Output {
 		field := returnStruct.FieldByName(name)
 		outdata[name] = field.Interface()
 	}

internal/dynfunc/handler_test.go

@@ -8,7 +8,7 @@ import (
 	"git.xdrm.io/go/aicra/api"
 )
 
-type testsignature signature
+type testsignature Signature
 
 // builds a mock service with provided arguments as Input and matched as Output
 func (s *testsignature) withArgs(dtypes ...reflect.Type) *testsignature {
@@ -52,7 +52,7 @@ func TestInput(t *testing.T) {
 		{
 			Name:           "none required none provided",
 			Spec:           (&testsignature{}).withArgs(),
-			Fn:             func() (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			Fn:             func(*api.Context) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			HasContext:     false,
 			Input:          []interface{}{},
 			ExpectedOutput: []interface{}{},
@@ -61,7 +61,7 @@ func TestInput(t *testing.T) {
 		{
 			Name: "int proxy (0)",
 			Spec: (&testsignature{}).withArgs(reflect.TypeOf(int(0))),
-			Fn: func(in intstruct) (*intstruct, api.Err) {
+			Fn: func(ctx *api.Context, in intstruct) (*intstruct, api.Err) {
 				return &intstruct{P1: in.P1}, api.ErrSuccess
 			},
 			HasContext:     false,
@@ -72,7 +72,7 @@ func TestInput(t *testing.T) {
 		{
 			Name: "int proxy (11)",
 			Spec: (&testsignature{}).withArgs(reflect.TypeOf(int(0))),
-			Fn: func(in intstruct) (*intstruct, api.Err) {
+			Fn: func(ctx *api.Context, in intstruct) (*intstruct, api.Err) {
 				return &intstruct{P1: in.P1}, api.ErrSuccess
 			},
 			HasContext:     false,
@@ -83,7 +83,7 @@ func TestInput(t *testing.T) {
 		{
 			Name: "*int proxy (nil)",
 			Spec: (&testsignature{}).withArgs(reflect.TypeOf(new(int))),
-			Fn: func(in intptrstruct) (*intptrstruct, api.Err) {
+			Fn: func(ctx *api.Context, in intptrstruct) (*intptrstruct, api.Err) {
 				return &intptrstruct{P1: in.P1}, api.ErrSuccess
 			},
 			HasContext:     false,
@@ -94,7 +94,7 @@ func TestInput(t *testing.T) {
 		{
 			Name: "*int proxy (28)",
 			Spec: (&testsignature{}).withArgs(reflect.TypeOf(new(int))),
-			Fn: func(in intptrstruct) (*intstruct, api.Err) {
+			Fn: func(ctx *api.Context, in intptrstruct) (*intstruct, api.Err) {
 				return &intstruct{P1: *in.P1}, api.ErrSuccess
 			},
 			HasContext:     false,
@@ -105,7 +105,7 @@ func TestInput(t *testing.T) {
 		{
 			Name: "*int proxy (13)",
 			Spec: (&testsignature{}).withArgs(reflect.TypeOf(new(int))),
-			Fn: func(in intptrstruct) (*intstruct, api.Err) {
+			Fn: func(ctx *api.Context, in intptrstruct) (*intstruct, api.Err) {
 				return &intstruct{P1: *in.P1}, api.ErrSuccess
 			},
 			HasContext:     false,
@@ -119,16 +119,9 @@ func TestInput(t *testing.T) {
 		t.Run(tcase.Name, func(t *testing.T) {
 			t.Parallel()
 
-			var dataIndex = 0
-			if tcase.HasContext {
-				dataIndex = 1
-			}
-
 			var handler = &Handler{
-				spec:       &signature{Input: tcase.Spec.Input, Output: tcase.Spec.Output},
+				signature: &Signature{Input: tcase.Spec.Input, Output: tcase.Spec.Output},
-				fn:         tcase.Fn,
+				fn:        tcase.Fn,
-				dataIndex:  dataIndex,
-				hasContext: tcase.HasContext,
 			}
 
 			// build input
@@ -138,7 +131,7 @@ func TestInput(t *testing.T) {
 				input[key] = val
 			}
 
