package handler

import (
	"archive/tar"
	"bytes"
	"compress/gzip"
	"context"
	"encoding/json"
	"errors"
	"io"
	"net/http"
	"path/filepath"
	"strconv"
	"time"

	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/data"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/tokens"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/utils"
	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/bearer"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
	"github.com/valyala/fasthttp"
	"go.uber.org/zap"
)

const (
	jsonHeader           = "application/json; charset=UTF-8"
	drainBufSize         = 4096
	explodeArchiveHeader = "X-Explode-Archive"
)

type putResponse struct {
	ObjectID    string `json:"object_id"`
	ContainerID string `json:"container_id"`
}

func newPutResponse(addr oid.Address) *putResponse {
	return &putResponse{
		ObjectID:    addr.Object().EncodeToString(),
		ContainerID: addr.Container().EncodeToString(),
	}
}

func (pr *putResponse) encode(w io.Writer) error {
	enc := json.NewEncoder(w)
	enc.SetIndent("", "\t")
	return enc.Encode(pr)
}

// Upload handles multipart upload request.
func (h *Handler) Upload(req *fasthttp.RequestCtx) {
	ctx, span := tracing.StartSpanFromContext(utils.GetContextFromRequest(req), "handler.Upload")
	defer span.End()

	var file MultipartFile

	scid, _ := req.UserValue("cid").(string)
	bodyStream := req.RequestBodyStream()
	drainBuf := make([]byte, drainBufSize)

	log := h.reqLogger(ctx)
	ctx = utils.SetReqLog(ctx, log.With(zap.String("cid", scid)))

	bktInfo, err := h.getBucketInfo(ctx, scid)
	if err != nil {
		h.logAndSendError(ctx, req, logs.FailedToGetBucketInfo, err)
		return
	}

	boundary := string(req.Request.Header.MultipartFormBoundary())
	if file, err = fetchMultipartFile(log, bodyStream, boundary); err != nil {
		h.logAndSendError(ctx, req, logs.CouldNotReceiveMultipartForm, err)
		return
	}

	filtered, err := filterHeaders(log, &req.Request.Header)
	if err != nil {
		h.logAndSendError(ctx, req, logs.FailedToFilterHeaders, err)
		return
	}

	if req.Request.Header.Peek(explodeArchiveHeader) != nil {
		h.explodeArchive(ctx, req, bktInfo, file, filtered)
	} else {
		h.uploadSingleObject(ctx, req, bktInfo, file, filtered)
	}

	// Multipart is multipart and thus can contain more than one part which
	// we ignore at the moment. Also, when dealing with chunked encoding
	// the last zero-length chunk might be left unread (because multipart
	// reader only cares about its boundary and doesn't look further) and
	// it will be (erroneously) interpreted as the start of the next
	// pipelined header. Thus, we need to drain the body buffer.
	for {
		_, err = bodyStream.Read(drainBuf)
		if err == io.EOF || errors.Is(err, io.ErrUnexpectedEOF) {
			break
		}
	}
}

func (h *Handler) uploadSingleObject(ctx context.Context, req *fasthttp.RequestCtx, bkt *data.BucketInfo, file MultipartFile, filtered map[string]string) {
	ctx, span := tracing.StartSpanFromContext(ctx, "handler.uploadSingleObject")
	defer span.End()

	setIfNotExist(filtered, object.AttributeFileName, file.FileName())

	attributes, err := h.extractAttributes(ctx, req, filtered)
	if err != nil {
		h.logAndSendError(ctx, req, logs.FailedToGetAttributes, err)
		return
	}

	idObj, err := h.uploadObject(ctx, bkt, attributes, file)
	if err != nil {
		h.logAndSendError(ctx, req, logs.FailedToUploadObject, err)
		return
	}
	h.reqLogger(ctx).Debug(logs.ObjectUploaded,
		zap.String("oid", idObj.EncodeToString()),
		zap.String("FileName", file.FileName()),
		logs.TagField(logs.TagExternalStorage),
	)

	addr := newAddress(bkt.CID, idObj)
	req.Response.Header.SetContentType(jsonHeader)
	// Try to return the response, otherwise, if something went wrong, throw an error.
	if err = newPutResponse(addr).encode(req); err != nil {
		h.logAndSendError(ctx, req, logs.CouldNotEncodeResponse, err)
		return
	}
}

func (h *Handler) uploadObject(ctx context.Context, bkt *data.BucketInfo, attrs []object.Attribute, file io.Reader) (oid.ID, error) {
	obj := object.New()
	obj.SetContainerID(bkt.CID)
	obj.SetOwnerID(*h.ownerID)
	obj.SetAttributes(attrs...)

