Merge #15638: Move-only: Pull wallet code out of libbitcoin_server

4d074e84a2cf419510e2920417799f62747f4b07 [build] Move AnalyzePSBT from psbt.cpp to node/psbt.cpp (Russell Yanofsky)
fd509bd1f71df628b933ea7a135a9a957a5e0136 [docs] Document src subdirectories and different libraries (John Newbery)
9eaeb7fb8d4ab0d4493849e6c17e314fd75fea9c [build] Move wallet load functions to wallet/load unit (John Newbery)
91a25d1e711bfc0617027eee18b9777ff368d6b9 [build] Add several util units (John Newbery)
99517866b62c261f990e1f897502855afc12f2a7 [build] Move several units into common libraries (John Newbery)
0509465542d63a5bbe7296f283f44dd491e74f78 [build] Move rpc rawtransaction util functions to rpc/rawtransaction_util.cpp (John Newbery)
1acc61f8746bc6efb905e121a9f607c4f5982b35 [build] Move rpc utility methods to rpc/util (John Newbery)
4a75c9d6512a5580e60104103ea11d2cd9586354 [build] Move policy settings to new src/policy/settings unit (John Newbery)
fdf8888b6f0c63e8a4cb1459752625e642d6a4dd [build] Move CheckTransaction from lib_server to lib_consensus (John Newbery)

Pull request description:

  This is a move-only commit. No code is changing and the moves can be easily verified with:

  ```sh
  git log -p -n1 --color-moved=dimmed_zebra
  ```

  This commit moves functions and variables that wallet code depends on out of libbitcoin_server.a, so the bitcoin-wallet tool can be built without libbitcoin_server.a in #15639, and attempting to access server state from wallet code will result in link errors instead of silently broken code.

  List of moves:

  - `CheckTransaction` moves from `consensus/tx_verify.cpp` to `consensus/tx_check.cpp`
  - `urlDecode` moves from `httpserver.cpp` to `util/url.cpp`
  - `TransactionErrorString` moves from `node/transaction.cpp` to `util/error.cpp`
  - `StringForFeeReason` and `FeeModeFromString` move from `policy/fees.cpp` to `util/fees.cpp`
  - `incrementalRelayFee` `dustRelayFee` and `nBytesPerSigOp` move from `policy/policy.cpp` to `policy/settings.cpp`
  - `SignalsOptInRBF` moves from `policy/rbf.cpp` to `util/rbf.cpp`
  - `fIsBareMultisigStd` moves from `validation.cpp` to `policy/settings.cpp`
  - `ConstructTransaction` `TxInErrorToJSON` and `SignTransaction` move from `rpc/rawtransaction.cpp` to `rpc/rawtransaction_util.cpp`
  - `RPCTypeCheck` `RPCTypeCheckArgument` `RPCTypeCheckObj` `AmountFromValue` `ParseHashV``ParseHashO` `ParseHexV` `ParseHexO` `HelpExampleCli` and `HelpExampleRpc` move from `rpc/server.cpp` to `rpc/util.cpp`
  - `AmountHighWarn` and `AmountErrMsg` move from `ui_interface.cpp` to `util/error.cpp`
  - `FormatStateMessage` and `strMessageMagic` move from `validation.cpp` to `util/validation.cpp`
  - `VerifyWallets` `LoadWallets` `StartWallets` `FlushWallets` `StopWallets` and `UnloadWallets` move from `wallet/init.cpp` to `wallet/node.cpp`

ACKs for commit 4d074e:
  jnewbery:
    utACK 4d074e84a2cf419510e2920417799f62747f4b07 (checked by doing the rebase myself and verifying no difference between my branch and 4d074e84a2cf419510e2920417799f62747f4b07)

Tree-SHA512: 5e1604a9fb06475f2b96da0de0baa8330f4dda834dc20a0183ef11e1e4c27631d1d1bbb9abf0054efc03d56945fdf9920f63366b6a4f200f665b742a479ff75c

