//go:build unix

package instanceguard

import (
	"errors"
	"os"
	"os/exec"
	"path/filepath"
	"testing"
	"time"

	"agent-system-backend/internal/store"
)

func TestAcquireSameResourceAcrossAliases(t *testing.T) {
	base := t.TempDir()
	real := filepath.Join(base, "real")
	if err := os.Mkdir(real, 0o755); err != nil {
		t.Fatal(err)
	}
	link := filepath.Join(base, "link")
	if err := os.Symlink(real, link); err != nil {
		t.Fatal(err)
	}
	held, err := Acquire(link)
	if err != nil {
		t.Fatal(err)
	}
	defer held.Release()
	if _, err := Acquire(real); !errors.Is(err, ErrBusy) {
		t.Fatalf("symlink alias: %v", err)
	}

	wd, err := os.Getwd()
	if err != nil {
		t.Fatal(err)
	}
	if err := os.Chdir(base); err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { _ = os.Chdir(wd) })
	if _, err := Acquire(filepath.Join(".", "real")); !errors.Is(err, ErrBusy) {
		t.Fatalf("relative path: %v", err)
	}
}

func TestHardlinkRejected(t *testing.T) {
	dir := t.TempDir()
	db := filepath.Join(dir, "agent-system.db")
	st, err := store.OpenSQLite(db)
	if err != nil {
		t.Fatal(err)
	}
	if err := st.Close(); err != nil {
		t.Fatal(err)
	}
	if err := os.Link(db, filepath.Join(dir, "alias.db")); err != nil {
		t.Fatal(err)
	}
	if _, err := Acquire(dir); !errors.Is(err, ErrHardlink) {
		t.Fatalf("hardlink: %v", err)
	}
}

func TestDatabaseReplacementRefusedBeforeOpen(t *testing.T) {
	dir := t.TempDir()
	st, release, err := openAndBind(t, dir, "")
	if err != nil {
		t.Fatal(err)
	}
	db := filepath.Join(dir, "agent-system.db")
	release()
	_ = st
	if err := os.Remove(db); err != nil {
		t.Fatal(err)
	}
	raw, err := os.ReadFile(db + ".lock")
	if err != nil {
		t.Fatal(err)
	}
	rec, err := parseRecord(string(raw))
	if err != nil || rec == nil {
		t.Fatal(err)
	}
	for i := 0; i < 16; i++ {
		if err := os.WriteFile(db, []byte("replaced"), 0o600); err != nil {
			t.Fatal(err)
		}
		_, ino, exists, err := statFile(db)
		if err != nil {
			t.Fatal(err)
		}
		if exists && ino != rec.DBIno {
			break
		}
		if err := os.Remove(db); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(filepath.Join(dir, "inode-burn-"+string(rune('a'+i))), []byte("x"), 0o600); err != nil {
			t.Fatal(err)
		}
	}
	lease, err := Acquire(dir)
	if err != nil {
		t.Fatal(err)
	}
	defer lease.Release()
	if err := lease.AutomaticRefusal(); !errors.Is(err, ErrDBReplaced) {
		t.Fatalf("replaced db: %v", err)
	}
	if _, err := os.Stat(db); err != nil {
		t.Fatal(err)
	}
}

func TestMissingRecordedDatabaseRefused(t *testing.T) {
	dir := t.TempDir()
	_, release, err := openAndBind(t, dir, "")
	if err != nil {
		t.Fatal(err)
	}
	release()
	db := filepath.Join(dir, "agent-system.db")
	if err := os.Remove(db); err != nil {
		t.Fatal(err)
	}
	lease, err := Acquire(dir)
	if err != nil {
		t.Fatal(err)
	}
	defer lease.Release()
	if err := lease.AutomaticRefusal(); !errors.Is(err, ErrDBMissing) {
		t.Fatalf("missing db: %v", err)
	}
}

