package tx

import (
	"bufio"
	"encoding/json"
	"errors"
	"fmt"
	"os"

	"github.com/spf13/viper"

	"github.com/cosmos/cosmos-sdk/client/context"
	"github.com/cosmos/cosmos-sdk/client/flags"
	"github.com/cosmos/cosmos-sdk/client/input"
	clientkeys "github.com/cosmos/cosmos-sdk/client/keys"
	"github.com/cosmos/cosmos-sdk/codec"
	"github.com/cosmos/cosmos-sdk/crypto/keys"
	sdk "github.com/cosmos/cosmos-sdk/types"
	"github.com/cosmos/cosmos-sdk/x/auth"
)

type (
	// Generator defines an interface a client can utilize to generate an
	// application-defined concrete transaction type. The type returned must
	// implement ClientTx.
	Generator interface {
		NewTx() ClientTx
	}

	// ClientTx defines an interface which an application-defined concrete transaction
	// type must implement. Namely, it must be able to set messages, generate
	// signatures, and provide canonical bytes to sign over. The transaction must
	// also know how to encode itself.
	ClientTx interface {
		sdk.Tx
		codec.ProtoMarshaler

		SetMsgs(...sdk.Msg) error
		GetSignatures() []sdk.Signature
		SetSignatures(...sdk.Signature)
		GetFee() sdk.Fee
		SetFee(sdk.Fee)
		GetMemo() string
		SetMemo(string)

		// CanonicalSignBytes returns the canonical JSON bytes to sign over, given a
		// chain ID, along with an account and sequence number. The JSON encoding
		// ensures all field names adhere to their proto definition, default values
		// are omitted, and follows the JSON Canonical Form.
		CanonicalSignBytes(cid string, num, seq uint64) ([]byte, error)
	}
)

// GenerateOrBroadcastTx will either generate and print and unsigned transaction
// or sign it and broadcast it returning an error upon failure.
func GenerateOrBroadcastTx(ctx context.CLIContext, txf Factory, msgs ...sdk.Msg) error {
	if ctx.GenerateOnly {
		return GenerateTx(ctx, txf, msgs...)
	}

	return BroadcastTx(ctx, txf, msgs...)
}

// GenerateTx will generate an unsigned transaction and print it to the writer
// specified by ctx.Output. If simulation was requested, the gas will be
// simulated and also printed to the same writer before the transaction is
// printed.
func GenerateTx(ctx context.CLIContext, txf Factory, msgs ...sdk.Msg) error {
	if txf.SimulateAndExecute() {
		if ctx.Offline {
			return errors.New("cannot estimate gas in offline mode")
		}

		txBytes, err := BuildSimTx(txf, msgs...)
		if err != nil {
			return err
		}

		_, adjusted, err := CalculateGas(ctx.QueryWithData, txBytes, txf.GasAdjustment())
		if err != nil {
			return err
		}

		txf = txf.WithGas(adjusted)
		_, _ = fmt.Fprintf(os.Stderr, "%s\n", GasEstimateResponse{GasEstimate: txf.Gas()})
	}

	tx, err := BuildUnsignedTx(txf, msgs...)
	if err != nil {
		return err
	}

	return ctx.Print(tx)
}

// BroadcastTx attempts to generate, sign and broadcast a transaction with the
// given set of messages. It will also simulate gas requirements if necessary.
// It will return an error upon failure.
func BroadcastTx(ctx context.CLIContext, txf Factory, msgs ...sdk.Msg) error {
	txf, err := PrepareFactory(ctx, txf)
	if err != nil {
		return err
	}

	if txf.SimulateAndExecute() || ctx.Simulate {
		txBytes, err := BuildSimTx(txf, msgs...)
		if err != nil {
			return err
		}

		_, adjusted, err := CalculateGas(ctx.QueryWithData, txBytes, txf.GasAdjustment())
		if err != nil {
			return err
		}

		txf = txf.WithGas(adjusted)
		_, _ = fmt.Fprintf(os.Stderr, "%s\n", GasEstimateResponse{GasEstimate: txf.Gas()})
	}

	if ctx.Simulate {
		return nil
	}

	tx, err := BuildUnsignedTx(txf, msgs...)
	if err != nil {
		return err
	}

	if !ctx.SkipConfirm {
		out, err := ctx.Marshaler.MarshalJSON(tx)
		if err != nil {
			return err
		}

		_, _ = fmt.Fprintf(os.Stderr, "%s\n\n", out)

		buf := bufio.NewReader(os.Stdin)
		ok, err := input.GetConfirmation("confirm transaction before signing and broadcasting", buf)
		if err != nil || !ok {
			_, _ = fmt.Fprintf(os.Stderr, "%s\n", "cancelled transaction")
			return err
		}
	}

	txBytes, err := Sign(txf, ctx.GetFromName(), clientkeys.DefaultKeyPass, tx)
	if err != nil {
		return err
	}

