//go:build linux

package host

import (
	"errors"
	"os"
	"path/filepath"
	"strconv"
	"testing"

	"github.com/carlosframework/platform/internal/stopevidence"
)

func TestRev4WritersPrefixCoverage(t *testing.T) {
	for _, shape := range []string{"deleted-wal", "nested", "deleted-nested", "empty-directory"} {
		t.Run(shape, func(t *testing.T) {
			fx := newWritersKernelFixture(t)
			fx.dropAgentHolds(t)
			// No journal identity exists for a file first opened after launch.
			fx.journal.Files = nil
			target := fx.db + "-wal"
			if shape == "nested" || shape == "deleted-nested" {
				target = filepath.Join(filepath.Dir(fx.db), "sqlite", "later.db")
			}
			if err := os.MkdirAll(filepath.Dir(target), 0700); err != nil {
				t.Fatal(err)
			}
			if err := os.WriteFile(target, nil, 0600); err != nil {
				t.Fatal(err)
			}
			held, err := os.Open(target)
			if err != nil {
				t.Fatal(err)
			}
			defer held.Close()
			if shape != "nested" {
				if err := os.Remove(target); err != nil {
					t.Fatal(err)
				}
				target += " (deleted)"
			}
			if shape == "empty-directory" {
				if err := os.Remove(fx.db); err != nil {
					t.Fatal(err)
				}
			}
			// A real descriptor retains its inode after unlink, unlike a dangling fixture symlink.
			pid := strconv.Itoa(os.Getpid())
			if err := os.Symlink(filepath.Join("/proc", pid), filepath.Join(fx.proc, pid)); err != nil {
				t.Fatal(err)
			}
			if _, err := fx.verify(t); !errors.Is(err, stopevidence.ErrForeignHolder) {
				t.Fatalf("foreign %s holder passed writers-stopped: %v", shape, err)
			}
		})
	}
}

func TestRev4WritersPrefixRetainsDescriptorIdentity(t *testing.T) {
	fx := newWritersKernelFixture(t)
	target := filepath.Join(filepath.Dir(fx.db), "sqlite", "later.db")
	if err := os.MkdirAll(filepath.Dir(target), 0700); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(target, nil, 0600); err != nil {
		t.Fatal(err)
	}
	rev3HoldTarget(t, fx, 20, 8, target)
	dev, ino := fileID(t, target)
	fx.hints = append(fx.hints, stopevidence.DescriptorHint{FD: 8, Device: dev, Inode: ino})
	got, err := fx.verify(t)
	if err != nil {
		t.Fatal(err)
	}
	want := stopevidence.Descriptor{PID: 20, TID: 20, FD: 8, Device: dev, Inode: ino}
	if len(got.Retained) != 2 || got.Retained[1] != want {
		t.Fatalf("lost prefix descriptor identity: %+v", got.Retained)
	}
	fx.hints = fx.hints[:1]
	if _, err := fx.verify(t); !errors.Is(err, stopevidence.ErrForeignHolder) {
		t.Fatalf("unhinted prefix: %v", err)
	}
}

func TestRev4WritersPrefixBoundaryAndScanErrors(t *testing.T) {
	t.Run("sibling", func(t *testing.T) {
		fx := newWritersKernelFixture(t)
		target := filepath.Join(filepath.Dir(fx.db)+"-old", "other.db")
		if err := os.MkdirAll(filepath.Dir(target), 0700); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(target, nil, 0600); err != nil {
			t.Fatal(err)
		}
		rev3HoldTarget(t, fx, 31, 8, target)
		if _, err := fx.verify(t); err != nil {
			t.Fatalf("sibling matched: %v", err)
		}
	})
	t.Run("empty-unreadable", func(t *testing.T) {
		fx := newWritersKernelFixture(t)
		fx.dropAgentHolds(t)
		for _, p := range []string{fx.db, fx.db + "-wal"} {
			if err := os.Remove(p); err != nil {
				t.Fatal(err)
			}
		}
		dir := filepath.Join(fx.proc, "31", "task", "31", "fd")
		if err := os.MkdirAll(dir, 0700); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(filepath.Join(dir, "8"), nil, 0600); err != nil {
			t.Fatal(err)
		}
		if _, err := fx.verify(t); err == nil {
			t.Fatal("unreadable table yielded writers-stopped")
		}
	})
}

func TestRev4WritersDeletedReplicatorIdentity(t *testing.T) {
	fx := newWritersKernelFixture(t)
	fx.dropAgentHolds(t)
	path := fx.db + "-wal"
	held, err := os.Open(path)
	if err != nil {
		t.Fatal(err)
	}
	defer held.Close()
	dev, ino := fileID(t, path)
	if err := os.Remove(path); err != nil {
		t.Fatal(err)
	}
	// Keep one real kernel descriptor table under the authenticated fixture
	// process. Readlink reports the deleted name; Stat still reaches the inode.
	fdDir := filepath.Join(fx.proc, "20", "task", "20", "fd")
	if err := os.Remove(fdDir); err != nil {
		t.Fatal(err)
	}
	if err := os.Symlink("/proc/self/fd", fdDir); err != nil {
		t.Fatal(err)
	}
	hint := stopevidence.DescriptorHint{FD: int(held.Fd()), Device: dev, Inode: ino}
	fx.hints = []stopevidence.DescriptorHint{hint}
	got, err := fx.verify(t)
	if err != nil {
		t.Fatal(err)
	}
	want := stopevidence.Descriptor{PID: 20, TID: 20, FD: hint.FD, Device: dev, Inode: ino}
	if len(got.Retained) != 1 || got.Retained[0] != want {
		t.Fatalf("deleted replicator identity: %+v", got.Retained)
	}
	fx.hints[0].Inode++
	if _, err := fx.verify(t); !errors.Is(err, stopevidence.ErrForeignHolder) {
		t.Fatalf("substituted hint exempted deleted file: %v", err)
	}
}