	prm := PrmObjectCreate{
		PrmAuth: PrmAuth{
			BearerToken: h.fetchBearerToken(ctx),
		},
		Object:                 obj,
		Payload:                file,
		ClientCut:              h.config.ClientCut(),
		WithoutHomomorphicHash: bkt.HomomorphicHashDisabled,
		BufferMaxSize:          h.config.BufferMaxSizeForPut(),
	}

	idObj, err := h.frostfs.CreateObject(ctx, prm)
	if err != nil {
		return oid.ID{}, err
	}

	return idObj, nil
}

func (h *Handler) extractAttributes(ctx context.Context, req *fasthttp.RequestCtx, filtered map[string]string) ([]object.Attribute, error) {
	now := time.Now()
	if rawHeader := req.Request.Header.Peek(fasthttp.HeaderDate); rawHeader != nil {
		if parsed, err := time.Parse(http.TimeFormat, string(rawHeader)); err != nil {
			h.reqLogger(ctx).Warn(logs.CouldNotParseClientTime, zap.String("Date header", string(rawHeader)), zap.Error(err),
				logs.TagField(logs.TagDatapath))
		} else {
			now = parsed
		}
	}
	if err := utils.PrepareExpirationHeader(ctx, h.frostfs, filtered, now); err != nil {
		h.reqLogger(ctx).Error(logs.CouldNotPrepareExpirationHeader, zap.Error(err), logs.TagField(logs.TagDatapath))
		return nil, err
	}
	attributes := make([]object.Attribute, 0, len(filtered))
	// prepares attributes from filtered headers
	for key, val := range filtered {
		attribute := newAttribute(key, val)
		attributes = append(attributes, attribute)
	}
	// sets Timestamp attribute if it wasn't set from header and enabled by settings
	if _, ok := filtered[object.AttributeTimestamp]; !ok && h.config.DefaultTimestamp() {
		timestamp := newAttribute(object.AttributeTimestamp, strconv.FormatInt(time.Now().Unix(), 10))
		attributes = append(attributes, timestamp)
	}

	return attributes, nil
}

func newAttribute(key string, val string) object.Attribute {
	attr := object.NewAttribute()
	attr.SetKey(key)
	attr.SetValue(val)
	return *attr
}

// explodeArchive read files from archive and creates objects for each of them.
// Sets FilePath attribute with name from tar.Header.
func (h *Handler) explodeArchive(ctx context.Context, req *fasthttp.RequestCtx, bkt *data.BucketInfo, file io.ReadCloser, filtered map[string]string) {
	ctx, span := tracing.StartSpanFromContext(ctx, "handler.explodeArchive")
	defer span.End()

	// remove user attributes which vary for each file in archive
	// to guarantee that they won't appear twice
	delete(filtered, object.AttributeFileName)
	delete(filtered, object.AttributeFilePath)

	commonAttributes, err := h.extractAttributes(ctx, req, filtered)
	if err != nil {
		h.logAndSendError(ctx, req, logs.FailedToGetAttributes, err)
		return
	}
	attributes := commonAttributes

	reader := file
	if bytes.EqualFold(req.Request.Header.Peek(fasthttp.HeaderContentEncoding), []byte("gzip")) {
		h.reqLogger(ctx).Debug(logs.GzipReaderSelected, logs.TagField(logs.TagDatapath))
		gzipReader, err := gzip.NewReader(file)
		if err != nil {
			h.logAndSendError(ctx, req, logs.FailedToCreateGzipReader, err)
			return
		}
		defer func() {
			if err := gzipReader.Close(); err != nil {
				h.reqLogger(ctx).Warn(logs.FailedToCloseReader, zap.Error(err), logs.TagField(logs.TagDatapath))
			}
		}()
		reader = gzipReader
	}

	tarReader := tar.NewReader(reader)
	for {
		obj, err := tarReader.Next()
		if errors.Is(err, io.EOF) {
			break
		} else if err != nil {
			h.logAndSendError(ctx, req, logs.FailedToReadFileFromTar, err)
			return
		}

		if isDir(obj.Name) {
			continue
		}

		// set varying attributes
		attributes = attributes[:len(commonAttributes)]
		fileName := filepath.Base(obj.Name)
		attributes = append(attributes, newAttribute(object.AttributeFilePath, obj.Name))
		attributes = append(attributes, newAttribute(object.AttributeFileName, fileName))

		idObj, err := h.uploadObject(ctx, bkt, attributes, tarReader)
		if err != nil {
			h.logAndSendError(ctx, req, logs.FailedToUploadObject, err)
			return
		}

		h.reqLogger(ctx).Debug(logs.ObjectUploaded,
			zap.String("oid", idObj.EncodeToString()),
			zap.String("FileName", fileName),
			logs.TagField(logs.TagExternalStorage),
		)
	}
}

func (h *Handler) fetchBearerToken(ctx context.Context) *bearer.Token {
	if tkn, err := tokens.LoadBearerToken(ctx); err == nil && tkn != nil {
		return tkn
	}
	return nil
}