package downloader

import (
	"context"
	"io"
	"net/http"
	"strconv"
	"time"

	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/response"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/tokens"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/utils"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/pool"
	"github.com/valyala/fasthttp"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/trace"
	"go.uber.org/zap"
)

// max bytes needed to detect content type according to http.DetectContentType docs.
const sizeToDetectType = 512

const (
	hdrObjectID    = "X-Object-Id"
	hdrOwnerID     = "X-Owner-Id"
	hdrContainerID = "X-Container-Id"
)

func headObject(ctx context.Context, req request, clnt *pool.Pool, objectAddress oid.Address) {
	ctx, span := utils.StartHTTPServerSpan(ctx, req.RequestCtx, "HEAD Object",
		trace.WithAttributes(
			attribute.String("cid", objectAddress.Container().EncodeToString()),
			attribute.String("oid", objectAddress.Object().EncodeToString()),
		))
	defer func() {
		utils.SetHTTPTraceInfo(ctx, span, req.RequestCtx)
		span.End()
	}()

	var start = time.Now()
	if err := tokens.StoreBearerToken(req.RequestCtx); err != nil {
		req.log.Error("could not fetch and store bearer token", zap.Error(err))
		response.Error(req.RequestCtx, "could not fetch and store bearer token", fasthttp.StatusBadRequest)
		return
	}

	btoken := bearerToken(req.RequestCtx)

	var prm pool.PrmObjectHead
	prm.SetAddress(objectAddress)
	if btoken != nil {
		prm.UseBearer(*btoken)
	}

	obj, err := clnt.HeadObject(ctx, prm)
	if err != nil {
		req.handleFrostFSErr(err, start)
		return
	}

	req.Response.Header.Set(fasthttp.HeaderContentLength, strconv.FormatUint(obj.PayloadSize(), 10))
	var contentType string
	for _, attr := range obj.Attributes() {
		key := attr.Key()
		val := attr.Value()
		if !isValidToken(key) || !isValidValue(val) {
			continue
		}

		key = utils.BackwardTransformIfSystem(key)

		req.Response.Header.Set(utils.UserAttributeHeaderPrefix+key, val)
		switch key {
		case object.AttributeTimestamp:
			value, err := strconv.ParseInt(val, 10, 64)
			if err != nil {
				req.log.Info("couldn't parse creation date",
					zap.String("key", key),
					zap.String("val", val),
					zap.Error(err))
				continue
			}
			req.Response.Header.Set(fasthttp.HeaderLastModified, time.Unix(value, 0).UTC().Format(http.TimeFormat))
		case object.AttributeContentType:
			contentType = val
		}
	}

	idsToResponse(&req.Response, &obj)

	if len(contentType) == 0 {
		contentType, _, err = readContentType(obj.PayloadSize(), func(sz uint64) (io.Reader, error) {
			var prmRange pool.PrmObjectRange
			prmRange.SetAddress(objectAddress)
			prmRange.SetLength(sz)
			if btoken != nil {
				prmRange.UseBearer(*btoken)
			}

			resObj, err := clnt.ObjectRange(ctx, prmRange)
			if err != nil {
				return nil, err
			}
			return &resObj, nil
		})
		if err != nil && err != io.EOF {
			req.handleFrostFSErr(err, start)
			return
		}
	}
	req.SetContentType(contentType)
}

func idsToResponse(resp *fasthttp.Response, obj *object.Object) {
	objID, _ := obj.ID()
	cnrID, _ := obj.ContainerID()
	resp.Header.Set(hdrObjectID, objID.String())
	resp.Header.Set(hdrOwnerID, obj.OwnerID().String())
	resp.Header.Set(hdrContainerID, cnrID.String())
}

// HeadByAddress handles head requests using simple cid/oid format.
func (d *Downloader) HeadByAddress(c *fasthttp.RequestCtx) {
	d.byAddress(c, headObject)
}

// HeadByAttribute handles attribute-based head requests.
func (d *Downloader) HeadByAttribute(c *fasthttp.RequestCtx) {
	d.byAttribute(c, headObject)
}