package state

import (
	"bytes"

	"github.com/tendermint/basecoin/types"
	. "github.com/tendermint/go-common"
	"github.com/tendermint/go-events"
	tmsp "github.com/tendermint/tmsp/types"
)

// If the tx is invalid, a TMSP error will be returned.
func ExecTx(s *State, pgz *types.Plugins, tx types.Tx, isCheckTx bool, evc events.Fireable) tmsp.Result {

	// TODO: do something with fees
	fees := types.Coins{}
	chainID := s.GetChainID()

	// Get the state. If isCheckTx, then we use a cache.
	// The idea is to throw away this cache after every EndBlock().
	var state types.AccountGetterSetter
	if isCheckTx {
		state = s.GetCheckCache()
	} else {
		state = s
	}

	// Exec tx
	switch tx := tx.(type) {
	case *types.SendTx:
		// First, get inputs
		accounts, res := getInputs(state, tx.Inputs)
		if res.IsErr() {
			return res.PrependLog("in getInputs()")
		}

		// Then, get or make outputs.
		accounts, res = getOrMakeOutputs(state, accounts, tx.Outputs)
		if res.IsErr() {
			return res.PrependLog("in getOrMakeOutputs()")
		}

		// Validate inputs and outputs
		signBytes := tx.SignBytes(chainID)
		inTotal, res := validateInputs(accounts, signBytes, tx.Inputs)
		if res.IsErr() {
			return res.PrependLog("in validateInputs()")
		}
		outTotal, res := validateOutputs(tx.Outputs)
		if res.IsErr() {
			return res.PrependLog("in validateOutputs()")
		}
		if !inTotal.IsEqual(outTotal.Plus(types.Coins{{"", tx.Fee}})) {
			return tmsp.ErrBaseInvalidOutput.AppendLog("Input total != output total + fees")
		}
		fees = fees.Plus(types.Coins{{"", tx.Fee}})

		// TODO: Fee validation for SendTx

		// Good! Adjust accounts
		adjustByInputs(state, accounts, tx.Inputs)
		adjustByOutputs(state, accounts, tx.Outputs, isCheckTx)

		/*
			// Fire events
			if !isCheckTx {
				if evc != nil {
					for _, i := range tx.Inputs {
						evc.FireEvent(types.EventStringAccInput(i.Address), types.EventDataTx{tx, nil, ""})
					}
					for _, o := range tx.Outputs {
						evc.FireEvent(types.EventStringAccOutput(o.Address), types.EventDataTx{tx, nil, ""})
					}
				}
			}
		*/

		return tmsp.OK

	case *types.AppTx:
		// First, get input account
		inAcc := state.GetAccount(tx.Input.Address)
		if inAcc == nil {
			return tmsp.ErrBaseUnknownAddress
		}

		// Validate input
		// pubKey should be present in either "inAcc" or "tx.Input"
		if res := checkInputPubKey(tx.Input.Address, inAcc, tx.Input); res.IsErr() {
			log.Info(Fmt("Can't find pubkey for %X", tx.Input.Address))
			return res
		}
		signBytes := tx.SignBytes(chainID)
		res := validateInput(inAcc, signBytes, tx.Input)
		if res.IsErr() {
			log.Info(Fmt("validateInput failed on %X: %v", tx.Input.Address, res))
			return res.PrependLog("in validateInput()")
		}
		if !tx.Input.Coins.IsGTE(types.Coins{{"", tx.Fee}}) {
			log.Info(Fmt("Sender did not send enough to cover the fee %X", tx.Input.Address))
			return tmsp.ErrBaseInsufficientFunds
		}

		// Validate call address
		plugin := pgz.GetByByte(tx.Type)
		if plugin != nil {
			return tmsp.ErrBaseUnknownAddress.AppendLog(
				Fmt("Unrecognized type byte %v", tx.Type))
		}

		// Good!
		coins := tx.Input.Coins.Minus(types.Coins{{"", tx.Fee}})
		inAcc.Sequence += 1
		inAcc.Balance = inAcc.Balance.Minus(tx.Input.Coins)

		// If this is a CheckTx, stop now.
		if isCheckTx {
			state.SetAccount(tx.Input.Address, inAcc)
			return tmsp.OK
		}

		// Create inAcc checkpoint
		inAccCopy := inAcc.Copy()

		// Run the tx.
		cache := types.NewAccountCache(state)
		cache.SetAccount(tx.Input.Address, inAcc)
		ctx := types.NewCallContext(cache, inAcc, coins)
		res = plugin.RunTx(ctx, tx.Data)
		if res.IsOK() {
			cache.Sync()
			log.Info("Successful execution")
			// Fire events
			/*
				if evc != nil {
					exception := ""
					if res.IsErr() {
						exception = res.Error()
					}
					evc.FireEvent(types.EventStringAccInput(tx.Input.Address), types.EventDataTx{tx, ret, exception})
					evc.FireEvent(types.EventStringAccOutput(tx.Address), types.EventDataTx{tx, ret, exception})
				}
			*/
		} else {
			log.Info("AppTx failed", "error", res)
			// Just return the coins and return.
			inAccCopy.Balance = inAccCopy.Balance.Plus(coins)
			// But take the gas
			// TODO
			state.SetAccount(tx.Input.Address, inAccCopy)
		}
		return res

	default:
		return tmsp.ErrBaseEncodingError.SetLog("Unknown tx type")
	}
}

//--------------------------------------------------------------------------------

