rest-api/main.go: Implement simple Beego API

rest-api/main.go

@@ -1,9 +1,16 @@
 package api
 
 import (
+	"api-broker-prototype/broker"
 	"api-broker-prototype/events"
 	"context"
 	"errors"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/beego/beego/v2/server/web"
+	"github.com/gofrs/uuid"
 )
 
 // serve a simple API to access requests
@@ -15,9 +22,134 @@ func Serve(ctx context.Context, store events.EventStore, port uint) error {
 		return errors.New("the supplied port is zero")
 	}
 
+	// TODO: This doesn't work, the controller is cloned without copying
+	// the store, so the store field is `nil` in the according handlers.
+	// As workaround, we store it in a global instead.
+	ctrl := &controller{
+		store: store,
+	}
+	g_store = store
+
+	// CopyRequestBody is required to to actually receive the body and to parse it as JSON
+	web.BConfig.CopyRequestBody = true
+	// AutoRender is suggested to be turned off for APIs
+	web.BConfig.WebConfig.AutoRender = false
+
+	web.Router("/up", ctrl, "get,head:HeadUp")
+	web.Router("/request/:external_uuid", ctrl, "post:PostRequest")
+	web.Router("/request/:external_uuid", ctrl, "get:GetRequest")
+
+	web.Run(fmt.Sprintf(":%d", port))
+
+	// TODO: reactivate
+	// Getting at something that can be cancelled seems complicated,
+	// so I'm leaving this feature out for now.
 	select {
 	case <-ctx.Done():
 		// cancelled by context
 		return ctx.Err()
 	}
 }
+
+var g_store events.EventStore
+
+// representation of the request during HTTP transfer
+type requestDTO struct {
+	Data string `json:"data"`
+}
+
+// asEvent converts the DTO to the internally used representation
+func (dto requestDTO) asEvent() broker.RequestEvent {
+	return broker.RequestEvent{
+		Request: dto.Data,
+	}
+}
+
+// representation of the (sucessful) response during HTTP transfer
+type responseDTO struct {
+	Created      time.Time `json:"created"`
+	ExternalUUID uuid.UUID `json:"external_uuid"`
+}
+
+// newResponseDTO converts the envelope to the externally used DTO
+func newResponseDTO(envelope events.Envelope) responseDTO {
+	return responseDTO{
+		Created:      envelope.Created(),
+		ExternalUUID: envelope.ExternalUUID(),
+	}
+}
+
+type controller struct {
+	web.Controller
+	store events.EventStore
+}
+
+func (ctrl *controller) HeadUp() {
+	ctrl.Ctx.WriteString("")
+}
+
+func (ctrl *controller) PostRequest() {
+	// extract external UUID from the path
+	external_uuid := uuid.FromStringOrNil(ctrl.GetString(":external_uuid"))
+	if external_uuid == uuid.Nil {
+		ctrl.Ctx.ResponseWriter.WriteHeader(http.StatusBadRequest)
+		ctrl.Ctx.WriteString("Bad Request")
+		return
+	}
+
+	// extract event from the body
+	request := requestDTO{}
+	if err := ctrl.BindJSON(&request); err != nil {
+		ctrl.Ctx.ResponseWriter.WriteHeader(http.StatusBadRequest)
+		ctrl.Ctx.WriteString("Bad Request")
+		return
+	}
+
+	// insert event
+	envelope, err := g_store.Insert(context.Background(), external_uuid, request.asEvent(), 0)
+	if err != nil {
+		if err == events.DuplicateEventUUID {
+			ctrl.Ctx.ResponseWriter.WriteHeader(http.StatusConflict)
+			ctrl.Ctx.WriteString("Conflict")
+			return
+		}
+
+		ctrl.Ctx.ResponseWriter.WriteHeader(http.StatusInternalServerError)
+		ctrl.Ctx.WriteString("Internal Server Error")
+		return
+	}
+
+	response := newResponseDTO(envelope)
+	ctrl.Ctx.ResponseWriter.WriteHeader(http.StatusCreated)
+	ctrl.JSONResp(response)
+}
+
+func (ctrl *controller) GetRequest() {
+	// extract external UUID from the path
+	external_uuid := uuid.FromStringOrNil(ctrl.GetString(":external_uuid"))
+	if external_uuid == uuid.Nil {
+		ctrl.Ctx.ResponseWriter.WriteHeader(http.StatusBadRequest)
+		ctrl.Ctx.WriteString(ctrl.GetString("external_uuid"))
+		return
+	}
+
+	// convert UUID to internal ID
+	id, err := g_store.ResolveUUID(context.Background(), external_uuid)
+	if err != nil {
+		ctrl.Ctx.ResponseWriter.WriteHeader(http.StatusNotFound)
+		ctrl.Ctx.WriteString("failed to resolve external UUID")
+		return
+	}
+
+	// load event
+	envelope, err := g_store.RetrieveOne(context.Background(), id)
+	if err != nil {
+		ctrl.Ctx.ResponseWriter.WriteHeader(http.StatusInternalServerError)
+		ctrl.Ctx.WriteString("failed to load event")
+		return
+	}
+
+	response := newResponseDTO(envelope)
+	ctrl.Ctx.ResponseWriter.WriteHeader(http.StatusOK)
+	ctrl.Ctx.JSONResp(response)
+}