package services

import (
	"context"
	"encoding/json"
	"fmt"
	"math/big"

	"github.com/coinbase/rosetta-sdk-go/types"
	ethCommon "github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/hexutil"
	"github.com/pkg/errors"

	"github.com/harmony-one/harmony/internal/params"
	"github.com/harmony-one/harmony/rosetta/common"
	"github.com/harmony-one/harmony/rpc"
)

// ConstructMetadataOptions is constructed by ConstructionPreprocess for ConstructionMetadata options
type ConstructMetadataOptions struct {
	TransactionMetadata *TransactionMetadata `json:"transaction_metadata"`
	OperationType       string               `json:"operation_type,omitempty"`
	GasPriceMultiplier  *float64             `json:"gas_price_multiplier,omitempty"`
}

// UnmarshalFromInterface ..
func (m *ConstructMetadataOptions) UnmarshalFromInterface(metadata interface{}) error {
	var T ConstructMetadataOptions
	dat, err := json.Marshal(metadata)
	if err != nil {
		return err
	}
	if err := json.Unmarshal(dat, &T); err != nil {
		return err
	}
	if T.TransactionMetadata == nil {
		return fmt.Errorf("transaction metadata is required")
	}
	if T.OperationType == "" {
		return fmt.Errorf("operation type is required")
	}
	*m = T
	return nil
}

// ConstructionPreprocess implements the /construction/preprocess endpoint.
// Note that `request.MaxFee` is never considered for this construction implementation.
func (s *ConstructAPI) ConstructionPreprocess(
	ctx context.Context, request *types.ConstructionPreprocessRequest,
) (*types.ConstructionPreprocessResponse, *types.Error) {
	if err := assertValidNetworkIdentifier(request.NetworkIdentifier, s.hmy.ShardID); err != nil {
		return nil, err
	}
	txMetadata := &TransactionMetadata{}
	if request.Metadata != nil {
		if err := txMetadata.UnmarshalFromInterface(request.Metadata); err != nil {
			return nil, common.NewError(common.InvalidTransactionConstructionError, map[string]interface{}{
				"message": errors.WithMessage(err, "invalid transaction metadata").Error(),
			})
		}
	}
	if txMetadata.FromShardID != nil && *txMetadata.FromShardID != s.hmy.ShardID {
		return nil, common.NewError(common.InvalidTransactionConstructionError, map[string]interface{}{
			"message": fmt.Sprintf("expect from shard ID to be %v", s.hmy.ShardID),
		})
	}

	components, rosettaError := GetOperationComponents(request.Operations)
	if rosettaError != nil {
		return nil, rosettaError
	}
	if components.From == nil {
		return nil, common.NewError(common.InvalidTransactionConstructionError, map[string]interface{}{
			"message": "sender address is not found for given operations",
		})
	}

	options, err := types.MarshalMap(ConstructMetadataOptions{
		TransactionMetadata: txMetadata,
		OperationType:       components.Type,
		GasPriceMultiplier:  request.SuggestedFeeMultiplier,
	})
	if err != nil {
		return nil, common.NewError(common.CatchAllError, map[string]interface{}{
			"message": err.Error(),
		})
	}
	return &types.ConstructionPreprocessResponse{
		Options: options,
		RequiredPublicKeys: []*types.AccountIdentifier{
			components.From,
		},
	}, nil
}

// ConstructMetadata with a set of operations will construct a valid transaction
type ConstructMetadata struct {
	Nonce       uint64               `json:"nonce"`
	GasLimit    uint64               `json:"gas_limit"`
	GasPrice    *big.Int             `json:"gas_price"`
	Transaction *TransactionMetadata `json:"transaction_metadata"`
}

// UnmarshalFromInterface ..
func (m *ConstructMetadata) UnmarshalFromInterface(blockArgs interface{}) error {
	var T ConstructMetadata
	dat, err := json.Marshal(blockArgs)
	if err != nil {
		return err
	}
	if err := json.Unmarshal(dat, &T); err != nil {
		return err
	}
	if T.GasPrice == nil {
		return fmt.Errorf("gas price is required")
	}
	if T.Transaction == nil {
		return fmt.Errorf("transaction metadata is required")
	}
	*m = T
	return nil
}

