package handler

import (
	"context"
	"errors"
	"fmt"
	"io"
	"net/url"
	"strings"

	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/cache"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/data"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/handler/middleware"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/response"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/tree"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/utils"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/bearer"
	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container"
	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
	"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/user"
	"github.com/panjf2000/ants/v2"
	"github.com/valyala/fasthttp"
	"go.uber.org/zap"
)

type Config interface {
	DefaultTimestamp() bool
	ZipCompression() bool
	ClientCut() bool
	IndexPageEnabled() bool
	IndexPageTemplate() string
	BufferMaxSizeForPut() uint64
	NamespaceHeader() string
}

// PrmContainer groups parameters of FrostFS.Container operation.
type PrmContainer struct {
	// Container identifier.
	ContainerID cid.ID
}

// PrmAuth groups authentication parameters for the FrostFS operation.
type PrmAuth struct {
	// Bearer token to be used for the operation. Overlaps PrivateKey. Optional.
	BearerToken *bearer.Token
}

// PrmObjectHead groups parameters of FrostFS.HeadObject operation.
type PrmObjectHead struct {
	// Authentication parameters.
	PrmAuth

	// Address to read the object header from.
	Address oid.Address
}

// PrmObjectGet groups parameters of FrostFS.GetObject operation.
type PrmObjectGet struct {
	// Authentication parameters.
	PrmAuth

	// Address to read the object header from.
	Address oid.Address
}

// PrmObjectRange groups parameters of FrostFS.RangeObject operation.
type PrmObjectRange struct {
	// Authentication parameters.
	PrmAuth

	// Address to read the object header from.
	Address oid.Address

	// Offset-length range of the object payload to be read.
	PayloadRange [2]uint64
}

// Object represents FrostFS object.
type Object struct {
	// Object header (doesn't contain payload).
	Header object.Object

	// Object payload part encapsulated in io.Reader primitive.
	// Returns ErrAccessDenied on read access violation.
	Payload io.ReadCloser
}

// PrmObjectCreate groups parameters of FrostFS.CreateObject operation.
type PrmObjectCreate struct {
	// Authentication parameters.
	PrmAuth

	Object *object.Object

	// Object payload encapsulated in io.Reader primitive.
	Payload io.Reader

	// Enables client side object preparing.
	ClientCut bool

	// Disables using Tillich-Zémor hash for payload.
	WithoutHomomorphicHash bool

	// Sets max buffer size to read payload.
	BufferMaxSize uint64
}

// PrmObjectSearch groups parameters of FrostFS.sear SearchObjects operation.
type PrmObjectSearch struct {
	// Authentication parameters.
	PrmAuth

	// Container to select the objects from.
	Container cid.ID

	Filters object.SearchFilters
}

type PrmInitMultiObjectReader struct {
	// payload range
	Off, Ln uint64

	Addr   oid.Address
	Bearer *bearer.Token
}

type ResObjectSearch interface {
	Read(buf []oid.ID) (int, error)
	Iterate(f func(oid.ID) bool) error
	Close()
}

var (
	// ErrAccessDenied is returned from FrostFS in case of access violation.
	ErrAccessDenied = errors.New("access denied")
	// ErrGatewayTimeout is returned from FrostFS in case of timeout, deadline exceeded etc.
	ErrGatewayTimeout = errors.New("gateway timeout")
)

// FrostFS represents virtual connection to FrostFS network.
type FrostFS interface {
	Container(context.Context, PrmContainer) (*container.Container, error)
	HeadObject(context.Context, PrmObjectHead) (*object.Object, error)
	GetObject(context.Context, PrmObjectGet) (*Object, error)
	RangeObject(context.Context, PrmObjectRange) (io.ReadCloser, error)
	CreateObject(context.Context, PrmObjectCreate) (oid.ID, error)
	SearchObjects(context.Context, PrmObjectSearch) (ResObjectSearch, error)
	InitMultiObjectReader(ctx context.Context, p PrmInitMultiObjectReader) (io.Reader, error)

	utils.EpochInfoFetcher
}

type ContainerResolver interface {
	Resolve(ctx context.Context, name string) (*cid.ID, error)
}

type Handler struct {
	log               *zap.Logger
	frostfs           FrostFS
	ownerID           *user.ID
	config            Config
	containerResolver ContainerResolver
	tree              *tree.Tree
	cache             *cache.BucketCache
	workerPool        *ants.Pool
}

type AppParams struct {
	Logger   *zap.Logger
	FrostFS  FrostFS
	Owner    *user.ID
	Resolver ContainerResolver
	Cache    *cache.BucketCache
}

func New(params *AppParams, config Config, tree *tree.Tree, workerPool *ants.Pool) *Handler {
	return &Handler{
		log:               params.Logger,
		frostfs:           params.FrostFS,
		ownerID:           params.Owner,
		config:            config,
		containerResolver: params.Resolver,
		tree:              tree,
		cache:             params.Cache,
		workerPool:        workerPool,
	}
}

