// Copyright (c) 2014-2016 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package txscript_test

import (
	"encoding/hex"
	"fmt"

	"github.com/daglabs/btcd/btcec"
	"github.com/daglabs/btcd/dagconfig"
	"github.com/daglabs/btcd/txscript"
	"github.com/daglabs/btcd/util"
	"github.com/daglabs/btcd/util/daghash"
	"github.com/daglabs/btcd/wire"
)

// This example demonstrates creating a script which pays to a bitcoin address.
// It also prints the created script hex and uses the DisasmString function to
// display the disassembled script.
func ExamplePayToAddrScript() {
	// Parse the address to send the coins to into a util.Address
	// which is useful to ensure the accuracy of the address and determine
	// the address type.  It is also required for the upcoming call to
	// PayToAddrScript.
	addressStr := "dagcoin:qqfgqp8l9l90zwetj84k2jcac2m8falvvy9uastr55"
	address, err := util.DecodeAddress(addressStr, util.Bech32PrefixDAGCoin)
	if err != nil {
		fmt.Println(err)
		return
	}

	// Create a public key script that pays to the address.
	script, err := txscript.PayToAddrScript(address)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Printf("Script Hex: %x\n", script)

	disasm, err := txscript.DisasmString(script)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println("Script Disassembly:", disasm)

	// Output:
	// Script Hex: 76a914128004ff2fcaf13b2b91eb654b1dc2b674f7ec6188ac
	// Script Disassembly: OP_DUP OP_HASH160 128004ff2fcaf13b2b91eb654b1dc2b674f7ec61 OP_EQUALVERIFY OP_CHECKSIG
}

// This example demonstrates extracting information from a standard public key
// script.
func ExampleExtractPkScriptAddrs() {
	// Start with a standard pay-to-pubkey-hash script.
	scriptHex := "76a914128004ff2fcaf13b2b91eb654b1dc2b674f7ec6188ac"
	script, err := hex.DecodeString(scriptHex)
	if err != nil {
		fmt.Println(err)
		return
	}

	// Extract and print details from the script.
	scriptClass, addresses, reqSigs, err := txscript.ExtractPkScriptAddrs(
		script, &dagconfig.MainNetParams)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println("Script Class:", scriptClass)
	fmt.Println("Addresses:", addresses)
	fmt.Println("Required Signatures:", reqSigs)

	// Output:
	// Script Class: pubkeyhash
	// Addresses: [dagcoin:qqfgqp8l9l90zwetj84k2jcac2m8falvvy9uastr55]
	// Required Signatures: 1
}

// This example demonstrates manually creating and signing a redeem transaction.
func ExampleSignTxOutput() {
	// Ordinarily the private key would come from whatever storage mechanism
	// is being used, but for this example just hard code it.
	privKeyBytes, err := hex.DecodeString("22a47fa09a223f2aa079edf85a7c2" +
		"d4f8720ee63e502ee2869afab7de234b80c")
	if err != nil {
		fmt.Println(err)
		return
	}
	privKey, pubKey := btcec.PrivKeyFromBytes(btcec.S256(), privKeyBytes)
	pubKeyHash := util.Hash160(pubKey.SerializeCompressed())
	addr, err := util.NewAddressPubKeyHash(pubKeyHash, util.Bech32PrefixDAGCoin)
	if err != nil {
		fmt.Println(err)
		return
	}

	// For this example, create a fake transaction that represents what
	// would ordinarily be the real transaction that is being spent.  It
	// contains a single output that pays to address in the amount of 1 BTC.
	prevOut := wire.NewOutpoint(&daghash.TxID{}, ^uint32(0))
	txIn := wire.NewTxIn(prevOut, []byte{txscript.Op0, txscript.Op0})
	pkScript, err := txscript.PayToAddrScript(addr)
	if err != nil {
		fmt.Println(err)
		return
	}
	txOut := wire.NewTxOut(100000000, pkScript)
	originTx := wire.NewNativeMsgTx(wire.TxVersion, []*wire.TxIn{txIn}, []*wire.TxOut{txOut})

	// Create the transaction to redeem the fake transaction.

	// Add the input(s) the redeeming transaction will spend.  There is no
	// signature script at this point since it hasn't been created or signed
	// yet, hence nil is provided for it.
	prevOut = wire.NewOutpoint(originTx.TxID(), 0)
	txIn = wire.NewTxIn(prevOut, nil)

	// Ordinarily this would contain that actual destination of the funds,
	// but for this example don't bother.
	txOut = wire.NewTxOut(0, nil)

	redeemTx := wire.NewNativeMsgTx(wire.TxVersion, []*wire.TxIn{txIn}, []*wire.TxOut{txOut})

	// Sign the redeeming transaction.
	lookupKey := func(a util.Address) (*btcec.PrivateKey, bool, error) {
		// Ordinarily this function would involve looking up the private
		// key for the provided address, but since the only thing being
		// signed in this example uses the address associated with the
		// private key from above, simply return it with the compressed
		// flag set since the address is using the associated compressed
		// public key.
		//
		// NOTE: If you want to prove the code is actually signing the
		// transaction properly, uncomment the following line which
		// intentionally returns an invalid key to sign with, which in
		// turn will result in a failure during the script execution
		// when verifying the signature.
		//
		// privKey.D.SetInt64(12345)
		//
		return privKey, true, nil
	}
	// Notice that the script database parameter is nil here since it isn't
	// used.  It must be specified when pay-to-script-hash transactions are
	// being signed.
	sigScript, err := txscript.SignTxOutput(&dagconfig.MainNetParams,
		redeemTx, 0, originTx.TxOut[0].PkScript, txscript.SigHashAll,
		txscript.KeyClosure(lookupKey), nil, nil)
	if err != nil {
		fmt.Println(err)
		return
	}
	redeemTx.TxIn[0].SignatureScript = sigScript

	// Prove that the transaction has been validly signed by executing the
	// script pair.
	flags := txscript.ScriptDiscourageUpgradableNops
	vm, err := txscript.NewEngine(originTx.TxOut[0].PkScript, redeemTx, 0, flags, nil)
	if err != nil {
		fmt.Println(err)
		return
	}
	if err := vm.Execute(); err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println("Transaction successfully signed")

	// Output:
	// Transaction successfully signed
}