package policy

import (
	"errors"
	"fmt"
	"math/big"
	"strings"

	"git.frostfs.info/TrueCloudLab/frostfs-contract/commonclient"
	"git.frostfs.info/TrueCloudLab/frostfs-contract/policy"
	client "git.frostfs.info/TrueCloudLab/frostfs-contract/rpcclient/policy"
	"git.frostfs.info/TrueCloudLab/policy-engine/pkg/chain"
	"git.frostfs.info/TrueCloudLab/policy-engine/pkg/engine"
	"github.com/google/uuid"
	"github.com/nspcc-dev/neo-go/pkg/neorpc/result"
	"github.com/nspcc-dev/neo-go/pkg/rpcclient/actor"
	neoinvoker "github.com/nspcc-dev/neo-go/pkg/rpcclient/invoker"
	"github.com/nspcc-dev/neo-go/pkg/util"
	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
	"github.com/nspcc-dev/neo-go/pkg/wallet"
)

var (
	ErrEmptyChainID = errors.New("chain id is not set")

	ErrEngineTargetTypeUnsupported = errors.New("this target type is not supported yet")
)

// ContractStorage is the interface to manage chain rules within Policy contract.
type ContractStorage struct {
	hash util.Uint160

	actor ContractStorageActor

	contractInterface *client.Contract
}

var _ engine.MorphRuleChainStorage = (*ContractStorage)(nil)

// ContractStorageReader is the interface to read data from Policy contract.
type ContractStorageReader struct {
	hash util.Uint160

	invoker ContractStorageInvoker

	contractReaderInterface *client.ContractReader
}

type ContractStorageActor interface {
	client.Actor
	GetRPCInvoker() neoinvoker.RPCInvoke
}

var _ engine.MorphRuleChainStorageReader = (*ContractStorageReader)(nil)

func NewContractStorage(actor ContractStorageActor, contract util.Uint160) *ContractStorage {
	return &ContractStorage{
		hash:              contract,
		actor:             actor,
		contractInterface: client.New(actor, contract),
	}
}

type contractStorageActorImpl struct {
	client.Actor
	rpcActor actor.RPCActor
}

var _ ContractStorageActor = &contractStorageActorImpl{}

func (c *contractStorageActorImpl) GetRPCInvoker() neoinvoker.RPCInvoke {
	return c.rpcActor
}

// NewContractStorageWithSimpleActor constructs core actor from `rpcActor`.
//
// Note: NewContractStorageWithSimpleActor is appropriate only for call-only-once cases (for example, in CLIs). Otherwise, it is unsafe,
// because core actor may use invalidated `rpcActor` if some connection errors occurred.
func NewContractStorageWithSimpleActor(rpcActor actor.RPCActor, acc *wallet.Account, contract util.Uint160) (*ContractStorage, error) {
	act, err := actor.NewSimple(rpcActor, acc)
	if err != nil {
		return nil, fmt.Errorf("failed to create simple actor: %w", err)
	}
	return NewContractStorage(&contractStorageActorImpl{Actor: act, rpcActor: rpcActor}, contract), nil
}

func (s *ContractStorage) AddMorphRuleChain(name chain.Name, target engine.Target, c *chain.Chain) (txHash util.Uint256, vub uint32, err error) {
	if len(c.ID) == 0 {
		err = ErrEmptyChainID
		return
	}

	var kind policy.Kind
	kind, err = policyKind(target.Type)
	if err != nil {
		return
	}
	fullName := prefixedChainName(name, c.ID)

	txHash, vub, err = s.contractInterface.AddChain(big.NewInt(int64(kind)), target.Name, fullName, c.Bytes())
	return
}

func (s *ContractStorage) RemoveMorphRuleChain(name chain.Name, target engine.Target, chainID chain.ID) (txHash util.Uint256, vub uint32, err error) {
	if len(chainID) == 0 {
		err = ErrEmptyChainID
		return
	}

	var kind policy.Kind
	kind, err = policyKind(target.Type)
	if err != nil {
		return
	}
	fullName := prefixedChainName(name, chainID)

	txHash, vub, err = s.contractInterface.RemoveChain(big.NewInt(int64(kind)), target.Name, fullName)
	return
}

func (s *ContractStorage) RemoveMorphRuleChainsByTarget(name chain.Name, target engine.Target) (txHash util.Uint256, vub uint32, err error) {
	var kind policy.Kind
	kind, err = policyKind(target.Type)
	if err != nil {
		return
	}
	fullName := prefixedChainName(name, nil)

