package tx

import (
	"encoding/hex"
	"testing"
)

// The published BIP143 native P2WPKH example, from bip-0143.mediawiki. The digest below is the
// specification's own, so this pins the preimage rather than checking it against itself.
const (
	bip143Hash = "c37af31116d1b27caf68aae9e3ac82f1477929014d5b917657d0eb49478cb670"

	// The second input's witness program is 1d0f172a…a1, which is what the scriptCode wraps.
	bip143Program = "1d0f172a0ecb48aee1be1f2687d2963ae33f71a1"

	// The first input's outpoint, and both inputs' outpoints in order.
	bip143Prev1 = "fff7f7881a8099afa6940d42d1e7f6362bec38171ea3edf433541db4e4ad969f"
	bip143Prev2 = "ef51e1b804cc89d182d279655c3aa89e815b1b309fe287d9b2b55d57b90ec68a"
)

// TestThePublishedBIP143Vector: the digest this package computes is the specification's.
func TestThePublishedBIP143Vector(t *testing.T) {
	transaction := New()
	transaction.Version = 1

	for _, prev := range []struct {
		txid     string
		index    uint32
		sequence uint32
	}{
		{bip143Prev1, 0, 0xffffffee},
		{bip143Prev2, 1, 0xffffffff},
	} {
		hash, err := hex.DecodeString(prev.txid)

		if err != nil {
			t.Fatal(err)
		}

		var outpoint [32]byte
		copy(outpoint[:], hash)

		transaction.AddInput(Outpoint{Hash: outpoint, Index: prev.index}, prev.sequence)
	}

	for _, output := range []struct {
		value  uint64
		script string
	}{
		{112340000, "76a9148280b37df378db99f66f85c95a783a76ac7a6d5988ac"},
		{223450000, "76a9143bde42dbee7e4dbe6a21b2d50ce2f0167faa815988ac"},
	} {
		script, err := hex.DecodeString(output.script)

		if err != nil {
			t.Fatal(err)
		}

		transaction.AddOutput(output.value, script)
	}

	transaction.LockTime = 17

	programRaw, err := hex.DecodeString(bip143Program)

	if err != nil {
		t.Fatal(err)
	}

	var program [20]byte
	copy(program[:], programRaw)

	// The second input is the P2WPKH one, and it spends 6 BTC.
	digest, err := transaction.SighashV0(1, P2WPKHScriptCode(program), 600000000, SighashAll)

	if err != nil {
		t.Fatal(err)
	}

	if got := hex.EncodeToString(digest[:]); got != bip143Hash {
		t.Fatalf("the digest is %s, the specification says %s", got, bip143Hash)
	}
}