package services

import (
	"context"
	"errors"
	"fmt"
	"io"
	"strings"
	"sync/atomic"

	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/data"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/creds/accessbox"
	grpcService "git.frostfs.info/TrueCloudLab/frostfs-s3-gw/internal/frostfs/services/tree"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/pkg/service/tree"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/bearer"
	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
	"go.uber.org/zap"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

type GetNodeByPathResponseInfoWrapper struct {
	response *grpcService.GetNodeByPathResponse_Info
}

func (n GetNodeByPathResponseInfoWrapper) GetNodeID() uint64 {
	return n.response.GetNodeId()
}

func (n GetNodeByPathResponseInfoWrapper) GetParentID() uint64 {
	return n.response.GetParentId()
}

func (n GetNodeByPathResponseInfoWrapper) GetTimestamp() uint64 {
	return n.response.GetTimestamp()
}

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

type GetSubTreeResponseBodyWrapper struct {
	response *grpcService.GetSubTreeResponse_Body
}

func (n GetSubTreeResponseBodyWrapper) GetNodeID() uint64 {
	return n.response.GetNodeId()
}

func (n GetSubTreeResponseBodyWrapper) GetParentID() uint64 {
	return n.response.GetParentId()
}

func (n GetSubTreeResponseBodyWrapper) GetTimestamp() uint64 {
	return n.response.GetTimestamp()
}

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

type ServiceClientGRPC struct {
	key        *keys.PrivateKey
	log        *zap.Logger
	clients    []treeClient
	startIndex atomic.Int32
}

type treeClient struct {
	address string
	conn    *grpc.ClientConn
	service grpcService.TreeServiceClient
}

func (c *ServiceClientGRPC) Endpoints() []string {
	res := make([]string, len(c.clients))
	for i, client := range c.clients {
		res[i] = client.address
	}
	return res
}

func NewTreeServiceClientGRPC(ctx context.Context, endpoints []string, key *keys.PrivateKey, log *zap.Logger, grpcOpts ...grpc.DialOption) (*ServiceClientGRPC, error) {
	res := &ServiceClientGRPC{
		key: key,
		log: log,
	}

	for _, addr := range endpoints {
		conn, err := grpc.Dial(addr, grpcOpts...)
		if err != nil {
			log.Warn("dial node tree service", zap.String("address", addr), zap.Error(err))
			continue
		}

		c := grpcService.NewTreeServiceClient(conn)
		if _, err = c.Healthcheck(ctx, &grpcService.HealthcheckRequest{}); err != nil {
			log.Warn("healthcheck tree service", zap.String("address", addr), zap.Error(err))
			continue
		}

		res.clients = append(res.clients, treeClient{
			address: addr,
			conn:    conn,
			service: c,
		})
	}

	if len(res.clients) == 0 {
		return nil, errors.New("no healthy tree grpc client")
	}

	return res, nil
}

func (c *ServiceClientGRPC) GetNodes(ctx context.Context, p *tree.GetNodesParams) ([]tree.NodeResponse, error) {
	request := &grpcService.GetNodeByPathRequest{
		Body: &grpcService.GetNodeByPathRequest_Body{
			ContainerId:   p.BktInfo.CID[:],
			TreeId:        p.TreeID,
			Path:          p.Path,
			Attributes:    p.Meta,
			PathAttribute: tree.FileNameKey,
			LatestOnly:    p.LatestOnly,
			AllAttributes: p.AllAttrs,
			BearerToken:   getBearer(ctx, p.BktInfo),
		},
	}

	if err := c.signRequest(request.Body, func(key, sign []byte) {
		request.Signature = &grpcService.Signature{
			Key:  key,
			Sign: sign,
		}
	}); err != nil {
		return nil, err
	}

	resp, err := requestWithRetry(ctx, request, c, func(client treeClient) grpcFunc[*grpcService.GetNodeByPathRequest, *grpcService.GetNodeByPathResponse] {
		return client.service.GetNodeByPath
	})
	if err != nil {
		return nil, handleError("failed to get node by path", err)
	}

	res := make([]tree.NodeResponse, len(resp.GetBody().GetNodes()))
	for i, info := range resp.GetBody().GetNodes() {
		res[i] = GetNodeByPathResponseInfoWrapper{info}
	}

