package backup

import (
	"context"
	"os"
	"path/filepath"
	"strings"
	"sync/atomic"
	"testing"

	"gitea.dooplex.hu/admin/felhom-controller/internal/settings"
)

// ── R-357 — the ONE restore that deletes and replaces data had no free-space gate ────────────────
//
// The two gentler paths both check (offbox_restore.go: the prepare gate and PlaceOffsiteRestore's
// missing-only merge). `offbox_reconstitute.go` contained ZERO references to offboxFree.
//
// Measured on demo-hp 2026-08-21: the destructive restore stopped the app, ran out of disk part-way,
// left 2 of 5 planted items in place and restarted the app — a half-restored dataset presented as a
// completed restore.
//
// WHAT THESE ASSERT IS THE NON-EFFECT, NOT THE ERROR STRING. The value of the fix is that the app is
// never stopped: a gate placed after StopStack would turn a refusal into an outage and would still
// return the right sentence. So `stops == 0` is the assertion that can fail on a wrong-but-plausible
// implementation, and the message is checked second.

// r357Provider counts StopStack so the non-effect is measurable, and reports the app as deployed so
// the reconstitute reaches the gate rather than refusing earlier for an unrelated reason.
type r357Provider struct {
	hdd   string
	stops int32
}

func (p *r357Provider) GetStackComposePath(string) (string, bool) { return "", false }
func (p *r357Provider) ListDeployedStacks() []StackSummary {
	return []StackSummary{{Name: "paperless-ngx"}}
}
func (p *r357Provider) GetStackHDDMounts(string) []string { return nil }
func (p *r357Provider) GetStackHDDPath(string) string     { return p.hdd }
func (p *r357Provider) GetImportRoot() string             { return "" }
func (p *r357Provider) GetDockerVolumes(string) []string  { return nil }
func (p *r357Provider) StopStack(string) error            { atomic.AddInt32(&p.stops, 1); return nil }
func (p *r357Provider) StartStack(string) error           { return nil }
func (p *r357Provider) RefreshAndIsRunning(string) bool   { return true }
func (p *r357Provider) GetStackRecoveryInfo(string) (RecoveryInfo, bool) {
	return RecoveryInfo{}, false
}
func (p *r357Provider) RecoverStackSecrets(string, []string) map[string]string { return nil }
func (p *r357Provider) RecreateStackDefinitionFromUnit(string, string, map[string]string) error {
	return nil
}
func (p *r357Provider) StartStackServices(string, []string) error { return nil }
func (p *r357Provider) GetStackClassifiedBinds(string) ([]ClassifiedBind, bool) {
	return nil, false
}

// newR357Manager builds a manager whose reconstitute reaches the headroom gate: a real scratch on
// disk, a stubbed snapshot lookup (no restic), and the app reported deployed.
func newR357Manager(t *testing.T) (*Manager, *r357Provider) {
	t.Helper()
	m, sett := newOffboxManager(t)
	drive := t.TempDir()
	if err := sett.AddStoragePath(settings.StoragePath{Path: drive, Label: "drive", Schedulable: true}); err != nil {
		t.Fatal(err)
	}
	prov := &r357Provider{hdd: drive}
	m.SetStackProvider(prov)

	scratch, _, err := m.offboxRestoreScratchDir("paperless-ngx")
	if err != nil {
		t.Fatal(err)
	}

	// THE FIXTURE MUST REACH StopStack WHEN THE GATE IS REMOVED, or `stops == 0` proves nothing.
	// The first draft of this test did not: without the gate the run refused earlier, at the stat
	// pre-pass over the placements, so the assertion passed against the pre-fix code. That is a hollow
	// test, and the red-proof is what exposed it — recorded here because the near-miss is the lesson.
	//
	// So the scratch is populated the way a real completed download leaves it: `mapOffsiteRestorePaths`
	// builds each src as filepath.Join(scratch, <full snapshot path>), so the snapshot's own absolute
	// path is mirrored underneath the scratch.
	const oldNs = "/mnt/old"
	snapPaths := []string{oldNs + "/backups/primary/paperless-ngx", oldNs + "/appdata/paperless-ngx"}
	for _, sp := range snapPaths {
		if err := os.MkdirAll(filepath.Join(scratch, sp), 0o755); err != nil {
			t.Fatal(err)
		}
	}
	m.SetOffboxLatestSnapshotFn(func(context.Context, string) (string, []string, error) {
		return "snap-1", snapPaths, nil
	})
	// No Docker in a unit test: the undo copy is seamed out. It runs BEFORE StopStack, so leaving it
	// real would make the fixture fail for a reason that has nothing to do with the gate.
	m.SetSafetyDumpFn(func(context.Context, DiscoveredDB, string) DumpResult { return DumpResult{} })
	return m, prov
}

func TestR357_DestructiveRestoreRefusesWithoutHeadroom(t *testing.T) {
	m, prov := newR357Manager(t)
	m.SetOffboxSizer(func(string) int64 { return 1024 * 1024 }) // the scratch is 1 MB
	m.SetOffboxFreeFn(func(string) int64 { return 300 * 1024 }) // 300 KB free

