package storage

import (
	"context"
	"io"
	"os"
	"path/filepath"
	"reflect"
	"testing"
)

// forgetRunner records every privileged call and plays the root half of `felhom-priv-apply unit-forget`: the unit file
// disappears from the unit dir, so the CONSEQUENCE (the drive is no longer listed) is observable, not just the calls.
type forgetRunner struct {
	unitDir string
	calls   [][]string
}

func (r *forgetRunner) RunStdin(ctx context.Context, _ io.Reader, name string, args ...string) ([]byte, []byte, error) {
	return r.Run(ctx, name, args...)
}

func (r *forgetRunner) Run(_ context.Context, name string, args ...string) ([]byte, []byte, error) {
	r.calls = append(r.calls, append([]string{name}, args...))
	if len(args) == 2 && args[0] == "unit-forget" {
		_ = os.Remove(filepath.Join(r.unitDir, args[1]))
	}
	return nil, nil, nil
}

type forgetCase struct {
	intent   DriveIntent
	present  bool // the by-uuid link resolves
	mounted  bool
	enabled  bool // the wants-symlink exists
	mountErr bool
}

const forgetUUID = "4ebfd36d-87d3-4b63-839e-a5a710fc799a"

func runForget(t *testing.T, c forgetCase, intent IntentReader) (int, *forgetRunner, *RegistryKnownTargets, string) {
	t.Helper()
	unitDir := t.TempDir()
	unit := "mnt-media_a.mount"
	writeUnit(t, unitDir, unit, renderMountUnit(MountSpec{Name: forgetUUID, UUID: forgetUUID, Where: "/mnt/media_a", FSType: "ext4"}))
	if c.enabled {
		if err := os.MkdirAll(filepath.Join(unitDir, "multi-user.target.wants"), 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.Symlink(filepath.Join(unitDir, unit), filepath.Join(unitDir, "multi-user.target.wants", unit)); err != nil {
			t.Fatal(err)
		}
	}
	devRoot := t.TempDir()
	if err := os.MkdirAll(filepath.Join(devRoot, "by-uuid"), 0o755); err != nil {
		t.Fatal(err)
	}
	if c.present {
		dev := filepath.Join(devRoot, "sdz1")
		if err := os.WriteFile(dev, nil, 0o600); err != nil {
			t.Fatal(err)
		}
		if err := os.Symlink(dev, filepath.Join(devRoot, "by-uuid", forgetUUID)); err != nil {
			t.Fatal(err)
		}
	}
	withDevDiskRoot(t, devRoot)
	hr := &fakeHostReader{}
	if c.mounted {
		hr.mounts = []Mount{{MountPoint: "/mnt/media_a", FSType: "ext4"}}
	}
	if c.mountErr {
		hr.mountsErr = os.ErrPermission
	}
	rr := &forgetRunner{unitDir: unitDir}
	ops := NewSudoHostOps(SudoHostOpsConfig{Runner: rr, Bins: Binaries{}.withDefaults(), UnitDir: unitDir,
		StageDir: t.TempDir(), Host: hr, Logger: quietLogger()})
	if intent == nil {
		intent = &fakeIntent{m: map[string]DriveIntent{"uuid:" + forgetUUID: c.intent}}
	}
	n := ops.ForgetRetiredDrives(context.Background(), intent)
	return n, rr, NewRegistryKnownTargets(unitDir, intent, quietLogger()), unitDir
}

// The R-1124 case: decommissioned, then unplugged. The unit is disabled and removed through the root checker, systemd
// is reloaded, and the CONSEQUENCE — the agent no longer lists the drive — holds. RED-PROOF (P1/redproof-forget.txt):
// with ForgetRetiredDrives' body replaced by `return 0` this test fails (the drive is still listed).
func TestForgetRetiredDrives_DecommissionedAndGone_UnitRemovedAndNotListed(t *testing.T) {
	n, rr, known, _ := runForget(t, forgetCase{intent: IntentDecommissioned, enabled: true}, nil)
	if n != 1 {
		t.Fatalf("removed = %d, want 1 (calls %v)", n, rr.calls)
	}
	pa := Binaries{}.withDefaults()
	want := [][]string{
		{pa.Systemctl, "disable", "--", "mnt-media_a.mount"},
		{pa.PrivApply, "unit-forget", "mnt-media_a.mount"},
		{pa.Systemctl, "daemon-reload"},
	}
	if !reflect.DeepEqual(rr.calls, want) {
		t.Fatalf("calls = %v\nwant    %v", rr.calls, want)
	}
	got, err := known.Known(context.Background())
	if err != nil {
		t.Fatal(err)
	}
	if len(got) != 0 {
		t.Fatalf("the forgotten drive is still listed: %+v", got)
	}
}

// Already disabled (the Tester 1 shape after a manual disable): no disable call, the removal still runs.
func TestForgetRetiredDrives_AlreadyDisabled_NoDisableCall(t *testing.T) {
	n, rr, _, _ := runForget(t, forgetCase{intent: IntentDecommissioned}, nil)
	pa := Binaries{}.withDefaults()
	want := [][]string{{pa.PrivApply, "unit-forget", "mnt-media_a.mount"}, {pa.Systemctl, "daemon-reload"}}
	if n != 1 || !reflect.DeepEqual(rr.calls, want) {
		t.Fatalf("n=%d calls=%v want %v", n, rr.calls, want)
	}
}

// Everything that must KEEP its unit: a decommissioned drive still plugged in (re-enroll is one click — H3), one still
// mounted, an enrolled or ejected drive that is merely absent (it comes back), a drive with no recorded intent, and an
// unreadable mount table. No privileged call at all, and the drive stays listed where it was listed.
// RED-PROOF: with the present-drive check removed, the "present" case calls unit-forget and fails.
func TestForgetRetiredDrives_KeepsEveryOtherUnit(t *testing.T) {
	for name, c := range map[string]forgetCase{
		"decommissioned but present": {intent: IntentDecommissioned, present: true, enabled: true},
		"decommissioned but mounted": {intent: IntentDecommissioned, mounted: true},
		"enrolled and absent":        {intent: IntentEnrolled},
		"ejected and absent":         {intent: IntentEjected},
		"no intent":                  {intent: IntentNew},
		"mount table unreadable":     {intent: IntentDecommissioned, mountErr: true},
	} {
		t.Run(name, func(t *testing.T) {
			n, rr, _, unitDir := runForget(t, c, nil)
			if n != 0 || len(rr.calls) != 0 {
				t.Fatalf("n=%d calls=%v — this unit must be kept", n, rr.calls)
			}
			if _, err := os.Stat(filepath.Join(unitDir, "mnt-media_a.mount")); err != nil {
				t.Fatalf("unit file gone: %v", err)
			}
		})
	}
}

// No intent store on the host (open failure): nothing is known to be retired, so nothing is forgotten.
func TestForgetRetiredDrives_NilIntent_ForgetsNothing(t *testing.T) {
	unitDir := t.TempDir()
	writeUnit(t, unitDir, "mnt-media_a.mount", renderMountUnit(MountSpec{Name: "x", UUID: forgetUUID, Where: "/mnt/media_a"}))
	rr := &forgetRunner{unitDir: unitDir}
	ops := NewSudoHostOps(SudoHostOpsConfig{Runner: rr, UnitDir: unitDir, StageDir: t.TempDir(), Host: &fakeHostReader{}, Logger: quietLogger()})
	if n := ops.ForgetRetiredDrives(context.Background(), nil); n != 0 || len(rr.calls) != 0 {
		t.Fatalf("n=%d calls=%v", n, rr.calls)
	}
}