package fleetupdate

import (
	"context"
	"errors"
	"path/filepath"
	"sync"
	"testing"
	"time"

	"github.com/oklog/ulid/v2"

	"gitea.dcglab.co.uk/steve/restic-manager/internal/api"
	"gitea.dcglab.co.uk/steve/restic-manager/internal/store"
)

type fakeHub struct {
	mu     sync.Mutex
	online map[string]bool
}

func (f *fakeHub) Connected(hostID string) bool {
	f.mu.Lock()
	defer f.mu.Unlock()
	return f.online[hostID]
}

type fakeDispatcher struct {
	mu    sync.Mutex
	calls []string // host IDs
	// after dispatch, set the host's agent_version to this on the
	// store so the worker observes the version transition.
	st         *store.Store
	target     string
	delayMS    int
	failOnHost map[string]string // host → error code
}

func (f *fakeDispatcher) DispatchUpdate(ctx context.Context, hostID, _ string) (string, string, error) {
	f.mu.Lock()
	f.calls = append(f.calls, hostID)
	if code, ok := f.failOnHost[hostID]; ok {
		f.mu.Unlock()
		return "", code, nil
	}
	st := f.st
	target := f.target
	delay := f.delayMS
	f.mu.Unlock()

	jobID := ulid.Make().String()
	if st != nil {
		_ = st.CreateJob(context.Background(), store.Job{
			ID: jobID, HostID: hostID, Kind: "update",
			ActorKind: "user", CreatedAt: time.Now().UTC(),
		})
	}
	if st != nil && target != "" {
		go func() {
			if delay > 0 {
				time.Sleep(time.Duration(delay) * time.Millisecond)
			}
			_ = st.MarkHostHello(context.Background(), hostID, target, "0.17", api.CurrentProtocolVersion, time.Now().UTC())
		}()
	}
	return jobID, "", nil
}

type recAlert struct {
	mu      sync.Mutex
	reasons []string
}

func (r *recAlert) RaiseFleetUpdateHalted(_ context.Context, _ string, reason string, _ time.Time) {
	r.mu.Lock()
	r.reasons = append(r.reasons, reason)
	r.mu.Unlock()
}

func openStore(t *testing.T) *store.Store {
	t.Helper()
	dir := t.TempDir()
	st, err := store.Open(context.Background(), filepath.Join(dir, "rm.db"))
	if err != nil {
		t.Fatalf("open: %v", err)
	}
	t.Cleanup(func() { _ = st.Close() })
	return st
}

func mustCreateAdmin(t *testing.T, st *store.Store) string {
	t.Helper()
	uid := ulid.Make().String()
	if err := st.CreateUser(context.Background(), store.User{
		ID: uid, Username: "u-" + uid[:6],
		PasswordHash: "x", Role: store.RoleAdmin, CreatedAt: time.Now().UTC(),
	}); err != nil {
		t.Fatalf("user: %v", err)
	}
	return uid
}

func mustCreateHost(t *testing.T, st *store.Store, name, version string) string {
	t.Helper()
	hostID := ulid.Make().String()
	if err := st.CreateHost(context.Background(), store.Host{
		ID: hostID, Name: name, OS: "linux", Arch: "amd64",
		EnrolledAt: time.Now().UTC(),
	}, "deadbeef-"+hostID, ""); err != nil {
		t.Fatalf("host: %v", err)
	}
	if version != "" {
		if err := st.MarkHostHello(context.Background(), hostID, version, "0.17", api.CurrentProtocolVersion, time.Now().UTC()); err != nil {
			t.Fatalf("hello: %v", err)
		}
	}
	return hostID
}

func waitForStatus(t *testing.T, st *store.Store, fuID, want string, timeout time.Duration) *store.FleetUpdate {
	t.Helper()
	deadline := time.Now().Add(timeout)
	for time.Now().Before(deadline) {
		fu, _, err := st.GetFleetUpdate(context.Background(), fuID)
		if err == nil && fu != nil && fu.Status == want {
			return fu
		}
		time.Sleep(20 * time.Millisecond)
	}
	t.Fatalf("status never reached %q", want)
	return nil
}

func TestWorkerTwoHostsBothSucceed(t *testing.T) {
	st := openStore(t)
	uid := mustCreateAdmin(t, st)
	h1 := mustCreateHost(t, st, "h1", "v0")
	h2 := mustCreateHost(t, st, "h2", "v0")