func TestRebuiltLockRefusedUntilAdopt(t *testing.T) {
	dir := t.TempDir()
	st, release, err := openAndBind(t, dir, "inst-a")
	if err != nil {
		t.Fatal(err)
	}
	release()
	_ = st.Close()
	if err := os.Remove(filepath.Join(dir, "agent-system.db.lock")); err != nil {
		t.Fatal(err)
	}
	lease, err := Acquire(dir)
	if err != nil {
		t.Fatal(err)
	}
	if err := lease.AutomaticRefusal(); err != nil {
		lease.Release()
		t.Fatal(err)
	}
	opened, err := store.OpenSQLite(lease.DBPath())
	if err != nil {
		lease.Release()
		t.Fatal(err)
	}
	err = Bind(opened, lease, BindOptions{InstanceID: "inst-a"})
	_ = opened.Close()
	lease.Release()
	if !errors.Is(err, ErrLockRebuilt) {
		t.Fatalf("rebuilt lock: %v", err)
	}

	adopted, err := Acquire(dir)
	if err != nil {
		t.Fatal(err)
	}
	defer adopted.Release()
	opened, err = store.OpenSQLite(adopted.DBPath())
	if err != nil {
		t.Fatal(err)
	}
	defer opened.Close()
	if err := Bind(opened, adopted, BindOptions{Adopt: true, InstanceID: "inst-a"}); err != nil {
		t.Fatal(err)
	}
}

func TestClearedLockRecordRefusedWhenInodeStays(t *testing.T) {
	dir := t.TempDir()
	st, release, err := openAndBind(t, dir, "inst-a")
	if err != nil {
		t.Fatal(err)
	}
	release()
	_ = st.Close()
	lockPath := filepath.Join(dir, "agent-system.db.lock")
	if err := os.Truncate(lockPath, 0); err != nil {
		t.Fatal(err)
	}
	lease, err := Acquire(dir)
	if err != nil {
		t.Fatal(err)
	}
	opened, err := store.OpenSQLite(lease.DBPath())
	if err != nil {
		lease.Release()
		t.Fatal(err)
	}
	err = Bind(opened, lease, BindOptions{InstanceID: "inst-a"})
	_ = opened.Close()
	lease.Release()
	if !errors.Is(err, ErrLockRebuilt) {
		t.Fatalf("cleared lock: %v", err)
	}
}

func TestInstanceMismatchPreservesEmpty(t *testing.T) {
	dir := t.TempDir()
	st, release, err := openAndBind(t, dir, "inst-a")
	if err != nil {
		t.Fatal(err)
	}
	release()
	_ = st.Close()

	lease, err := Acquire(dir)
	if err != nil {
		t.Fatal(err)
	}
	opened, err := store.OpenSQLite(lease.DBPath())
	if err != nil {
		lease.Release()
		t.Fatal(err)
	}
	err = Bind(opened, lease, BindOptions{InstanceID: "inst-b"})
	_ = opened.Close()
	lease.Release()
	if !errors.Is(err, ErrInstanceMismatch) {
		t.Fatalf("mismatch: %v", err)
	}

	lease, err = Acquire(dir)
	if err != nil {
		t.Fatal(err)
	}
	defer lease.Release()
	opened, err = store.OpenSQLite(lease.DBPath())
	if err != nil {
		t.Fatal(err)
	}
	defer opened.Close()
	if err := Bind(opened, lease, BindOptions{}); err != nil {
		t.Fatal(err)
	}
	marker, ok, err := opened.LoadInstanceGuard()
	if err != nil || !ok || marker.InstanceID != "inst-a" {
		t.Fatalf("empty id should keep marker: ok=%v id=%q err=%v", ok, marker.InstanceID, err)
	}
}

