package backup

import (
	"context"
	"io"
	"log"
	"os"
	"path/filepath"
	"strings"
	"testing"
)

// R-355's second half. The naming defect does not stop at the backup: writeSafetyDump filters the
// discovered databases with `db.StackName == stackName`, so an app whose database is attributed to the
// wrong stack has NO database as far as the destructive restore is concerned. It therefore takes no
// undo copy, and the fail-closed refusal that protects every other app cannot fire — the guard is not
// bypassed, it is never reached.
//
// Measured live on 2026-08-21: a destructive restore of `paperless-ngx` ran to completion over a live
// 72-table PostgreSQL with `find /mnt -name "pre-restore-*"` empty both before and after.

func newSafetyTestManager() *Manager {
	return &Manager{logger: log.New(io.Discard, "", 0)}
}

// TestR355_SafetyDumpIsTakenForTheCorrectlyAttributedApp is scenario B: the undo copy exists.
func TestR355_SafetyDumpIsTakenForTheCorrectlyAttributedApp(t *testing.T) {
	nsRoot := t.TempDir()
	m := newSafetyTestManager()

	// Post-fix attribution: the compose project label resolves this container to `paperless-ngx`.
	m.discoverDBs = func(ctx context.Context) ([]DiscoveredDB, error) {
		return []DiscoveredDB{
			{StackName: "paperless-ngx", DBType: DBTypePostgres, ContainerName: "paperless-postgres", ContainerID: "cid"},
		}, nil
	}
	m.safetyDumpFn = func(ctx context.Context, db DiscoveredDB, dumpDir string) DumpResult {
		p := filepath.Join(dumpDir, string(db.StackName)+"-"+string(db.DBType)+".sql")
		if err := os.MkdirAll(dumpDir, 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(p, []byte("-- 72 tables\n"), 0o644); err != nil {
			t.Fatal(err)
		}
		return DumpResult{DB: db, FilePath: p, Size: 13}
	}

	// v0.220.0 (R-379): writeSafetyDump returns the SET it wrote, so a rollback can re-apply EVERY
	// database's undo. `.First()` is the value this signature returned before; these assertions are
	// unchanged in meaning.
	set, err := m.writeSafetyDump(context.Background(), "paperless-ngx", nsRoot)
	safety := set.First()
	if err != nil {
		t.Fatalf("writeSafetyDump: %v", err)
	}
	if safety == "" {
		t.Fatal("no safety dump was taken for an app that HAS a database — the restore would proceed with no undo")
	}
	if _, err := os.Stat(safety); err != nil {
		t.Fatalf("the safety dump path %q is not on disk: %v", safety, err)
	}
	if !strings.Contains(filepath.Base(safety), "pre-restore-") {
		t.Errorf("the undo copy must carry the pre-restore prefix so it can never be replayed as a source; got %q", filepath.Base(safety))
	}
	// The consequence that matters: it lives inside THIS app's unit, not a phantom's.
	if got, want := filepath.Dir(safety), AppDBDumpPath(nsRoot, "paperless-ngx"); got != want {
		t.Errorf("undo copy written to %q, want %q", got, want)
	}
}

// TestR355_MisattributedAppGetsNoUndoCopy demonstrates the WRONG OUTCOME — the state the fix removes.
// It models the pre-fix attribution (`paperless`) against a restore of `paperless-ngx` and asserts the
// undo silently does not happen. This is the shape that made a destructive restore unrecoverable.
func TestR355_MisattributedAppGetsNoUndoCopy(t *testing.T) {
	nsRoot := t.TempDir()
	m := newSafetyTestManager()

	// PRE-FIX attribution: deriveStackName gave `paperless` for container `paperless-postgres`.
	m.discoverDBs = func(ctx context.Context) ([]DiscoveredDB, error) {
		return []DiscoveredDB{
			{StackName: "paperless", DBType: DBTypePostgres, ContainerName: "paperless-postgres", ContainerID: "cid"},
		}, nil
	}
	called := false
	m.safetyDumpFn = func(ctx context.Context, db DiscoveredDB, dumpDir string) DumpResult {
		called = true
		return DumpResult{DB: db}
	}

	// v0.220.0 (R-379): writeSafetyDump returns the SET it wrote, so a rollback can re-apply EVERY
	// database's undo. `.First()` is the value this signature returned before; these assertions are
	// unchanged in meaning.
	set, err := m.writeSafetyDump(context.Background(), "paperless-ngx", nsRoot)
	safety := set.First()
	if err != nil {
		t.Fatalf("writeSafetyDump: %v", err)
	}
	if safety != "" || called {
		t.Fatalf("precondition lost: the misattributed shape now takes an undo copy (safety=%q called=%v) — "+
			"this test documents the defect and must keep failing to find one", safety, called)
	}
	// And this is precisely why it was invisible: no error, no dump, and the caller reads
	// `hasDB == false` — indistinguishable from an app that genuinely has no database.
}

// TestR355_RestoreRefusesWhenTheUndoCannotBeTaken is scenario C, the fail-closed direction. The
// invariant already existed and was proven working live on 2026-08-21 for `romm`; this pins it for the
// app that could not reach it before, so the two cannot drift apart.
func TestR355_RestoreRefusesWhenTheUndoCannotBeTaken(t *testing.T) {
	nsRoot := t.TempDir()
	m := newSafetyTestManager()

	m.discoverDBs = func(ctx context.Context) ([]DiscoveredDB, error) {
		return []DiscoveredDB{
			{StackName: "paperless-ngx", DBType: DBTypePostgres, ContainerName: "paperless-postgres", ContainerID: "cid"},
		}, nil
	}
	m.safetyDumpFn = func(ctx context.Context, db DiscoveredDB, dumpDir string) DumpResult {
		return DumpResult{DB: db, Error: os.ErrPermission}
	}

	// v0.220.0 (R-379): writeSafetyDump returns the SET it wrote, so a rollback can re-apply EVERY
	// database's undo. `.First()` is the value this signature returned before; these assertions are
	// unchanged in meaning.
	set, err := m.writeSafetyDump(context.Background(), "paperless-ngx", nsRoot)
	safety := set.First()
	if err == nil {
		t.Fatal("a database that cannot be dumped must be a hard error — the undo would not exist")
	}
	if safety != "" {
		t.Errorf("a failed undo must return no path, got %q", safety)
	}
	// The message must say the restore did not start, because that is the customer's only signal.
	if !strings.Contains(err.Error(), "nem indult el") {
		t.Errorf("the refusal must state that the restore did not start; got %q", err.Error())
	}
}