package tenant

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

func newFS(t *testing.T) (*FS, string) {
	t.Helper()
	dir := t.TempDir()
	fs, err := Open(filepath.Join(dir, "user"))
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { _ = fs.Close() })
	return fs, dir
}

func TestWriteReadStat(t *testing.T) {
	fs, _ := newFS(t)
	if err := fs.WriteFile("a/b/note.md", []byte("hello")); err != nil {
		t.Fatal(err)
	}
	got, err := fs.ReadFile("a/b/note.md")
	if err != nil {
		t.Fatal(err)
	}
	if string(got) != "hello" {
		t.Errorf("got %q", got)
	}
	fi, err := fs.Stat("a/b/note.md")
	if err != nil {
		t.Fatal(err)
	}
	if fi.Size() != 5 {
		t.Errorf("size %d", fi.Size())
	}
}

func TestRemove(t *testing.T) {
	fs, _ := newFS(t)
	_ = fs.WriteFile("x.md", []byte("x"))
	if err := fs.Remove("x.md"); err != nil {
		t.Fatal(err)
	}
	if _, err := fs.ReadFile("x.md"); !errors.Is(err, ErrNotFound) {
		t.Errorf("expected ErrNotFound, got %v", err)
	}
}

func TestList(t *testing.T) {
	fs, _ := newFS(t)
	_ = fs.WriteFile("one.md", []byte("1"))
	_ = fs.WriteFile("sub/two.md", []byte("2"))
	root, err := fs.List(".")
	if err != nil {
		t.Fatal(err)
	}
	if len(root) != 2 {
		t.Errorf("root entries: %v", root)
	}
	sub, err := fs.List("sub")
	if err != nil {
		t.Fatal(err)
	}
	if len(sub) != 1 || sub[0] != "two.md" {
		t.Errorf("sub entries: %v", sub)
	}
}

// TestPathTraversalAttacks covers every traversal vector we care
// about. They must all be blocked.
func TestPathTraversalAttacks(t *testing.T) {
	fs, dir := newFS(t)
	// Plant a file outside the tenant root that we'll try to reach.
	outside := filepath.Join(dir, "secret.txt")
	if err := os.WriteFile(outside, []byte("classified"), 0o600); err != nil {
		t.Fatal(err)
	}

	cases := []string{
		"../secret.txt",
		"../../secret.txt",
		"a/../../secret.txt",
		"./../secret.txt",
		"/etc/passwd",
		`\windows\system32`,
		"\x00",
		"foo\x00bar",
		"..",
		".",
		"",
	}
	for _, p := range cases {
		t.Run(p, func(t *testing.T) {
			if _, err := fs.ReadFile(p); err == nil {
				t.Errorf("ReadFile(%q) succeeded unexpectedly", p)
			}
			if err := fs.WriteFile(p, []byte("x")); err == nil {
				t.Errorf("WriteFile(%q) succeeded unexpectedly", p)
			}
			if err := fs.Remove(p); err == nil {
				t.Errorf("Remove(%q) succeeded unexpectedly", p)
			}
		})
	}
}

// TestSymlinkEscapeBlocked verifies that a symlink whose target is
// outside the tenant root cannot be used to read or write files.
// os.Root refuses to follow symlinks that escape the root.
func TestSymlinkEscapeBlocked(t *testing.T) {
	if runtime.GOOS == "windows" {
		t.Skip("symlink semantics differ on windows")
	}
	fs, dir := newFS(t)

	outside := filepath.Join(dir, "outside.txt")
	if err := os.WriteFile(outside, []byte("classified"), 0o600); err != nil {
		t.Fatal(err)
	}
	// Drop a symlink inside the tenant dir pointing at the outside
	// file. We do this via os directly because FS doesn't expose
	// symlink creation (and rightfully so).
	if err := os.Symlink(outside, filepath.Join(fs.Dir(), "escape")); err != nil {
		t.Fatal(err)
	}
	if _, err := fs.ReadFile("escape"); err == nil {
		t.Errorf("ReadFile through symlink succeeded; expected error")
	}
}

func TestRootIsolation(t *testing.T) {
	// Two FS instances rooted at sibling dirs cannot see each other.
	parent := t.TempDir()
	a, err := Open(filepath.Join(parent, "a"))
	if err != nil {
		t.Fatal(err)
	}
	defer a.Close()
	b, err := Open(filepath.Join(parent, "b"))
	if err != nil {
		t.Fatal(err)
	}
	defer b.Close()
	_ = a.WriteFile("note.md", []byte("a"))
	if _, err := b.ReadFile("note.md"); !errors.Is(err, ErrNotFound) {
		t.Errorf("b read a's file: %v", err)
	}
	if _, err := b.ReadFile("../a/note.md"); err == nil {
		t.Errorf("b reached a via traversal")
	}
}

func TestMissingFileReturnsErrNotFound(t *testing.T) {
	fs, _ := newFS(t)
	if _, err := fs.ReadFile("missing.md"); !errors.Is(err, ErrNotFound) {
		t.Errorf("got %v", err)
	}
	if _, err := fs.Stat("missing.md"); !errors.Is(err, ErrNotFound) {
		t.Errorf("got %v", err)
	}
}

func TestPermissions(t *testing.T) {
	if runtime.GOOS == "windows" {
		t.Skip("permission semantics differ on windows")
	}
	fs, _ := newFS(t)
	fi, err := os.Stat(fs.Dir())
	if err != nil {
		t.Fatal(err)
	}
	if mode := fi.Mode().Perm(); mode != 0o700 {
		t.Errorf("expected 0700 on tenant dir, got %o", mode)
	}
}