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

//go:build linux

package nfsfs

import (
	"os"
	"path/filepath"
	"testing"
)

func TestLocalSparse(t *testing.T) {
	root := t.TempDir()
	if err := os.WriteFile(filepath.Join(root, "s.bin"), make([]byte, 8192), 0o644); err != nil {
		t.Fatal(err)
	}
	l, err := NewLocal(root)
	if err != nil {
		t.Fatal(err)
	}
	rootHandle, err := l.Root()
	if err != nil {
		t.Fatal(err)
	}
	fh, _, err := l.Lookup(rootHandle, "s.bin")
	if err != nil {
		t.Fatal(err)
	}
	// The file is all data: the only hole is the virtual one every file
	// carries at its end, so the seek answers the size with the eof flag,
	// RFC 7862 section 15.11.
	off, eof, err := l.SeekHole(fh, 0)
	if err != nil || off != 8192 || !eof {
		t.Fatalf("hole in a full file: %d %v %v", off, eof, err)
	}
	if off, eof, err := l.SeekData(fh, 0); err != nil || off != 0 || eof {
		t.Fatalf("seek data: %d %v %v", off, eof, err)
	}
	// A seek past the end is NXIO, not an answer.
	if _, _, err := l.SeekData(fh, 8193); err != ErrBeyondEOF {
		t.Fatalf("seek past the end: %v", err)
	}
	// Punching a hole moves the first hole to the punched offset.
	if err := l.Deallocate(fh, 4096, 4096); err != nil {
		t.Fatalf("deallocate: %v", err)
	}
	off, eof, err = l.SeekHole(fh, 0)
	if err != nil || off != 4096 || eof {
		t.Fatalf("seek hole: %d %v %v", off, eof, err)
	}
	// No data follows inside the hole: the answer names the size with
	// the eof flag.
	if off, eof, err := l.SeekData(fh, 4096); err != nil || off != 8192 || !eof {
		t.Fatalf("data in the hole: %d %v %v", off, eof, err)
	}
	// Allocate reserves the space without moving the hole back.
	if err := l.Allocate(fh, 4096, 4096); err != nil {
		t.Fatalf("allocate: %v", err)
	}
	if off, eof, err := l.SeekHole(fh, 0); err != nil || off != 4096 || eof {
		t.Fatalf("seek hole after allocate: %d %v %v", off, eof, err)
	}
	// Allocate past the end grows the file to the end of the reserved
	// range, which RFC 7862 section 15.1 requires.
	if err := l.Allocate(fh, 8192, 4096); err != nil {
		t.Fatalf("allocate past eof: %v", err)
	}
	info, err := l.Getattr(fh)
	if err != nil || info.Size != 12288 {
		t.Fatalf("size after the allocate past eof: %d, %v", info.Size, err)
	}
}