	return res, nil
}

func (c *ServiceClientGRPC) GetSubTree(ctx context.Context, bktInfo *data.BucketInfo, treeID string, rootID uint64, depth uint32) ([]tree.NodeResponse, error) {
	request := &grpcService.GetSubTreeRequest{
		Body: &grpcService.GetSubTreeRequest_Body{
			ContainerId: bktInfo.CID[:],
			TreeId:      treeID,
			RootId:      rootID,
			Depth:       depth,
			BearerToken: getBearer(ctx, bktInfo),
		},
	}

	if err := c.signRequest(request.Body, func(key, sign []byte) {
		request.Signature = &grpcService.Signature{
			Key:  key,
			Sign: sign,
		}
	}); err != nil {
		return nil, err
	}

	cli, err := requestWithRetry(ctx, request, c, func(client treeClient) grpcFunc[*grpcService.GetSubTreeRequest, grpcService.TreeService_GetSubTreeClient] {
		return client.service.GetSubTree
	})
	if err != nil {
		return nil, handleError("failed to get sub tree client", err)
	}

	var subtree []tree.NodeResponse
	for {
		resp, err := cli.Recv()
		if err == io.EOF {
			break
		} else if err != nil {
			return nil, handleError("failed to get sub tree", err)
		}
		subtree = append(subtree, GetSubTreeResponseBodyWrapper{resp.Body})
	}

	return subtree, nil
}

func (c *ServiceClientGRPC) AddNode(ctx context.Context, bktInfo *data.BucketInfo, treeID string, parent uint64, meta map[string]string) (uint64, error) {
	request := &grpcService.AddRequest{
		Body: &grpcService.AddRequest_Body{
			ContainerId: bktInfo.CID[:],
			TreeId:      treeID,
			ParentId:    parent,
			Meta:        metaToKV(meta),
			BearerToken: getBearer(ctx, bktInfo),
		},
	}
	if err := c.signRequest(request.Body, func(key, sign []byte) {
		request.Signature = &grpcService.Signature{
			Key:  key,
			Sign: sign,
		}
	}); err != nil {
		return 0, err
	}

	resp, err := requestWithRetry(ctx, request, c, func(client treeClient) grpcFunc[*grpcService.AddRequest, *grpcService.AddResponse] {
		return client.service.Add
	})
	if err != nil {
		return 0, handleError("failed to add node", err)
	}

	return resp.GetBody().GetNodeId(), nil
}

func (c *ServiceClientGRPC) AddNodeByPath(ctx context.Context, bktInfo *data.BucketInfo, treeID string, path []string, meta map[string]string) (uint64, error) {
	request := &grpcService.AddByPathRequest{
		Body: &grpcService.AddByPathRequest_Body{
			ContainerId:   bktInfo.CID[:],
			TreeId:        treeID,
			Path:          path,
			Meta:          metaToKV(meta),
			PathAttribute: tree.FileNameKey,
			BearerToken:   getBearer(ctx, bktInfo),
		},
	}

	if err := c.signRequest(request.Body, func(key, sign []byte) {
		request.Signature = &grpcService.Signature{
			Key:  key,
			Sign: sign,
		}
	}); err != nil {
		return 0, err
	}

	resp, err := requestWithRetry(ctx, request, c, func(client treeClient) grpcFunc[*grpcService.AddByPathRequest, *grpcService.AddByPathResponse] {
		return client.service.AddByPath
	})
	if err != nil {
		return 0, handleError("failed to add node by path", err)
	}

	body := resp.GetBody()
	if body == nil {
		return 0, errors.New("nil body in tree service response")
	} else if len(body.Nodes) == 0 {
		return 0, errors.New("empty list of added nodes in tree service response")
	}

