package util

import (
	"bytes"
	"io"
	
	"github.com/p9c/p9/pkg/chainhash"
	"github.com/p9c/p9/pkg/wire"
)

// TxIndexUnknown is the value returned for a transaction index that is unknown.
// This is typically because the transaction has not been inserted into a block
// yet.
const TxIndexUnknown = -1

// Tx defines a bitcoin transaction that provides easier and more efficient
// manipulation of raw transactions. It also memorizes the hash for the
// transaction on its first access so subsequent accesses don't have to repeat
// the relatively expensive hashing operations.
type Tx struct {
	msgTx         *wire.MsgTx     // Underlying MsgTx
	txHash        *chainhash.Hash // Cached transaction hash
	txHashWitness *chainhash.Hash // Cached transaction witness hash
	txHasWitness  *bool           // If the transaction has witness data
	txIndex       int             // Position within a block or TxIndexUnknown
}

// MsgTx returns the underlying wire.MsgTx for the transaction.
func (t *Tx) MsgTx() *wire.MsgTx {
	// Return the cached transaction.
	return t.msgTx
}

// Hash returns the hash of the transaction. This is equivalent to calling
// TxHash on the underlying wire.MsgTx, however it caches the result so
// subsequent calls are more efficient.
func (t *Tx) Hash() *chainhash.Hash {
	// Return the cached hash if it has already been generated.
	if t.txHash != nil {
		return t.txHash
	}
	// Cache the hash and return it.
	hash := t.msgTx.TxHash()
	t.txHash = &hash
	return &hash
}

// // WitnessHash returns the witness hash (wtxid) of the transaction. This is
// // equivalent to calling WitnessHash on the underlying wire.MsgTx, however it
// // caches the result so subsequent calls are more efficient.
// func (t *Tx) WitnessHash() *chainhash.Hash {
// 	// Return the cached hash if it has already been generated.
// 	if t.txHashWitness != nil {
// 		return t.txHashWitness
// 	}
// 	// Cache the hash and return it.
// 	hash := t.msgTx.WitnessHash()
// 	t.txHashWitness = &hash
// 	return &hash
// }

// // HasWitness returns false if none of the inputs within the transaction contain
// // witness data, true false otherwise. This equivalent to calling HasWitness on
// // the underlying wire.MsgTx, however it caches the result so subsequent calls
// // are more efficient.
// func (t *Tx) HasWitness() bool {
// 	if t.txHashWitness != nil {
// 		return *t.txHasWitness
// 	}
// 	hasWitness := t.msgTx.HasWitness()
// 	t.txHasWitness = &hasWitness
// 	return hasWitness
// }

// Index returns the saved index of the transaction within a block. This value
// will be TxIndexUnknown if it hasn't already explicitly been set.
func (t *Tx) Index() int {
	return t.txIndex
}

// SetIndex sets the index of the transaction in within a block.
func (t *Tx) SetIndex(index int) {
	t.txIndex = index
}

// NewTx returns a new instance of a bitcoin transaction given an underlying
// wire.MsgTx. See Tx.
func NewTx(msgTx *wire.MsgTx) *Tx {
	return &Tx{
		msgTx:   msgTx,
		txIndex: TxIndexUnknown,
	}
}

// NewTxFromBytes returns a new instance of a bitcoin transaction given the
// serialized bytes. See Tx.
func NewTxFromBytes(serializedTx []byte) (*Tx, error) {
	br := bytes.NewReader(serializedTx)
	return NewTxFromReader(br)
}

// NewTxFromReader returns a new instance of a bitcoin transaction given a
// Reader to deserialize the transaction. See Tx.
func NewTxFromReader(r io.Reader) (*Tx, error) {
	// Deserialize the bytes into a MsgTx.
	var msgTx wire.MsgTx
	e := msgTx.Deserialize(r)
	if e != nil {
		return nil, e
	}
	t := Tx{
		msgTx:   &msgTx,
		txIndex: TxIndexUnknown,
	}
	return &t, nil
}