package policy

import (
	"crypto/sha256"
	"errors"
	"fmt"
	"math/big"
	"strings"

	"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/mr-tron/base58"
	"github.com/nspcc-dev/neo-go/pkg/rpcclient/actor"
	"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 the policy contract.
type ContractStorage struct {
	contractInterface *client.Contract
}

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

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

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(act, contract), nil
}

func transformNameIfContainer(target engine.Target) (name string) {
	name = target.Name
	if target.Type == engine.Container {
		// Container name can be too long and, thus, cannot be
		// used as a key name for policy-contract storage.
		encoded := sha256.Sum224([]byte(target.Name))
		name = base58.FastBase58Encoding(encoded[:])
	}
	return
}

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

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

	txHash, vub, err = s.contractInterface.AddChain(big.NewInt(int64(kind)), targetName, 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 chainID == "" {
		err = ErrEmptyChainID
		return
	}

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

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

func (s *ContractStorage) ListMorphRuleChains(name chain.Name, target engine.Target) ([]*chain.Chain, error) {
	kind, err := policyKind(target.Type)
	if err != nil {
		return nil, err
	}
	targetName := transformNameIfContainer(target)

	items, err := s.contractInterface.ListChainsByPrefix(big.NewInt(int64(kind)), targetName, []byte(name))
	if err != nil {
		return nil, 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 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) {
	if typ == engine.Namespace {
		return policy.Namespace, nil
	} else if typ == engine.Container {
		return policy.Container, nil
	}
	return policy.Kind(0), ErrEngineTargetTypeUnsupported
}