package tree

import (
	"context"
	"errors"
	"fmt"
	"io"
	"sort"
	"time"

	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/data"
	"golang.org/x/exp/slices"
)

type nodeMeta struct {
	key   string
	value []byte
}

func (m nodeMeta) GetKey() string {
	return m.key
}

func (m nodeMeta) GetValue() []byte {
	return m.value
}

type nodeResponse struct {
	meta      []nodeMeta
	nodeID    uint64
	parentID  uint64
	timestamp uint64
}

func (n nodeResponse) GetNodeID() []uint64 {
	return []uint64{n.nodeID}
}

func (n nodeResponse) GetParentID() []uint64 {
	return []uint64{n.parentID}
}

func (n nodeResponse) GetTimestamp() []uint64 {
	return []uint64{n.timestamp}
}

func (n nodeResponse) GetMeta() []Meta {
	res := make([]Meta, len(n.meta))
	for i, value := range n.meta {
		res[i] = value
	}
	return res
}

func (n nodeResponse) getValue(key string) string {
	for _, value := range n.meta {
		if value.key == key {
			return string(value.value)
		}
	}
	return ""
}

type ServiceClientMemory struct {
	containers map[string]containerInfo
}

type containerInfo struct {
	bkt   *data.BucketInfo
	trees map[string]memoryTree
}

type memoryTree struct {
	idCounter uint64
	treeData  *treeNodeMemory
}

type treeNodeMemory struct {
	data     nodeResponse
	parent   *treeNodeMemory
	children []*treeNodeMemory
}

func (t *treeNodeMemory) getNode(nodeID uint64) *treeNodeMemory {
	if t.data.nodeID == nodeID {
		return t
	}

	for _, child := range t.children {
		if node := child.getNode(nodeID); node != nil {
			return node
		}
	}

	return nil
}

func (t *memoryTree) getNodesByPath(path []string) []nodeResponse {
	if len(path) == 0 {
		return nil
	}

	var res []nodeResponse
	for _, child := range t.treeData.children {
		res = child.listNodesByPath(res, path)
	}

	return res
}

func (t *treeNodeMemory) listNodesByPath(res []nodeResponse, path []string) []nodeResponse {
	if len(path) == 0 || t.data.getValue(FileNameKey) != path[0] {
		return res
	}

	if len(path) == 1 {
		return append(res, t.data)
	}

	for _, ch := range t.children {
		res = ch.listNodesByPath(res, path[1:])
	}

	return res
}

func (t *memoryTree) createPathIfNotExist(parent *treeNodeMemory, path []string) *treeNodeMemory {
	if len(path) == 0 {
		return parent
	}

	var node *treeNodeMemory
	for _, child := range parent.children {
		if len(child.data.meta) == 1 && child.data.getValue(FileNameKey) == path[0] {
			node = child
			break
		}
	}

	if node == nil {
		node = &treeNodeMemory{
			data: nodeResponse{
				meta:      []nodeMeta{{key: FileNameKey, value: []byte(path[0])}},
				nodeID:    t.idCounter,
				parentID:  parent.data.nodeID,
				timestamp: uint64(time.Now().UnixMicro()),
			},
			parent: parent,
		}
		t.idCounter++
		parent.children = append(parent.children, node)
	}

	return t.createPathIfNotExist(node, path[1:])
}

func (t *treeNodeMemory) removeChild(nodeID uint64) {
	ind := -1
	for i, ch := range t.children {
		if ch.data.nodeID == nodeID {
			ind = i
			break
		}
	}
	if ind != -1 {
		t.children = append(t.children[:ind], t.children[ind+1:]...)
	}
}

func (t *treeNodeMemory) listNodes(res []NodeResponse, depth uint32) []NodeResponse {
	res = append(res, t.data)

	if depth == 0 {
		return res
	}

	for _, ch := range t.children {
		res = ch.listNodes(res, depth-1)
	}
	return res
}

func NewTreeServiceClientMemory() (*ServiceClientMemory, error) {
	return &ServiceClientMemory{
		containers: make(map[string]containerInfo),
	}, nil
}

type nodeResponseWrapper struct {
	nodeResponse
	allAttr bool
	attrs   []string
}

