From 6f1a54cd1689925a8bcae3f55eaef2a640b4d270 Mon Sep 17 00:00:00 2001
From: Jack Grigg <jack@z.cash>
Date: Tue, 29 Jun 2021 19:49:00 +0100
Subject: [PATCH] Introduce libzcash::RawAddress type

Currently, `libzcash::PaymentAddress` serves two purposes: it represents
the result of parsing a string encoding provided by a user, and it holds
the possible shielded protocol addresses that can be used in transaction
outputs. In order to add support for Unified Addresses, we split these
purposes across two separate types.

We also add two new visitors to enable converting between these types:

- `RecipientForPaymentAddress` returns the "preferred protocol address"
  that should be used in transaction outputs, or `std::nullopt` if the
  payment address encoding was invalid.

- `GetRawAddresses` returns all protocol addresses contained within the
  given payment address, or an empty set if the payment address encoding
  was invalid.

For the existing address encodings, the implementations of these are
trivial.
---
 src/zcash/Address.cpp | 36 ++++++++++++++++++++++++++++++++++++
 src/zcash/Address.hpp | 28 ++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+)

diff --git a/src/zcash/Address.cpp b/src/zcash/Address.cpp
index 4c1fad1c7..40d4c4089 100644
--- a/src/zcash/Address.cpp
+++ b/src/zcash/Address.cpp
@@ -35,3 +35,39 @@ bool IsValidViewingKey(const libzcash::ViewingKey& vk) {
 bool IsValidSpendingKey(const libzcash::SpendingKey& zkey) {
     return !std::holds_alternative<libzcash::InvalidEncoding>(zkey);
 }
+
+std::optional<libzcash::RawAddress> RecipientForPaymentAddress::operator()(
+    const libzcash::InvalidEncoding& no) const
+{
+    return std::nullopt;
+}
+
+std::optional<libzcash::RawAddress> RecipientForPaymentAddress::operator()(
+    const libzcash::SproutPaymentAddress &zaddr) const
+{
+    return zaddr;
+}
+
+std::optional<libzcash::RawAddress> RecipientForPaymentAddress::operator()(
+    const libzcash::SaplingPaymentAddress &zaddr) const
+{
+    return zaddr;
+}
+
+std::set<libzcash::RawAddress> GetRawAddresses::operator()(
+    const libzcash::InvalidEncoding& no) const
+{
+    return {};
+}
+
+std::set<libzcash::RawAddress> GetRawAddresses::operator()(
+    const libzcash::SproutPaymentAddress &zaddr) const
+{
+    return {zaddr};
+}
+
+std::set<libzcash::RawAddress> GetRawAddresses::operator()(
+    const libzcash::SaplingPaymentAddress &zaddr) const
+{
+    return {zaddr};
+}
diff --git a/src/zcash/Address.hpp b/src/zcash/Address.hpp
index a8fbacac9..cb1edf082 100644
--- a/src/zcash/Address.hpp
+++ b/src/zcash/Address.hpp
@@ -8,12 +8,16 @@
 #include <variant>
 
 namespace libzcash {
+/** Protocol addresses that can receive funds in a transaction. */
+typedef std::variant<SproutPaymentAddress, SaplingPaymentAddress> RawAddress;
+
 class InvalidEncoding {
 public:
     friend bool operator==(const InvalidEncoding &a, const InvalidEncoding &b) { return true; }
     friend bool operator<(const InvalidEncoding &a, const InvalidEncoding &b) { return true; }
 };
 
+/** Addresses that can appear in a string encoding. */
 typedef std::variant<InvalidEncoding, SproutPaymentAddress, SaplingPaymentAddress> PaymentAddress;
 typedef std::variant<InvalidEncoding, SproutViewingKey, SaplingExtendedFullViewingKey> ViewingKey;
 typedef std::variant<InvalidEncoding, SproutSpendingKey, SaplingExtendedSpendingKey> SpendingKey;
@@ -43,4 +47,28 @@ bool IsValidViewingKey(const libzcash::ViewingKey& vk);
 /** Check whether a SpendingKey is not an InvalidEncoding. */
 bool IsValidSpendingKey(const libzcash::SpendingKey& zkey);
 
+/**
+ * Returns the protocol address that should be used in transaction outputs.
+ */
+class RecipientForPaymentAddress {
+public:
+    RecipientForPaymentAddress() {}
+
+    std::optional<libzcash::RawAddress> operator()(const libzcash::InvalidEncoding& no) const;
+    std::optional<libzcash::RawAddress> operator()(const libzcash::SproutPaymentAddress &zaddr) const;
+    std::optional<libzcash::RawAddress> operator()(const libzcash::SaplingPaymentAddress &zaddr) const;
+};
+
+/**
+ * Returns all protocol addresses contained within the given payment address.
+ */
+class GetRawAddresses {
+public:
+    GetRawAddresses() {}
+
+    std::set<libzcash::RawAddress> operator()(const libzcash::InvalidEncoding& no) const;
+    std::set<libzcash::RawAddress> operator()(const libzcash::SproutPaymentAddress &zaddr) const;
+    std::set<libzcash::RawAddress> operator()(const libzcash::SaplingPaymentAddress &zaddr) const;
+};
+
 #endif // ZC_ADDRESS_H_