func TestLockReleasedAfterKill(t *testing.T) {
	if os.Getenv("U8_GUARD_ROLE") == "hold" {
		lease, err := Acquire(os.Getenv("U8_GUARD_DIR"))
		if err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(os.Getenv("U8_GUARD_READY"), []byte("ready"), 0o600); err != nil {
			t.Fatal(err)
		}
		time.Sleep(30 * time.Second)
		lease.Release()
		return
	}
	dir := t.TempDir()
	ready := filepath.Join(dir, "ready")
	cmd := exec.Command(os.Args[0], "-test.run=TestLockReleasedAfterKill")
	cmd.Env = append(os.Environ(), "U8_GUARD_ROLE=hold", "U8_GUARD_DIR="+dir, "U8_GUARD_READY="+ready)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	if err := cmd.Start(); err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() {
		if cmd.Process != nil {
			_ = cmd.Process.Kill()
			_, _ = cmd.Process.Wait()
		}
	})
	deadline := time.Now().Add(10 * time.Second)
	for time.Now().Before(deadline) {
		if _, err := os.Stat(ready); err == nil {
			break
		}
		time.Sleep(20 * time.Millisecond)
	}
	if _, err := os.Stat(ready); err != nil {
		t.Fatal(err)
	}
	if _, err := Acquire(dir); !errors.Is(err, ErrBusy) {
		t.Fatalf("held: %v", err)
	}
	if err := cmd.Process.Kill(); err != nil {
		t.Fatal(err)
	}
	_, _ = cmd.Process.Wait()
	lease, err := Acquire(dir)
	if err != nil {
		t.Fatal(err)
	}
	lease.Release()
}

func TestMissingDataDirIsCreatedBeforeLock(t *testing.T) {
	dir := filepath.Join(t.TempDir(), "nested", "data")
	lease, err := Acquire(dir)
	if err != nil {
		t.Fatal(err)
	}
	lease.Release()
	if _, err := os.Stat(dir); err != nil {
		t.Fatal(err)
	}
}

func TestLockSymlinkCannotAliasDatabase(t *testing.T) {
	dir := t.TempDir()
	db := filepath.Join(dir, "agent-system.db")
	st, err := store.OpenSQLite(db)
	if err != nil {
		t.Fatal(err)
	}
	if err := st.Close(); err != nil {
		t.Fatal(err)
	}
	if err := os.Remove(db + ".lock"); err != nil && !os.IsNotExist(err) {
		t.Fatal(err)
	}
	if err := os.Symlink(db, db+".lock"); err != nil {
		t.Fatal(err)
	}
	before, err := os.ReadFile(db)
	if err != nil {
		t.Fatal(err)
	}
	if _, err := Acquire(dir); !errors.Is(err, ErrLockAliased) {
		t.Fatalf("symlink lock: %v", err)
	}
	after, err := os.ReadFile(db)
	if err != nil {
		t.Fatal(err)
	}
	if string(before) != string(after) {
		t.Fatal("aliased lock wrote into the database")
	}
}

func TestSymlinkedDatabaseLocksResolvedFile(t *testing.T) {
	base := t.TempDir()
	realDir := filepath.Join(base, "real")
	aliasDir := filepath.Join(base, "alias")
	if err := os.Mkdir(realDir, 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.Mkdir(aliasDir, 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(realDir, "agent-system.db"), []byte{}, 0o600); err != nil {
		t.Fatal(err)
	}
	if err := os.Symlink(filepath.Join(realDir, "agent-system.db"), filepath.Join(aliasDir, "agent-system.db")); err != nil {
		t.Fatal(err)
	}
	held, err := Acquire(aliasDir)
	if err != nil {
		t.Fatal(err)
	}
	defer held.Release()
	if _, err := os.Stat(filepath.Join(realDir, "agent-system.db.lock")); err != nil {
		t.Fatal(err)
	}
	if _, err := Acquire(realDir); !errors.Is(err, ErrBusy) {
		t.Fatalf("resolved db lock: %v", err)
	}
}

func openAndBind(t *testing.T, dir, instanceID string) (*store.Store, func(), error) {
	t.Helper()
	lease, err := Acquire(dir)
	if err != nil {
		return nil, nil, err
	}
	if err := lease.AutomaticRefusal(); err != nil {
		lease.Release()
		return nil, nil, err
	}
	st, err := store.OpenSQLite(lease.DBPath())
	if err != nil {
		lease.Release()
		return nil, nil, err
	}
	if err := Bind(st, lease, BindOptions{InstanceID: instanceID}); err != nil {
		_ = st.Close()
		lease.Release()
		return nil, nil, err
	}
	return st, func() {
		_ = st.Close()
		lease.Release()
	}, nil
}