	hub := &fakeHub{online: map[string]bool{h1: true, h2: true}}
	disp := &fakeDispatcher{st: st, target: "v2", delayMS: 30}
	alerts := &recAlert{}
	w := NewWorker(st, hub, disp, alerts)
	w.pollPeriod = 20 * time.Millisecond
	w.hostTimeout = 2 * time.Second

	fuID, err := w.Start(context.Background(), uid, "v2", []string{h1, h2})
	if err != nil {
		t.Fatalf("start: %v", err)
	}
	waitForStatus(t, st, fuID, "completed", 5*time.Second)
	_, hosts, _ := st.GetFleetUpdate(context.Background(), fuID)
	for _, h := range hosts {
		if h.Status != "succeeded" {
			t.Errorf("host %s status %q want succeeded", h.HostID, h.Status)
		}
	}
	if n := len(alerts.reasons); n != 0 {
		t.Errorf("unexpected halt alert: %v", alerts.reasons)
	}
}

func TestWorkerSecondHostTimesOutHalts(t *testing.T) {
	st := openStore(t)
	uid := mustCreateAdmin(t, st)
	h1 := mustCreateHost(t, st, "h1", "v0")
	h2 := mustCreateHost(t, st, "h2", "v0")
	h3 := mustCreateHost(t, st, "h3", "v0")

	hub := &fakeHub{online: map[string]bool{h1: true, h2: true, h3: true}}
	// h1 dispatches normally (transitions to v2). h2 dispatch returns
	// success but never transitions.
	disp := &fakeDispatcher{st: st, target: "v2", delayMS: 20, failOnHost: map[string]string{
		h2: "", // not a code-failure; simulate by clearing target on this disp run
	}}
	// Actually: drop h2 from the auto-transition by faking with a
	// per-host store setter. Easiest: subclass via a wrapper.
	_ = disp
	customDisp := &perHostDispatcher{base: disp, st: st, target: "v2", noTransition: map[string]bool{h2: true}}

	alerts := &recAlert{}
	w := NewWorker(st, hub, customDisp, alerts)
	w.pollPeriod = 20 * time.Millisecond
	w.hostTimeout = 200 * time.Millisecond

	fuID, err := w.Start(context.Background(), uid, "v2", []string{h1, h2, h3})
	if err != nil {
		t.Fatalf("start: %v", err)
	}
	waitForStatus(t, st, fuID, "halted", 3*time.Second)
	_, hosts, _ := st.GetFleetUpdate(context.Background(), fuID)
	gotStatus := map[string]string{}
	for _, h := range hosts {
		gotStatus[h.HostID] = h.Status
	}
	if gotStatus[h1] != "succeeded" {
		t.Errorf("h1: %q", gotStatus[h1])
	}
	if gotStatus[h2] != "failed" {
		t.Errorf("h2: %q", gotStatus[h2])
	}
	if gotStatus[h3] != "pending" {
		t.Errorf("h3: %q", gotStatus[h3])
	}
	alerts.mu.Lock()
	defer alerts.mu.Unlock()
	if len(alerts.reasons) != 1 {
		t.Errorf("alert reasons: %v", alerts.reasons)
	}
}

// perHostDispatcher lets a test omit the auto-transition for selected
// hosts so we can simulate timeout.
type perHostDispatcher struct {
	mu           sync.Mutex
	base         *fakeDispatcher
	st           *store.Store
	target       string
	noTransition map[string]bool
}

func (p *perHostDispatcher) DispatchUpdate(_ context.Context, hostID, _ string) (string, string, error) {
	p.mu.Lock()
	skip := p.noTransition[hostID]
	p.mu.Unlock()
	jobID := ulid.Make().String()
	_ = p.st.CreateJob(context.Background(), store.Job{
		ID: jobID, HostID: hostID, Kind: "update",
		ActorKind: "user", CreatedAt: time.Now().UTC(),
	})
	if !skip {
		go func() {
			time.Sleep(20 * time.Millisecond)
			_ = p.st.MarkHostHello(context.Background(), hostID, p.target, "0.17", api.CurrentProtocolVersion, time.Now().UTC())
		}()
	}
	return jobID, "", nil
}

func TestWorkerHostOfflineHalts(t *testing.T) {
	st := openStore(t)
	uid := mustCreateAdmin(t, st)
	h1 := mustCreateHost(t, st, "h1", "v0")
	h2 := mustCreateHost(t, st, "h2", "v0")
	hub := &fakeHub{online: map[string]bool{h1: false, h2: true}}
	disp := &fakeDispatcher{st: st, target: "v2"}
	alerts := &recAlert{}
	w := NewWorker(st, hub, disp, alerts)
	w.pollPeriod = 20 * time.Millisecond
	w.hostTimeout = 500 * time.Millisecond

