/*
Copyright 2017 The Fission Authors.

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.
*/

package storagesvc

import (
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"strconv"
	"time"

	"github.com/gorilla/mux"
	"github.com/graymeta/stow"
	"github.com/pkg/errors"
	"go.opencensus.io/plugin/ochttp"
	"go.uber.org/zap"
)

type (
	// Storage is an interface to force storage level details implementation.
	Storage interface {
		getStorageType() StorageType
		dial() (stow.Location, error)
		// getSubDir() string
		getContainerName() string
		getUploadFileName() string
	}

	// StorageService is a struct to hold all things for storage service
	StorageService struct {
		logger        *zap.Logger
		storageClient *StowClient
		port          int
	}

	UploadResponse struct {
		ID string `json:"id"`
	}
)

// Functions handling storage interface
func getStorageType(storage Storage) string {
	return string(storage.getStorageType())
}

func getStorageLocation(config *storageConfig) (stow.Location, error) {
	return config.storage.dial()
}

// Handle multipart file uploads.
func (ss *StorageService) uploadHandler(w http.ResponseWriter, r *http.Request) {
	// handle upload
	r.ParseMultipartForm(0)
	file, handler, err := r.FormFile("uploadfile")
	if err != nil {
		http.Error(w, "missing upload file", http.StatusBadRequest)
		return
	}
	defer file.Close()

	// stow wants the file size, but that's different from the
	// content length, the content length being the size of the
	// encoded file in the HTTP request. So we require an
	// "X-File-Size" header in bytes.

	fileSizeS, ok := r.Header["X-File-Size"]
	if !ok {
		ss.logger.Error("upload is missing the 'X-File-Size' header",
			zap.String("filename", handler.Filename))
		http.Error(w, "missing X-File-Size header", http.StatusBadRequest)
		return
	}

	fileSize, err := strconv.Atoi(fileSizeS[0])
	if err != nil {
		ss.logger.Error("error parsing 'X-File-Size' header",
			zap.Error(err),
			zap.Strings("header", fileSizeS),
			zap.String("filename", handler.Filename))
		http.Error(w, "missing or bad X-File-Size header", http.StatusBadRequest)
		return
	}

	// TODO: allow headers to add more metadata (e.g. environment and function metadata)
	ss.logger.Debug("handling upload",
		zap.String("filename", handler.Filename))

	id, err := ss.storageClient.putFile(file, int64(fileSize))
	if err != nil {
		ss.logger.Error("error saving uploaded file",
			zap.Error(err),
			zap.String("filename", handler.Filename))
		http.Error(w, "Error saving uploaded file", http.StatusInternalServerError)
		return
	}

	// respond with an ID that can be used to retrieve the file
	ur := &UploadResponse{
		ID: id,
	}
	resp, err := json.Marshal(ur)
	if err != nil {
		ss.logger.Error("error marshaling uploaded file response",
			zap.Error(err),
			zap.String("filename", handler.Filename))
		http.Error(w, "Error marshaling response", http.StatusInternalServerError)
		return
	}
	w.Write(resp)
}

func (ss *StorageService) getIdFromRequest(r *http.Request) (string, error) {
	values := r.URL.Query()
	ids, ok := values["id"]
	if !ok || len(ids) == 0 {
		return "", errors.New("missing `id' query param")
	}
	return ids[0], nil
}

func (ss *StorageService) deleteHandler(w http.ResponseWriter, r *http.Request) {
	// get id from request
	fileId, err := ss.getIdFromRequest(r)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	err = ss.storageClient.removeFileByID(fileId)
	if err != nil {
		msg := fmt.Sprintf("Error deleting item: %v", err)
		http.Error(w, msg, http.StatusInternalServerError)
		return
	}
	w.WriteHeader(http.StatusOK)
}

func (ss *StorageService) downloadHandler(w http.ResponseWriter, r *http.Request) {
	// get id from request
	fileId, err := ss.getIdFromRequest(r)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	// Get the file (called "item" in stow's jargon), open it,
	// stream it to response
	err = ss.storageClient.copyFileToStream(fileId, w)
	if err != nil {
		ss.logger.Error("error getting file from storage client", zap.Error(err), zap.String("file_id", fileId))
		if err == ErrNotFound {
			http.Error(w, "Error retrieving item: not found", http.StatusNotFound)
		} else if err == ErrRetrievingItem {
			http.Error(w, "Error retrieving item", http.StatusBadRequest)
		} else if err == ErrOpeningItem {
			http.Error(w, "Error opening item", http.StatusBadRequest)
		} else if err == ErrWritingFileIntoResponse {
			http.Error(w, "Error writing response", http.StatusInternalServerError)
		}
		return
	}
}

func (ss *StorageService) healthHandler(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusOK)
}

func MakeStorageService(logger *zap.Logger, storageClient *StowClient, port int) *StorageService {
	return &StorageService{
		logger:        logger.Named("storage_service"),
		storageClient: storageClient,
		port:          port,
	}
}

func (ss *StorageService) Start(port int) {
	r := mux.NewRouter()
	r.HandleFunc("/v1/archive", ss.uploadHandler).Methods("POST")
	r.HandleFunc("/v1/archive", ss.downloadHandler).Methods("GET")
	r.HandleFunc("/v1/archive", ss.deleteHandler).Methods("DELETE")
	r.HandleFunc("/healthz", ss.healthHandler).Methods("GET")

	address := fmt.Sprintf(":%v", port)

	err := http.ListenAndServe(address, &ochttp.Handler{
		Handler: r,
	})

	ss.logger.Fatal("done listening", zap.Error(err))
}

// Start runs storage service
func Start(logger *zap.Logger, storage Storage, port int) error {
	enablePruner := true
	// create a storage client
	storageClient, err := MakeStowClient(logger, storage)
	if err != nil {
		return errors.Wrap(err, "Error creating stowClient")
	}

	// create http handlers
	storageService := MakeStorageService(logger, storageClient, port)
	go storageService.Start(port)

	// enablePruner prevents storagesvc unit test from needing to talk to kubernetes
	if enablePruner {
		// get the prune interval and start the archive pruner
		pruneInterval, err := strconv.Atoi(os.Getenv("PRUNE_INTERVAL"))
		if err != nil {
			pruneInterval = defaultPruneInterval
		}
		pruner, err := MakeArchivePruner(logger, storageClient, time.Duration(pruneInterval))
		if err != nil {
			return errors.Wrap(err, "Error creating archivePruner")
		}
		go pruner.Start()
	}

	logger.Info("storage service started")
	return nil
}