// Copyright 2018 Google Inc.
//
// 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 filemem

import (
	"testing"

	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
)

const (
	page     = usermem.PageSize
	hugepage = usermem.HugePageSize
)

func TestFindUnallocatedRange(t *testing.T) {
	for _, test := range []struct {
		desc      string
		usage     *usageSegmentDataSlices
		length    uint64
		alignment uint64
		start     uint64
	}{
		{
			desc:      "Initial allocation succeeds",
			usage:     &usageSegmentDataSlices{},
			length:    page,
			alignment: page,
			start:     0,
		},
		{
			desc: "Allocation begins at start of file",
			usage: &usageSegmentDataSlices{
				Start:  []uint64{page},
				End:    []uint64{2 * page},
				Values: []usageInfo{{refs: 1}},
			},
			length:    page,
			alignment: page,
			start:     0,
		},
		{
			desc: "In-use frames are not allocatable",
			usage: &usageSegmentDataSlices{
				Start:  []uint64{0, page},
				End:    []uint64{page, 2 * page},
				Values: []usageInfo{{refs: 1}, {refs: 2}},
			},
			length:    page,
			alignment: page,
			start:     2 * page,
		},
		{
			desc: "Reclaimable frames are not allocatable",
			usage: &usageSegmentDataSlices{
				Start:  []uint64{0, page, 2 * page},
				End:    []uint64{page, 2 * page, 3 * page},
				Values: []usageInfo{{refs: 1}, {refs: 0}, {refs: 1}},
			},
			length:    page,
			alignment: page,
			start:     3 * page,
		},
		{
			desc: "Gaps between in-use frames are allocatable",
			usage: &usageSegmentDataSlices{
				Start:  []uint64{0, 2 * page},
				End:    []uint64{page, 3 * page},
				Values: []usageInfo{{refs: 1}, {refs: 1}},
			},
			length:    page,
			alignment: page,
			start:     page,
		},
		{
			desc: "Inadequately-sized gaps are rejected",
			usage: &usageSegmentDataSlices{
				Start:  []uint64{0, 2 * page},
				End:    []uint64{page, 3 * page},
				Values: []usageInfo{{refs: 1}, {refs: 1}},
			},
			length:    2 * page,
			alignment: page,
			start:     3 * page,
		},
		{
			desc: "Hugepage alignment is honored",
			usage: &usageSegmentDataSlices{
				Start: []uint64{0, hugepage + page},
				// Hugepage-sized gap here that shouldn't be allocated from
				// since it's incorrectly aligned.
				End:    []uint64{page, hugepage + 2*page},
				Values: []usageInfo{{refs: 1}, {refs: 1}},
			},
			length:    hugepage,
			alignment: hugepage,
			start:     2 * hugepage,
		},
	} {
		t.Run(test.desc, func(t *testing.T) {
			var usage usageSet
			if err := usage.ImportSortedSlices(test.usage); err != nil {
				t.Fatalf("Failed to initialize usage from %v: %v", test.usage, err)
			}
			if got, want := findUnallocatedRange(&usage, test.length, test.alignment), test.start; got != want {
				t.Errorf("findUnallocatedRange(%v, %d, %d): got %d, wanted %d", test.usage, test.length, test.alignment, got, want)
			}
		})
	}
}