5 files changed, 201 insertions, 40 deletions

diff --git a/src/node/README.md b/src/node/README.md
new file mode 100644
index 000000000..e99a71753
--- /dev/null
+++ b/src/node/README.md
@@ -0,0 +1,22 @@
+# src/node/
+
+The [`src/node/`](./) directory contains code that needs to access node state
+(state in `CChain`, `CBlockIndex`, `CCoinsView`, `CTxMemPool`, and similar
+classes).
+
+Code in [`src/node/`](./) is meant to be segregated from code in
+[`src/wallet/`](../wallet/) and [`src/qt/`](../qt/), to ensure wallet and GUI
+code changes don't interfere with node operation, to allow wallet and GUI code
+to run in separate processes, and to perhaps eventually allow wallet and GUI
+code to be maintained in separate source repositories.
+
+As a rule of thumb, code in one of the [`src/node/`](./),
+[`src/wallet/`](../wallet/), or [`src/qt/`](../qt/) directories should avoid
+calling code in the other directories directly, and only invoke it indirectly
+through the more limited [`src/interfaces/`](../interfaces/) classes.
+
+The [`src/node/`](./) directory is a new directory introduced in
+[#14978](https://github.com/bitcoin/bitcoin/pull/14978) and at the moment is
+sparsely populated. Eventually more substantial files like
+[`src/validation.cpp`](../validation.cpp) and
+[`src/txmempool.cpp`](../txmempool.cpp) might be moved there.
diff --git a/src/node/psbt.cpp b/src/node/psbt.cpp
new file mode 100644
index 000000000..12559c5a5
--- /dev/null
+++ b/src/node/psbt.cpp
@@ -0,0 +1,134 @@
+// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <coins.h>
+#include <consensus/tx_verify.h>
+#include <node/psbt.h>
+#include <policy/policy.h>
+#include <policy/settings.h>
+
+#include <numeric>
+
+PSBTAnalysis AnalyzePSBT(PartiallySignedTransaction psbtx)
+{
+    // Go through each input and build status
+    PSBTAnalysis result;
+
+    bool calc_fee = true;
+    bool all_final = true;
+    bool only_missing_sigs = true;
+    bool only_missing_final = false;
+    CAmount in_amt = 0;
+
+    result.inputs.resize(psbtx.tx->vin.size());
+
+    for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
+        PSBTInput& input = psbtx.inputs[i];
+        PSBTInputAnalysis& input_analysis = result.inputs[i];
+
+        // Check for a UTXO
+        CTxOut utxo;
+        if (psbtx.GetInputUTXO(utxo, i)) {
+            in_amt += utxo.nValue;
+            input_analysis.has_utxo = true;
+        } else {
+            input_analysis.has_utxo = false;
+            input_analysis.is_final = false;
+            input_analysis.next = PSBTRole::UPDATER;
+            calc_fee = false;
+        }
+
+        // Check if it is final
+        if (!utxo.IsNull() && !PSBTInputSigned(input)) {
+            input_analysis.is_final = false;
+            all_final = false;
+
+            // Figure out what is missing
+            SignatureData outdata;
+            bool complete = SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, 1, &outdata);
+
+            // Things are missing
+            if (!complete) {
+                input_analysis.missing_pubkeys = outdata.missing_pubkeys;
+                input_analysis.missing_redeem_script = outdata.missing_redeem_script;
+                input_analysis.missing_witness_script = outdata.missing_witness_script;
+                input_analysis.missing_sigs = outdata.missing_sigs;
+
+                // If we are only missing signatures and nothing else, then next is signer
+                if (outdata.missing_pubkeys.empty() && outdata.missing_redeem_script.IsNull() && outdata.missing_witness_script.IsNull() && !outdata.missing_sigs.empty()) {
+                    input_analysis.next = PSBTRole::SIGNER;
+                } else {
+                    only_missing_sigs = false;
+                    input_analysis.next = PSBTRole::UPDATER;
+                }
+            } else {
+                only_missing_final = true;
+                input_analysis.next = PSBTRole::FINALIZER;
+            }
+        } else if (!utxo.IsNull()){
+            input_analysis.is_final = true;
+        }
+    }
+
+    if (all_final) {
+        only_missing_sigs = false;
+        result.next = PSBTRole::EXTRACTOR;
+    }
+    if (calc_fee) {
+        // Get the output amount
+        CAmount out_amt = std::accumulate(psbtx.tx->vout.begin(), psbtx.tx->vout.end(), CAmount(0),
+            [](CAmount a, const CTxOut& b) {
+                return a += b.nValue;
+            }
+        );
+
+        // Get the fee
+        CAmount fee = in_amt - out_amt;
+        result.fee = fee;
+
+        // Estimate the size
+        CMutableTransaction mtx(*psbtx.tx);
+        CCoinsView view_dummy;
+        CCoinsViewCache view(&view_dummy);
+        bool success = true;
+
+        for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
+            PSBTInput& input = psbtx.inputs[i];
+            Coin newcoin;
+
+            if (!SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, 1, nullptr, true) || !psbtx.GetInputUTXO(newcoin.out, i)) {
+                success = false;
+                break;
+            } else {
+                mtx.vin[i].scriptSig = input.final_script_sig;
+                mtx.vin[i].scriptWitness = input.final_script_witness;
+                newcoin.nHeight = 1;
+                view.AddCoin(psbtx.tx->vin[i].prevout, std::move(newcoin), true);
+            }
+        }
+
+        if (success) {
+            CTransaction ctx = CTransaction(mtx);
+            size_t size = GetVirtualTransactionSize(ctx, GetTransactionSigOpCost(ctx, view, STANDARD_SCRIPT_VERIFY_FLAGS));
+            result.estimated_vsize = size;
+            // Estimate fee rate
+            CFeeRate feerate(fee, size);
+            result.estimated_feerate = feerate;
+        }
+
+        if (only_missing_sigs) {
+            result.next = PSBTRole::SIGNER;
+        } else if (only_missing_final) {
+            result.next = PSBTRole::FINALIZER;
+        } else if (all_final) {
+            result.next = PSBTRole::EXTRACTOR;
+        } else {
+            result.next = PSBTRole::UPDATER;
+        }
+    } else {
+        result.next = PSBTRole::UPDATER;
+    }
+
+    return result;
+}
diff --git a/src/node/psbt.h b/src/node/psbt.h
new file mode 100644
index 000000000..e04366a20
--- /dev/null
+++ b/src/node/psbt.h
@@ -0,0 +1,43 @@
+// Copyright (c) 2009-2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_NODE_PSBT_H
+#define BITCOIN_NODE_PSBT_H
+
+#include <psbt.h>
+
+/**
+ * Holds an analysis of one input from a PSBT
+ */
+struct PSBTInputAnalysis {
+    bool has_utxo; //!< Whether we have UTXO information for this input
+    bool is_final; //!< Whether the input has all required information including signatures
+    PSBTRole next; //!< Which of the BIP 174 roles needs to handle this input next
+
+    std::vector<CKeyID> missing_pubkeys; //!< Pubkeys whose BIP32 derivation path is missing
+    std::vector<CKeyID> missing_sigs;    //!< Pubkeys whose signatures are missing
+    uint160 missing_redeem_script;       //!< Hash160 of redeem script, if missing
+    uint256 missing_witness_script;      //!< SHA256 of witness script, if missing
+};
+
+/**
+ * Holds the results of AnalyzePSBT (miscellaneous information about a PSBT)
+ */
+struct PSBTAnalysis {
+    Optional<size_t> estimated_vsize;      //!< Estimated weight of the transaction
+    Optional<CFeeRate> estimated_feerate;  //!< Estimated feerate (fee / weight) of the transaction
+    Optional<CAmount> fee;                 //!< Amount of fee being paid by the transaction
+    std::vector<PSBTInputAnalysis> inputs; //!< More information about the individual inputs of the transaction
+    PSBTRole next;                         //!< Which of the BIP 174 roles needs to handle the transaction next
+};
+
+/**
+ * Provides helpful miscellaneous information about where a PSBT is in the signing workflow.
+ *
+ * @param[in] psbtx the PSBT to analyze
+ * @return A PSBTAnalysis with information about the provided PSBT.
+ */
+PSBTAnalysis AnalyzePSBT(PartiallySignedTransaction psbtx);
+
+#endif // BITCOIN_NODE_PSBT_H
diff --git a/src/node/transaction.cpp b/src/node/transaction.cpp
index 7b9b4310e..5ffb15ed3 100644
--- a/src/node/transaction.cpp
+++ b/src/node/transaction.cpp
@@ -6,38 +6,13 @@
 #include <consensus/validation.h>
 #include <net.h>
 #include <txmempool.h>
+#include <util/validation.h>
 #include <validation.h>
 #include <validationinterface.h>
 #include <node/transaction.h>
 
