/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

   JUCE is an open source library subject to commercial or open-source
   licensing.

   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

//==============================================================================
/**
    Performs a simple reverb effect on a stream of audio data.

    This is a simple stereo reverb, based on the technique and tunings used in FreeVerb.
    Use setSampleRate() to prepare it, and then call processStereo() or processMono() to
    apply the reverb to your audio data.

    @see ReverbAudioSource
*/
class Reverb
{
public:
    //==============================================================================
    Reverb()
    {
        setParameters (Parameters());
        setSampleRate (44100.0);
    }

    //==============================================================================
    /** Holds the parameters being used by a Reverb object. */
    struct Parameters
    {
        Parameters() noexcept
          : roomSize   (0.5f),
            damping    (0.5f),
            wetLevel   (0.33f),
            dryLevel   (0.4f),
            width      (1.0f),
            freezeMode (0)
        {}

        float roomSize;     /**< Room size, 0 to 1.0, where 1.0 is big, 0 is small. */
        float damping;      /**< Damping, 0 to 1.0, where 0 is not damped, 1.0 is fully damped. */
        float wetLevel;     /**< Wet level, 0 to 1.0 */
        float dryLevel;     /**< Dry level, 0 to 1.0 */
        float width;        /**< Reverb width, 0 to 1.0, where 1.0 is very wide. */
        float freezeMode;   /**< Freeze mode - values < 0.5 are "normal" mode, values > 0.5
                                 put the reverb into a continuous feedback loop. */
    };

    //==============================================================================
    /** Returns the reverb's current parameters. */
    const Parameters& getParameters() const noexcept    { return parameters; }

    /** Applies a new set of parameters to the reverb.
        Note that this doesn't attempt to lock the reverb, so if you call this in parallel with
        the process method, you may get artifacts.
    */
    void setParameters (const Parameters& newParams)
    {
        const float wetScaleFactor = 3.0f;
        const float dryScaleFactor = 2.0f;

        const float wet = newParams.wetLevel * wetScaleFactor;
        dryGain.setValue (newParams.dryLevel * dryScaleFactor);
        wetGain1.setValue (0.5f * wet * (1.0f + newParams.width));
        wetGain2.setValue (0.5f * wet * (1.0f - newParams.width));

        gain = isFrozen (newParams.freezeMode) ? 0.0f : 0.015f;
        parameters = newParams;
        updateDamping();
    }

    //==============================================================================
    /** Sets the sample rate that will be used for the reverb.
        You must call this before the process methods, in order to tell it the correct sample rate.
    */
    void setSampleRate (const double sampleRate)
    {
        jassert (sampleRate > 0);

        static const short combTunings[] = { 1116, 1188, 1277, 1356, 1422, 1491, 1557, 1617 }; // (at 44100Hz)
        static const short allPassTunings[] = { 556, 441, 341, 225 };
        const int stereoSpread = 23;
        const int intSampleRate = (int) sampleRate;

        for (int i = 0; i < numCombs; ++i)
        {
            comb[0][i].setSize ((intSampleRate * combTunings[i]) / 44100);
            comb[1][i].setSize ((intSampleRate * (combTunings[i] + stereoSpread)) / 44100);
        }

        for (int i = 0; i < numAllPasses; ++i)
        {
            allPass[0][i].setSize ((intSampleRate * allPassTunings[i]) / 44100);
            allPass[1][i].setSize ((intSampleRate * (allPassTunings[i] + stereoSpread)) / 44100);
        }

        const double smoothTime = 0.01;
        damping .reset (sampleRate, smoothTime);
        feedback.reset (sampleRate, smoothTime);
        dryGain .reset (sampleRate, smoothTime);
        wetGain1.reset (sampleRate, smoothTime);
        wetGain2.reset (sampleRate, smoothTime);
    }

    /** Clears the reverb's buffers. */
    void reset()
    {
        for (int j = 0; j < numChannels; ++j)
        {
            for (int i = 0; i < numCombs; ++i)
                comb[j][i].clear();

            for (int i = 0; i < numAllPasses; ++i)
                allPass[j][i].clear();
        }
    }

