package core

import (
	"errors"
	"fmt"
	"sync"

	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/ethutil"
	"github.com/ethereum/go-ethereum/event"
	"github.com/ethereum/go-ethereum/logger"
)

var (
	txplogger = logger.NewLogger("TXP")

	ErrInvalidSender = errors.New("Invalid sender")
)

const txPoolQueueSize = 50

type TxPoolHook chan *types.Transaction
type TxMsg struct {
	Tx *types.Transaction
}

const (
	minGasPrice = 1000000
)

type TxProcessor interface {
	ProcessTransaction(tx *types.Transaction)
}

// The tx pool a thread safe transaction pool handler. In order to
// guarantee a non blocking pool we use a queue channel which can be
// independently read without needing access to the actual pool.
type TxPool struct {
	mu sync.RWMutex
	// Queueing channel for reading and writing incoming
	// transactions to
	queueChan chan *types.Transaction
	// Quiting channel
	quit chan bool
	// The actual pool
	//pool *list.List
	txs map[string]*types.Transaction

	SecondaryProcessor TxProcessor

	subscribers []chan TxMsg

	eventMux *event.TypeMux
}

func NewTxPool(eventMux *event.TypeMux) *TxPool {
	return &TxPool{
		txs:       make(map[string]*types.Transaction),
		queueChan: make(chan *types.Transaction, txPoolQueueSize),
		quit:      make(chan bool),
		eventMux:  eventMux,
	}
}

func (pool *TxPool) ValidateTransaction(tx *types.Transaction) error {
	if len(tx.To()) != 0 && len(tx.To()) != 20 {
		return fmt.Errorf("Invalid recipient. len = %d", len(tx.To()))
	}

	// Validate curve param
	v, _, _ := tx.Curve()
	if v > 28 || v < 27 {
		return fmt.Errorf("tx.v != (28 || 27) => %v", v)
	}

	// Validate sender address
	senderAddr := tx.From()
	if senderAddr == nil || len(senderAddr) != 20 {
		return ErrInvalidSender
	}

	/* XXX this kind of validation needs to happen elsewhere in the gui when sending txs.
	   Other clients should do their own validation. Value transfer could throw error
	   but doesn't necessarily invalidate the tx. Gas can still be payed for and miner
	   can still be rewarded for their inclusion and processing.
	sender := pool.stateQuery.GetAccount(senderAddr)
	totAmount := new(big.Int).Set(tx.Value())
	// Make sure there's enough in the sender's account. Having insufficient
	// funds won't invalidate this transaction but simple ignores it.
	if sender.Balance().Cmp(totAmount) < 0 {
		return fmt.Errorf("Insufficient amount in sender's (%x) account", tx.From())
	}
	*/

	return nil
}

func (self *TxPool) addTx(tx *types.Transaction) {
	self.txs[string(tx.Hash())] = tx
}

func (self *TxPool) add(tx *types.Transaction) error {
	if self.txs[string(tx.Hash())] != nil {
		return fmt.Errorf("Known transaction (%x)", tx.Hash()[0:4])
	}

	err := self.ValidateTransaction(tx)
	if err != nil {
		return err
	}

	self.addTx(tx)

	var to string
	if len(tx.To()) > 0 {
		to = ethutil.Bytes2Hex(tx.To()[:4])
	} else {
		to = "[NEW_CONTRACT]"
	}
	var from string
	if len(tx.From()) > 0 {
		from = ethutil.Bytes2Hex(tx.From()[:4])
	} else {
		return errors.New(fmt.Sprintf("FROM ADDRESS MUST BE POSITIVE (was %v)", tx.From()))
	}
	txplogger.Debugf("(t) %x => %s (%v) %x\n", from, to, tx.Value, tx.Hash())

	// Notify the subscribers
	go self.eventMux.Post(TxPreEvent{tx})

	return nil
}

func (self *TxPool) Size() int {
	return len(self.txs)
}

func (self *TxPool) Add(tx *types.Transaction) error {
	self.mu.Lock()
	defer self.mu.Unlock()
	return self.add(tx)
}
func (self *TxPool) AddTransactions(txs []*types.Transaction) {
	self.mu.Lock()
	defer self.mu.Unlock()

	for _, tx := range txs {
		if err := self.add(tx); err != nil {
			txplogger.Debugln(err)
		} else {
			txplogger.Debugf("tx %x\n", tx.Hash()[0:4])
		}
	}
}

func (self *TxPool) GetTransactions() (txs types.Transactions) {
	self.mu.RLock()
	defer self.mu.RUnlock()

	txs = make(types.Transactions, self.Size())
	i := 0
	for _, tx := range self.txs {
		txs[i] = tx
		i++
	}

	return
}

func (pool *TxPool) RemoveInvalid(query StateQuery) {
	pool.mu.Lock()

	var removedTxs types.Transactions
	for _, tx := range pool.txs {
		sender := query.GetAccount(tx.From())
		err := pool.ValidateTransaction(tx)
		if err != nil || sender.Nonce() >= tx.Nonce() {
			removedTxs = append(removedTxs, tx)
		}
	}
	pool.mu.Unlock()

	pool.RemoveSet(removedTxs)
}

func (self *TxPool) RemoveSet(txs types.Transactions) {
	self.mu.Lock()
	defer self.mu.Unlock()

	for _, tx := range txs {
		delete(self.txs, string(tx.Hash()))
	}
}

func (pool *TxPool) Flush() {
	pool.txs = make(map[string]*types.Transaction)
}

func (pool *TxPool) Start() {
}

func (pool *TxPool) Stop() {
	pool.Flush()

	txplogger.Infoln("Stopped")
}