 #include <future>
 
-std::string TransactionErrorString(const TransactionError err)
-{
-    switch (err) {
-        case TransactionError::OK:
-            return "No error";
-        case TransactionError::MISSING_INPUTS:
-            return "Missing inputs";
-        case TransactionError::ALREADY_IN_CHAIN:
-            return "Transaction already in block chain";
-        case TransactionError::P2P_DISABLED:
-            return "Peer-to-peer functionality missing or disabled";
-        case TransactionError::MEMPOOL_REJECTED:
-            return "Transaction rejected by AcceptToMemoryPool";
-        case TransactionError::MEMPOOL_ERROR:
-            return "AcceptToMemoryPool failed";
-        case TransactionError::INVALID_PSBT:
-            return "PSBT is not sane";
-        case TransactionError::PSBT_MISMATCH:
-            return "PSBTs not compatible (different transactions)";
-        case TransactionError::SIGHASH_MISMATCH:
-            return "Specified sighash value does not match existing value";
-        // no default case, so the compiler can warn about missing cases
-    }
-    assert(false);
-}
-
 TransactionError BroadcastTransaction(const CTransactionRef tx, uint256& hashTx, std::string& err_string, const CAmount& highfee)
 {
     std::promise<void> promise;
diff --git a/src/node/transaction.h b/src/node/transaction.h
index 3457ececa..51033f94e 100644
--- a/src/node/transaction.h
+++ b/src/node/transaction.h
@@ -8,20 +8,7 @@
 #include <attributes.h>
 #include <primitives/transaction.h>
 #include <uint256.h>
-
-enum class TransactionError {
-    OK, //!< No error
-    MISSING_INPUTS,
-    ALREADY_IN_CHAIN,
-    P2P_DISABLED,
-    MEMPOOL_REJECTED,
-    MEMPOOL_ERROR,
-    INVALID_PSBT,
-    PSBT_MISMATCH,
-    SIGHASH_MISMATCH,
-};
-
-std::string TransactionErrorString(const TransactionError error);
+#include <util/error.h>
 
 /**
  * Broadcast a transaction