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

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

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

   By using JUCE, you agree to the terms of both the JUCE 6 End-User License
   Agreement and JUCE Privacy Policy (both effective as of the 16th June 2020).

   End User License Agreement: www.juce.com/juce-6-licence
   Privacy Policy: www.juce.com/juce-privacy-policy

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

   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
{

#if JUCE_UNIT_TESTS

class InterpolatorTests  : public UnitTest
{
public:
    InterpolatorTests()
        : UnitTest ("InterpolatorTests", UnitTestCategories::audio)
    {
    }

private:
    template<typename InterpolatorType>
    void runInterplatorTests (const String& interpolatorName)
    {
        auto createGaussian = [] (std::vector<float>& destination, float scale, float centreInSamples, float width)
        {
            for (size_t i = 0; i < destination.size(); ++i)
            {
                auto x = (((float) i) - centreInSamples) * width;
                destination[i] = std::exp (-(x * x));
            }

            FloatVectorOperations::multiply (destination.data(), scale, (int) destination.size());
        };

        auto findGaussianPeak = [] (const std::vector<float>& input) -> float
        {
            auto max = std::max_element (std::begin (input), std::end (input));
            auto maxPrev = max - 1;
            jassert (maxPrev >= std::begin (input));
            auto maxNext = max + 1;
            jassert (maxNext < std::end (input));
            auto quadraticMaxLoc = (*maxPrev - *maxNext) / (2.0f * ((*maxNext + *maxPrev) - (2.0f * *max)));
            return quadraticMaxLoc + (float) std::distance (std::begin (input), max);
        };

        auto expectAllElementsWithin = [this] (const std::vector<float>& v1, const std::vector<float>& v2, float tolerance)
        {
            expectEquals ((int) v1.size(), (int) v2.size());

            for (size_t i = 0; i < v1.size(); ++i)
                expectWithinAbsoluteError (v1[i], v2[i], tolerance);
        };

        InterpolatorType interpolator;

        constexpr size_t inputSize = 1001;
        static_assert (inputSize > 800 + InterpolatorType::getBaseLatency(),
                       "The test InterpolatorTests input buffer is too small");

        std::vector<float> input (inputSize);
        constexpr auto inputGaussianMidpoint = (float) (inputSize - 1) / 2.0f;
        constexpr auto inputGaussianValueAtEnds = 0.000001f;
        const auto inputGaussianWidth = std::sqrt (-std::log (inputGaussianValueAtEnds)) / inputGaussianMidpoint;

        createGaussian (input, 1.0f, inputGaussianMidpoint, inputGaussianWidth);

        for (auto speedRatio : { 0.4, 0.8263, 1.0, 1.05, 1.2384, 1.6 })
        {
            const auto expectedGaussianMidpoint = (inputGaussianMidpoint + InterpolatorType::getBaseLatency()) / (float) speedRatio;
            const auto expectedGaussianWidth = inputGaussianWidth * (float) speedRatio;

            const auto outputBufferSize = (size_t) std::floor ((float) input.size() / speedRatio);

            for (int numBlocks : { 1, 5 })
            {
                const auto inputBlockSize = (float) input.size() / (float) numBlocks;
                const auto outputBlockSize = (int) std::floor (inputBlockSize / speedRatio);

                std::vector<float> output (outputBufferSize, std::numeric_limits<float>::min());

                beginTest (interpolatorName + " process " + String (numBlocks) + " blocks ratio " + String (speedRatio));

                interpolator.reset();

                {
                    auto* inputPtr = input.data();
                    auto* outputPtr = output.data();

                    for (int i = 0; i < numBlocks; ++i)
                    {
                        auto numInputSamplesRead = interpolator.process (speedRatio, inputPtr, outputPtr, outputBlockSize);
                        inputPtr += numInputSamplesRead;
                        outputPtr += outputBlockSize;
                    }
                }

                expectWithinAbsoluteError (findGaussianPeak (output), expectedGaussianMidpoint, 0.1f);

                std::vector<float> expectedOutput (output.size());
                createGaussian (expectedOutput, 1.0f, expectedGaussianMidpoint, expectedGaussianWidth);

                expectAllElementsWithin (output, expectedOutput, 0.02f);

                beginTest (interpolatorName + " process adding " + String (numBlocks) + " blocks ratio " + String (speedRatio));

                interpolator.reset();

                constexpr float addingGain = 0.7384f;

                {
                    auto* inputPtr = input.data();
                    auto* outputPtr = output.data();

                    for (int i = 0; i < numBlocks; ++i)
                    {
                        auto numInputSamplesRead = interpolator.processAdding (speedRatio, inputPtr, outputPtr, outputBlockSize, addingGain);
                        inputPtr += numInputSamplesRead;
                        outputPtr += outputBlockSize;
                    }
                }

                expectWithinAbsoluteError (findGaussianPeak (output), expectedGaussianMidpoint, 0.1f);

                std::vector<float> additionalOutput (output.size());
                createGaussian (additionalOutput, addingGain, expectedGaussianMidpoint, expectedGaussianWidth);
                FloatVectorOperations::add (expectedOutput.data(), additionalOutput.data(), (int) additionalOutput.size());

                expectAllElementsWithin (output, expectedOutput, 0.02f);
            }

            beginTest (interpolatorName + " process wrap 0 ratio " + String (speedRatio));

            std::vector<float> doubleLengthOutput (2 * outputBufferSize, std::numeric_limits<float>::min());

            interpolator.reset();
            interpolator.process (speedRatio, input.data(), doubleLengthOutput.data(), (int) doubleLengthOutput.size(),
                                  (int) input.size(), 0);

            std::vector<float> expectedDoubleLengthOutput (doubleLengthOutput.size());
            createGaussian (expectedDoubleLengthOutput, 1.0f, expectedGaussianMidpoint, expectedGaussianWidth);

            expectAllElementsWithin (doubleLengthOutput, expectedDoubleLengthOutput, 0.02f);

            beginTest (interpolatorName + " process wrap double ratio " + String (speedRatio));

            interpolator.reset();
            interpolator.process (speedRatio, input.data(), doubleLengthOutput.data(), (int) doubleLengthOutput.size(),
                                  (int) input.size(), (int) input.size());

            std::vector<float> secondGaussian (doubleLengthOutput.size());
            createGaussian (secondGaussian, 1.0f, expectedGaussianMidpoint + (float) outputBufferSize, expectedGaussianWidth);
            FloatVectorOperations::add (expectedDoubleLengthOutput.data(), secondGaussian.data(), (int) expectedDoubleLengthOutput.size());

            expectAllElementsWithin (doubleLengthOutput, expectedDoubleLengthOutput, 0.02f);
        }
    }

public:
    void runTest() override
    {
        runInterplatorTests<WindowedSincInterpolator> ("WindowedSincInterpolator");
        runInterplatorTests<LagrangeInterpolator>     ("LagrangeInterpolator");
        runInterplatorTests<CatmullRomInterpolator>   ("CatmullRomInterpolator");
        runInterplatorTests<LinearInterpolator>       ("LinearInterpolator");
    }
};

static InterpolatorTests interpolatorTests;

#endif

} // namespace juce