//
//  AudioPan.h
//  hifi
//
//  Created by Craig Hansen-Sturm on 9/1/14.
//  Copyright 2014 High Fidelity, Inc.
//
//  Distributed under the Apache License, Version 2.0.
//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//

#ifndef hifi_AudioPan_h
#define hifi_AudioPan_h

class AudioPan
{
    float32_t _pan;
    float32_t _gainLeft;
    float32_t _gainRight;
  
    static float32_t ONE_MINUS_EPSILON;
    static float32_t ZERO_PLUS_EPSILON;
    static float32_t ONE_HALF_MINUS_EPSILON;
    static float32_t ONE_HALF_PLUS_EPSILON;
    
    void updateCoefficients() {
        
        // implement constant power sin^2 + cos^2 = 1 panning law
        
        if (_pan >= ONE_MINUS_EPSILON) { // full right
            _gainLeft = 0.0f;
            _gainRight = 1.0f;
        }
        else if (_pan <= ZERO_PLUS_EPSILON) { // full left
            _gainLeft = 1.0f;
            _gainRight = 0.0f;
        }
        else if ((_pan >= ONE_HALF_MINUS_EPSILON) && (_pan <= ONE_HALF_PLUS_EPSILON)) {  // center
            _gainLeft = 1.0f / SQUARE_ROOT_OF_2;
            _gainRight = 1.0f / SQUARE_ROOT_OF_2;
        }
        else { // intermediate cases
            _gainLeft = cosf( TWO_PI * _pan );
            _gainRight = sinf( TWO_PI * _pan );
        }
    }
    
public:
    AudioPan() {
        initialize();
    }
    
    ~AudioPan() {
        finalize();
    }
    
    void initialize() {
        setParameters(0.5f);
    }
    
    void finalize() {
    }
    
    void reset() {
        initialize();
    }
    
    void setParameters(const float32_t pan) {
        // pan ranges between 0.0 and 1.0f inclusive.  0.5f is midpoint between full left and full right
        _pan = std::min(std::max(pan, 0.0f), 1.0f);
        updateCoefficients();
    }
    
    void getParameters(float32_t& pan) {
        pan = _pan;
    }
    
    void render(AudioBufferFloat32& frameBuffer) {
        
        if (frameBuffer.getChannelCount() != 2) {
            return;
        }
        
        float32_t** samples = frameBuffer.getFrameData();
        
        bool frameAlignment16 = (frameBuffer.getFrameCount() & 0x0F) == 0;
        if (frameAlignment16) {
            
            if (frameBuffer.getChannelCount() == 2) {
                
                for (uint16_t i = 0; i < frameBuffer.getFrameCount(); i += 16) {
                    samples[0][i + 0] *= _gainLeft;
                    samples[0][i + 1] *= _gainLeft;
                    samples[0][i + 2] *= _gainLeft;
                    samples[0][i + 3] *= _gainLeft;
                    samples[0][i + 4] *= _gainLeft;
                    samples[0][i + 5] *= _gainLeft;
                    samples[0][i + 6] *= _gainLeft;
                    samples[0][i + 7] *= _gainLeft;
                    samples[0][i + 8] *= _gainLeft;
                    samples[0][i + 9] *= _gainLeft;
                    samples[0][i + 10] *= _gainLeft;
                    samples[0][i + 11] *= _gainLeft;
                    samples[0][i + 12] *= _gainLeft;
                    samples[0][i + 13] *= _gainLeft;
                    samples[0][i + 14] *= _gainLeft;
                    samples[0][i + 15] *= _gainLeft;
                    samples[1][i + 0] *= _gainRight;
                    samples[1][i + 1] *= _gainRight;
                    samples[1][i + 2] *= _gainRight;
                    samples[1][i + 3] *= _gainRight;
                    samples[1][i + 4] *= _gainRight;
                    samples[1][i + 5] *= _gainRight;
                    samples[1][i + 6] *= _gainRight;
                    samples[1][i + 7] *= _gainRight;
                    samples[1][i + 8] *= _gainRight;
                    samples[1][i + 9] *= _gainRight;
                    samples[1][i + 10] *= _gainRight;
                    samples[1][i + 11] *= _gainRight;
                    samples[1][i + 12] *= _gainRight;
                    samples[1][i + 13] *= _gainRight;
                    samples[1][i + 14] *= _gainRight;
                    samples[1][i + 15] *= _gainRight;
                }
            }
            else {
                assert("unsupported channel format");
            }
        }
        else {
            for (uint16_t i = 0; i < frameBuffer.getFrameCount(); i += 1) {
                samples[0][i] *= _gainLeft;
                samples[1][i] *= _gainRight;
            }
        }
    }
};

#endif // AudioPan_h