package tree

import (
	"context"
	"errors"
	"fmt"
	"strings"

	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/api"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/api/layer"
	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/data"
	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
)

type (
	Tree struct {
		service ServiceClient
	}

	// ServiceClient is a client to interact with tree service.
	// Each method must return ErrNodeNotFound or ErrNodeAccessDenied if relevant.
	ServiceClient interface {
		GetNodes(ctx context.Context, p *GetNodesParams) ([]NodeResponse, error)
		GetSubTree(ctx context.Context, bktInfo *data.BucketInfo, treeID string, rootID []uint64, depth uint32, sort bool) ([]NodeResponse, error)
	}

	treeNode struct {
		ObjID oid.ID
		Meta  map[string]string
	}

	multiSystemNode struct {
		// the first element is latest
		nodes []*treeNode
	}

	GetNodesParams struct {
		CnrID      cid.ID
		BktInfo    *data.BucketInfo
		TreeID     string
		Path       []string
		Meta       []string
		LatestOnly bool
		AllAttrs   bool
	}
)

var (
	// ErrNodeNotFound is returned from ServiceClient in case of not found error.
	ErrNodeNotFound = layer.ErrNodeNotFound

	// ErrNodeAccessDenied is returned from ServiceClient service in case of access denied error.
	ErrNodeAccessDenied = layer.ErrNodeAccessDenied
)

const (
	FileNameKey      = "FileName"
	settingsFileName = "bucket-settings"

	oidKV      = "OID"
	uploadIDKV = "UploadId"
	sizeKV     = "Size"

	// keys for delete marker nodes.
	isDeleteMarkerKV = "IsDeleteMarker"

	// versionTree -- ID of a tree with object versions.
	versionTree = "version"
	systemTree  = "system"

	separator = "/"
)

// NewTree creates instance of Tree using provided address and create grpc connection.
func NewTree(service ServiceClient) *Tree {
	return &Tree{service: service}
}

type Meta interface {
	GetKey() string
	GetValue() []byte
}

type NodeResponse interface {
	GetMeta() []Meta
	GetTimestamp() []uint64
	GetNodeID() []uint64
	GetParentID() []uint64
}

func newTreeNode(nodeInfo NodeResponse) (*treeNode, error) {
	tNode := &treeNode{
		Meta: make(map[string]string, len(nodeInfo.GetMeta())),
	}

	for _, kv := range nodeInfo.GetMeta() {
		switch kv.GetKey() {
		case oidKV:
			if err := tNode.ObjID.DecodeString(string(kv.GetValue())); err != nil {
				return nil, err
			}
		default:
			tNode.Meta[kv.GetKey()] = string(kv.GetValue())
		}
	}

	return tNode, nil
}

func (n *treeNode) Get(key string) (string, bool) {
	value, ok := n.Meta[key]
	return value, ok
}

func (n *treeNode) FileName() (string, bool) {
	value, ok := n.Meta[FileNameKey]
	return value, ok
}

func newNodeVersion(node NodeResponse) (*api.NodeVersion, error) {
	tNode, err := newTreeNode(node)
	if err != nil {
		return nil, fmt.Errorf("invalid tree node: %w", err)
	}

	return newNodeVersionFromTreeNode(tNode), nil
}

func newNodeVersionFromTreeNode(treeNode *treeNode) *api.NodeVersion {
	_, isDeleteMarker := treeNode.Get(isDeleteMarkerKV)
	size, _ := treeNode.Get(sizeKV)
	version := &api.NodeVersion{
		BaseNodeVersion: api.BaseNodeVersion{
			OID: treeNode.ObjID,
		},
		DeleteMarker: isDeleteMarker,
		IsPrefixNode: size == "",
	}

	return version
}

func newMultiNode(nodes []NodeResponse) (*multiSystemNode, error) {
	var (
		err          error
		index        int
		maxTimestamp uint64
	)

	if len(nodes) == 0 {
		return nil, errors.New("multi node must have at least one node")
	}

