ObsidianDragon/src/data/transaction_history_cache.h

#pragma once

#include "wallet_state.h"

#include <array>
#include <cstdint>
#include <ctime>
#include <mutex>
#include <string>
#include <unordered_map>
#include <vector>

struct sqlite3;

namespace dragonx {
namespace data {

class TransactionHistoryCache {
public:
    struct LoadResult {
        bool loaded = false;
        bool invalidated = false;
        int tipHeight = 0;
        std::string tipHash;
        std::time_t updatedAt = 0;
        std::vector<TransactionInfo> transactions;
        std::unordered_map<std::string, int> shieldedScanHeights;
    };

    // Everything one snapshot write needs, BY VALUE, so it can run on the history writer thread after the UI
    // state it came from has moved on (and after lockKey() zeroed the live key). Move-only; the private key
    // copy is wiped by writeSnapshot() and, for a job that never ran (superseded), by the destructor.
    struct SnapshotJob {
        std::string walletIdentity;
        std::array<unsigned char, 32> key{};
        int tipHeight = 0;
        std::string tipHash;
        std::vector<TransactionInfo> transactions;
        std::time_t updatedAt = 0;
        std::unordered_map<std::string, int> shieldedScanHeights;

        SnapshotJob() = default;
        SnapshotJob(const SnapshotJob&) = delete;
        SnapshotJob& operator=(const SnapshotJob&) = delete;
        SnapshotJob(SnapshotJob&&) = default;
        SnapshotJob& operator=(SnapshotJob&&) = default;
        ~SnapshotJob();
    };

    TransactionHistoryCache();
    explicit TransactionHistoryCache(std::string databasePath);
    ~TransactionHistoryCache();

    TransactionHistoryCache(const TransactionHistoryCache&) = delete;
    TransactionHistoryCache& operator=(const TransactionHistoryCache&) = delete;

    static std::string defaultDatabasePath();
    static std::string walletIdentityFromAddresses(const std::vector<std::string>& shieldedAddresses,
                                                   const std::vector<std::string>& transparentAddresses);
    static std::string walletIdentityHash(const std::string& walletIdentity);

    bool ensureOpen();
    bool unlockWithPassphrase(const std::string& walletIdentity, const std::string& passphrase);
    // Unlock an UNENCRYPTED wallet's cache without Argon2id: the "secret" is derivable from the DB, so a
    // cheap domain-separated BLAKE2b KDF is security-equivalent and avoids a ~50-100 ms UI-thread stall.
    bool unlockUnencrypted(const std::string& walletIdentity);
    void lockKey();
    bool hasKey() const;
    bool isUnlockedFor(const std::string& walletIdentity) const;
    // Copy of the live key if it is unlocked for `walletIdentity` (keyOut untouched otherwise). Caller wipes it.
    bool captureKey(const std::string& walletIdentity, std::array<unsigned char, 32>& keyOut) const;
    // Non-reversible id of the key last installed. Survives lockKey(), so re-unlocking with the same
    // passphrase gives the same id and a passphrase change gives another. 0 = never unlocked.
    std::uint64_t keyId() const;

    LoadResult load(const std::string& walletIdentity,
                    int currentTipHeight,
                    const std::string& currentTipHash);
    bool replace(const std::string& walletIdentity,
                 int tipHeight,
                 const std::string& tipHash,
                 const std::vector<TransactionInfo>& transactions,
                 std::time_t updatedAt,
                 const std::unordered_map<std::string, int>& shieldedScanHeights = {});
    // Thread-safe snapshot write (the history writer thread; replace() wraps it): JSON + AEAD with no lock
    // held, then INSERT OR REPLACE + prune under the DB lock. Always wipes job.key. False for a keyless job.
    bool writeSnapshot(SnapshotJob&& job);
    void clearWallet(const std::string& walletIdentity);
    int snapshotCount();

private:
    bool exec(const char* sql);
    bool createSchema();
    std::vector<unsigned char> getOrCreateSalt(const std::string& walletHash);
    static bool deriveKeyFast(const std::string& walletHash,
                              const std::vector<unsigned char>& salt,
                              std::array<unsigned char, 32>& keyOut);   // BLAKE2b, label-separated
    static bool deriveKey(const std::string& passphrase,
                          const std::vector<unsigned char>& salt,
                          std::array<unsigned char, 32>& keyOut);
    static bool encryptPayload(const std::array<unsigned char, 32>& key,
                               const std::string& walletHash,
                               const std::string& plainText,
                               std::vector<unsigned char>& nonce,
                               std::vector<unsigned char>& cipherText);
    bool decryptPayload(const std::string& walletHash,
                        const std::vector<unsigned char>& nonce,
                        const std::vector<unsigned char>& cipherText,
                        std::string& plainText) const;
    bool readSnapshot(const std::string& walletHash,
                      int& tipHeight,
                      std::string& tipHash,
                      std::time_t& updatedAt,
                      std::vector<unsigned char>& nonce,
                      std::vector<unsigned char>& cipherText);
    void clearWalletByHash(const std::string& walletHash);
    // Delete snapshot + salt rows for every wallet hash except the live one, bounding the
    // DB so generating a new address (which changes the hash) doesn't orphan history forever.
    // Also keeps `alsoKeepWalletHash` (the wallet unlocked now, if any): a delayed writer job for the previous
    // wallet must not delete the salt of the wallet just switched to.
    void pruneOtherWallets(const std::string& keepWalletHash, const std::string& alsoKeepWalletHash);
    void close();

    // Lock order: db_mutex_ then key_mutex_. key_mutex_ is never held across I/O or the KDF. Only the UI
    // thread changes the key fields; the writer thread reads unlocked_wallet_hash_ (prune) under both locks.
    mutable std::recursive_mutex db_mutex_;   // db_ and every SQL statement
    mutable std::mutex key_mutex_;            // key_, key_ready_, unlocked_wallet_hash_, key_id_
    sqlite3* db_ = nullptr;
    std::string database_path_;
    std::array<unsigned char, 32> key_{};
    bool key_ready_ = false;
    std::string unlocked_wallet_hash_;
    std::uint64_t key_id_ = 0;
};

} // namespace data
} // namespace dragonx