-			var output, err = handler.Handle(api.Context{}, input)
+			var output, err = handler.Handle(&api.Context{}, input)
 			if err != tcase.ExpectedErr {
 				t.Fatalf("expected api error <%v> got <%v>", tcase.ExpectedErr, err)
 			}

internal/dynfunc/signature.go

@@ -9,15 +9,17 @@ import (
 	"git.xdrm.io/go/aicra/internal/config"
 )
 
-// signature represents input/output arguments for a dynamic function
+// Signature represents input/output arguments for service from the aicra configuration
-type signature struct {
+type Signature struct {
-	Input  map[string]reflect.Type
+	// Input arguments of the service
+	Input map[string]reflect.Type
+	// Output arguments of the service
 	Output map[string]reflect.Type
 }
 
-// builds a spec from the configuration service
+// BuildSignature builds a signature for a service configuration
-func signatureFromService(service config.Service) *signature {
+func BuildSignature(service config.Service) *Signature {
-	s := &signature{
+	s := &Signature{
 		Input:  make(map[string]reflect.Type),
 		Output: make(map[string]reflect.Type),
 	}
@@ -44,31 +46,32 @@ func signatureFromService(service config.Service) *signature {
 	return s
 }
 
-// checks for HandlerFn input arguments
+// ValidateInput validates a handler's input arguments against the service signature
-func (s *signature) checkInput(impl reflect.Type, index int) error {
+func (s *Signature) ValidateInput(handlerType reflect.Type) error {
-	var requiredInput, structIndex = index, index
+	ctxType := reflect.TypeOf(api.Context{})
-	if len(s.Input) > 0 { // arguments struct
+
-		requiredInput++
+	// missing or invalid first arg: api.Context
+	if handlerType.NumIn() < 1 || ctxType.AssignableTo(handlerType.In(0)) {
+		return errMissingHandlerContextArgument
 	}
 
-	// missing arguments
+	// no input required
-	if impl.NumIn() > requiredInput {
-		return errUnexpectedInput
-	}
-
-	// none required
 	if len(s.Input) == 0 {
+		// input struct provided
+		if handlerType.NumIn() > 1 {
+			return errUnexpectedInput
+		}
 		return nil
 	}
 
 	// too much arguments
-	if impl.NumIn() != requiredInput {
+	if handlerType.NumIn() > 2 {
-		return errMissingHandlerArgumentParam
+		return errMissingHandlerInputArgument
 	}
 
 	// arg must be a struct
-	structArg := impl.In(structIndex)
+	inStruct := handlerType.In(1)
-	if structArg.Kind() != reflect.Struct {
+	if inStruct.Kind() != reflect.Struct {
 		return errMissingParamArgument
 	}
 
@@ -78,9 +81,9 @@ func (s *signature) checkInput(impl reflect.Type, index int) error {
 			return fmt.Errorf("%s: %w", name, errUnexportedName)
 		}
 
-		field, exists := structArg.FieldByName(name)
+		field, exists := inStruct.FieldByName(name)
 		if !exists {
-			return fmt.Errorf("%s: %w", name, errMissingParamFromConfig)
+			return fmt.Errorf("%s: %w", name, errMissingConfigArgument)
 		}
 
 		if !ptype.AssignableTo(field.Type) {
@@ -91,16 +94,18 @@ func (s *signature) checkInput(impl reflect.Type, index int) error {
 	return nil
 }
 
-// checks for HandlerFn output arguments
+// ValidateOutput validates a handler's output arguments against the service signature
-func (s signature) checkOutput(impl reflect.Type) error {
+func (s Signature) ValidateOutput(handlerType reflect.Type) error {
-	if impl.NumOut() < 1 {
+	errType := reflect.TypeOf(api.ErrUnknown)
-		return errMissingHandlerOutput
+
+	if handlerType.NumOut() < 1 {
+		return errMissingHandlerErrorArgument
 	}
 
 	// last output must be api.Err
-	errOutput := impl.Out(impl.NumOut() - 1)
+	lastArgType := handlerType.Out(handlerType.NumOut() - 1)
-	if !errOutput.AssignableTo(reflect.TypeOf(api.ErrUnknown)) {
+	if !lastArgType.AssignableTo(errType) {
-		return errMissingHandlerErrorOutput
+		return errMissingHandlerErrorArgument
 	}
 
