package persistence

// Regression: when a transaction's apply fails AND its rollback fails, the
// journal is the only durable record of the pre-transaction before-images.
// Deleting it at commit time made the corruption permanent; it must be kept
// so the next Recover call (or operator repair) can retry the rollback.

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

func TestCommitKeepsJournalAfterFailedRollback(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "character.yaml")
	if err := os.WriteFile(path, []byte("before"), 0600); err != nil {
		t.Fatal(err)
	}
	journalDir := filepath.Join(dir, "journals")
	txn := NewTransaction(journalDir)
	if err := txn.Replace(path, []byte("after"), 0600); err != nil {
		t.Fatal(err)
	}
	// Deterministically force both the apply and the rollback writes to
	// fail after the snapshot: the target becomes a nonempty directory,
	// so WriteFile cannot create the file and rollback cannot restore it.
	if err := os.Remove(path); err != nil {
		t.Fatal(err)
	}
	if err := os.Mkdir(path, 0700); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(path, "blocker"), []byte("x"), 0600); err != nil {
		t.Fatal(err)
	}

	err := txn.Commit()
	if err == nil || !strings.Contains(err.Error(), "rollback failed") {
		t.Fatalf("need an apply+rollback failure, got: %v", err)
	}
	entries, err := ListJournalFiles(journalDir)
	if err != nil {
		t.Fatal(err)
	}
	if len(entries) == 0 {
		t.Fatal("failed rollback deleted the only durable before-image; restart cannot recover the pre-transaction state")
	}
}

// TestRecoverRetriesKeptRollbackJournal: after the operator repairs the
// fault that broke the rollback, the next Recover completes it.
func TestRecoverRetriesKeptRollbackJournal(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "character.yaml")
	if err := os.WriteFile(path, []byte("before"), 0600); err != nil {
		t.Fatal(err)
	}
	journalDir := filepath.Join(dir, "journals")
	txn := NewTransaction(journalDir)
	if err := txn.Replace(path, []byte("after"), 0600); err != nil {
		t.Fatal(err)
	}
	if err := os.Remove(path); err != nil {
		t.Fatal(err)
	}
	if err := os.Mkdir(path, 0700); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(path, "blocker"), []byte("x"), 0600); err != nil {
		t.Fatal(err)
	}
	if err := txn.Commit(); err == nil {
		t.Fatal("expected the injected apply/rollback failure")
	}

	// Operator repair: put the pre-transaction file back.
	if err := os.RemoveAll(path); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(path, []byte("after"), 0600); err != nil {
		t.Fatal(err)
	}
	if err := Recover(journalDir); err != nil {
		t.Fatalf("recovery retry failed: %v", err)
	}
	data, err := os.ReadFile(path)
	if err != nil {
		t.Fatal(err)
	}
	if string(data) != "before" {
		t.Fatalf("recovery did not roll back to the before-image: %q", data)
	}
	entries, err := ListJournalFiles(journalDir)
	if err != nil {
		t.Fatal(err)
	}
	if len(entries) != 0 {
		t.Fatalf("completed recovery left journals behind: %v", entries)
	}
}