    //==============================================================================
    /** Applies the reverb to two stereo channels of audio data. */
    void processStereo (float* const left, float* const right, const int numSamples) noexcept
    {
        jassert (left != nullptr && right != nullptr);

        for (int i = 0; i < numSamples; ++i)
        {
            const float input = (left[i] + right[i]) * gain;
            float outL = 0, outR = 0;

            const float damp    = damping.getNextValue();
            const float feedbck = feedback.getNextValue();

            for (int j = 0; j < numCombs; ++j)  // accumulate the comb filters in parallel
            {
                outL += comb[0][j].process (input, damp, feedbck);
                outR += comb[1][j].process (input, damp, feedbck);
            }

            for (int j = 0; j < numAllPasses; ++j)  // run the allpass filters in series
            {
                outL = allPass[0][j].process (outL);
                outR = allPass[1][j].process (outR);
            }

            const float dry  = dryGain.getNextValue();
            const float wet1 = wetGain1.getNextValue();
            const float wet2 = wetGain2.getNextValue();

            left[i]  = outL * wet1 + outR * wet2 + left[i]  * dry;
            right[i] = outR * wet1 + outL * wet2 + right[i] * dry;
        }
    }

    /** Applies the reverb to a single mono channel of audio data. */
    void processMono (float* const samples, const int numSamples) noexcept
    {
        jassert (samples != nullptr);

        for (int i = 0; i < numSamples; ++i)
        {
            const float input = samples[i] * gain;
            float output = 0;

            const float damp    = damping.getNextValue();
            const float feedbck = feedback.getNextValue();

            for (int j = 0; j < numCombs; ++j)  // accumulate the comb filters in parallel
                output += comb[0][j].process (input, damp, feedbck);

            for (int j = 0; j < numAllPasses; ++j)  // run the allpass filters in series
                output = allPass[0][j].process (output);

            const float dry  = dryGain.getNextValue();
            const float wet1 = wetGain1.getNextValue();

            samples[i] = output * wet1 + samples[i] * dry;
        }
    }

private:
    //==============================================================================
    static bool isFrozen (const float freezeMode) noexcept  { return freezeMode >= 0.5f; }

    void updateDamping() noexcept
    {
        const float roomScaleFactor = 0.28f;
        const float roomOffset = 0.7f;
        const float dampScaleFactor = 0.4f;

        if (isFrozen (parameters.freezeMode))
            setDamping (0.0f, 1.0f);
        else
            setDamping (parameters.damping * dampScaleFactor,
                        parameters.roomSize * roomScaleFactor + roomOffset);
    }

    void setDamping (const float dampingToUse, const float roomSizeToUse) noexcept
    {
        damping.setValue (dampingToUse);
        feedback.setValue (roomSizeToUse);
    }

    //==============================================================================
    class CombFilter
    {
    public:
        CombFilter() noexcept   : bufferSize (0), bufferIndex (0), last (0)  {}

        void setSize (const int size)
        {
            if (size != bufferSize)
            {
                bufferIndex = 0;
                buffer.malloc ((size_t) size);
                bufferSize = size;
            }

            clear();
        }

        void clear() noexcept
        {
            last = 0;
            buffer.clear ((size_t) bufferSize);
        }

        float process (const float input, const float damp, const float feedbackLevel) noexcept
        {
            const float output = buffer[bufferIndex];
            last = (output * (1.0f - damp)) + (last * damp);
            JUCE_UNDENORMALISE (last);

            float temp = input + (last * feedbackLevel);
            JUCE_UNDENORMALISE (temp);
            buffer[bufferIndex] = temp;
            bufferIndex = (bufferIndex + 1) % bufferSize;
            return output;
        }

    private:
        HeapBlock<float> buffer;
        int bufferSize, bufferIndex;
        float last;

        JUCE_DECLARE_NON_COPYABLE (CombFilter)
    };

    //==============================================================================
    class AllPassFilter
    {
    public:
        AllPassFilter() noexcept  : bufferSize (0), bufferIndex (0) {}

        void setSize (const int size)
        {
            if (size != bufferSize)
            {
                bufferIndex = 0;
                buffer.malloc ((size_t) size);
                bufferSize = size;
            }

            clear();
        }

        void clear() noexcept
        {
            buffer.clear ((size_t) bufferSize);
        }

        float process (const float input) noexcept
        {
            const float bufferedValue = buffer [bufferIndex];
            float temp = input + (bufferedValue * 0.5f);
            JUCE_UNDENORMALISE (temp);
            buffer [bufferIndex] = temp;
            bufferIndex = (bufferIndex + 1) % bufferSize;
            return bufferedValue - input;
        }

    private:
        HeapBlock<float> buffer;
        int bufferSize, bufferIndex;

        JUCE_DECLARE_NON_COPYABLE (AllPassFilter)
    };

    //==============================================================================
    enum { numCombs = 8, numAllPasses = 4, numChannels = 2 };

    Parameters parameters;
    float gain;

    CombFilter comb [numChannels][numCombs];
    AllPassFilter allPass [numChannels][numAllPasses];

    LinearSmoothedValue<float> damping, feedback, dryGain, wetGain1, wetGain2;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (Reverb)
};

} // namespace juce