	treeNodes := make([]*treeNode, len(nodes))

	for i, node := range nodes {
		if treeNodes[i], err = newTreeNode(node); err != nil {
			return nil, fmt.Errorf("parse system node response: %w", err)
		}

		if timestamp := getMaxTimestamp(node); timestamp > maxTimestamp {
			index = i
			maxTimestamp = timestamp
		}
	}

	treeNodes[0], treeNodes[index] = treeNodes[index], treeNodes[0]

	return &multiSystemNode{
		nodes: treeNodes,
	}, nil
}

func (m *multiSystemNode) Latest() *treeNode {
	return m.nodes[0]
}

func (m *multiSystemNode) Old() []*treeNode {
	return m.nodes[1:]
}

func (c *Tree) GetLatestVersion(ctx context.Context, cnrID *cid.ID, objectName string) (*api.NodeVersion, error) {
	nodes, err := c.GetVersions(ctx, cnrID, objectName)
	if err != nil {
		return nil, err
	}

	latestNode, err := getLatestVersionNode(nodes)
	if err != nil {
		return nil, err
	}

	return newNodeVersion(latestNode)
}

func (c *Tree) GetVersions(ctx context.Context, cnrID *cid.ID, objectName string) ([]NodeResponse, error) {
	meta := []string{oidKV, isDeleteMarkerKV, sizeKV}
	path := pathFromName(objectName)

	p := &GetNodesParams{
		CnrID:      *cnrID,
		TreeID:     versionTree,
		Path:       path,
		Meta:       meta,
		LatestOnly: false,
		AllAttrs:   false,
	}

	return c.service.GetNodes(ctx, p)
}

func (c *Tree) CheckSettingsNodeExist(ctx context.Context, bktInfo *data.BucketInfo) error {
	_, err := c.getSystemNode(ctx, bktInfo, settingsFileName)
	if err != nil {
		return err
	}

	return nil
}

func (c *Tree) getSystemNode(ctx context.Context, bktInfo *data.BucketInfo, name string) (*multiSystemNode, error) {
	p := &GetNodesParams{
		CnrID:      bktInfo.CID,
		BktInfo:    bktInfo,
		TreeID:     systemTree,
		Path:       []string{name},
		LatestOnly: false,
		AllAttrs:   true,
	}
	nodes, err := c.service.GetNodes(ctx, p)
	if err != nil {
		return nil, err
	}

	nodes = filterMultipartNodes(nodes)

	if len(nodes) == 0 {
		return nil, ErrNodeNotFound
	}

	return newMultiNode(nodes)
}

func filterMultipartNodes(nodes []NodeResponse) []NodeResponse {
	res := make([]NodeResponse, 0, len(nodes))

LOOP:
	for _, node := range nodes {
		for _, meta := range node.GetMeta() {
			if meta.GetKey() == uploadIDKV {
				continue LOOP
			}
		}

		res = append(res, node)
	}

	return res
}

func getLatestVersionNode(nodes []NodeResponse) (NodeResponse, error) {
	var (
		maxCreationTime uint64
		targetIndexNode = -1
	)

	for i, node := range nodes {
		if !checkExistOID(node.GetMeta()) {
			continue
		}

		if currentCreationTime := getMaxTimestamp(node); currentCreationTime > maxCreationTime {
			targetIndexNode = i
			maxCreationTime = currentCreationTime
		}
	}

	if targetIndexNode == -1 {
		return nil, layer.ErrNodeNotFound
	}

	return nodes[targetIndexNode], nil
}

func checkExistOID(meta []Meta) bool {
	for _, kv := range meta {
		if kv.GetKey() == "OID" {
			return true
		}
	}

	return false
}

// pathFromName splits name by '/'.
func pathFromName(objectName string) []string {
	return strings.Split(objectName, separator)
}