	txHash, vub, err = s.contractInterface.RemoveChainsByPrefix(big.NewInt(int64(kind)), target.Name, fullName)
	return
}

func listChains(name chain.Name, target engine.Target, rpcInvoker neoinvoker.RPCInvoke, hash util.Uint160) ([]*chain.Chain, error) {
	kind, err := policyKind(target.Type)
	if err != nil {
		return nil, err
	}

	const (
		method    = "iteratorChainsByPrefix"
		batchSize = neoinvoker.DefaultIteratorResultItems
	)

	inv := neoinvoker.New(rpcInvoker, nil)
	params := []any{
		big.NewInt(int64(kind)), target.Name, []byte(name),
	}

	items, err := commonclient.ReadIteratorItems(inv, batchSize, hash, method, params...)
	if err != nil {
		return nil, fmt.Errorf("read items error: %w", err)
	}
	var chains []*chain.Chain
	for _, item := range items {
		serialized, err := bytesFromStackItem(item)
		if err != nil {
			return nil, err
		}
		c := new(chain.Chain)
		if err := c.DecodeBytes(serialized); err != nil {
			return nil, err
		}
		chains = append(chains, c)
	}
	return chains, nil
}

func (s *ContractStorage) ListMorphRuleChains(name chain.Name, target engine.Target) ([]*chain.Chain, error) {
	return listChains(name, target, s.actor.GetRPCInvoker(), s.hash)
}

func (s *ContractStorage) ListTargetsIterator(targetType engine.TargetType) (uuid.UUID, result.Iterator, error) {
	kind, err := policyKind(targetType)
	if err != nil {
		return uuid.UUID{}, result.Iterator{}, err
	}
	return s.contractInterface.ListTargets(big.NewInt(int64(kind)))
}

func (s *ContractStorage) GetAdmin() (util.Uint160, error) {
	return s.contractInterface.GetAdmin()
}

func (s *ContractStorage) SetAdmin(addr util.Uint160) (util.Uint256, uint32, error) {
	return s.contractInterface.SetAdmin(addr)
}

type ContractStorageInvoker interface {
	client.Invoker
	GetRPCInvoker() neoinvoker.RPCInvoke
}

func NewContractStorageReader(inv ContractStorageInvoker, contract util.Uint160) *ContractStorageReader {
	return &ContractStorageReader{
		hash:                    contract,
		invoker:                 inv,
		contractReaderInterface: client.NewReader(inv, contract),
	}
}

func (s *ContractStorageReader) ListMorphRuleChains(name chain.Name, target engine.Target) ([]*chain.Chain, error) {
	return listChains(name, target, s.invoker.GetRPCInvoker(), s.hash)
}

func (s *ContractStorageReader) GetAdmin() (util.Uint160, error) {
	return s.contractReaderInterface.GetAdmin()
}

func (s *ContractStorageReader) ListTargetsIterator(targetType engine.TargetType) (uuid.UUID, result.Iterator, error) {
	kind, err := policyKind(targetType)
	if err != nil {
		return uuid.UUID{}, result.Iterator{}, err
	}
	return s.contractReaderInterface.ListTargets(big.NewInt(int64(kind)))
}

func bytesFromStackItem(param stackitem.Item) ([]byte, error) {
	switch param.Type() {
	case stackitem.BufferT, stackitem.ByteArrayT, stackitem.IntegerT:
		return param.TryBytes()
	case stackitem.AnyT:
		if param.Value() == nil {
			return nil, nil
		}
		fallthrough
	default:
		return nil, fmt.Errorf("chain/client: %s is not a byte array type", param.Type())
	}
}

func prefixedChainName(name chain.Name, chainID chain.ID) []byte {
	return []byte(strings.ToLower(fmt.Sprintf("%s:%s", name, chainID)))
}

func policyKind(typ engine.TargetType) (policy.Kind, error) {
	switch typ {
	case engine.Namespace:
		return policy.Namespace, nil
	case engine.Container:
		return policy.Container, nil
	case engine.User:
		return policy.Kind(engine.User), nil
	case engine.Group:
		return policy.Kind(engine.Group), nil
	default:
		return policy.Kind(0), ErrEngineTargetTypeUnsupported
	}
}