// Copyright (c) 2018-2019 The Decred developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package txscript

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"testing"

	"github.com/btcsuite/btcd/wire"
)

var (
	// manyInputsBenchTx is a transaction that contains a lot of inputs which is
	// useful for benchmarking signature hash calculation.
	manyInputsBenchTx wire.MsgTx

	// A mock previous output script to use in the signing benchmark.
	prevOutScript = hexToBytes("a914f5916158e3e2c4551c1796708db8367207ed13bb87")
)

func init() {
	// tx 620f57c92cf05a7f7e7f7d28255d5f7089437bc48e34dcfebf7751d08b7fb8f5
	txHex, err := ioutil.ReadFile("data/many_inputs_tx.hex")
	if err != nil {
		panic(fmt.Sprintf("unable to read benchmark tx file: %v", err))
	}

	txBytes := hexToBytes(string(txHex))
	err = manyInputsBenchTx.Deserialize(bytes.NewReader(txBytes))
	if err != nil {
		panic(err)
	}
}

// BenchmarkCalcSigHash benchmarks how long it takes to calculate the signature
// hashes for all inputs of a transaction with many inputs.
func BenchmarkCalcSigHash(b *testing.B) {
	b.ReportAllocs()
	for i := 0; i < b.N; i++ {
		for j := 0; j < len(manyInputsBenchTx.TxIn); j++ {
			_, err := CalcSignatureHash(prevOutScript, SigHashAll,
				&manyInputsBenchTx, j)
			if err != nil {
				b.Fatalf("failed to calc signature hash: %v", err)
			}
		}
	}
}