	// broadcast to a Tendermint node
	res, err := ctx.BroadcastTx(txBytes)
	if err != nil {
		return err
	}

	return ctx.Print(res)
}

// BuildUnsignedTx builds a transaction to be signed given a set of messages. The
// transaction is initially created via the provided factory's generator. Once
// created, the fee, memo, and messages are set.
func BuildUnsignedTx(txf Factory, msgs ...sdk.Msg) (ClientTx, error) {
	if txf.chainID == "" {
		return nil, fmt.Errorf("chain ID required but not specified")
	}

	fees := txf.fees
	if !txf.gasPrices.IsZero() {
		if !fees.IsZero() {
			return nil, errors.New("cannot provide both fees and gas prices")
		}

		glDec := sdk.NewDec(int64(txf.gas))

		// Derive the fees based on the provided gas prices, where
		// fee = ceil(gasPrice * gasLimit).
		fees = make(sdk.Coins, len(txf.gasPrices))
		for i, gp := range txf.gasPrices {
			fee := gp.Amount.Mul(glDec)
			fees[i] = sdk.NewCoin(gp.Denom, fee.Ceil().RoundInt())
		}
	}

	tx := txf.txGenerator.NewTx()
	tx.SetFee(auth.NewStdFee(txf.gas, fees))
	tx.SetMsgs(msgs...)
	tx.SetMemo(txf.memo)
	tx.SetSignatures()

	return tx, nil
}

// BuildSimTx creates an unsigned tx with an empty single signature and returns
// the encoded transaction or an error if the unsigned transaction cannot be
// built.
func BuildSimTx(txf Factory, msgs ...sdk.Msg) ([]byte, error) {
	tx, err := BuildUnsignedTx(txf, msgs...)
	if err != nil {
		return nil, err
	}

	// Create an empty signature literal as the ante handler will populate with a
	// sentinel pubkey.
	tx.SetSignatures(auth.NewStdSignature(nil, nil))

	return tx.Marshal()
}

// CalculateGas simulates the execution of a transaction and returns the
// simulation response obtained by the query and the adjusted gas amount.
func CalculateGas(
	queryFunc func(string, []byte) ([]byte, int64, error), txBytes []byte, adjustment float64,
) (sdk.SimulationResponse, uint64, error) {

	bz, _, err := queryFunc("/app/simulate", txBytes)
	if err != nil {
		return sdk.SimulationResponse{}, 0, err
	}

	var simRes sdk.SimulationResponse
	if err := json.Unmarshal(bz, &simRes); err != nil {
		return sdk.SimulationResponse{}, 0, err
	}

	return simRes, uint64(adjustment * float64(simRes.GasUsed)), nil
}

// PrepareFactory ensures the account defined by ctx.GetFromAddress() exists and
// if the account number and/or the account sequence number are zero (not set),
// they will be queried for and set on the provided Factory. A new Factory with
// the updated fields will be returned.
func PrepareFactory(ctx context.CLIContext, txf Factory) (Factory, error) {
	from := ctx.GetFromAddress()

	if err := txf.accountRetriever.EnsureExists(from); err != nil {
		return txf, err
	}

	initNum, initSeq := txf.accountNumber, txf.sequence
	if initNum == 0 || initSeq == 0 {
		num, seq, err := txf.accountRetriever.GetAccountNumberSequence(from)
		if err != nil {
			return txf, err
		}

		if initNum == 0 {
			txf = txf.WithAccountNumber(num)
		}
		if initSeq == 0 {
			txf = txf.WithSequence(seq)
		}
	}

	return txf, nil
}

// Sign signs a given tx with the provided name and passphrase. If the Factory's
// Keybase is not set, a new one will be created based on the client's backend.
// The bytes signed over are canconical. The resulting signature will be set on
// the transaction. Finally, the marshaled transaction is returned. An error is
// returned upon failure.
//
// Note, It is assumed the Factory has the necessary fields set that are required
// by the CanonicalSignBytes call.
func Sign(txf Factory, name, passphrase string, tx ClientTx) ([]byte, error) {
	if txf.keybase == nil {
		keybase, err := keys.NewKeyring(
			sdk.KeyringServiceName(),
			viper.GetString(flags.FlagKeyringBackend),
			viper.GetString(flags.FlagHome),
			os.Stdin,
		)
		if err != nil {
			return nil, err
		}

		txf = txf.WithKeybase(keybase)
	}

	signBytes, err := tx.CanonicalSignBytes(txf.chainID, txf.accountNumber, txf.sequence)
	if err != nil {
		return nil, err
	}

	sigBytes, pubkey, err := txf.keybase.Sign(name, passphrase, signBytes)
	if err != nil {
		return nil, err
	}

	tx.SetSignatures(auth.NewStdSignature(pubkey, sigBytes))
	return tx.Marshal()
}

// GasEstimateResponse defines a response definition for tx gas estimation.
type GasEstimateResponse struct {
	GasEstimate uint64 `json:"gas_estimate" yaml:"gas_estimate"`
}

func (gr GasEstimateResponse) String() string {
	return fmt.Sprintf("gas estimate: %d", gr.GasEstimate)
}