func (n nodeResponseWrapper) GetMeta() []Meta {
	res := make([]Meta, 0, len(n.meta))
	for _, value := range n.meta {
		if n.allAttr || slices.Contains(n.attrs, value.key) {
			res = append(res, value)
		}
	}
	return res
}

func (c *ServiceClientMemory) GetNodes(_ context.Context, p *GetNodesParams) ([]NodeResponse, error) {
	cnr, ok := c.containers[p.BktInfo.CID.EncodeToString()]
	if !ok {
		return nil, nil
	}

	tr, ok := cnr.trees[p.TreeID]
	if !ok {
		return nil, nil
	}

	res := tr.getNodesByPath(p.Path)
	sort.Slice(res, func(i, j int) bool {
		return res[i].timestamp < res[j].timestamp
	})

	if p.LatestOnly && len(res) != 0 {
		res = res[len(res)-1:]
	}

	res2 := make([]NodeResponse, len(res))
	for i, n := range res {
		res2[i] = nodeResponseWrapper{
			nodeResponse: n,
			allAttr:      p.AllAttrs,
			attrs:        p.Meta,
		}
	}

	return res2, nil
}

func (c *ServiceClientMemory) GetSubTree(_ context.Context, bktInfo *data.BucketInfo, treeID string, rootID []uint64, depth uint32, sort bool) ([]NodeResponse, error) {
	cnr, ok := c.containers[bktInfo.CID.EncodeToString()]
	if !ok {
		return nil, nil
	}

	tr, ok := cnr.trees[treeID]
	if !ok {
		return nil, ErrNodeNotFound
	}

	if len(rootID) != 1 {
		return nil, errors.New("invalid rootID")
	}

	node := tr.treeData.getNode(rootID[0])
	if node == nil {
		return nil, ErrNodeNotFound
	}

	if sort {
		sortNode(tr.treeData)
	}

	// we depth-1 in case of uint32 and 0 as mark to get all subtree leads to overflow and depth is getting quite big to walk all tree levels
	return node.listNodes(nil, depth-1), nil
}

type SubTreeStreamMemoryImpl struct {
	res    []NodeResponse
	offset int
	err    error
}

func (s *SubTreeStreamMemoryImpl) Next() (NodeResponse, error) {
	if s.err != nil {
		return nil, s.err
	}
	if s.offset > len(s.res)-1 {
		return nil, io.EOF
	}
	s.offset++
	return s.res[s.offset-1], nil
}

func (c *ServiceClientMemory) GetSubTreeStream(_ context.Context, bktInfo *data.BucketInfo, treeID string, rootID []uint64, depth uint32) (SubTreeStream, error) {
	cnr, ok := c.containers[bktInfo.CID.EncodeToString()]
	if !ok {
		return &SubTreeStreamMemoryImpl{err: ErrNodeNotFound}, nil
	}

	tr, ok := cnr.trees[treeID]
	if !ok {
		return nil, ErrNodeNotFound
	}

	if len(rootID) != 1 {
		return nil, errors.New("invalid rootID")
	}

	node := tr.treeData.getNode(rootID[0])
	if node == nil {
		return nil, ErrNodeNotFound
	}

	sortNode(tr.treeData)

	return &SubTreeStreamMemoryImpl{
		res:    node.listNodes(nil, depth-1),
		offset: 0,
	}, nil
}

func newContainerInfo(bktInfo *data.BucketInfo, treeID string) containerInfo {
	return containerInfo{
		bkt: bktInfo,
		trees: map[string]memoryTree{
			treeID: {
				idCounter: 1,
				treeData: &treeNodeMemory{
					data: nodeResponse{
						timestamp: uint64(time.Now().UnixMicro()),
					},
				},
			},
		},
	}
}

func newMemoryTree() memoryTree {
	return memoryTree{
		idCounter: 1,
		treeData: &treeNodeMemory{
			data: nodeResponse{
				timestamp: uint64(time.Now().UnixMicro()),
			},
		},
	}
}

func (c *ServiceClientMemory) AddNode(ctx context.Context, bktInfo *data.BucketInfo, treeID string, parent uint64, meta map[string]string) (uint64, error) {
	return c.AddNodeBase(ctx, bktInfo, treeID, parent, meta, true)
}