func (c *Tree) GetSubTreeByPrefix(ctx context.Context, bktInfo *data.BucketInfo, prefix string, latestOnly bool) ([]NodeResponse, string, error) {
	rootID, tailPrefix, err := c.determinePrefixNode(ctx, bktInfo, versionTree, prefix)
	if err != nil {
		return nil, "", err
	}
	subTree, err := c.service.GetSubTree(ctx, bktInfo, versionTree, rootID, 2, false)
	if err != nil {
		if errors.Is(err, layer.ErrNodeNotFound) {
			return nil, "", nil
		}
		return nil, "", err
	}

	nodesMap := make(map[string][]NodeResponse, len(subTree))
	for _, node := range subTree {
		if MultiID(rootID).Equal(node.GetNodeID()) {
			continue
		}

		fileName := GetFilename(node)
		if !strings.HasPrefix(fileName, tailPrefix) {
			continue
		}

		nodes := nodesMap[fileName]

		// Add all nodes if flag latestOnly is false.
		// Add all intermediate nodes
		// and only latest leaf (object) nodes. To do this store and replace last leaf (object) node in nodes[0]
		if len(nodes) == 0 {
			nodes = []NodeResponse{node}
		} else if !latestOnly || isIntermediate(node) {
			nodes = append(nodes, node)
		} else if isIntermediate(nodes[0]) {
			nodes = append([]NodeResponse{node}, nodes...)
		} else if getMaxTimestamp(node) > getMaxTimestamp(nodes[0]) {
			nodes[0] = node
		}

		nodesMap[fileName] = nodes
	}

	result := make([]NodeResponse, 0, len(subTree))
	for _, nodes := range nodesMap {
		result = append(result, nodes...)
	}

	return result, strings.TrimSuffix(prefix, tailPrefix), nil
}

func (c *Tree) determinePrefixNode(ctx context.Context, bktInfo *data.BucketInfo, treeID, prefix string) ([]uint64, string, error) {
	rootID := []uint64{0}
	path := strings.Split(prefix, separator)
	tailPrefix := path[len(path)-1]

	if len(path) > 1 {
		var err error
		rootID, err = c.getPrefixNodeID(ctx, bktInfo, treeID, path[:len(path)-1])
		if err != nil {
			return nil, "", err
		}
	}

	return rootID, tailPrefix, nil
}

func (c *Tree) getPrefixNodeID(ctx context.Context, bktInfo *data.BucketInfo, treeID string, prefixPath []string) ([]uint64, error) {
	p := &GetNodesParams{
		CnrID:      bktInfo.CID,
		BktInfo:    bktInfo,
		TreeID:     treeID,
		Path:       prefixPath,
		LatestOnly: false,
		AllAttrs:   true,
	}
	nodes, err := c.service.GetNodes(ctx, p)
	if err != nil {
		return nil, err
	}

	var intermediateNodes []uint64
	for _, node := range nodes {
		if isIntermediate(node) {
			intermediateNodes = append(intermediateNodes, node.GetNodeID()...)
		}
	}

	if len(intermediateNodes) == 0 {
		return nil, layer.ErrNodeNotFound
	}

	return intermediateNodes, nil
}

func GetFilename(node NodeResponse) string {
	for _, kv := range node.GetMeta() {
		if kv.GetKey() == FileNameKey {
			return string(kv.GetValue())
		}
	}

	return ""
}

func isIntermediate(node NodeResponse) bool {
	if len(node.GetMeta()) != 1 {
		return false
	}

	return node.GetMeta()[0].GetKey() == FileNameKey
}

func getMaxTimestamp(node NodeResponse) uint64 {
	var maxTimestamp uint64

	for _, timestamp := range node.GetTimestamp() {
		if timestamp > maxTimestamp {
			maxTimestamp = timestamp
		}
	}

	return maxTimestamp
}

type MultiID []uint64

func (m MultiID) Equal(id MultiID) bool {
	seen := make(map[uint64]struct{}, len(m))

	for i := range m {
		seen[m[i]] = struct{}{}
	}

	for i := range id {
		if _, ok := seen[id[i]]; !ok {
			return false
		}
	}

	return true
}