wallet: feature: transfer amount with fee included

To transfer ~5 XMR to an address such that your balance drops by exactly 5 XMR, provide a `subtractfeefrom` flag to the `transfer` command. For example:

    transfer 76bDHojqFYiFCCYYtzTveJ8oFtmpNp3X1TgV2oKP7rHmZyFK1RvyE4r8vsJzf7SyNohMnbKT9wbcD3XUTgsZLX8LU5JBCfm 5 subtractfeefrom=all

If my walet balance was exactly 30 XMR before this transaction, it will be exactly 25 XMR afterwards and the destination address will receive slightly
less than 5 XMR. You can manually select which destinations fund the transaction fee and which ones do not by providing the destination index.
For example:

    transfer 75sr8AAr... 3 74M7W4eg... 4 7AbWqDZ6... 5 subtractfeefrom=0,2

This will drop your balance by exactly 12 XMR including fees and will spread the fee cost proportionally (3:5 ratio) over destinations with addresses
`75sr8AAr...` and `7AbWqDZ6...`, respectively.

Disclaimer: This feature was paid for by @LocalMonero.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/wallet/wallet2.h b/src/wallet/wallet2.h
index 877e5afd0..9dcece0af 100644
--- a/src/wallet/wallet2.h
+++ b/src/wallet/wallet2.h
@@ -598,6 +598,7 @@ private:
 
     typedef std::vector<transfer_details> transfer_container;
     typedef serializable_unordered_multimap<crypto::hash, payment_details> payment_container;
+    typedef std::set<uint32_t> unique_index_container;
 
     struct multisig_sig
     {
@@ -1111,11 +1112,11 @@ private:
     bool parse_unsigned_tx_from_str(const std::string &unsigned_tx_st, unsigned_tx_set &exported_txs) const;
     bool load_tx(const std::string &signed_filename, std::vector<tools::wallet2::pending_tx> &ptx, std::function<bool(const signed_tx_set&)> accept_func = NULL);
     bool parse_tx_from_str(const std::string &signed_tx_st, std::vector<tools::wallet2::pending_tx> &ptx, std::function<bool(const signed_tx_set &)> accept_func);
-    std::vector<wallet2::pending_tx> create_transactions_2(std::vector<cryptonote::tx_destination_entry> dsts, const size_t fake_outs_count, const uint64_t unlock_time, uint32_t priority, const std::vector<uint8_t>& extra, uint32_t subaddr_account, std::set<uint32_t> subaddr_indices);     // pass subaddr_indices by value on purpose
+    std::vector<wallet2::pending_tx> create_transactions_2(std::vector<cryptonote::tx_destination_entry> dsts, const size_t fake_outs_count, const uint64_t unlock_time, uint32_t priority, const std::vector<uint8_t>& extra, uint32_t subaddr_account, std::set<uint32_t> subaddr_indices, const unique_index_container& subtract_fee_from_outputs = {});     // pass subaddr_indices by value on purpose
     std::vector<wallet2::pending_tx> create_transactions_all(uint64_t below, const cryptonote::account_public_address &address, bool is_subaddress, const size_t outputs, const size_t fake_outs_count, const uint64_t unlock_time, uint32_t priority, const std::vector<uint8_t>& extra, uint32_t subaddr_account, std::set<uint32_t> subaddr_indices);
     std::vector<wallet2::pending_tx> create_transactions_single(const crypto::key_image &ki, const cryptonote::account_public_address &address, bool is_subaddress, const size_t outputs, const size_t fake_outs_count, const uint64_t unlock_time, uint32_t priority, const std::vector<uint8_t>& extra);
     std::vector<wallet2::pending_tx> create_transactions_from(const cryptonote::account_public_address &address, bool is_subaddress, const size_t outputs, std::vector<size_t> unused_transfers_indices, std::vector<size_t> unused_dust_indices, const size_t fake_outs_count, const uint64_t unlock_time, uint32_t priority, const std::vector<uint8_t>& extra);
-    bool sanity_check(const std::vector<wallet2::pending_tx> &ptx_vector, std::vector<cryptonote::tx_destination_entry> dsts) const;
+    bool sanity_check(const std::vector<wallet2::pending_tx> &ptx_vector, const std::vector<cryptonote::tx_destination_entry>& dsts, const unique_index_container& subtract_fee_from_outputs = {}) const;
     void cold_tx_aux_import(const std::vector<pending_tx>& ptx, const std::vector<std::string>& tx_device_aux);
     void cold_sign_tx(const std::vector<pending_tx>& ptx_vector, signed_tx_set &exported_txs, std::vector<cryptonote::address_parse_info> &dsts_info, std::vector<std::string> & tx_device_aux);
     uint64_t cold_key_image_sync(uint64_t &spent, uint64_t &unspent);