1// Copyright (c) The Bitcoin Core developers
2// Distributed under the MIT software license, see the accompanying
3// file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5#ifndef BITCOIN_INDEX_TXOSPENDERINDEX_H
6#define BITCOIN_INDEX_TXOSPENDERINDEX_H
7
8#include <index/base.h>
9#include <interfaces/chain.h>
10#include <primitives/transaction.h>
11#include <uint256.h>
12#include <util/expected.h>
13
14#include <cstddef>
15#include <cstdint>
16#include <memory>
17#include <optional>
18#include <string>
19#include <utility>
20#include <vector>
21
22struct CDiskTxPos;
23
24inline constexpr bool DEFAULT_TXOSPENDERINDEX{false};
25
26struct TxoSpender {
27    CTransactionRef tx;
28    uint256 block_hash;
29};
30
31/**
32 * TxoSpenderIndex is used to look up which transaction spent a given output.
33 * The index is written to a LevelDB database and, for each input of each transaction in a block,
34 * records the outpoint that is spent and the hash of the spending transaction.
35 */
36class TxoSpenderIndex final : public BaseIndex
37{
38private:
39    std::unique_ptr<BaseIndex::DB> m_db;
40    std::pair<uint64_t, uint64_t> m_siphash_key;
41    bool AllowPrune() const override { return false; }
42    void WriteSpenderInfos(const std::vector<std::pair<COutPoint, CDiskTxPos>>& items);
43    void EraseSpenderInfos(const std::vector<std::pair<COutPoint, CDiskTxPos>>& items);
44    util::Expected<TxoSpender, std::string> ReadTransaction(const CDiskTxPos& pos) const;
45
46protected:
47    interfaces::Chain::NotifyOptions CustomOptions() override;
48
49    bool CustomAppend(const interfaces::BlockInfo& block) override;
50
51    bool CustomRemove(const interfaces::BlockInfo& block) override;
52
53    BaseIndex::DB& GetDB() const override;
54
55public:
56    explicit TxoSpenderIndex(std::unique_ptr<interfaces::Chain> chain, size_t n_cache_size, bool f_memory = false, bool f_wipe = false);
57
58    /**
59     * Search the index for a transaction that spends the given outpoint.
60     *
61     * @param[in] txo  The outpoint to search for.
62     *
63     * @return  std::nullopt               if the outpoint has not been spent on-chain.
64     *          std::optional{TxoSpender}  if the output has been spent on-chain. Contains the spending transaction
65     *                                     and the block it was confirmed in.
66     *          util::Unexpected{error}    if something unexpected happened (i.e. disk or deserialization error).
67     */
68    util::Expected<std::optional<TxoSpender>, std::string> FindSpender(const COutPoint& txo) const;
69};
70
71/// The global txo spender index. May be null.
72extern std::unique_ptr<TxoSpenderIndex> g_txospenderindex;
73
74
75#endif // BITCOIN_INDEX_TXOSPENDERINDEX_H
76