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

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For this technical preview, this file is not subject to commercial licensing.

   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
{
namespace dsp
{

/**
    Applies a gain to audio samples as single samples or AudioBlocks.

    @tags{DSP}
*/
template <typename FloatType>
class Gain
{
public:
    Gain() noexcept = default;

    //==============================================================================
    /** Applies a new gain as a linear value. */
    void setGainLinear (FloatType newGain) noexcept             { gain.setTargetValue (newGain); }

    /** Applies a new gain as a decibel value. */
    void setGainDecibels (FloatType newGainDecibels) noexcept   { setGainLinear (Decibels::decibelsToGain<FloatType> (newGainDecibels)); }

    /** Returns the current gain as a linear value. */
    FloatType getGainLinear() const noexcept                    { return gain.getTargetValue(); }

    /** Returns the current gain in decibels. */
    FloatType getGainDecibels() const noexcept                  { return Decibels::gainToDecibels<FloatType> (getGainLinear()); }

    /** Sets the length of the ramp used for smoothing gain changes. */
    void setRampDurationSeconds (double newDurationSeconds) noexcept
    {
        if (rampDurationSeconds != newDurationSeconds)
        {
            rampDurationSeconds = newDurationSeconds;
            reset();
        }
    }

    /** Returns the ramp duration in seconds. */
    double getRampDurationSeconds() const noexcept              { return rampDurationSeconds; }

    /** Returns true if the current value is currently being interpolated. */
    bool isSmoothing() const noexcept                           { return gain.isSmoothing(); }

    //==============================================================================
    /** Called before processing starts. */
    void prepare (const ProcessSpec& spec) noexcept
    {
        sampleRate = spec.sampleRate;
        reset();
    }

    /** Resets the internal state of the gain */
    void reset() noexcept
    {
        if (sampleRate > 0)
            gain.reset (sampleRate, rampDurationSeconds);
    }

    //==============================================================================
    /** Returns the result of processing a single sample. */
    template <typename SampleType>
    SampleType JUCE_VECTOR_CALLTYPE processSample (SampleType s) noexcept
    {
        return s * gain.getNextValue();
    }

    /** Processes the input and output buffers supplied in the processing context. */
    template <typename ProcessContext>
    void process (const ProcessContext& context) noexcept
    {
        auto&& inBlock  = context.getInputBlock();
        auto&& outBlock = context.getOutputBlock();

        jassert (inBlock.getNumChannels() == outBlock.getNumChannels());
        jassert (inBlock.getNumSamples() == outBlock.getNumSamples());

        auto len         = inBlock.getNumSamples();
        auto numChannels = inBlock.getNumChannels();

        if (context.isBypassed)
        {
            gain.skip (static_cast<int> (len));

            if (context.usesSeparateInputAndOutputBlocks())
                outBlock.copyFrom (inBlock);

            return;
        }

        if (numChannels == 1)
        {
            auto* src = inBlock.getChannelPointer (0);
            auto* dst = outBlock.getChannelPointer (0);

            for (size_t i = 0; i < len; ++i)
                dst[i] = src[i] * gain.getNextValue();
        }
        else
        {
            auto* gains = static_cast<FloatType*> (alloca (sizeof (FloatType) * len));

            for (size_t i = 0; i < len; ++i)
                gains[i] = gain.getNextValue();

            for (size_t chan = 0; chan < numChannels; ++chan)
                FloatVectorOperations::multiply (outBlock.getChannelPointer (chan),
                                                 inBlock.getChannelPointer (chan),
                                                 gains, static_cast<int> (len));
        }
    }

private:
    //==============================================================================
    SmoothedValue<FloatType> gain;
    double sampleRate = 0, rampDurationSeconds = 0;
};

} // namespace dsp
} // namespace juce