package handler

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

	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/response"
	"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.uber.org/zap"
)

type readCloser struct {
	io.Reader
	io.Closer
}

// initializes io.Reader with the limited size and detects Content-Type from it.
// Returns r's error directly. Also returns the processed data.
func readContentType(maxSize uint64, rInit func(uint64) (io.Reader, error)) (string, []byte, error) {
	if maxSize > sizeToDetectType {
		maxSize = sizeToDetectType
	}

	buf := make([]byte, maxSize) // maybe sync-pool the slice?

	r, err := rInit(maxSize)
	if err != nil {
		return "", nil, err
	}

	n, err := r.Read(buf)
	if err != nil && err != io.EOF {
		return "", nil, err
	}

	buf = buf[:n]

	return http.DetectContentType(buf), buf, err // to not lose io.EOF
}

func (h *Handler) receiveFile(ctx context.Context, req request, objectAddress oid.Address) {
	var (
		err      error
		dis      = "inline"
		start    = time.Now()
		filename string
	)

	var prm pool.PrmObjectGet
	prm.SetAddress(objectAddress)
	if btoken := bearerToken(ctx); btoken != nil {
		prm.UseBearer(*btoken)
	}

	rObj, err := h.pool.GetObject(ctx, prm)
	if err != nil {
		req.handleFrostFSErr(err, start)
		return
	}

	// we can't close reader in this function, so how to do it?

	if req.Request.URI().QueryArgs().GetBool("download") {
		dis = "attachment"
	}

	payloadSize := rObj.Header.PayloadSize()

	req.Response.Header.Set(fasthttp.HeaderContentLength, strconv.FormatUint(payloadSize, 10))
	var contentType string
	for _, attr := range rObj.Header.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.AttributeFileName:
			filename = val
		case object.AttributeTimestamp:
			value, err := strconv.ParseInt(val, 10, 64)
			if err != nil {
				req.log.Info(logs.CouldntParseCreationDate,
					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, &rObj.Header)

	if len(contentType) == 0 {
		// determine the Content-Type from the payload head
		var payloadHead []byte

		contentType, payloadHead, err = readContentType(payloadSize, func(uint64) (io.Reader, error) {
			return rObj.Payload, nil
		})
		if err != nil && err != io.EOF {
			req.log.Error(logs.CouldNotDetectContentTypeFromPayload, zap.Error(err))
			response.Error(req.RequestCtx, "could not detect Content-Type from payload: "+err.Error(), fasthttp.StatusBadRequest)
			return
		}

		// reset payload reader since a part of the data has been read
		var headReader io.Reader = bytes.NewReader(payloadHead)

		if err != io.EOF { // otherwise, we've already read full payload
			headReader = io.MultiReader(headReader, rObj.Payload)
		}

		// note: we could do with io.Reader, but SetBodyStream below closes body stream
		// if it implements io.Closer and that's useful for us.
		rObj.Payload = readCloser{headReader, rObj.Payload}
	}
	req.SetContentType(contentType)

	req.Response.Header.Set(fasthttp.HeaderContentDisposition, dis+"; filename="+path.Base(filename))

	req.Response.SetBodyStream(rObj.Payload, int(payloadSize))
}