 	// no output -> ok
@@ -108,19 +113,19 @@ func (s signature) checkOutput(impl reflect.Type) error {
 		return nil
 	}
 
-	if impl.NumOut() != 2 {
+	if handlerType.NumOut() < 2 {
-		return errMissingParamOutput
+		return errMissingHandlerOutputArgument
 	}
 
 	// fail if first output is not a pointer to struct
-	structOutputPtr := impl.Out(0)
+	outStructPtr := handlerType.Out(0)
-	if structOutputPtr.Kind() != reflect.Ptr {
+	if outStructPtr.Kind() != reflect.Ptr {
-		return errMissingParamOutput
+		return errWrongOutputArgumentType
 	}
 
-	structOutput := structOutputPtr.Elem()
+	outStruct := outStructPtr.Elem()
-	if structOutput.Kind() != reflect.Struct {
+	if outStruct.Kind() != reflect.Struct {
-		return errMissingParamOutput
+		return errWrongOutputArgumentType
 	}
 
 	// fail on invalid output
@@ -129,9 +134,9 @@ func (s signature) checkOutput(impl reflect.Type) error {
 			return fmt.Errorf("%s: %w", name, errUnexportedName)
 		}
 
-		field, exists := structOutput.FieldByName(name)
+		field, exists := outStruct.FieldByName(name)
 		if !exists {
-			return fmt.Errorf("%s: %w", name, errMissingOutputFromConfig)
+			return fmt.Errorf("%s: %w", name, errMissingConfigArgument)
 		}
 