// byNativeAddress is a wrapper for function (e.g. request.headObject, request.receiveFile) that
// prepares request and object address to it.
func (h *Handler) byNativeAddress(c *fasthttp.RequestCtx, f func(context.Context, request, oid.Address)) {
	idCnr, _ := c.UserValue("cid").(string)
	idObj, _ := url.PathUnescape(c.UserValue("oid").(string))

	ctx := utils.GetContextFromRequest(c)
	reqLog := utils.GetReqLogOrDefault(ctx, h.log)
	log := reqLog.With(zap.String("cid", idCnr), zap.String("oid", idObj))

	bktInfo, err := h.getBucketInfo(ctx, idCnr, log)
	if err != nil {
		logAndSendBucketError(c, log, err)
		return
	}

	objID := new(oid.ID)
	if err = objID.DecodeString(idObj); err != nil {
		log.Error(logs.WrongObjectID, zap.Error(err))
		response.Error(c, "wrong object id", fasthttp.StatusBadRequest)
		return
	}

	addr := newAddress(bktInfo.CID, *objID)

	f(ctx, *newRequest(c, log), addr)
}

// byS3Path is a wrapper for function (e.g. request.headObject, request.receiveFile) that
// resolves object address from S3-like path <bucket name>/<object key>.
func (h *Handler) byS3Path(c *fasthttp.RequestCtx, f func(context.Context, request, oid.Address)) {
	bucketname := c.UserValue("cid").(string)
	key := c.UserValue("oid").(string)

	ctx := utils.GetContextFromRequest(c)
	reqLog := utils.GetReqLogOrDefault(ctx, h.log)
	log := reqLog.With(zap.String("bucketname", bucketname), zap.String("key", key))

	unescapedKey, err := url.QueryUnescape(key)
	if err != nil {
		logAndSendBucketError(c, log, err)
		return
	}

	bktInfo, err := h.getBucketInfo(ctx, bucketname, log)
	if err != nil {
		logAndSendBucketError(c, log, err)
		return
	}

	foundOid, err := h.tree.GetLatestVersion(ctx, &bktInfo.CID, unescapedKey)
	if err != nil {
		if errors.Is(err, tree.ErrNodeAccessDenied) {
			response.Error(c, "Access Denied", fasthttp.StatusForbidden)
		} else {
			response.Error(c, "object wasn't found", fasthttp.StatusNotFound)
			log.Error(logs.GetLatestObjectVersion, zap.Error(err))
		}
		return
	}
	if foundOid.DeleteMarker {
		log.Error(logs.ObjectWasDeleted)
		response.Error(c, "object deleted", fasthttp.StatusNotFound)
		return
	}
	addr := newAddress(bktInfo.CID, foundOid.OID)

	f(ctx, *newRequest(c, log), addr)
}

// byAttribute is a wrapper similar to byNativeAddress.
func (h *Handler) byAttribute(c *fasthttp.RequestCtx, f func(context.Context, request, oid.Address)) {
	scid, _ := c.UserValue("cid").(string)
	key, _ := c.UserValue("attr_key").(string)
	val, _ := c.UserValue("attr_val").(string)

	ctx := utils.GetContextFromRequest(c)
	log := utils.GetReqLogOrDefault(ctx, h.log)

	key, err := url.QueryUnescape(key)
	if err != nil {
		log.Error(logs.FailedToUnescapeQuery, zap.String("cid", scid), zap.String("attr_key", key), zap.Error(err))
		response.Error(c, "could not unescape attr_key: "+err.Error(), fasthttp.StatusBadRequest)
		return
	}

	val, err = url.QueryUnescape(val)
	if err != nil {
		log.Error(logs.FailedToUnescapeQuery, zap.String("cid", scid), zap.String("attr_val", val), zap.Error(err))
		response.Error(c, "could not unescape attr_val: "+err.Error(), fasthttp.StatusBadRequest)
		return
	}

	log = log.With(zap.String("cid", scid), zap.String("attr_key", key), zap.String("attr_val", val))

	bktInfo, err := h.getBucketInfo(ctx, scid, log)
	if err != nil {
		logAndSendBucketError(c, log, err)
		return
	}

