// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

package linalg

import (
	"math"
	"testing"

	"sourcedock.dev/petrbalvin/tensor/internal/core"
)

// TestFitEvaluatePolynomial moved with FitPolynomial from the root
// package: a quadratic fit of y = 2 + x must recover it perfectly.
func TestFitEvaluatePolynomial(t *testing.T) {
	x := mustFloats(t, []float64{0, 1, 2}, 3)
	y := mustFloats(t, []float64{2, 3, 4}, 3)
	coeffs, err := FitPolynomial(x, y, 1)
	if err != nil {
		t.Fatal(err)
	}
	if math.Abs(coeffs.FloatAt(0)-2) > 1e-9 || math.Abs(coeffs.FloatAt(1)-1) > 1e-9 {
		t.Errorf("poly coeffs: %v", coeffs.RawFloats())
	}
	q, _ := core.FromFloats([]float64{5, 7}, 2)
	out, err := core.EvaluatePolynomial(coeffs, q)
	if err != nil {
		t.Fatal(err)
	}
	if math.Abs(out.FloatAt(0)-7) > 1e-9 || math.Abs(out.FloatAt(1)-9) > 1e-9 {
		t.Errorf("poly eval: %v", out.RawFloats())
	}
}