Implement SetupGeneration for DescriptorScriptPubKeyMan

Summary:
Backport of Core [[bitcoin/bitcoin#16528 | PR16528]] [20/43] : bitcoin/bitcoin@e014886

Depends on D8417

Test Plan:
  ninja all check-all

Reviewers: #bitcoin_abc, PiRK, majcosta

Reviewed By: #bitcoin_abc, PiRK, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8418

src/wallet/scriptpubkeyman.cpp

@@ -2,6 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <chainparams.h>
 #include <config.h>
 #include <key_io.h>
 #include <outputtype.h>
@@ -1600,6 +1601,69 @@ bool DescriptorScriptPubKeyMan::AddDescriptorKeyWithDB(WalletBatch &batch,
     }
 }
 
+bool DescriptorScriptPubKeyMan::SetupDescriptorGeneration(
+    const CExtKey &master_key) {
+    LOCK(cs_desc_man);
+    assert(m_storage.IsWalletFlagSet(WALLET_FLAG_DESCRIPTORS));
+
+    // Ignore when there is already a descriptor
+    if (m_wallet_descriptor.descriptor) {
+        return false;
+    }
+
+    int64_t creation_time = GetTime();
+
+    std::string xpub = EncodeExtPubKey(master_key.Neuter());
+
+    // Build descriptor string
+    std::string desc_prefix;
+    std::string desc_suffix = "/*)";
+    switch (m_address_type) {
+        case OutputType::LEGACY: {
+            desc_prefix = "pkh(" + xpub + "/44'";
+            break;
+        }
+        default:
+            assert(false);
+    }
+
+    // Mainnet derives at 0', testnet and regtest derive at 1'
+    if (m_storage.GetChainParams().IsTestChain()) {
+        desc_prefix += "/1'";
+    } else {
+        desc_prefix += "/0'";
+    }
+
+    std::string internal_path = m_internal ? "/1" : "/0";
+    std::string desc_str = desc_prefix + "/0'" + internal_path + desc_suffix;
+
+    // Make the descriptor
+    FlatSigningProvider keys;
+    std::string error;
+    std::unique_ptr<Descriptor> desc = Parse(desc_str, keys, error, false);
+    WalletDescriptor w_desc(std::move(desc), creation_time, 0, 0, 0);
+    m_wallet_descriptor = w_desc;
+
+    // Store the master private key, and descriptor
+    WalletBatch batch(m_storage.GetDatabase());
+    if (!AddDescriptorKeyWithDB(batch, master_key.key,
+                                master_key.key.GetPubKey())) {
+        throw std::runtime_error(
+            std::string(__func__) +
+            ": writing descriptor master private key failed");
+    }
+    if (!batch.WriteDescriptor(GetID(), m_wallet_descriptor)) {
+        throw std::runtime_error(std::string(__func__) +
+                                 ": writing descriptor failed");
+    }
+
+    // TopUp
+    TopUp();
+
+    m_storage.UnsetBlankWalletFlag(batch);
+    return true;
+}
+
 bool DescriptorScriptPubKeyMan::IsHDEnabled() const {
     LOCK(cs_desc_man);
     return m_wallet_descriptor.descriptor->IsRange();

src/wallet/scriptpubkeyman.h

@@ -19,6 +19,7 @@
 #include <boost/signals2/signal.hpp>
 
 enum class OutputType;
+class CChainParams;
 struct bilingual_str;
 
 // Wallet storage things that ScriptPubKeyMans need in order to be able to store
@@ -33,6 +34,7 @@ class WalletStorage {
     virtual ~WalletStorage() = default;
     virtual const std::string GetDisplayName() const = 0;
     virtual WalletDatabase &GetDatabase() = 0;
+    virtual const CChainParams &GetChainParams() const = 0;
     virtual bool IsWalletFlagSet(uint64_t) const = 0;
     virtual void UnsetBlankWalletFlag(WalletBatch &) = 0;
     virtual bool CanSupportFeature(enum WalletFeature) const = 0;
@@ -675,6 +677,9 @@ class DescriptorScriptPubKeyMan : public ScriptPubKeyMan {
 
     bool IsHDEnabled() const override;
 
+    //! Setup descriptors based on the given CExtkey
+    bool SetupDescriptorGeneration(const CExtKey &master_key);
+
     bool HavePrivateKeys() const override;
 
     int64_t GetOldestKeyPoolTime() const override;

src/wallet/wallet.h

@@ -862,6 +862,9 @@ class CWallet final : public WalletStorage,
         assert(NotifyUnload.empty());
     }
 
+    /* Returns the chain params used by this wallet. */
+    const CChainParams &GetChainParams() const override { return chainParams; }
+
     bool IsCrypted() const;
     bool IsLocked() const override;
     bool Lock();