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

   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
{

/**
    Generates a signal based on a user-supplied function.

    @tags{DSP}
*/
template <typename SampleType>
class Oscillator
{
public:
    /** The NumericType is the underlying primitive type used by the SampleType (which
        could be either a primitive or vector)
    */
    using NumericType = typename SampleTypeHelpers::ElementType<SampleType>::Type;

    /** Creates an uninitialised oscillator. Call initialise before first use. */
    Oscillator() = default;

    /** Creates an oscillator with a periodic input function (-pi..pi).

        If lookup table is not zero, then the function will be approximated
        with a lookup table.
    */
    Oscillator (const std::function<NumericType(NumericType)>& function,
                size_t lookupTableNumPoints = 0)
    {
        initialise (function, lookupTableNumPoints);
    }

    /** Returns true if the Oscillator has been initialised. */
    bool isInitialised() const noexcept     { return static_cast<bool> (generator); }

    /** Initialises the oscillator with a waveform. */
    void initialise (const std::function<NumericType(NumericType)>& function,
                     size_t lookupTableNumPoints = 0)
    {
        if (lookupTableNumPoints != 0)
        {
            auto* table = new LookupTableTransform<NumericType> (function,
                                                                 -MathConstants<NumericType>::pi,
                                                                 MathConstants<NumericType>::pi,
                                                                 lookupTableNumPoints);

            lookupTable.reset (table);
            generator = [table] (NumericType x) { return (*table) (x); };
        }
        else
        {
            generator = function;
        }
    }

    //==============================================================================
    /** Sets the frequency of the oscillator. */
    void setFrequency (NumericType newFrequency, bool force = false) noexcept
    {
        if (force)
        {
            frequency.setCurrentAndTargetValue (newFrequency);
            return;
        }

        frequency.setTargetValue (newFrequency);
    }

    /** Returns the current frequency of the oscillator. */
    NumericType getFrequency() const noexcept                    { return frequency.getTargetValue(); }

    //==============================================================================
    /** Called before processing starts. */
    void prepare (const ProcessSpec& spec) noexcept
    {
        sampleRate = static_cast<NumericType> (spec.sampleRate);
        rampBuffer.resize ((int) spec.maximumBlockSize);

        reset();
    }

    /** Resets the internal state of the oscillator */
    void reset() noexcept
    {
        phase.reset();

        if (sampleRate > 0)
            frequency.reset (sampleRate, 0.05);
    }

    //==============================================================================
    /** Returns the result of processing a single sample. */
    SampleType JUCE_VECTOR_CALLTYPE processSample (SampleType input) noexcept
    {
        jassert (isInitialised());
        auto increment = MathConstants<NumericType>::twoPi * frequency.getNextValue() / sampleRate;
        return input + generator (phase.advance (increment) - MathConstants<NumericType>::pi);
    }

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

        // this is an output-only processor
        jassert (outBlock.getNumSamples() <= static_cast<size_t> (rampBuffer.size()));

        auto len           = outBlock.getNumSamples();
        auto numChannels   = outBlock.getNumChannels();
        auto inputChannels = inBlock.getNumChannels();
        auto baseIncrement = MathConstants<NumericType>::twoPi / sampleRate;

        if (context.isBypassed)
            context.getOutputBlock().clear();

        if (frequency.isSmoothing())
        {
            auto* buffer = rampBuffer.getRawDataPointer();

            for (size_t i = 0; i < len; ++i)
                buffer[i] = phase.advance (baseIncrement * frequency.getNextValue())
                              - MathConstants<NumericType>::pi;

            if (! context.isBypassed)
            {
                size_t ch;

                if (context.usesSeparateInputAndOutputBlocks())
                {
                    for (ch = 0; ch < jmin (numChannels, inputChannels); ++ch)
                    {
                        auto* dst = outBlock.getChannelPointer (ch);
                        auto* src = inBlock.getChannelPointer (ch);

                        for (size_t i = 0; i < len; ++i)
                            dst[i] = src[i] + generator (buffer[i]);
                    }
                }
                else
                {
                    for (ch = 0; ch < jmin (numChannels, inputChannels); ++ch)
                    {
                        auto* dst = outBlock.getChannelPointer (ch);

                        for (size_t i = 0; i < len; ++i)
                            dst[i] += generator (buffer[i]);
                    }
                }

                for (; ch < numChannels; ++ch)
                {
                    auto* dst = outBlock.getChannelPointer (ch);

                    for (size_t i = 0; i < len; ++i)
                        dst[i] = generator (buffer[i]);
                }
            }
        }
        else
        {
            auto freq = baseIncrement * frequency.getNextValue();
            auto p = phase;

            if (context.isBypassed)
            {
                frequency.skip (static_cast<int> (len));
                p.advance (freq * static_cast<NumericType> (len));
            }
            else
            {
                size_t ch;

                if (context.usesSeparateInputAndOutputBlocks())
                {
                    for (ch = 0; ch < jmin (numChannels, inputChannels); ++ch)
                    {
                        p = phase;
                        auto* dst = outBlock.getChannelPointer (ch);
                        auto* src = inBlock.getChannelPointer (ch);

                        for (size_t i = 0; i < len; ++i)
                            dst[i] = src[i] + generator (p.advance (freq) - MathConstants<NumericType>::pi);
                    }
                }
                else
                {
                    for (ch = 0; ch < jmin (numChannels, inputChannels); ++ch)
                    {
                        p = phase;
                        auto* dst = outBlock.getChannelPointer (ch);

                        for (size_t i = 0; i < len; ++i)
                            dst[i] += generator (p.advance (freq) - MathConstants<NumericType>::pi);
                    }
                }

                for (; ch < numChannels; ++ch)
                {
                    p = phase;
                    auto* dst = outBlock.getChannelPointer (ch);

                    for (size_t i = 0; i < len; ++i)
                        dst[i] = generator (p.advance (freq) - MathConstants<NumericType>::pi);
                }
            }

            phase = p;
        }
    }

private:
    //==============================================================================
    std::function<NumericType(NumericType)> generator;
    std::unique_ptr<LookupTableTransform<NumericType>> lookupTable;
    Array<NumericType> rampBuffer;
    SmoothedValue<NumericType> frequency { static_cast<NumericType> (440.0) };
    NumericType sampleRate = 48000.0;
    Phase<NumericType> phase;
};

} // namespace dsp
} // namespace juce