op-pedal/src/MidiMapper.hpp

// Copyright (c) 2026 Ourpad Network
// See LICENSE file in the project root for full license text.

#pragma once

#include <cstdint>
#include <string>
#include <vector>
#include <mutex>
#include <memory>

namespace pipedal {

class MixerEngine;
struct MidiEvent;

/// Types of mixer parameters that can be mapped from MIDI CC.
enum class MidiTargetType {
    ChannelVolume,  ///< Channel fader (-inf .. +12 dB)
    ChannelPan,     ///< Channel pan (-1 .. +1)
    ChannelMute,    ///< Channel mute toggle
    ChannelSolo,    ///< Channel solo toggle
    BusVolume,      ///< Bus fader (-inf .. +12 dB)
    BusMute,        ///< Bus mute toggle
    MasterVolume,   ///< Master bus volume
    MasterMute,     ///< Master bus mute
};

/// A single mapping entry: MIDI CC# + channel → mixer parameter.
struct MidiMappingEntry {
    int midiChannel = -1;   ///< MIDI channel (-1 = omni / any)
    int ccNumber = 0;       ///< MIDI CC number (0-127)
    MidiTargetType targetType = MidiTargetType::ChannelVolume;
    int64_t targetId = 0;   ///< channel index for Channel*, bus ID for Bus*

    /// Output range: CC=0 maps to minValue, CC=127 maps to maxValue.
    float minValue = 0.0f;
    float maxValue = 1.0f;

    /// Convert between enum and string (for JSON serialization).
    static MidiTargetType targetTypeFromString(const std::string& str);
    static const char* targetTypeToString(MidiTargetType type);
};

/// MIDI CC → mixer parameter mapper.
///
/// Receives MIDI CC events (0xB0) from the real-time audio thread and applies
/// them to the MixerEngine via atomic parameter setters.
///
/// The mapping table is configured from the non-real-time thread; a mutex
/// protects the table while the RT path snapshots the current mapping set.
class MidiMapper {
public:
    MidiMapper();
    ~MidiMapper();

    /// Set the mixer engine to control. Must be set before processing events.
    void setMixerEngine(MixerEngine* engine) { mixerEngine_ = engine; }

    /// Process a MIDI event. Returns true if a mapping consumed the event.
    /// RT-safe: uses atomic mixer setters directly.
    bool processEvent(const MidiEvent& event);

    // --- Mapping table management (non-RT thread) ---

    /// Replace the entire mapping table.
    void setMappings(const std::vector<MidiMappingEntry>& mappings);

    /// Add a single mapping entry.
    void addMapping(const MidiMappingEntry& entry);

    /// Remove all mappings matching the given MIDI channel and CC number.
    bool removeMapping(int midiChannel, int ccNumber);

    /// Remove a specific mapping entry by index.
    bool removeMappingByIndex(size_t index);

    /// Clear all mappings.
    void clearMappings();

    /// Get a copy of the current mapping table.
    std::vector<MidiMappingEntry> getMappings() const;

    // --- Persistence ---

    /// Serialize mappings to JSON string.
    std::string getMappingsJson() const;

    /// Deserialize mappings from JSON string.
    void setMappingsFromJson(const std::string& json);

    /// Default config file path.
    static std::string defaultConfigPath();

    /// Load mappings from default config file.
    void loadFromFile();

    /// Save mappings to default config file.
    void saveToFile() const;

    // --- Learn mode ---

    /// Enable/disable MIDI learn mode.
    /// When enabled, each incoming CC event is captured and cached
    /// so the next call to commitLearnMapping() will create a mapping.
    void setLearnMode(bool enabled);

    /// True if learn mode is active.
    bool learnMode() const { return learnMode_; }

    /// Set the target parameter for the next learned mapping.
    /// Call this when the user touches a UI control.
    void setPendingLearnTarget(MidiTargetType type, int64_t id);

    /// Get the last-learned MIDI event info.
    /// Returns true if a CC event was captured since learn mode was enabled
    /// or since the last clearLastLearnedEvent().
    bool getLastLearnedEvent(int& outMidiChannel, int& outCcNumber) const;

    /// Commit the current pending learn target + last CC into a mapping entry.
    /// Returns the new entry, or nullopt if no CC was captured.
    bool commitLearnMapping();

    /// Clear cached last-learned CC event.
    void clearLastLearnedEvent();

    /// Get pending learn target info.
    bool getPendingLearnTarget(MidiTargetType& outType, int64_t& outId) const;

private:
    MixerEngine* mixerEngine_ = nullptr;

    // Mapping table — mutable for snapshot-copy in RT path
    std::vector<MidiMappingEntry> mappings_;
    mutable std::mutex mappingsMutex_;

    // Learn mode state
    bool learnMode_ = false;
    MidiTargetType pendingTargetType_ = MidiTargetType::ChannelVolume;
    int64_t pendingTargetId_ = 0;
    int lastLearnedMidiChannel_ = -1;
    int lastLearnedCcNumber_ = -1;
    mutable std::mutex learnMutex_;

    // Apply a single mapping entry value to the mixer (RT-safe).
    void applyValue(const MidiMappingEntry& entry, uint8_t ccValue);
};

} // namespace pipedal