#ifndef SYNTH_ENGINE_H
#define SYNTH_ENGINE_H

#include <stdint.h>

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

private:
    uint32_t _sampleRate;
    uint32_t _phase;      // Phase accumulator for the oscillator.
    uint32_t _increment;  // Phase increment per sample, determines frequency.
};

#endif // SYNTH_ENGINE_H