	fuID, err := w.Start(context.Background(), uid, "v2", []string{h1, h2})
	if err != nil {
		t.Fatalf("start: %v", err)
	}
	waitForStatus(t, st, fuID, "halted", 2*time.Second)
	_, hosts, _ := st.GetFleetUpdate(context.Background(), fuID)
	if hosts[0].Status != "failed" {
		t.Errorf("h1 status: %q", hosts[0].Status)
	}
	if hosts[1].Status != "pending" {
		t.Errorf("h2 status: %q", hosts[1].Status)
	}
}

func TestWorkerAlreadyAtTargetSkipped(t *testing.T) {
	st := openStore(t)
	uid := mustCreateAdmin(t, st)
	h1 := mustCreateHost(t, st, "h1", "v2")
	h2 := mustCreateHost(t, st, "h2", "v0")
	hub := &fakeHub{online: map[string]bool{h1: true, h2: true}}
	disp := &fakeDispatcher{st: st, target: "v2", delayMS: 20}
	alerts := &recAlert{}
	w := NewWorker(st, hub, disp, alerts)
	w.pollPeriod = 20 * time.Millisecond
	w.hostTimeout = 2 * time.Second

	fuID, err := w.Start(context.Background(), uid, "v2", []string{h1, h2})
	if err != nil {
		t.Fatalf("start: %v", err)
	}
	waitForStatus(t, st, fuID, "completed", 4*time.Second)
	_, hosts, _ := st.GetFleetUpdate(context.Background(), fuID)
	want := map[string]string{h1: "skipped", h2: "succeeded"}
	for _, h := range hosts {
		if h.Status != want[h.HostID] {
			t.Errorf("host %s: got %q want %q", h.HostID, h.Status, want[h.HostID])
		}
	}
}

func TestWorkerCancelMidRun(t *testing.T) {
	st := openStore(t)
	uid := mustCreateAdmin(t, st)
	h1 := mustCreateHost(t, st, "h1", "v0")
	h2 := mustCreateHost(t, st, "h2", "v0")
	hub := &fakeHub{online: map[string]bool{h1: true, h2: true}}
	// h1's transition is delayed long enough that we can cancel
	// before it lands; h2 should never be touched.
	disp := &fakeDispatcher{st: st, target: "v2", delayMS: 500}
	alerts := &recAlert{}
	w := NewWorker(st, hub, disp, alerts)
	w.pollPeriod = 50 * time.Millisecond
	w.hostTimeout = 5 * time.Second

	fuID, err := w.Start(context.Background(), uid, "v2", []string{h1, h2})
	if err != nil {
		t.Fatalf("start: %v", err)
	}
	// Give the worker a moment to dispatch h1.
	time.Sleep(100 * time.Millisecond)
	if err := w.Cancel(context.Background(), fuID); err != nil {
		t.Fatalf("cancel: %v", err)
	}
	waitForStatus(t, st, fuID, "cancelled", 2*time.Second)

	// h2 should never be dispatched.
	disp.mu.Lock()
	defer disp.mu.Unlock()
	for _, c := range disp.calls {
		if c == h2 {
			t.Errorf("h2 dispatched after cancel")
		}
	}
}

func TestWorkerStartWhileActiveErrors(t *testing.T) {
	st := openStore(t)
	uid := mustCreateAdmin(t, st)
	h1 := mustCreateHost(t, st, "h1", "v0")
	h2 := mustCreateHost(t, st, "h2", "v0")
	hub := &fakeHub{online: map[string]bool{h1: true, h2: true}}
	disp := &fakeDispatcher{st: st, target: "v2", delayMS: 5_000}
	w := NewWorker(st, hub, disp, &recAlert{})
	w.pollPeriod = 50 * time.Millisecond
	w.hostTimeout = 2 * time.Second
	if _, err := w.Start(context.Background(), uid, "v2", []string{h1}); err != nil {
		t.Fatalf("first start: %v", err)
	}
	_, err := w.Start(context.Background(), uid, "v2", []string{h2})
	if !errors.Is(err, store.ErrFleetUpdateRunning) {
		t.Fatalf("err: %v want ErrFleetUpdateRunning", err)
	}
}