// ConstructionMetadata implements the /construction/metadata endpoint.
func (s *ConstructAPI) ConstructionMetadata(
	ctx context.Context, request *types.ConstructionMetadataRequest,
) (*types.ConstructionMetadataResponse, *types.Error) {
	if err := assertValidNetworkIdentifier(request.NetworkIdentifier, s.hmy.ShardID); err != nil {
		return nil, err
	}
	options := &ConstructMetadataOptions{}
	if err := options.UnmarshalFromInterface(request.Options); err != nil {
		return nil, common.NewError(common.InvalidTransactionConstructionError, map[string]interface{}{
			"message": errors.WithMessage(err, "invalid metadata option(s)").Error(),
		})
	}

	if len(request.PublicKeys) != 1 {
		return nil, common.NewError(common.InvalidTransactionConstructionError, map[string]interface{}{
			"message": "require sender public key only",
		})
	}
	senderAddr, rosettaError := getAddressFromPublicKey(request.PublicKeys[0])
	if rosettaError != nil {
		return nil, rosettaError
	}
	nonce, err := s.hmy.GetPoolNonce(ctx, *senderAddr)
	if err != nil {
		return nil, common.NewError(common.CatchAllError, map[string]interface{}{
			"message": err.Error(),
		})
	}

	data := hexutil.Bytes{}
	if options.TransactionMetadata.Data != nil {
		var err error
		if data, err = hexutil.Decode(*options.TransactionMetadata.Data); err != nil {
			return nil, common.NewError(common.InvalidTransactionConstructionError, map[string]interface{}{
				"message": errors.WithMessage(err, "invalid tx data format").Error(),
			})
		}
	}

	var estGasUsed uint64
	if !isStakingOperation(options.OperationType) {
		if options.OperationType == common.ContractCreationOperation {
			estGasUsed, err = rpc.EstimateGas(ctx, s.hmy, rpc.CallArgs{Data: &data}, nil)
			estGasUsed *= 2 // HACK to account for imperfect contract creation estimation
		} else {
			estGasUsed, err = rpc.EstimateGas(ctx, s.hmy, rpc.CallArgs{To: &ethCommon.Address{}, Data: &data}, nil)
		}
	} else {
		return nil, common.NewError(common.InvalidTransactionConstructionError, map[string]interface{}{
			"message": "staking operations are not supported",
		})
	}
	if err != nil {
		return nil, common.NewError(common.InvalidTransactionConstructionError, map[string]interface{}{
			"message": errors.WithMessage(err, "invalid transaction data").Error(),
		})
	}
	gasMul := float64(1)
	if options.GasPriceMultiplier != nil && *options.GasPriceMultiplier > 1 {
		gasMul = *options.GasPriceMultiplier
	}
	suggestedFee, suggestedPrice := getSuggestedFeeAndPrice(gasMul, new(big.Int).SetUint64(estGasUsed))

	metadata, err := types.MarshalMap(ConstructMetadata{
		Nonce:       nonce,
		GasPrice:    suggestedPrice,
		GasLimit:    estGasUsed,
		Transaction: options.TransactionMetadata,
	})
	if err != nil {
		return nil, common.NewError(common.CatchAllError, map[string]interface{}{
			"message": err.Error(),
		})
	}
	return &types.ConstructionMetadataResponse{
		Metadata:     metadata,
		SuggestedFee: suggestedFee,
	}, nil
}

// getSuggestedFeeAndPrice ..
func getSuggestedFeeAndPrice(
	gasMul float64, estGasUsed *big.Int,
) ([]*types.Amount, *big.Int) {
	if estGasUsed == nil {
		estGasUsed = big.NewInt(0).SetUint64(params.TxGas)
	}
	if gasMul < 1 {
		gasMul = 1
	}
	gasPriceFloat := big.NewFloat(0).Mul(big.NewFloat(DefaultGasPrice), big.NewFloat(gasMul))
	gasPriceTruncated, _ := gasPriceFloat.Uint64()
	gasPrice := new(big.Int).SetUint64(gasPriceTruncated)
	return []*types.Amount{
		{
			Value:    fmt.Sprintf("%v", new(big.Int).Mul(gasPrice, estGasUsed)),
			Currency: &common.Currency,
		},
	}, gasPrice
}

// isStakingOperation ..
func isStakingOperation(op string) bool {
	for _, stakingOp := range common.StakingOperationTypes {
		if stakingOp == op {
			return true
		}
	}
	return false
}