#include "stats.hpp"
#include <fmt/core.h>
#include <numeric>
#include <numbers>

void Stats::dump(std::string msg)
{
  fmt::println("{}: sum: {}, sumsq: {}, n: {}, "
            "min: {}, max: {}, mean: {}, stddev: {}",
            msg, sum, sumsq, n, min, max, mean(),
            stddev());
}

// WARNING: got this code from google AI. PROBABLY BULLSHIT
void Stats::t_test(Stats& other) {
  double n1 = this->n;
  double n2 = other.n;

  double mean1 = this->mean();
  double mean2 = other.mean();

  double var1 = this->variance();
  double var2 = other.variance();

  // calculate t-stat
  double delta_mean = mean1 - mean2;
  double pooled_se = std::sqrt((var1 / n1) + (var2 / n2));
  double t_stat = delta_mean / pooled_se;

  // calculate degrees of freedom
  double num = std::pow((var1 / n1) + (var2 / n2), 2);
  double den = (std::pow(var1 / n1, 2) / (n1 - 1)) + (std::pow(var2 / n2, 2) / (n2 - 1));
  double df = num / den;

  double x = df / (df + t_stat * t_stat);

  double p_val = std::tgamma((df + 1.0) / 2.0) / (std::sqrt(df * std::numbers::pi) * std::tgamma(df / 2.0)) * std::pow(1.0 + (t_stat * t_stat) / df, -(df + 1.0) / 2.0);

  fmt::println("t_stat={}, df={}, p_val={}",
      t_stat, df, p_val);
}