//
// Created by david on 28.02.2026.
//
#include <gtest/gtest.h>
#include "library.h"
#include "npy.hpp"
#include <utility>
#include <vector>
#include <string>
#include <filesystem>

// Demonstrate some basic assertions.
TEST(HelloTest, BasicAssertions) {
    // Expect two strings not to be equal.
    EXPECT_STRNE("hello", "world from test1.cpp");
    // Expect equality.
    EXPECT_EQ(7 * 6, 42);
    printf("asdf");
    hello();
}

TEST(HelloTest, Load_npy_matrix) {
    // "C:\\Users\\david\\Documents\\src\\libpasada\\cmake-build-debug\\google-tests"
    std::cout <<   std::filesystem::current_path() << std::endl;
    const std::string path {"test1/data1.npy"};
    npy::npy_data d = npy::read_npy<double>(path);
    std::vector<double> data = d.data;
    std::vector<unsigned long> shape = d.shape;
    bool fortran_order = d.fortran_order;

    std::vector<unsigned long> expect_shape {2, 2};
    std::vector<double> expect_data {1.0, 2.0, 3.0, 4.0};

    EXPECT_EQ(shape, expect_shape);
    EXPECT_EQ(fortran_order, false);
    EXPECT_DOUBLE_EQ(data[0], expect_data[0]);
    EXPECT_DOUBLE_EQ(data[1], expect_data[1]);
    EXPECT_DOUBLE_EQ(data[2], expect_data[2]);
    EXPECT_DOUBLE_EQ(data[3], expect_data[3]);
}

TEST(HelloTest, Save_npy_matrix) {
    const std::vector<double> data{1, 2, 3, 4, 5, 6};

    npy::npy_data_ptr<double> d;
    d.data_ptr = data.data();
    d.shape = {2, 3};
    d.fortran_order = false;

    const std::string path{"test1/data2.npy"};
    npy::write_npy(path, d);
}

/** Shift register implemented as a circular buffer. */
class Buf {
protected:
    std::vector<double> data;
    size_t size;
    size_t n;
public:
    Buf(size_t N): size(N), n(0) {
        data.resize(N);
        data.assign(N, 0.0);
    }
    void push(double val) {
        data[n] = val;
        n = (n+1) % size;
    }
};

/** Running filter base. */
class Filt : Buf {
protected:
    std::vector<double> taps;
    size_t shift;
    size_t offset;
public:
    Filt(size_t N, size_t shift, size_t offset, std::vector<double> taps): Buf(N), shift(shift), offset(offset), taps(taps) {
        if (taps.size() != N) throw std::invalid_argument("taps.size() != N");
    }
    double filter(double val) {
        this->push(val);
        return this->peek();
    }
    double peek() {
        double sum = 0;
        for (size_t i = offset; i < this->size; i++) {
            //size_t n = (this->n - i + shift - 1) % this->size; // unsigned % size ... bad if u is negative
            size_t n = (this->size + this->n - i + shift - 1) % this->size;
            //std::cout << " t[" << i << "] * v[" << n << "]" << std::endl;
            sum += this->data[n] * this->taps[i];
        }
        return sum;
    }
    void push(double val) {
        Buf::push(val);
    }
};

class IirFilter {
protected:
    Filt y;
    Filt x;
public:
    IirFilter(std::vector<double> b, std::vector<double> a) : x(b.size(), 0, 0, b), y(a.size(), 1, 1, a) {
        if (b.size() != a.size()) throw std::invalid_argument("b.size() != a.size()");
    }
    double filter(double val) {
        //std::cout << "x.filter(" << val << ")" << std::endl;
        double xv = x.filter(val);
        //std::cout << "xv=" << xv << std::endl;
        //std::cout << "y.peek()" << std::endl;
        double yv = y.peek();
        //std::cout << "yv=" << yv << std::endl;
        //std::cout << "---" << std::endl;
        double yo = xv - yv;
        y.push(yo);
        return yo;
    }
};

// TODO: copy npy files from CMake output folder
// TODO: add npy files to CMakeLists.txt so they are copied into output folder
TEST(HelloTest, Test_IIR_1_Apply_IIR) {
    npy::npy_data x = npy::read_npy<double>("test1/iir_t1_x.npy");
    npy::npy_data y_e = npy::read_npy<double>("test1/iir_t1_y.npy");
    size_t N = x.shape[0];
    EXPECT_EQ(x.shape[0], y_e.shape[0]);

    npy::npy_data a = npy::read_npy<double>("test1/iir_t1_a.npy");
    npy::npy_data b = npy::read_npy<double>("test1/iir_t1_b.npy");

    //EXPECT_EQ(6, b.data.size());

    IirFilter filter(b.data, a.data);
    std::vector<double> y;
    y.resize(N);
    for (size_t i = 0; i < N; i++) {
        y[i] = filter.filter(x.data[i]);
    }
    // assert y == y_e, nb. upto 5 digits
    double abs_err = 1e-5;
    for (size_t i = 0; i < N; i++) {
        ASSERT_NEAR(y_e.data[i], y[i], abs_err);
    }

    npy::npy_data_ptr<double> d;
    d.data_ptr = y.data();
    d.shape = {(unsigned long)N};
    const std::string path{"test1/iir_t1_y_out.npy"};
    npy::write_npy(path, d);
}