// Copyright 2017 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package s2

import "testing"

func TestInterleaveUint32(t *testing.T) {
	x, y := uint32(13356), uint32(1073728367)
	gotX, gotY := deinterleaveUint32(interleaveUint32(x, y))
	if gotX != x || gotY != y {
		t.Errorf("deinterleave after interleave = %d, %d; want %d, %d", gotX, gotY, x, y)
	}
}

func referenceBitInterleave(x, y uint32) uint64 {
	var ret uint64
	for i := uint(0); i < 32; i++ {
		ret |= uint64((x>>i)&1) << (i * 2)
		ret |= uint64((y>>i)&1) << (i*2 + 1)
	}
	return ret
}

func TestInterleaveUint32AgainstReference(t *testing.T) {
	// TODO(nsch): Add the remaining parts of the tests later. (the various other primes and bit AND-ings.)
	for i := 0; i < 100000; i++ {
		wantEven := uint32(i) * 14233781
		wantOdd := uint32(i) * 18400439

		gotInter := interleaveUint32(wantEven, wantOdd)
		wantInter := referenceBitInterleave(wantEven, wantOdd)
		if gotInter != wantInter {
			t.Fatalf("interleaveUint32(%d, %d) = %d, want %d", wantEven, wantOdd, gotInter, wantInter)
		}

		gotEven, gotOdd := deinterleaveUint32(gotInter)
		if gotEven != wantEven {
			t.Fatalf("interleave: %d vs %d", gotEven, wantEven)
		}
		if gotOdd != wantOdd {
			t.Fatalf("interleave: %d vs %d", gotOdd, wantOdd)
		}
	}
}

func TestInterleaveBasics(t *testing.T) {
	tests := []struct {
		x, y uint32
		want uint64
	}{
		// Interleave zeroes.
		{0, 0, 0},
		// Interleave ones.
		{1, 0, 1}, {0, 1, 2}, {1, 1, 3},
		// Interleave all bits.
		{0xffffffff, 0, 0x5555555555555555},
		{0, 0xffffffff, 0xaaaaaaaaaaaaaaaa},
		{0xffffffff, 0xffffffff, 0xffffffffffffffff},
	}
	for _, tt := range tests {
		if got := interleaveUint32(tt.x, tt.y); got != tt.want {
			t.Errorf("interleaveUint32(%d, %d) = %d, want %d", tt.x, tt.y, got, tt.want)
		}
	}
}