#ifndef SYNTH_ENGINE_H
#define SYNTH_ENGINE_H

#include <stdint.h>
#include <vector>
#include <utility>

#if defined(ARDUINO_ARCH_RP2040)
#include <pico/mutex.h>
class SynthMutex {
public:
    SynthMutex() { mutex_init(&mtx); }
    void lock() { mutex_enter_blocking(&mtx); }
    void unlock() { mutex_exit(&mtx); }
private:
    mutex_t mtx;
};
template <typename Mutex>
class SynthLockGuard {
public:
    explicit SynthLockGuard(Mutex& m) : m_mutex(m) { m_mutex.lock(); }
    ~SynthLockGuard() { m_mutex.unlock(); }
    SynthLockGuard(const SynthLockGuard&) = delete;
    SynthLockGuard& operator=(const SynthLockGuard&) = delete;
private:
    Mutex& m_mutex;
};
#else
#include <mutex>
using SynthMutex = std::mutex;
template <typename Mutex>
using SynthLockGuard = std::lock_guard<Mutex>;
#endif

// Fixed-point constants
#define FP_SHIFT 15
#define FP_ONE (1 << FP_SHIFT)
#define FP_HALF (1 << (FP_SHIFT - 1))
#define FP_MAX 32767
#define FP_MIN -32768

/**
 * @class SynthEngine
 * @brief A portable, platform-agnostic synthesizer engine.
 *
 * This class contains the core digital signal processing (DSP) logic.
 * It has no dependencies on any specific hardware, OS, or audio API.
 * It works by filling a provided buffer with 16-bit signed audio samples.
 *
 * The oscillator uses a 32-bit unsigned integer as a phase accumulator,
 * which is highly efficient and avoids floating-point math in the audio loop,
 * making it ideal for the RP2040.
 */
class SynthEngine {
public:
    enum Waveform {
        SAWTOOTH,
        SQUARE,
        SINE
    };

    /**
     * @brief Constructs the synthesizer engine.
     * @param sampleRate The audio sample rate in Hz (e.g., 44100).
     */
    ~SynthEngine();
    SynthEngine(uint32_t sampleRate);

    /**
     * @brief Fills a buffer with audio samples. This is the main audio callback.
     * @param buffer Pointer to the output buffer to be filled.
     * @param numFrames The number of audio frames (samples) to generate.
     */
    void process(int16_t* buffer, uint32_t numFrames);

    /**
     * @brief Sets the frequency of the oscillator.
     * @param freq The frequency in Hz.
     */
    void setFrequency(float freq);

    /**
     * @brief Sets the output volume.
     * @param vol Volume from 0.0 (silent) to 1.0 (full).
     */
    void setVolume(float vol);

    /**
     * @brief Sets the oscillator's waveform.
     * @param form The waveform to use.
     */
    void setWaveform(Waveform form);

    /**
     * @brief Opens or closes the sound gate.
     * @param isOpen True to produce sound, false for silence.
     */
    void setGate(bool isOpen);

    /**
     * @brief Gets the current frequency of the oscillator.
     * @return The frequency in Hz.
     */
    float getFrequency() const;

    // --- Grid Synth ---
    struct GridCell {
        enum Type { EMPTY, FIXED_OSCILLATOR, INPUT_OSCILLATOR, WAVETABLE, NOISE, LFO, GATE_INPUT, ADSR_ATTACK, ADSR_DECAY, ADSR_SUSTAIN, ADSR_RELEASE, FORK, WIRE, LPF, HPF, VCA, BITCRUSHER, DISTORTION, RECTIFIER, PITCH_SHIFTER, GLITCH, OPERATOR, DELAY, REVERB, SINK };
        enum Op { OP_ADD, OP_MUL, OP_SUB, OP_DIV, OP_MIN, OP_MAX };
        
        Type type = EMPTY;
        int32_t param = FP_HALF; // 0.0 to 1.0 -> 0 to 32768
        int rotation = 0;   // 0:N, 1:E, 2:S, 3:W (Output direction)
        int32_t value = 0; // Current output sample (Q15)
        int32_t next_value = 0; // For double-buffering
        int32_t phase = 0; // For Oscillator, Noise state, Filter state
        uint32_t phase_accumulator = 0; // For Oscillators (Fixed point optimization)
    };

    static const int GRID_W = 12;
    static const int GRID_H = 12;
    
    static const size_t MAX_SERIALIZED_GRID_SIZE = 1024;
    size_t exportGrid(uint8_t* buffer);
    int importGrid(const uint8_t* buffer, size_t size);
    void loadPreset(int preset);
    void rebuildProcessingOrder();
    void updateGraph();
    void clearGrid();

    GridCell grid[GRID_W][GRID_H];
    SynthMutex gridMutex;

    // Helper to process one sample step of the grid
    int32_t processGridStep();

private:
    uint32_t _sampleRate;
    uint32_t _phase;      // Phase accumulator for the oscillator.
    uint32_t _increment;  // Phase increment per sample, determines frequency.
    float _volume;
    Waveform _waveform;
    float _freqToPhaseInc; // Pre-calculated constant for frequency to phase increment conversion
    bool _isGateOpen;
    uint32_t _rngState;
    std::vector<std::pair<int, int>> _processing_order;
    void rebuildProcessingOrder_locked();

    bool isConnected(int tx, int ty, int from_x, int from_y);
    int32_t getInput(int tx, int ty, int from_x, int from_y, int depth = 0);
    int32_t getSummedInput(int x, int y, GridCell& c, int depth = 0);

    // Internal random number generator
    int32_t _random();
};

#endif // SYNTH_ENGINE_H