	// The first node is the leaf that we add, according to tree service docs.
	return body.Nodes[0], nil
}

func (c *ServiceClientGRPC) MoveNode(ctx context.Context, bktInfo *data.BucketInfo, treeID string, nodeID, parentID uint64, meta map[string]string) error {
	request := &grpcService.MoveRequest{
		Body: &grpcService.MoveRequest_Body{
			ContainerId: bktInfo.CID[:],
			TreeId:      treeID,
			NodeId:      nodeID,
			ParentId:    parentID,
			Meta:        metaToKV(meta),
			BearerToken: getBearer(ctx, bktInfo),
		},
	}

	if err := c.signRequest(request.Body, func(key, sign []byte) {
		request.Signature = &grpcService.Signature{
			Key:  key,
			Sign: sign,
		}
	}); err != nil {
		return err
	}

	_, err := requestWithRetry(ctx, request, c, func(client treeClient) grpcFunc[*grpcService.MoveRequest, *grpcService.MoveResponse] {
		return client.service.Move
	})
	if err != nil {
		return handleError("failed to move node", err)
	}

	return nil
}

func (c *ServiceClientGRPC) RemoveNode(ctx context.Context, bktInfo *data.BucketInfo, treeID string, nodeID uint64) error {
	request := &grpcService.RemoveRequest{
		Body: &grpcService.RemoveRequest_Body{
			ContainerId: bktInfo.CID[:],
			TreeId:      treeID,
			NodeId:      nodeID,
			BearerToken: getBearer(ctx, bktInfo),
		},
	}
	if err := c.signRequest(request.Body, func(key, sign []byte) {
		request.Signature = &grpcService.Signature{
			Key:  key,
			Sign: sign,
		}
	}); err != nil {
		return err
	}

	_, err := requestWithRetry(ctx, request, c, func(cl treeClient) grpcFunc[*grpcService.RemoveRequest, *grpcService.RemoveResponse] {
		return cl.service.Remove
	})
	if err != nil {
		return handleError("failed to remove node", err)
	}

	return nil
}

type grpcFunc[Req any, Resp any] func(context.Context, Req, ...grpc.CallOption) (Resp, error)

func requestWithRetry[Req any, Resp any](ctx context.Context, req Req, c *ServiceClientGRPC, fn func(client treeClient) grpcFunc[Req, Resp]) (res Resp, err error) {
	start := int(c.startIndex.Load())
	for i := start; i < start+len(c.clients); i++ {
		index := i % len(c.clients)
		res, err = fn(c.clients[index])(ctx, req)
		if !shouldTryAgain(err) {
			c.startIndex.Store(int32(index))
			return res, err
		}
		c.log.Debug("tree request error", zap.String("address", c.clients[index].address), zap.Error(err))
	}

	return res, err
}

func shouldTryAgain(err error) bool {
	if err == nil {
		return false
	}

	code := status.Code(unwrapErr(err))
	if code == codes.Unavailable || code == codes.Unimplemented {
		return true
	}

	errText := err.Error()
	if strings.Contains(errText, "not found") ||
		strings.Contains(errText, "shard is in read-only mode") ||
		strings.Contains(errText, "shard is in degraded mode") {
		return true
	}

	return false
}

func unwrapErr(err error) error {
	for e := errors.Unwrap(err); e != nil; e = errors.Unwrap(err) {
		err = e
	}

	return err
}

func metaToKV(meta map[string]string) []*grpcService.KeyValue {
	result := make([]*grpcService.KeyValue, 0, len(meta))

	for key, value := range meta {
		result = append(result, &grpcService.KeyValue{Key: key, Value: []byte(value)})
	}

	return result
}

func getBearer(ctx context.Context, bktInfo *data.BucketInfo) []byte {
	if bd, ok := ctx.Value(api.BoxData).(*accessbox.Box); ok && bd != nil && bd.Gate != nil {
		if bd.Gate.BearerToken != nil {
			if bktInfo.Owner.Equals(bearer.ResolveIssuer(*bd.Gate.BearerToken)) {
				return bd.Gate.BearerToken.Marshal()
			}
		}
	}
	return nil
}

func handleError(msg string, err error) error {
	if strings.Contains(err.Error(), "not found") {
		return fmt.Errorf("%w: %s", tree.ErrNodeNotFound, err.Error())
	} else if strings.Contains(err.Error(), "is denied by") {
		return fmt.Errorf("%w: %s", tree.ErrNodeAccessDenied, err.Error())
	}
	return fmt.Errorf("%s: %w", msg, err)
}