package backup

import (
	"context"
	"os"
	"strings"
	"testing"
)

// placeFixture builds a manager + provider with a scratch dir for stack on drive, a snapshot whose
// paths anchor on `oldNs`, and (per `full`) the reconstructed scratch srcs on disk. Returns the copier
// invocation counter pointer and the scratch dir. Free/size seams default to "plenty of room".
func placeFixture(t *testing.T, full bool) (*Manager, *offbox3aProvider, string, *int) {
	t.Helper()
	drive := t.TempDir()
	m, _, prov := classifiedOffboxManager(t, drive)
	prov.hdd["immich"] = drive

	scratch, liveNs, err := m.offboxRestoreScratchDir("immich")
	if err != nil {
		t.Fatal(err)
	}
	if err := os.MkdirAll(scratch, 0o755); err != nil {
		t.Fatal(err)
	}
	// Snapshot paths anchored on a synthetic POSIX namespace (drive-churn realistic; also avoids the
	// Windows volume-letter that filepath.Join can't nest — prod paths are Linux, no volume).
	oldNs := "/felhomdata/ns"
	unitP := oldNs + "/backups/primary/immich"
	dataP := oldNs + "/appdata/immich"
	snapPaths := []string{unitP, dataP}

	// Create the reconstructed scratch srcs the code will stat — computed via the pure mapper so the
	// fixture matches the code's own path arithmetic (no hand-predicting OS separators).
	placements, err := mapOffsiteRestorePaths(snapPaths, "immich", scratch, liveNs)
	if err != nil {
		t.Fatal(err)
	}
	for _, pl := range placements {
		if !full && !pl.isUnit {
			continue // unit-only scratch: userdata src deliberately absent (Scenario C)
		}
		if err := os.MkdirAll(pl.src, 0o755); err != nil {
			t.Fatal(err)
		}
	}

	m.SetOffboxFreeFn(func(string) int64 { return 100 << 30 })
	m.SetOffboxSizer(func(string) int64 { return 1 << 20 })
	m.SetOffboxRunner(func(_ context.Context, _ []string, args ...string) ([]byte, error) {
		if contains(args, "snapshots") {
			return []byte(`[{"short_id":"a","time":"2026-07-15T00:00:00Z","paths":["` + unitP + `","` + dataP + `"]}]`), nil
		}
		return nil, nil
	})
	var copies int
	m.SetOffboxPlaceCopier(func(_, _ string) (int, error) { copies++; return 1, nil })
	return m, prov, scratch, &copies
}

// A (F-3a-1a): undeployed placement refused with ZERO copies (never merges onto the SSD namespace).
func TestPlace_UndeployedRefused(t *testing.T) {
	m, prov, scratch, copies := placeFixture(t, true)
	prov.hdd["immich"] = "" // undeployed
	err := m.PlaceOffsiteRestore(context.Background(), "immich")
	if err == nil || !strings.Contains(err.Error(), "nincs telepítve") {
		t.Fatalf("undeployed must refuse with 'nincs telepítve', got %v", err)
	}
	if *copies != 0 {
		t.Errorf("copier must NOT run for an undeployed app, got %d", *copies)
	}
	if _, sErr := os.Stat(scratch); sErr != nil {
		t.Error("scratch must be untouched on refusal")
	}
}

// B (F-3a-1b): placement headroom gate refuses BEFORE any copy.
func TestPlace_HeadroomRefused(t *testing.T) {
	m, _, _, copies := placeFixture(t, true)
	m.SetOffboxFreeFn(func(string) int64 { return 1 }) // 1 byte free
	m.SetOffboxSizer(func(string) int64 { return 1 << 30 })
	err := m.PlaceOffsiteRestore(context.Background(), "immich")
	if err == nil || !strings.Contains(err.Error(), "Nincs elég szabad hely") {
		t.Fatalf("headroom gate must refuse, got %v", err)
	}
	if *copies != 0 {
		t.Errorf("copier must NOT run when headroom fails, got %d", *copies)
	}
}

// C (F-3a-4): a unit-only scratch (userdata src absent) refuses with ZERO copies (stat pre-pass).
func TestPlace_IncompleteScratchRefusedNoCopies(t *testing.T) {
	m, _, _, copies := placeFixture(t, false) // full=false → userdata src missing
	err := m.PlaceOffsiteRestore(context.Background(), "immich")
	if err == nil || !strings.Contains(err.Error(), "hiányos") {
		t.Fatalf("incomplete scratch must refuse with 'hiányos', got %v", err)
	}
	if *copies != 0 {
		t.Errorf("stat pre-pass must refuse BEFORE any copy, got %d copies", *copies)
	}
}

// E (F-3a-2): success removes the scratch (ready-gate flips false); failure keeps it.
func TestPlace_ScratchLifecycle(t *testing.T) {
	// success
	m, _, scratch, copies := placeFixture(t, true)
	if err := m.PlaceOffsiteRestore(context.Background(), "immich"); err != nil {
		t.Fatalf("placement: %v", err)
	}
	if *copies == 0 {
		t.Error("expected at least one copy on success")
	}
	if _, sErr := os.Stat(scratch); !os.IsNotExist(sErr) {
		t.Errorf("scratch must be removed after success, stat err=%v", sErr)
	}
	if m.OffboxFullScratchReady("immich") {
		t.Error("OffboxFullScratchReady must be false after cleanup")
	}

	// failure keeps the scratch
	m2, _, scratch2, _ := placeFixture(t, true)
	m2.SetOffboxPlaceCopier(func(_, _ string) (int, error) { return 0, os.ErrPermission })
	if err := m2.PlaceOffsiteRestore(context.Background(), "immich"); err == nil {
		t.Fatal("a copier failure must surface as an error")
	}
	if _, sErr := os.Stat(scratch2); sErr != nil {
		t.Errorf("scratch must be KEPT after a failed placement (retry), stat err=%v", sErr)
	}
}

// D (F-3a-3): mapping refuses the namespace root itself among the snapshot paths.
func TestMapOffsiteRestorePaths_RefusesNamespaceRoot(t *testing.T) {
	oldNs := "/old/ns"
	snap := []string{oldNs + "/backups/primary/app", oldNs} // oldNs itself must be refused
	if _, err := mapOffsiteRestorePaths(snap, "app", "/scratch", "/new/ns"); err == nil {
		t.Error("the namespace root itself among snapshot paths must be refused (F-3a-3)")
	}
}