//go:build linux

/*
   Copyright The containerd Authors.

   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 fs

import (
	"bytes"
	"io"
	"math/rand"
	"os"
	"os/exec"
	"path/filepath"
	"syscall"
	"testing"

	"github.com/containerd/continuity/testutil"
	"github.com/containerd/continuity/testutil/loopback"
)

func TestCopyFileSparse(t *testing.T) {
	dir := t.TempDir()

	type testCase struct {
		name string
		// parts alternates: data length, hole length, data length, ...
		// A 0 data length at the start means the file begins with a hole.
		parts []int64
	}

	tests := []testCase{
		{
			name:  "DataHoleData",
			parts: []int64{4096, 1024 * 1024, 4096},
		},
		{
			name:  "HoleOnly",
			parts: []int64{0, 1024 * 1024, 1},
		},
		{
			name:  "HoleAtStart",
			parts: []int64{0, 1024 * 1024, 4096},
		},
		{
			name:  "HoleAtEnd",
			parts: []int64{4096, 1024 * 1024},
		},
		{
			name:  "MultipleHoles",
			parts: []int64{4096, 512 * 1024, 4096, 512 * 1024, 4096},
		},
		{
			name:  "NoHoles",
			parts: []int64{64 * 1024},
		},
	}

	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			srcPath := filepath.Join(dir, tc.name+"-src")
			dstPath := filepath.Join(dir, tc.name+"-dst")

			applier := createSparseFile(tc.name+"-src", 42, 0o644, tc.parts...)
			if err := applier.Apply(dir); err != nil {
				t.Fatal(err)
			}

			if err := CopyFile(dstPath, srcPath); err != nil {
				t.Fatalf("CopyFile failed: %v", err)
			}

			// Verify content matches exactly.
			srcData, err := os.ReadFile(srcPath)
			if err != nil {
				t.Fatal(err)
			}
			dstData, err := os.ReadFile(dstPath)
			if err != nil {
				t.Fatal(err)
			}
			if !bytes.Equal(srcData, dstData) {
				t.Fatal("source and destination file contents differ")
			}

			// Verify sparseness is preserved: destination should not use
			// significantly more blocks than the source.
			srcStat, err := os.Stat(srcPath)
			if err != nil {
				t.Fatal(err)
			}
			dstStat, err := os.Stat(dstPath)
			if err != nil {
				t.Fatal(err)
			}

			srcBlocks := srcStat.Sys().(*syscall.Stat_t).Blocks
			dstBlocks := dstStat.Sys().(*syscall.Stat_t).Blocks

			t.Logf("src size=%d blocks=%d, dst size=%d blocks=%d",
				srcStat.Size(), srcBlocks, dstStat.Size(), dstBlocks)

			if srcStat.Size() != dstStat.Size() {
				t.Fatalf("size mismatch: src=%d dst=%d", srcStat.Size(), dstStat.Size())
			}

			// Allow some slack for filesystem metadata, but destination
			// should not use more than 10% extra blocks.
			maxBlocks := srcBlocks + srcBlocks/10 + 8
			if dstBlocks > maxBlocks {
				t.Fatalf("destination is not sparse: src blocks=%d, dst blocks=%d (max allowed=%d)",
					srcBlocks, dstBlocks, maxBlocks)
			}
		})
	}
}

func TestCopyReflinkWithXFS(t *testing.T) {
	testutil.RequiresRoot(t)
	mnt := t.TempDir()

	loop, err := loopback.New(1 << 30) // sparse file (max=1GB)
	if err != nil {
		t.Fatal(err)
	}
	mkfs := []string{"mkfs.xfs", "-m", "crc=1", "-n", "ftype=1", "-m", "reflink=1"}
	if out, err := exec.Command(mkfs[0], append(mkfs[1:], loop.Device)...).CombinedOutput(); err != nil {
		// not fatal
		t.Skipf("could not mkfs (%v) %s: %v (out: %q)", mkfs, loop.Device, err, string(out))
	}
	loopbackSize, err := loop.HardSize()
	if err != nil {
		t.Fatal(err)
	}
	t.Logf("Loopback file size (after mkfs (%v)): %d", mkfs, loopbackSize)
	if out, err := exec.Command("mount", loop.Device, mnt).CombinedOutput(); err != nil {
		// not fatal
		t.Skipf("could not mount %s: %v (out: %q)", loop.Device, err, string(out))
	}
	unmounted := false
	defer func() {
		if !unmounted {
			testutil.Unmount(t, mnt)
		}
		loop.Close()
	}()

	aPath := filepath.Join(mnt, "a")
	aSize := int64(100 << 20) // 100MB
	a, err := os.Create(aPath)
	if err != nil {
		t.Fatal(err)
	}
	randReader := rand.New(rand.NewSource(42))
	if _, err := io.CopyN(a, randReader, aSize); err != nil {
		a.Close()
		t.Fatal(err)
	}
	if err := a.Close(); err != nil {
		t.Fatal(err)
	}
	bPath := filepath.Join(mnt, "b")
	if err := CopyFile(bPath, aPath); err != nil {
		t.Fatal(err)
	}
	testutil.Unmount(t, mnt)
	unmounted = true
	loopbackSize, err = loop.HardSize()
	if err != nil {
		t.Fatal(err)
	}
	t.Logf("Loopback file size (after copying a %d-byte file): %d", aSize, loopbackSize)
	// 170 MiB is needed since Ubuntu 24.04. 120 MiB was enough for Ubuntu 22.04.
	allowedSize := int64(170 << 20)
	if loopbackSize > allowedSize {
		t.Fatalf("expected <= %d, got %d", allowedSize, loopbackSize)
	}
}