// The accounts from the TxInputs must either already have
// crypto.PubKey.(type) != nil, (it must be known),
// or it must be specified in the TxInput.  If redeclared,
// the TxInput is modified and input.PubKey set to nil.
func getInputs(state types.AccountGetter, ins []types.TxInput) (map[string]*types.Account, tmsp.Result) {
	accounts := map[string]*types.Account{}
	for _, in := range ins {
		// Account shouldn't be duplicated
		if _, ok := accounts[string(in.Address)]; ok {
			return nil, tmsp.ErrBaseDuplicateAddress
		}
		acc := state.GetAccount(in.Address)
		if acc == nil {
			return nil, tmsp.ErrBaseUnknownAddress
		}
		// PubKey should be present in either "account" or "in"
		if res := checkInputPubKey(in.Address, acc, in); res.IsErr() {
			return nil, res
		}
		accounts[string(in.Address)] = acc
	}
	return accounts, tmsp.OK
}

func getOrMakeOutputs(state types.AccountGetter, accounts map[string]*types.Account, outs []types.TxOutput) (map[string]*types.Account, tmsp.Result) {
	if accounts == nil {
		accounts = make(map[string]*types.Account)
	}

	for _, out := range outs {
		// Account shouldn't be duplicated
		if _, ok := accounts[string(out.Address)]; ok {
			return nil, tmsp.ErrBaseDuplicateAddress
		}
		acc := state.GetAccount(out.Address)
		// output account may be nil (new)
		if acc == nil {
			acc = &types.Account{
				PubKey:   nil,
				Sequence: 0,
			}
		}
		accounts[string(out.Address)] = acc
	}
	return accounts, tmsp.OK
}

// Input must not have a redundant PubKey (i.e. Account already has PubKey).
// NOTE: Account has PubKey if Sequence > 0
func checkInputPubKey(address []byte, acc *types.Account, in types.TxInput) tmsp.Result {
	if acc.PubKey == nil {
		if in.PubKey == nil {
			return tmsp.ErrBaseUnknownPubKey.AppendLog("PubKey not present in either acc or input")
		}
		if !bytes.Equal(in.PubKey.Address(), address) {
			return tmsp.ErrBaseInvalidPubKey.AppendLog("Input PubKey address does not match address")
		}
		acc.PubKey = in.PubKey
	} else {
		if in.PubKey != nil {
			// NOTE: allow redundant pubkey.
			if !bytes.Equal(in.PubKey.Address(), address) {
				return tmsp.ErrBaseInvalidPubKey.AppendLog("Input PubKey address does not match address")
			}
		}
	}
	return tmsp.OK
}

// Validate inputs and compute total amount of coins
func validateInputs(accounts map[string]*types.Account, signBytes []byte, ins []types.TxInput) (total types.Coins, res tmsp.Result) {

	for _, in := range ins {
		acc := accounts[string(in.Address)]
		if acc == nil {
			PanicSanity("validateInputs() expects account in accounts")
		}
		res = validateInput(acc, signBytes, in)
		if res.IsErr() {
			return
		}
		// Good. Add amount to total
		total = total.Plus(in.Coins)
	}
	return total, tmsp.OK
}

func validateInput(acc *types.Account, signBytes []byte, in types.TxInput) (res tmsp.Result) {
	// Check TxInput basic
	if res := in.ValidateBasic(); res.IsErr() {
		return res
	}
	// Check sequence/coins
	seq, balance := acc.Sequence, acc.Balance
	if seq+1 != in.Sequence {
		return tmsp.ErrBaseInvalidSequence.AppendLog(Fmt("Got %v, expected %v. (acc.seq=%v)", in.Sequence, seq+1, acc.Sequence))
	}
	// Check amount
	if !balance.IsGTE(in.Coins) {
		return tmsp.ErrBaseInsufficientFunds
	}
	// Check signatures
	if !acc.PubKey.VerifyBytes(signBytes, in.Signature) {
		return tmsp.ErrBaseInvalidSignature.AppendLog(Fmt("SignBytes: %X", signBytes))
	}
	return tmsp.OK
}

func validateOutputs(outs []types.TxOutput) (total types.Coins, res tmsp.Result) {
	for _, out := range outs {
		// Check TxOutput basic
		if res := out.ValidateBasic(); res.IsErr() {
			return nil, res
		}
		// Good. Add amount to total
		total = total.Plus(out.Coins)
	}
	return total, tmsp.OK
}

func adjustByInputs(state types.AccountSetter, accounts map[string]*types.Account, ins []types.TxInput) {
	for _, in := range ins {
		acc := accounts[string(in.Address)]
		if acc == nil {
			PanicSanity("adjustByInputs() expects account in accounts")
		}
		if !acc.Balance.IsGTE(in.Coins) {
			PanicSanity("adjustByInputs() expects sufficient funds")
		}
		acc.Balance = acc.Balance.Minus(in.Coins)
		acc.Sequence += 1
		state.SetAccount(in.Address, acc)
	}
}

func adjustByOutputs(state types.AccountSetter, accounts map[string]*types.Account, outs []types.TxOutput, isCheckTx bool) {
	for _, out := range outs {
		acc := accounts[string(out.Address)]
		if acc == nil {
			PanicSanity("adjustByOutputs() expects account in accounts")
		}
		acc.Balance = acc.Balance.Plus(out.Coins)
		if !isCheckTx {
			state.SetAccount(out.Address, acc)
		}
	}
}