// Copyright 2025 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0
package core
import (
"context"
"strings"
"testing"
)
func TestMiddlewares(t *testing.T) {
t.Run("creates slice of middlewares", func(t *testing.T) {
m1 := func(next StreamingFunc[string, string, struct{}]) StreamingFunc[string, string, struct{}] {
return next
}
m2 := func(next StreamingFunc[string, string, struct{}]) StreamingFunc[string, string, struct{}] {
return next
}
result := Middlewares(m1, m2)
if len(result) != 2 {
t.Errorf("len(result) = %d, want 2", len(result))
}
})
t.Run("returns empty slice when no middlewares", func(t *testing.T) {
result := Middlewares[string, string, struct{}]()
if len(result) != 0 {
t.Errorf("len(result) = %d, want 0", len(result))
}
})
t.Run("returns single middleware slice", func(t *testing.T) {
m := func(next StreamingFunc[string, string, struct{}]) StreamingFunc[string, string, struct{}] {
return next
}
result := Middlewares(m)
if len(result) != 1 {
t.Errorf("len(result) = %d, want 1", len(result))
}
})
}
func TestChainMiddleware(t *testing.T) {
t.Run("empty chain returns identity", func(t *testing.T) {
handler := func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
return "original:" + input, nil
}
chained := ChainMiddleware[string, string, struct{}]()(handler)
result, err := chained(context.Background(), "test", nil)
if err != nil {
t.Fatalf("unexpected error: %v", err)
}
if result != "original:test" {
t.Errorf("result = %q, want %q", result, "original:test")
}
})
t.Run("single middleware is applied", func(t *testing.T) {
handler := func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
return "handler:" + input, nil
}
middleware := func(next StreamingFunc[string, string, struct{}]) StreamingFunc[string, string, struct{}] {
return func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
result, err := next(ctx, "m1:"+input, cb)
return "m1:" + result, err
}
}
chained := ChainMiddleware(middleware)(handler)
result, err := chained(context.Background(), "test", nil)
if err != nil {
t.Fatalf("unexpected error: %v", err)
}
// Expected: m1: wraps output, m1: prepends to input
if result != "m1:handler:m1:test" {
t.Errorf("result = %q, want %q", result, "m1:handler:m1:test")
}
})
t.Run("multiple middlewares execute in order", func(t *testing.T) {
var executionOrder []string
handler := func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
executionOrder = append(executionOrder, "handler")
return input, nil
}
m1 := func(next StreamingFunc[string, string, struct{}]) StreamingFunc[string, string, struct{}] {
return func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
executionOrder = append(executionOrder, "m1-before")
result, err := next(ctx, input, cb)
executionOrder = append(executionOrder, "m1-after")
return result, err
}
}
m2 := func(next StreamingFunc[string, string, struct{}]) StreamingFunc[string, string, struct{}] {
return func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
executionOrder = append(executionOrder, "m2-before")
result, err := next(ctx, input, cb)
executionOrder = append(executionOrder, "m2-after")
return result, err
}
}
// ChainMiddleware(m1, m2) should execute as: m1 -> m2 -> handler -> m2 -> m1
chained := ChainMiddleware(m1, m2)(handler)
_, err := chained(context.Background(), "test", nil)
if err != nil {
t.Fatalf("unexpected error: %v", err)
}
expected := []string{"m1-before", "m2-before", "handler", "m2-after", "m1-after"}
if len(executionOrder) != len(expected) {
t.Errorf("execution order length = %d, want %d", len(executionOrder), len(expected))
}
for i, step := range expected {
if i >= len(executionOrder) || executionOrder[i] != step {
t.Errorf("step %d = %q, want %q", i, executionOrder[i], step)
}
}
})
t.Run("middleware can modify input", func(t *testing.T) {
handler := func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
return input, nil
}
uppercase := func(next StreamingFunc[string, string, struct{}]) StreamingFunc[string, string, struct{}] {
return func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
return next(ctx, strings.ToUpper(input), cb)
}
}
chained := ChainMiddleware(uppercase)(handler)
result, err := chained(context.Background(), "hello", nil)
if err != nil {
t.Fatalf("unexpected error: %v", err)
}
if result != "HELLO" {
t.Errorf("result = %q, want %q", result, "HELLO")
}
})
t.Run("middleware can modify output", func(t *testing.T) {
handler := func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
return input, nil
}
addSuffix := func(next StreamingFunc[string, string, struct{}]) StreamingFunc[string, string, struct{}] {
return func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
result, err := next(ctx, input, cb)
return result + "!", err
}
}
chained := ChainMiddleware(addSuffix)(handler)
result, err := chained(context.Background(), "hello", nil)
if err != nil {
t.Fatalf("unexpected error: %v", err)
}
if result != "hello!" {
t.Errorf("result = %q, want %q", result, "hello!")
}
})
t.Run("middleware can short-circuit", func(t *testing.T) {
handlerCalled := false
handler := func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
handlerCalled = true
return input, nil
}
shortCircuit := func(next StreamingFunc[string, string, struct{}]) StreamingFunc[string, string, struct{}] {
return func(ctx context.Context, input string, cb func(context.Context, struct{}) error) (string, error) {
if input == "skip" {
return "skipped", nil
}
return next(ctx, input, cb)
}
}
chained := ChainMiddleware(shortCircuit)(handler)
result, err := chained(context.Background(), "skip", nil)
if err != nil {
t.Fatalf("unexpected error: %v", err)
}
if handlerCalled {
t.Error("handler should not have been called")
}
if result != "skipped" {
t.Errorf("result = %q, want %q", result, "skipped")
}
})
}