 		// ignore types evalutating to nil

internal/dynfunc/signature_test.go

@@ -20,22 +20,22 @@ func TestInputCheck(t *testing.T) {
 		{
 			Name:  "no input 0 given",
 			Input: map[string]reflect.Type{},
-			Fn:    func() {},
+			Fn:    func(*api.Context) {},
-			FnCtx: func(api.Context) {},
+			FnCtx: func(*api.Context) {},
 			Err:   nil,
 		},
 		{
 			Name:  "no input 1 given",
 			Input: map[string]reflect.Type{},
-			Fn:    func(int) {},
+			Fn:    func(*api.Context, int) {},
-			FnCtx: func(api.Context, int) {},
+			FnCtx: func(*api.Context, int) {},
 			Err:   errUnexpectedInput,
 		},
 		{
 			Name:  "no input 2 given",
 			Input: map[string]reflect.Type{},
-			Fn:    func(int, string) {},
+			Fn:    func(*api.Context, int, string) {},
-			FnCtx: func(api.Context, int, string) {},
+			FnCtx: func(*api.Context, int, string) {},
 			Err:   errUnexpectedInput,
 		},
 		{
@@ -43,17 +43,17 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(int(0)),
 			},
-			Fn:    func() {},
+			Fn:    func(*api.Context) {},
-			FnCtx: func(api.Context) {},
+			FnCtx: func(*api.Context) {},
-			Err:   errMissingHandlerArgumentParam,
+			Err:   errMissingHandlerInputArgument,
 		},
 		{
 			Name: "1 input non-struct given",
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(int(0)),
 			},
-			Fn:    func(int) {},
+			Fn:    func(*api.Context, int) {},
-			FnCtx: func(api.Context, int) {},
+			FnCtx: func(*api.Context, int) {},
 			Err:   errMissingParamArgument,
 		},
 		{
@@ -61,8 +61,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"test1": reflect.TypeOf(int(0)),
 			},
-			Fn:    func(struct{}) {},
+			Fn:    func(*api.Context, struct{}) {},
-			FnCtx: func(api.Context, struct{}) {},
+			FnCtx: func(*api.Context, struct{}) {},
 			Err:   errUnexportedName,
 		},
 		{
@@ -70,17 +70,17 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(int(0)),
 			},
-			Fn:    func(struct{}) {},
+			Fn:    func(*api.Context, struct{}) {},
-			FnCtx: func(api.Context, struct{}) {},
+			FnCtx: func(*api.Context, struct{}) {},
-			Err:   errMissingParamFromConfig,
+			Err:   errMissingConfigArgument,
 		},
 		{
 			Name: "1 input invalid given",
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(int(0)),
 			},
-			Fn:    func(struct{ Test1 string }) {},
+			Fn:    func(*api.Context, struct{ Test1 string }) {},
-			FnCtx: func(api.Context, struct{ Test1 string }) {},
+			FnCtx: func(*api.Context, struct{ Test1 string }) {},
 			Err:   errWrongParamTypeFromConfig,
 		},
 		{
@@ -88,8 +88,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(int(0)),
 			},
-			Fn:    func(struct{ Test1 int }) {},
+			Fn:    func(*api.Context, struct{ Test1 int }) {},
-			FnCtx: func(api.Context, struct{ Test1 int }) {},
+			FnCtx: func(*api.Context, struct{ Test1 int }) {},
 			Err:   nil,
 		},
 		{
@@ -97,17 +97,17 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(new(int)),
 			},
-			Fn:    func(struct{}) {},
+			Fn:    func(*api.Context, struct{}) {},
-			FnCtx: func(api.Context, struct{}) {},
+			FnCtx: func(*api.Context, struct{}) {},
-			Err:   errMissingParamFromConfig,
+			Err:   errMissingConfigArgument,
 		},
 		{
 			Name: "1 input ptr invalid given",
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(new(int)),
 			},
-			Fn:    func(struct{ Test1 string }) {},
+			Fn:    func(*api.Context, struct{ Test1 string }) {},
-			FnCtx: func(api.Context, struct{ Test1 string }) {},
+			FnCtx: func(*api.Context, struct{ Test1 string }) {},
 			Err:   errWrongParamTypeFromConfig,
 		},
 		{
@@ -115,8 +115,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(new(int)),
 			},
-			Fn:    func(struct{ Test1 *string }) {},
+			Fn:    func(*api.Context, struct{ Test1 *string }) {},
-			FnCtx: func(api.Context, struct{ Test1 *string }) {},
+			FnCtx: func(*api.Context, struct{ Test1 *string }) {},