	_, err := m.ReconstituteFromOffsite(context.Background(), "paperless-ngx", false)

	// THE ASSERTION THAT MATTERS, AND IT IS CHECKED FIRST ON PURPOSE. On 2026-08-21 the app went down
	// and came back over a half-written dataset. A gate placed after StopStack would return the right
	// sentence and still take the outage, so the error text cannot be the primary assertion — and if
	// this is checked second, a removed gate reports "no error returned" instead of naming the outage.
	if n := atomic.LoadInt32(&prov.stops); n != 0 {
		t.Fatalf("THE APP WAS STOPPED (%d call(s)) for a restore with 300 KB free for a 1 MB copy — "+
			"the whole point of this gate is that the customer's app never goes down for a restore "+
			"that cannot run (err=%v)", n, err)
	}
	if err == nil {
		t.Fatal("the destructive restore proceeded with 300 KB free for a 1 MB copy")
	}
	for _, want := range []string{"Nincs elég szabad hely", "szükséges", "szabad"} {
		if !strings.Contains(err.Error(), want) {
			t.Errorf("the refusal must name need and free like its two siblings; missing %q in %q", want, err.Error())
		}
	}
}

func TestR357_UnknownSizeFailsClosed(t *testing.T) {
	// The fail-open hole this closes is subtle: with need = 0 the comparison `free < need` is FALSE,
	// so an unmeasurable scratch sailed straight into the destructive phase. A gate that is present
	// and inert is worse than no gate, because it reads as protection.
	m, prov := newR357Manager(t)
	m.SetOffboxSizer(func(string) int64 { return 0 })
	m.SetOffboxFreeFn(func(string) int64 { return 100 << 30 }) // plenty free — irrelevant

	_, err := m.ReconstituteFromOffsite(context.Background(), "paperless-ngx", false)
	if n := atomic.LoadInt32(&prov.stops); n != 0 {
		t.Fatalf("THE APP WAS STOPPED (%d call(s)) on an unknown size — fail-closed means refuse "+
			"BEFORE the stop, not report an error after it (err=%v)", n, err)
	}
	if err == nil {
		t.Fatal("an unmeasurable scratch was allowed into the destructive restore")
	}
	if !strings.Contains(err.Error(), "nem állapítható meg") {
		t.Errorf("want the size-unknown wording already used by OffboxRestorePrepareFull; got %q", err.Error())
	}
}

func TestR357_UnknownFreeSpaceFailsClosed(t *testing.T) {
	// The mirror hole: free = 0 and need = 0 also compares false. Both probes fail closed.
	m, prov := newR357Manager(t)
	m.SetOffboxSizer(func(string) int64 { return 1024 })
	m.SetOffboxFreeFn(func(string) int64 { return 0 })

	_, err := m.ReconstituteFromOffsite(context.Background(), "paperless-ngx", false)
	if n := atomic.LoadInt32(&prov.stops); n != 0 {
		t.Fatalf("THE APP WAS STOPPED (%d call(s)) on an unknown free reading (err=%v)", n, err)
	}
	if err == nil {
		t.Fatal("an unmeasurable free-space reading was allowed into the destructive restore")
	}
}

func TestR357_AmpleSpaceIsUnchanged(t *testing.T) {
	// The gate must not become a new way to fail an ordinary restore. With room to spare it does not
	// fire, and the run proceeds past it — which here means it fails LATER, for its own unrelated
	// reasons, never with a headroom sentence.
	m, _ := newR357Manager(t)
	m.SetOffboxSizer(func(string) int64 { return 1024 })
	m.SetOffboxFreeFn(func(string) int64 { return 100 << 30 })

	_, err := m.ReconstituteFromOffsite(context.Background(), "paperless-ngx", false)
	if err != nil && strings.Contains(err.Error(), "Nincs elég szabad hely") {
		t.Fatalf("the headroom gate fired with 100 GiB free for a 1 KiB copy: %v", err)
	}
	if err != nil && strings.Contains(err.Error(), "nem állapítható meg") {
		t.Fatalf("the size-unknown branch fired on a measurable scratch: %v", err)
	}
}