Add multi API example (#192)

_examples/multi-api/main.go

@@ -0,0 +1,118 @@
+// Package main implements an example where two versioned API revisions are mounted into root web service
+// and are available through a service selector in Swagger UI.
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/go-chi/chi/v5/middleware"
+	"github.com/swaggest/openapi-go"
+	"github.com/swaggest/openapi-go/openapi3"
+	"github.com/swaggest/rest/nethttp"
+	"github.com/swaggest/rest/web"
+	swg "github.com/swaggest/swgui"
+	swgui "github.com/swaggest/swgui/v5emb"
+	"github.com/swaggest/usecase"
+)
+
+func main() {
+	fmt.Println("Swagger UI at http://localhost:8010/api/docs.")
+	if err := http.ListenAndServe("localhost:8010", service()); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func service() *web.Service {
+	// Creating root service, to host versioned APIs.
+	s := web.NewService(openapi3.NewReflector())
+	s.OpenAPISchema().SetTitle("Security and Mount Example")
+
+	// Each versioned API is exposed with its own OpenAPI schema.
+	v1r := openapi3.NewReflector()
+	v1r.SpecEns().WithServers(openapi3.Server{URL: "/api/v1/"}).WithInfo(openapi3.Info{Title: "My API of version 1"})
+	apiV1 := web.NewService(v1r)
+
+	v2r := openapi3.NewReflector()
+	v2r.SpecEns().WithServers(openapi3.Server{URL: "/api/v2/"})
+	apiV2 := web.NewService(v2r)
+
+	// Versioned APIs may or may not have their own middlewares and wraps.
+	apiV1.Wrap(
+		middleware.BasicAuth("Admin Access", map[string]string{"admin": "admin"}),
+		nethttp.HTTPBasicSecurityMiddleware(s.OpenAPICollector, "Admin", "Admin access"),
+		nethttp.OpenAPIAnnotationsMiddleware(s.OpenAPICollector, func(oc openapi.OperationContext) error {
+			oc.SetTags(append(oc.Tags(), "V1")...)
+			return nil
+		}),
+	)
+	apiV1.Post("/sum", sum())
+	apiV1.Post("/mul", mul())
+	// Once all API use cases are added, schema can be served too.
+	apiV1.Method(http.MethodGet, "/openapi.json", specHandler(apiV1.OpenAPICollector.SpecSchema()))
+
+	apiV2.Post("/summarization", sum())
+	apiV2.Post("/multiplication", mul())
+	apiV2.Method(http.MethodGet, "/openapi.json", specHandler(apiV2.OpenAPICollector.SpecSchema()))
+
+	// Prepared versioned API services are mounted with their base URLs into root service.
+	s.Mount("/api/v1", apiV1)
+	s.Mount("/api/v2", apiV2)
+
+	// Root docs needs a bit of hackery to expose versioned APIs as separate services.
+	s.Docs("/api/docs", swgui.NewWithConfig(swg.Config{
+		ShowTopBar: true,
+		SettingsUI: map[string]string{
+			// When "urls" are configured, Swagger UI ignores "url" and switches to multi API mode.
+			"urls": `[
+	{"url": "/api/v1/openapi.json", "name": "APIv1"}, 
+	{"url": "/api/v2/openapi.json", "name": "APIv2"}
+]`,
+			`"urls.primaryName"`: `"APIv2"`, // Using APIv2 as default.
+		},
+	}))
+
+	// Blanket handler, for example to serve static content.
+	s.Mount("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte("blanket handler got a request: " + r.URL.String()))
+	}))
+
+	return s
+}
+
+func specHandler(s openapi.SpecSchema) http.Handler {
+	j, err := json.Marshal(s)
+	if err != nil {
+		panic(err)
+	}
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write(j)
+	})
+}
+
+func mul() usecase.Interactor {
+	return usecase.NewInteractor(func(ctx context.Context, input []int, output *int) error {
+		*output = 1
+
+		for _, v := range input {
+			*output *= v
+		}
+
+		return nil
+	})
+}
+
+func sum() usecase.Interactor {
+	return usecase.NewInteractor(func(ctx context.Context, input []int, output *int) error {
+		for _, v := range input {
+			*output += v
+		}
+
+		return nil
+	})
+}