 			Err:   errWrongParamTypeFromConfig,
 		},
 		{
@@ -124,8 +124,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(new(int)),
 			},
-			Fn:    func(struct{ Test1 *int }) {},
+			Fn:    func(*api.Context, struct{ Test1 *int }) {},
-			FnCtx: func(api.Context, struct{ Test1 *int }) {},
+			FnCtx: func(*api.Context, struct{ Test1 *int }) {},
 			Err:   nil,
 		},
 		{
@@ -133,8 +133,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(string("")),
 			},
-			Fn:    func(struct{ Test1 string }) {},
+			Fn:    func(*api.Context, struct{ Test1 string }) {},
-			FnCtx: func(api.Context, struct{ Test1 string }) {},
+			FnCtx: func(*api.Context, struct{ Test1 string }) {},
 			Err:   nil,
 		},
 		{
@@ -142,8 +142,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(uint(0)),
 			},
-			Fn:    func(struct{ Test1 uint }) {},
+			Fn:    func(*api.Context, struct{ Test1 uint }) {},
-			FnCtx: func(api.Context, struct{ Test1 uint }) {},
+			FnCtx: func(*api.Context, struct{ Test1 uint }) {},
 			Err:   nil,
 		},
 		{
@@ -151,8 +151,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(float64(0)),
 			},
-			Fn:    func(struct{ Test1 float64 }) {},
+			Fn:    func(*api.Context, struct{ Test1 float64 }) {},
-			FnCtx: func(api.Context, struct{ Test1 float64 }) {},
+			FnCtx: func(*api.Context, struct{ Test1 float64 }) {},
 			Err:   nil,
 		},
 		{
@@ -160,8 +160,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf([]byte("")),
 			},
-			Fn:    func(struct{ Test1 []byte }) {},
+			Fn:    func(*api.Context, struct{ Test1 []byte }) {},
-			FnCtx: func(api.Context, struct{ Test1 []byte }) {},
+			FnCtx: func(*api.Context, struct{ Test1 []byte }) {},
 			Err:   nil,
 		},
 		{
@@ -169,8 +169,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf([]rune("")),
 			},
-			Fn:    func(struct{ Test1 []rune }) {},
+			Fn:    func(*api.Context, struct{ Test1 []rune }) {},
-			FnCtx: func(api.Context, struct{ Test1 []rune }) {},
+			FnCtx: func(*api.Context, struct{ Test1 []rune }) {},
 			Err:   nil,
 		},
 		{
@@ -178,8 +178,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(new(string)),
 			},
-			Fn:    func(struct{ Test1 *string }) {},
+			Fn:    func(*api.Context, struct{ Test1 *string }) {},
-			FnCtx: func(api.Context, struct{ Test1 *string }) {},
+			FnCtx: func(*api.Context, struct{ Test1 *string }) {},
 			Err:   nil,
 		},
 		{
@@ -187,8 +187,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(new(uint)),
 			},
-			Fn:    func(struct{ Test1 *uint }) {},
+			Fn:    func(*api.Context, struct{ Test1 *uint }) {},
-			FnCtx: func(api.Context, struct{ Test1 *uint }) {},
+			FnCtx: func(*api.Context, struct{ Test1 *uint }) {},
 			Err:   nil,
 		},
 		{
@@ -196,8 +196,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(new(float64)),
 			},
-			Fn:    func(struct{ Test1 *float64 }) {},
+			Fn:    func(*api.Context, struct{ Test1 *float64 }) {},
-			FnCtx: func(api.Context, struct{ Test1 *float64 }) {},
+			FnCtx: func(*api.Context, struct{ Test1 *float64 }) {},
 			Err:   nil,
 		},
 		{
@@ -205,8 +205,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(new([]byte)),
 			},
-			Fn:    func(struct{ Test1 *[]byte }) {},
+			Fn:    func(*api.Context, struct{ Test1 *[]byte }) {},
-			FnCtx: func(api.Context, struct{ Test1 *[]byte }) {},
+			FnCtx: func(*api.Context, struct{ Test1 *[]byte }) {},
 			Err:   nil,
 		},
 		{
@@ -214,8 +214,8 @@ func TestInputCheck(t *testing.T) {
 			Input: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(new([]rune)),
 			},
-			Fn:    func(struct{ Test1 *[]rune }) {},
+			Fn:    func(*api.Context, struct{ Test1 *[]rune }) {},
-			FnCtx: func(api.Context, struct{ Test1 *[]rune }) {},
+			FnCtx: func(*api.Context, struct{ Test1 *[]rune }) {},
 			Err:   nil,
 		},
 	}
@@ -225,47 +225,27 @@ func TestInputCheck(t *testing.T) {
 			t.Parallel()
 
