handler.go

/*
 * Copyright (C) 2023-2024
 * Das Land Schleswig-Holstein vertreten durch den
 * Ministerpräsidenten des Landes Schleswig-Holstein
 * Staatskanzlei
 * Abteilung Digitalisierung und zentrales IT-Management der Landesregierung
 *
 * Lizenziert unter der EUPL, Version 1.2 oder - sobald
 * diese von der Europäischen Kommission genehmigt wurden -
 * Folgeversionen der EUPL ("Lizenz");
 * Sie dürfen dieses Werk ausschließlich gemäß
 * dieser Lizenz nutzen.
 * Eine Kopie der Lizenz finden Sie hier:
 *
 * https://joinup.ec.europa.eu/collection/eupl/eupl-text-eupl-12
 *
 * Sofern nicht durch anwendbare Rechtsvorschriften
 * gefordert oder in schriftlicher Form vereinbart, wird
 * die unter der Lizenz verbreitete Software "so wie sie
 * ist", OHNE JEGLICHE GEWÄHRLEISTUNG ODER BEDINGUNGEN -
 * ausdrücklich oder stillschweigend - verbreitet.
 * Die sprachspezifischen Genehmigungen und Beschränkungen
 * unter der Lizenz sind dem Lizenztext zu entnehmen.
 */

package server

import (
	pb "antragsraum-proxy/gen/go"
	"bytes"
	"context"
	"fmt"
	"github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/credentials/insecure"
	"google.golang.org/grpc/status"
	"io"
	"mime/multipart"
	"net/http"
)

func RegisterHomeEndpoint(mux *runtime.ServeMux) {
	err := mux.HandlePath("GET", "/", func(w http.ResponseWriter, r *http.Request, pathParams map[string]string) {
		defer func() {
			if err := recover(); err != nil {
				logger.Error("failed to recover: %v", err)
				http.Error(w, fmt.Sprintf("failed to recover: %v", err), http.StatusInternalServerError)
			}
		}()
	})

	if err != nil {
		logger.Fatal("failed to register home endpoint: %v", err)
	}
}

func RegisterFileUploadEndpoint(mux *runtime.ServeMux) {
	err := mux.HandlePath("POST", "/api/v1/file", func(w http.ResponseWriter, r *http.Request, _ map[string]string) {
		if err := r.ParseMultipartForm(32 << 20); err != nil {
			http.Error(w, "invalid multipart form", http.StatusBadRequest)
			return
		}

		file, header, err := r.FormFile("file")
		if err != nil {
			http.Error(w, "file retrieval error", http.StatusBadRequest)
			return
		}
		defer file.Close()

		conn, err := grpc.NewClient(getGrpcServerUrl(r.Header.Get(GrpcAddressHeader), conf), grpc.WithTransportCredentials(insecure.NewCredentials()))
		if err != nil {
			http.Error(w, "gRPC connection error", http.StatusInternalServerError)
			return
		}
		defer conn.Close()

		client := pb.NewBinaryFileServiceClient(conn)
		stream, err := client.UploadBinaryFileAsStream(r.Context())
		if err != nil {
			http.Error(w, "stream creation error", http.StatusInternalServerError)
			return
		}

		meta := &pb.GrpcUploadBinaryFileRequest{
			Request: &pb.GrpcUploadBinaryFileRequest_Metadata{
				Metadata: &pb.GrpcUploadBinaryFileMetaData{
					FileName: header.Filename,
				},
			},
		}
		if err := stream.Send(meta); err != nil {
			http.Error(w, "Metadata send error", http.StatusInternalServerError)
			return
		}

		buf := make([]byte, 1024*1024)
		for {
			n, err := file.Read(buf)
			if err == io.EOF {
				break
			}
			if err != nil {
				http.Error(w, "File read error", http.StatusInternalServerError)
				return
			}
			if err := stream.Send(&pb.GrpcUploadBinaryFileRequest{
				Request: &pb.GrpcUploadBinaryFileRequest_FileContent{FileContent: buf[:n]},
			}); err != nil {
				http.Error(w, "Chunk send error", http.StatusInternalServerError)
				return
			}
		}

		resp, err := stream.CloseAndRecv()
		if err != nil {
			http.Error(w, "Response error", http.StatusInternalServerError)
			return
		}

		w.WriteHeader(http.StatusOK)
		w.Write([]byte(resp.FileId))
	})

	if err != nil {
		logger.Fatal("Endpoint registration failed: %v", err)
	}
}

func RegisterGetFileEndpoint(mux *runtime.ServeMux) {
	err := mux.HandlePath("POST", "/api/v1/file/content/{fileId}", func(w http.ResponseWriter, r *http.Request, vars map[string]string) {
		var fileBuffer bytes.Buffer

		conn, err := grpc.NewClient(getGrpcServerUrl(r.Header.Get(GrpcAddressHeader), conf), grpc.WithTransportCredentials(insecure.NewCredentials()))
		if err != nil {
			http.Error(w, "gRPC connection error", http.StatusInternalServerError)
			return
		}
		defer conn.Close()

		client := pb.NewBinaryFileServiceClient(conn)
		req := &pb.GrpcGetBinaryFileDataRequest{FileId: vars["fileId"]}
		clientStream, err := client.GetBinaryFileContent(r.Context(), req)
		if err != nil {
			http.Error(w, "stream creation error", http.StatusInternalServerError)
			return
		}

		for {
			resp, err := clientStream.Recv()
			if err == io.EOF {
				break
			}
			if err != nil {
				http.Error(w, "Error receiving file chunks", http.StatusInternalServerError)
				return
			}

			_, err = fileBuffer.Write(resp.FileContent)
			if err != nil {
				http.Error(w, "Error writing file data", http.StatusInternalServerError)
				return
			}
		}

		w.Header().Set("Content-Type", "multipart/form-data")
		w.Header().Set("Content-Disposition", `attachment; filename="file"`)
		w.WriteHeader(http.StatusOK)

		mw := multipart.NewWriter(w)
		part, err := mw.CreateFormFile("file", "file")
		if err != nil {
			http.Error(w, "Error creating multipart form file", http.StatusInternalServerError)
			return
		}

		_, err = fileBuffer.WriteTo(part)
		if err != nil {
			http.Error(w, "Error writing file data to multipart", http.StatusInternalServerError)
			return
		}

		err = mw.Close()
		if err != nil {
			http.Error(w, "Error closing multipart writer", http.StatusInternalServerError)
			return
		}
	})

	if err != nil {
		logger.Fatal("Endpoint registration failed: %v", err)
	}
}

func ErrorHandler(ctx context.Context, mux *runtime.ServeMux, marshaler runtime.Marshaler, w http.ResponseWriter, r *http.Request, err error) {
	st, ok := status.FromError(err)
	if !ok {
		runtime.DefaultHTTPErrorHandler(ctx, mux, marshaler, w, r, err)
		return
	}

	statusCodeMap := map[codes.Code]int{
		codes.InvalidArgument: http.StatusBadRequest,
		codes.AlreadyExists:   http.StatusConflict,
		codes.Unavailable:     http.StatusServiceUnavailable,
	}

	httpStatusCode := http.StatusInternalServerError

	if code, exists := statusCodeMap[st.Code()]; exists {
		httpStatusCode = code
	}

	w.Header().Set("Content-Type", marshaler.ContentType(r))
	w.WriteHeader(httpStatusCode)

	_, writeErr := w.Write([]byte(st.Message()))
	if writeErr != nil {
		logger.Fatal("failed to handle grpc error: %v", writeErr)
	}
}