	res, err := h.search(ctx, bktInfo.CID, key, val, object.MatchStringEqual)
	if err != nil {
		log.Error(logs.CouldNotSearchForObjects, zap.Error(err))
		response.Error(c, "could not search for objects: "+err.Error(), fasthttp.StatusBadRequest)
		return
	}

	defer res.Close()

	buf := make([]oid.ID, 1)

	n, err := res.Read(buf)
	if n == 0 {
		if errors.Is(err, io.EOF) {
			log.Error(logs.ObjectNotFound, zap.Error(err))
			response.Error(c, "object not found", fasthttp.StatusNotFound)
			return
		}

		log.Error(logs.ReadObjectListFailed, zap.Error(err))
		response.Error(c, "read object list failed: "+err.Error(), fasthttp.StatusBadRequest)
		return
	}

	var addrObj oid.Address
	addrObj.SetContainer(bktInfo.CID)
	addrObj.SetObject(buf[0])

	f(ctx, *newRequest(c, log), addrObj)
}

// resolveContainer decode container id, if it's not a valid container id
// then trey to resolve name using provided resolver.
func (h *Handler) resolveContainer(ctx context.Context, containerID string) (*cid.ID, error) {
	cnrID := new(cid.ID)
	err := cnrID.DecodeString(containerID)
	if err != nil {
		cnrID, err = h.containerResolver.Resolve(ctx, containerID)
		if err != nil && strings.Contains(err.Error(), "not found") {
			err = fmt.Errorf("%w: %s", new(apistatus.ContainerNotFound), err.Error())
		}
	}
	return cnrID, err
}

func (h *Handler) getBucketInfo(ctx context.Context, containerName string, log *zap.Logger) (*data.BucketInfo, error) {
	ns, err := middleware.GetNamespace(ctx)
	if err != nil {
		return nil, err
	}

	if bktInfo := h.cache.Get(ns, containerName); bktInfo != nil {
		return bktInfo, nil
	}

	cnrID, err := h.resolveContainer(ctx, containerName)
	if err != nil {
		return nil, err
	}

	bktInfo, err := h.readContainer(ctx, *cnrID)
	if err != nil {
		return nil, err
	}

	if err = h.cache.Put(bktInfo); err != nil {
		log.Warn(logs.CouldntPutBucketIntoCache,
			zap.String("bucket name", bktInfo.Name),
			zap.Stringer("bucket cid", bktInfo.CID),
			zap.Error(err))
	}

	return bktInfo, nil
}

func (h *Handler) readContainer(ctx context.Context, cnrID cid.ID) (*data.BucketInfo, error) {
	prm := PrmContainer{ContainerID: cnrID}
	res, err := h.frostfs.Container(ctx, prm)
	if err != nil {
		return nil, fmt.Errorf("get frostfs container '%s': %w", cnrID.String(), err)
	}

	bktInfo := &data.BucketInfo{
		CID:  cnrID,
		Name: cnrID.EncodeToString(),
	}

	if domain := container.ReadDomain(*res); domain.Name() != "" {
		bktInfo.Name = domain.Name()
		bktInfo.Zone = domain.Zone()
	}

	bktInfo.HomomorphicHashDisabled = container.IsHomomorphicHashingDisabled(*res)

	return bktInfo, err
}

func (h *Handler) browseIndex(c *fasthttp.RequestCtx) {
	if !h.config.IndexPageEnabled() {
		c.SetStatusCode(fasthttp.StatusNotFound)
		return
	}

	cidURLParam := c.UserValue("cid").(string)
	oidURLParam := c.UserValue("oid").(string)

	ctx := utils.GetContextFromRequest(c)
	reqLog := utils.GetReqLogOrDefault(ctx, h.log)
	log := reqLog.With(zap.String("cid", cidURLParam), zap.String("oid", oidURLParam))

	unescapedKey, err := url.QueryUnescape(oidURLParam)
	if err != nil {
		logAndSendBucketError(c, log, err)
		return
	}

	bktInfo, err := h.getBucketInfo(ctx, cidURLParam, log)
	if err != nil {
		logAndSendBucketError(c, log, err)
		return
	}

	listFunc := h.getDirObjectsS3
	isNativeList := false

	err = h.tree.CheckSettingsNodeExist(ctx, bktInfo)
	if err != nil {
		if errors.Is(err, tree.ErrNodeNotFound) {
			// tree probe failed, try to use native
			listFunc = h.getDirObjectsNative
			isNativeList = true
		} else {
			logAndSendBucketError(c, log, err)
			return
		}
	}

	h.browseObjects(c, browseParams{
		bucketInfo:  bktInfo,
		prefix:      unescapedKey,
		listObjects: listFunc,
		isNative:    isNativeList,
	})
}