// Copyright (c) 2023 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_KERNEL_NOTIFICATIONS_INTERFACE_H

#define BITCOIN_KERNEL_NOTIFICATIONS_INTERFACE_H

#include <cstdint>

#include <variant>

class CBlockIndex;

enum class SynchronizationState;

struct bilingual_str;

namespace kernel {

//! Result type for use with std::variant to indicate that an operation should be interrupted.

struct Interrupted{};

enum class Warning;

//! Simple result type for functions that need to propagate an interrupt status and don't have other return values.

using InterruptResult = std::variant<std::monostate, Interrupted>;

template <typename T>

bool IsInterrupted(const T& result)

{

    return std::holds_alternative<kernel::Interrupted>(result);

}

/**

 * A base class defining functions for notifying about certain kernel

 * events.

 */

class Notifications

{

public:

    virtual ~Notifications() = default;

    [[nodiscard]] virtual InterruptResult blockTip(SynchronizationState state, CBlockIndex& index) { return {}; }

    virtual void headerTip(SynchronizationState state, int64_t height, int64_t timestamp, bool presync) {}

    virtual void progress(const bilingual_str& title, int progress_percent, bool resume_possible) {}

    virtual void warningSet(Warning id, const bilingual_str& message) {}

    virtual void warningUnset(Warning id) {}

    //! The flush error notification is sent to notify the user that an error

    //! occurred while flushing block data to disk. Kernel code may ignore flush

    //! errors that don't affect the immediate operation it is trying to

    //! perform. Applications can choose to handle the flush error notification

    //! by logging the error, or notifying the user, or triggering an early

    //! shutdown as a precaution against causing more errors.

    virtual void flushError(const bilingual_str& message) {}

    //! The fatal error notification is sent to notify the user when an error

    //! occurs in kernel code that can't be recovered from. After this

    //! notification is sent, whatever function triggered the error should also

    //! return an error code or raise an exception. Applications can choose to

    //! handle the fatal error notification by logging the error, or notifying

    //! the user, or triggering an early shutdown as a precaution against

    //! causing more errors.

    virtual void fatalError(const bilingual_str& message) {}

};

} // namespace kernel

#endif // BITCOIN_KERNEL_NOTIFICATIONS_INTERFACE_H