tensor/internal/core/tensor_test.go

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

package core

import (
	"strings"
	"testing"
)

func mustFromInts(t *testing.T, vals []int64, shape ...int) *Array {
	t.Helper()
	a, err := FromInts(vals, shape...)
	if err != nil {
		t.Fatalf("FromInts(%v, %v): %v", vals, shape, err)
	}
	return a
}

func mustFromFloats(t *testing.T, vals []float64, shape ...int) *Array {
	t.Helper()
	a, err := FromFloats(vals, shape...)
	if err != nil {
		t.Fatalf("FromFloats(%v, %v): %v", vals, shape, err)
	}
	return a
}

func TestConstructors(t *testing.T) {
	a := mustFromInts(t, []int64{1, 2, 3, 4, 5, 6}, 2, 3)
	if a.NDim() != 2 || a.Len() != 6 || a.Dtype() != Int {
		t.Fatalf("accessors: ndim %d len %d dtype %s", a.NDim(), a.Len(), a.Dtype())
	}
	shape := a.Shape()
	if len(shape) != 2 || shape[0] != 2 || shape[1] != 3 {
		t.Fatalf("shape: %v", shape)
	}

	f := mustFromFloats(t, []float64{1.5, 2.5}, 2)
	if f.Dtype() != Float || f.Len() != 2 {
		t.Fatalf("float array: %s len %d", f.Dtype(), f.Len())
	}
}

func TestConstructorErrors(t *testing.T) {
	if _, err := FromInts(nil); err == nil || !strings.Contains(err.Error(), "at least one dimension") {
		t.Fatalf("no shape: %v", err)
	}
	if _, err := FromInts([]int64{1}, 2); err == nil || !strings.Contains(err.Error(), "do not fill the shape") {
		t.Fatalf("wrong fill: %v", err)
	}
	if _, err := FromInts([]int64{1}, -1); err == nil || !strings.Contains(err.Error(), "zero or greater") {
		t.Fatalf("negative dim: %v", err)
	}
}

func TestFilledConstructors(t *testing.T) {
	z, err := Zeros(Int, 2, 2)
	if err != nil {
		t.Fatalf("Zeros: %v", err)
	}
	if v, _ := IntAt(z, 1, 1); v != 0 {
		t.Fatalf("Zeros value: %d", v)
	}

	o, err := Ones(Float, 3)
	if err != nil {
		t.Fatalf("Ones: %v", err)
	}
	if v, _ := FloatAt(o, 2); v != 1.0 {
		t.Fatalf("Ones value: %v", v)
	}

	fi, err := FullI(7, 2)
	if err != nil {
		t.Fatalf("FullI: %v", err)
	}
	if v, _ := IntAt(fi, 0); v != 7 {
		t.Fatalf("FullI value: %d", v)
	}

	ff, err := FullF(2.5, 2, 2)
	if err != nil {
		t.Fatalf("FullF: %v", err)
	}
	if v, _ := FloatAt(ff, 1, 0); v != 2.5 {
		t.Fatalf("FullF value: %v", v)
	}
}

func TestRange(t *testing.T) {
	r := mustFromInts(t, []int64{0, 1, 2, 3}, 4)
	got, err := Range(0, 4)
	if err != nil {
		t.Fatalf("Range: %v", err)
	}
	if !Equal(r, got) {
		t.Fatalf("Range: %s", got)
	}

	by, err := RangeBy(10, 0, -3)
	if err != nil {
		t.Fatalf("RangeBy: %v", err)
	}
	want := mustFromInts(t, []int64{10, 7, 4, 1}, 4)
	if !Equal(want, by) {
		t.Fatalf("RangeBy negative: %s", by)
	}

	empty, err := Range(5, 5)
	if err != nil {
		t.Fatalf("Range empty: %v", err)
	}
	if empty.Len() != 0 {
		t.Fatalf("Range empty len: %d", empty.Len())
	}

	if _, err := RangeBy(0, 5, 0); err == nil || !strings.Contains(err.Error(), "step cannot be zero") {
		t.Fatalf("RangeBy zero step: %v", err)
	}

	// The walk stops instead of looping when the next value would wrap.
	big, err := RangeBy(9223372036854775805, 9223372036854775807, 2)
	if err != nil {
		t.Fatalf("RangeBy wrap: %v", err)
	}
	if big.Len() != 1 {
		t.Fatalf("RangeBy wrap len: %d", big.Len())
	}
}

func TestEqual(t *testing.T) {
	a := mustFromInts(t, []int64{1, 2}, 2)
	b := mustFromInts(t, []int64{1, 2}, 2)
	c := mustFromInts(t, []int64{1, 2, 3}, 3)
	f := mustFromFloats(t, []float64{1, 2}, 2)

	if !Equal(a, b) {
		t.Fatalf("equal arrays must compare equal")
	}
	if Equal(a, c) {
		t.Fatalf("different shapes must not compare equal")
	}
	if Equal(a, f) {
		t.Fatalf("int 1 must not equal float 1.0")
	}
	if Equal(a, nil) {
		t.Fatalf("an array never equals nil")
	}
}

func TestImmutability(t *testing.T) {
	vals := []int64{1, 2, 3}
	a := mustFromInts(t, vals, 3)

	// The constructor copies: later changes to vals never reach the array.
	vals[0] = 99
	if v, _ := IntAt(a, 0); v != 1 {
		t.Fatalf("FromInts must copy: got %d", v)
	}

	// Shape returns a copy, so mutating it cannot corrupt the array.
	shape := a.Shape()
	shape[0] = 100
	if a.Shape()[0] != 3 {
		t.Fatalf("Shape must copy: got %d", a.Shape()[0])
	}
}

func TestString(t *testing.T) {
	a := mustFromInts(t, []int64{1, 2, 3, 4}, 2, 2)
	if got := a.String(); got != "int (2, 2) [1, 2, 3, 4]" {
		t.Fatalf("String: %q", got)
	}
	f := mustFromFloats(t, []float64{1.5, 2}, 2)
	if got := f.String(); got != "float (2) [1.5, 2]" {
		t.Fatalf("String float: %q", got)
	}
}

func TestStringMultidim(t *testing.T) {
	// Ranks 1 and 2 stay flat; rank 3+ wraps per trailing dimension,
	// with size-1 dimensions transparent.
	c, _ := FromInts([]int64{1, 2, 3, 4, 5, 6, 7, 8}, 2, 2, 2)
	want := "int (2, 2, 2) [[[1, 2], [3, 4]], [[5, 6], [7, 8]]]"
	if got := c.String(); got != want {
		t.Errorf("3-D:\n got %q\nwant %q", got, want)
	}
	s, _ := FromFloats([]float64{7, 9, 11}, 1, 1, 3)
	if got := s.String(); got != "float (1, 1, 3) [7, 9, 11]" {
		t.Errorf("size-1 dims: %q", got)
	}
}