From cb7f34895c164cde330db7577cca629934524298 Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@mit.edu>
Date: Mon, 12 Mar 2018 16:31:56 -0700
Subject: [PATCH] keychain/btwallet: support coin type configuration

This commit allows for secret keyrings to be initialized
with a specific coin type, which allows us to use
different derivation paths for bitcion and litecoin.

It also provide default constants for Bitcion and
Litecoin BIP 44 coin types.
---
 keychain/btcwallet.go | 43 ++++++++++++++++++++++++++++++-------------
 1 file changed, 30 insertions(+), 13 deletions(-)

diff --git a/keychain/btcwallet.go b/keychain/btcwallet.go
index 2d9f2d8b..8826e495 100644
--- a/keychain/btcwallet.go
+++ b/keychain/btcwallet.go
@@ -10,15 +10,21 @@ import (
 	"github.com/roasbeef/btcwallet/walletdb"
 )
 
-var (
-	// lightningKeyScope is the key scope that will be used within the
-	// waddrmgr to create an HD chain for deriving all of our required
-	// keys.
-	lightningKeyScope = waddrmgr.KeyScope{
-		Purpose: BIP0043Purpose,
-		Coin:    0,
-	}
+const (
+	// CoinTypeBitcoin specifies the BIP44 coin type for Bitcoin key
+	// derivation.
+	CoinTypeBitcoin uint32 = 0
 
+	// CoinTypeTestnet specifies the BIP44 coin type for all testnet key
+	// derivation.
+	CoinTypeTestnet = 1
+
+	// CoinTypeLitecoin specifies the BIP44 coin type for Litecoin key
+	// derivation.
+	CoinTypeLitecoin = 2
+)
+
+var (
 	// lightningAddrSchema is the scope addr schema for all keys that we
 	// derive. We'll treat them all as p2wkh addresses, as atm we must
 	// specify a particular type.
@@ -44,6 +50,10 @@ type BtcWalletKeyRing struct {
 	// transactions in order to derive addresses and lookup relevant keys
 	wallet *wallet.Wallet
 
+	// chainKeyScope defines the purpose and coin type to be used when generating
+	// keys for this keyring.
+	chainKeyScope waddrmgr.KeyScope
+
 	// lightningScope is a pointer to the scope that we'll be using as a
 	// sub key manager to derive all the keys that we require.
 	lightningScope *waddrmgr.ScopedKeyManager
@@ -54,9 +64,18 @@ type BtcWalletKeyRing struct {
 //
 // NOTE: The passed waddrmgr.Manager MUST be unlocked in order for the keychain
 // to function.
-func NewBtcWalletKeyRing(w *wallet.Wallet) SecretKeyRing {
+func NewBtcWalletKeyRing(w *wallet.Wallet, coinType uint32) SecretKeyRing {
+	// Construct the key scope that will be used within the waddrmgr to
+	// create an HD chain for deriving all of our required keys. A different
+	// scope is used for each specific coin type.
+	chainKeyScope := waddrmgr.KeyScope{
+		Purpose: BIP0043Purpose,
+		Coin:    coinType,
+	}
+
 	return &BtcWalletKeyRing{
-		wallet: w,
+		wallet:        w,
+		chainKeyScope: chainKeyScope,
 	}
 }
 
@@ -80,9 +99,7 @@ func (b *BtcWalletKeyRing) keyScope() (*waddrmgr.ScopedKeyManager, error) {
 
 	// If the manager is indeed unlocked, then we'll fetch the scope, cache
 	// it, and return to the caller.
-	lnScope, err := b.wallet.Manager.FetchScopedKeyManager(
-		lightningKeyScope,
-	)
+	lnScope, err := b.wallet.Manager.FetchScopedKeyManager(b.chainKeyScope)
 	if err != nil {
 		return nil, err
 	}