func (c *ServiceClientMemory) AddNodeBase(_ context.Context, bktInfo *data.BucketInfo, treeID string, parent uint64, meta map[string]string, needSort bool) (uint64, error) {
	cnr, ok := c.containers[bktInfo.CID.EncodeToString()]
	if !ok {
		cnr = newContainerInfo(bktInfo, treeID)
		c.containers[bktInfo.CID.EncodeToString()] = cnr
	}

	tr, ok := cnr.trees[treeID]
	if !ok {
		tr = newMemoryTree()
		cnr.trees[treeID] = tr
	}

	parentNode := tr.treeData.getNode(parent)
	if parentNode == nil {
		return 0, ErrNodeNotFound
	}

	newID := tr.idCounter
	tr.idCounter++

	tn := &treeNodeMemory{
		data: nodeResponse{
			meta:      metaToNodeMeta(meta),
			nodeID:    newID,
			parentID:  parent,
			timestamp: uint64(time.Now().UnixMicro()),
		},
		parent: parentNode,
	}

	parentNode.children = append(parentNode.children, tn)
	if needSort {
		sortNodes(parentNode.children)
	}
	cnr.trees[treeID] = tr

	return newID, nil
}

func (c *ServiceClientMemory) AddNodeByPath(_ context.Context, bktInfo *data.BucketInfo, treeID string, path []string, meta map[string]string) (uint64, error) {
	cnr, ok := c.containers[bktInfo.CID.EncodeToString()]
	if !ok {
		cnr = newContainerInfo(bktInfo, treeID)
		c.containers[bktInfo.CID.EncodeToString()] = cnr
	}

	tr, ok := cnr.trees[treeID]
	if !ok {
		tr = newMemoryTree()
		cnr.trees[treeID] = tr
	}

	parentNode := tr.createPathIfNotExist(tr.treeData, path)
	if parentNode == nil {
		return 0, fmt.Errorf("create path '%s'", path)
	}

	newID := tr.idCounter
	tr.idCounter++

	tn := &treeNodeMemory{
		data: nodeResponse{
			meta:      metaToNodeMeta(meta),
			nodeID:    newID,
			parentID:  parentNode.data.nodeID,
			timestamp: uint64(time.Now().UnixMicro()),
		},
		parent: parentNode,
	}

	parentNode.children = append(parentNode.children, tn)
	cnr.trees[treeID] = tr

	return newID, nil
}

func (c *ServiceClientMemory) MoveNode(_ context.Context, bktInfo *data.BucketInfo, treeID string, nodeID, parentID uint64, meta map[string]string) error {
	cnr, ok := c.containers[bktInfo.CID.EncodeToString()]
	if !ok {
		return ErrNodeNotFound
	}

	tr, ok := cnr.trees[treeID]
	if !ok {
		return ErrNodeNotFound
	}

	node := tr.treeData.getNode(nodeID)
	if node == nil {
		return ErrNodeNotFound
	}

	newParent := tr.treeData.getNode(parentID)
	if newParent == nil {
		return ErrNodeNotFound
	}

	node.data.meta = metaToNodeMeta(meta)
	node.data.parentID = parentID

	newParent.children = append(newParent.children, node)
	node.parent.removeChild(nodeID)

	return nil
}

func sortNode(node *treeNodeMemory) {
	if node == nil {
		return
	}

	sortNodes(node.children)

	for _, child := range node.children {
		sortNode(child)
	}
}

func sortNodes(list []*treeNodeMemory) {
	sort.Slice(list, func(i, j int) bool {
		return list[i].data.getValue(FileNameKey) < list[j].data.getValue(FileNameKey)
	})
}

func (c *ServiceClientMemory) RemoveNode(_ context.Context, bktInfo *data.BucketInfo, treeID string, nodeID uint64) error {
	cnr, ok := c.containers[bktInfo.CID.EncodeToString()]
	if !ok {
		return ErrNodeNotFound
	}

	tr, ok := cnr.trees[treeID]
	if !ok {
		return ErrNodeNotFound
	}

	node := tr.treeData.getNode(nodeID)
	if node == nil {
		return ErrNodeNotFound
	}

	node.parent.removeChild(nodeID)

	return nil
}

func metaToNodeMeta(m map[string]string) []nodeMeta {
	result := make([]nodeMeta, 0, len(m))

	for key, value := range m {
		result = append(result, nodeMeta{key: key, value: []byte(value)})
	}

	return result
}