 			// mock spec
-			s := signature{
+			s := Signature{
 				Input:  tcase.Input,
 				Output: nil,
 			}
 
-			t.Run("with-context", func(t *testing.T) {
+			err := s.ValidateInput(reflect.TypeOf(tcase.FnCtx))
-				err := s.checkInput(reflect.TypeOf(tcase.FnCtx), 1)
+			if err == nil && tcase.Err != nil {
-				if err == nil && tcase.Err != nil {
+				t.Errorf("expected an error: '%s'", tcase.Err.Error())
-					t.Errorf("expected an error: '%s'", tcase.Err.Error())
+				t.FailNow()
-					t.FailNow()
+			}
-				}
+			if err != nil && tcase.Err == nil {
-				if err != nil && tcase.Err == nil {
+				t.Errorf("unexpected error: '%s'", err.Error())
-					t.Errorf("unexpected error: '%s'", err.Error())
+				t.FailNow()
-					t.FailNow()
+			}
-				}
 
-				if err != nil && tcase.Err != nil {
+			if err != nil && tcase.Err != nil {
-					if !errors.Is(err, tcase.Err) {
+				if !errors.Is(err, tcase.Err) {
-						t.Errorf("expected the error <%s> got <%s>", tcase.Err, err)
+					t.Errorf("expected the error <%s> got <%s>", tcase.Err, err)
-						t.FailNow()
-					}
-				}
-			})
-			t.Run("without-context", func(t *testing.T) {
-				err := s.checkInput(reflect.TypeOf(tcase.Fn), 0)
-				if err == nil && tcase.Err != nil {
-					t.Errorf("expected an error: '%s'", tcase.Err.Error())
 					t.FailNow()
 				}
-				if err != nil && tcase.Err == nil {
+			}
-					t.Errorf("unexpected error: '%s'", err.Error())
-					t.FailNow()
-				}
-
-				if err != nil && tcase.Err != nil {
-					if !errors.Is(err, tcase.Err) {
-						t.Errorf("expected the error <%s> got <%s>", tcase.Err, err)
-						t.FailNow()
-					}
-				}
-			})
 		})
 	}
 }
@@ -279,25 +259,37 @@ func TestOutputCheck(t *testing.T) {
 		// no input -> missing api.Err
 		{
 			Output: map[string]reflect.Type{},
-			Fn:     func() {},
+			Fn:     func(*api.Context) {},
-			Err:    errMissingHandlerOutput,
+			Err:    errMissingHandlerOutputArgument,
 		},
 		// no input -> with last type not api.Err
 		{
 			Output: map[string]reflect.Type{},
-			Fn:     func() bool { return true },
+			Fn:     func(*api.Context) bool { return true },
-			Err:    errMissingHandlerErrorOutput,
+			Err:    errMissingHandlerErrorArgument,
 		},
 		// no input -> with api.Err
 		{
 			Output: map[string]reflect.Type{},
-			Fn:     func() api.Err { return api.ErrSuccess },
+			Fn:     func(*api.Context) api.Err { return api.ErrSuccess },
 			Err:    nil,
 		},
+		// no input -> missing *api.Context
+		{
+			Output: map[string]reflect.Type{},
+			Fn:     func(*api.Context) api.Err { return api.ErrSuccess },
+			Err:    errMissingHandlerContextArgument,
+		},
+		// no input -> invlaid *api.Context type
+		{
+			Output: map[string]reflect.Type{},
+			Fn:     func(*api.Context, int) api.Err { return api.ErrSuccess },
+			Err:    errMissingHandlerContextArgument,
+		},
 		// func can have output if not specified
 		{
 			Output: map[string]reflect.Type{},
-			Fn:     func() (*struct{}, api.Err) { return nil, api.ErrSuccess },
+			Fn:     func(*api.Context) (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			Err:    nil,
 		},
 		// missing output struct in func
@@ -306,7 +298,7 @@ func TestOutputCheck(t *testing.T) {
 				"Test1": reflect.TypeOf(int(0)),
 			},
 			Fn:  func() api.Err { return api.ErrSuccess },
-			Err: errMissingParamOutput,
+			Err: errWrongOutputArgumentType,
 		},
 		// output not a pointer
 		{
@@ -314,7 +306,7 @@ func TestOutputCheck(t *testing.T) {
 				"Test1": reflect.TypeOf(int(0)),
 			},
 			Fn:  func() (int, api.Err) { return 0, api.ErrSuccess },
-			Err: errMissingParamOutput,
+			Err: errWrongOutputArgumentType,
 		},
 		// output not a pointer to struct
 		{
@@ -322,7 +314,7 @@ func TestOutputCheck(t *testing.T) {
 				"Test1": reflect.TypeOf(int(0)),
 			},
 			Fn:  func() (*int, api.Err) { return nil, api.ErrSuccess },
-			Err: errMissingParamOutput,
+			Err: errWrongOutputArgumentType,
 		},
 		// unexported param name
 		{
@@ -338,7 +330,7 @@ func TestOutputCheck(t *testing.T) {
 				"Test1": reflect.TypeOf(int(0)),
 			},
 			Fn:  func() (*struct{}, api.Err) { return nil, api.ErrSuccess },
-			Err: errMissingParamFromConfig,
+			Err: errMissingConfigArgument,
 		},
 		// output field invalid type
 		{
@@ -371,12 +363,12 @@ func TestOutputCheck(t *testing.T) {
 			t.Parallel()
 
 			// mock spec
-			s := signature{
+			s := Signature{
 				Input:  nil,
 				Output: tcase.Output,
 			}
 
-			err := s.checkOutput(reflect.TypeOf(tcase.Fn))
+			err := s.ValidateOutput(reflect.TypeOf(tcase.Fn))
 			if err == nil && tcase.Err != nil {
 				t.Errorf("expected an error: '%s'", tcase.Err.Error())
 				t.FailNow()