package dispenser

import (
	"context"
	"errors"
	"reflect"
	"sync"
	"testing"
	"time"
)

func maintenanceClient(t *testing.T, p *scriptedTransport) (*Client, *time.Time) {
	t.Helper()
	transportAddress(t)
	now := time.Unix(100, 0)
	c := &Client{port: p, done: make(chan struct{}), activityWake: make(chan struct{}, 1), sequenceTiming: sequenceTiming{now: func() time.Time { return now }, wait: waitForSequence}}
	t.Cleanup(c.Close)
	return c, &now
}

func TestMaintenanceIdleScheduling(t *testing.T) {
	c, now := maintenanceClient(t, &scriptedTransport{})
	c.StartMaintenance()
	first := c.activity.next
	c.StartMaintenance()
	if c.activity.next != first {
		t.Fatal("repeated start reset the timer")
	}
	*now = now.Add(59 * time.Second)
	c.maintainIdleCard()
	if len(c.port.(*scriptedTransport).writes) != 0 {
		t.Fatal("maintenance ran before one minute")
	}
	release1 := c.BeginForeground()
	release2 := c.BeginForeground()
	release1()
	if _, enabled := c.maintenanceDelay(); enabled {
		t.Fatal("timer enabled while another issuance active")
	}
	*now = now.Add(20 * time.Second)
	release2()
	release2()
	if delay, enabled := c.maintenanceDelay(); !enabled || delay != time.Minute {
		t.Fatalf("after last release delay=%v enabled=%t", delay, enabled)
	}
	c.StopMaintenance()
	if _, enabled := c.maintenanceDelay(); enabled {
		t.Fatal("stop left timer enabled")
	}
}

func TestMaintenanceUsesCommonEligibility(t *testing.T) {
	for _, tc := range []struct {
		name    string
		st      []byte
		pending bool
		age     time.Duration
		fc7     bool
	}{
		{"clear", status(0x30), false, 0, true},
		{"staging", status(0x34), true, 3 * time.Second, true},
		{"too early", status(0x30), true, time.Second, false},
		{"encoder", status(0x33), true, time.Minute, false},
		{"empty", status(0x38), false, 0, false},
		{"uncertain", status(0x35), false, 0, false},
		{"movement", []byte{0x31, 0x30, 0x30, 0x34}, true, time.Minute, false},
		{"invalid", status(0x40), true, time.Minute, false},
	} {
		t.Run(tc.name, func(t *testing.T) {
			p := &scriptedTransport{chunks: [][]byte{vendorACK, apReply(tc.st), vendorACK}}
			c, now := maintenanceClient(t, p)
			c.StartMaintenance()
			*now = now.Add(time.Minute)
			c.deliveryPending = tc.pending
			c.deliveryStarted = now.Add(-tc.age)
			callbacks := 0
			c.OnStockUpdate(func(string) { callbacks++ })
			c.maintainIdleCard()
			want := []string{"AP"}
			if tc.fc7 {
				want = append(want, "FC7")
			}
			if got := wireCommands(p); !reflect.DeepEqual(got, want) {
				t.Errorf("commands=%v want %v", got, want)
			}
			if callbacks != 0 {
				t.Errorf("maintenance published %d stock callbacks", callbacks)
			}
			if tc.pending && !tc.fc7 && !c.deliveryPending {
				t.Error("ineligible maintenance cleared pending")
			}
			if delay, enabled := c.maintenanceDelay(); !enabled || delay != time.Minute {
				t.Errorf("next maintenance delay=%v enabled=%t", delay, enabled)
			}
		})
	}
}

func TestMaintenanceForegroundBetweenAPAndFC7(t *testing.T) {
	p := &scriptedTransport{chunks: [][]byte{vendorACK, apReply(status(0x30)), vendorACK}}
	c, now := maintenanceClient(t, p)
	c.StartMaintenance()
	*now = now.Add(time.Minute)
	var release func()
	p.afterRead = func() {
		if len(p.chunks) == 1 && release == nil {
			release = c.BeginForeground()
		}
	}
	c.maintainIdleCard()
	if got := wireCommands(p); !reflect.DeepEqual(got, []string{"AP"}) {
		t.Errorf("foreground during AP commands=%v want AP only", got)
	}
	if release == nil {
		t.Fatal("barrier not reached")
	}
	release()
	if delay, _ := c.maintenanceDelay(); delay != time.Minute {
		t.Errorf("foreground completion delay=%v", delay)
	}
}

func TestMaintenanceAdmissionConditions(t *testing.T) {
	c, _ := maintenanceClient(t, &scriptedTransport{})
	c.StartMaintenance()
	generation := c.activity.generation
	ctx, cancel := context.WithCancel(context.Background())
	if !c.admitMaintenance(ctx, generation) {
		t.Fatal("idle admission rejected")
	}
	cancel()
	if c.admitMaintenance(ctx, generation) {
		t.Fatal("canceled admission accepted")
	}
	expired, stop := context.WithDeadline(context.Background(), time.Now().Add(-time.Second))
	defer stop()
	if c.admitMaintenance(expired, generation) {
		t.Fatal("expired admission accepted")
	}
	release := c.BeginForeground()
	if c.admitMaintenance(context.Background(), generation) {
		t.Fatal("foreground/stale admission accepted")
	}
	release()
	if c.admitMaintenance(context.Background(), generation) {
		t.Fatal("obsolete generation accepted")
	}
	generation = c.activity.generation
	c.StopMaintenance()
	if c.admitMaintenance(context.Background(), generation) {
		t.Fatal("stopped admission accepted")
	}
}

func TestPassivePollGenerationAtDispatch(t *testing.T) {
	c, _ := maintenanceClient(t, &scriptedTransport{})
	generation, _ := c.passiveGeneration()
	release := c.BeginForeground()
	for _, active := range []bool{true, false} {
		if !active {
			release()
		}
		response := make(chan cmdResp, 1)
		c.handle(cmdReq{ctx: context.Background(), typ: cmdStatus, passive: true, generation: generation, respCh: response})
		<-response
		if len(c.port.(*scriptedTransport).writes) != 0 {
			t.Errorf("active=%t stale passive request touched port", active)
		}
	}
}

func TestMaintenanceStopWaitsForAdmittedRead(t *testing.T) {
	p := &scriptedTransport{chunks: [][]byte{vendorACK, apReply(status(0x30)), vendorACK}}
	c, now := maintenanceClient(t, p)
	c.StartMaintenance()
	*now = now.Add(time.Minute)
	entered, resume := make(chan struct{}), make(chan struct{})
	var once sync.Once
	p.afterRead = func() { once.Do(func() { close(entered); <-resume }) }
	finished := make(chan struct{})
	go func() { c.maintainIdleCard(); close(finished) }()
	<-entered
	stopped := make(chan struct{})
	go func() { c.StopMaintenance(); close(stopped) }()
	// Wait until stop has disabled admission.
	for {
		c.activity.Lock()
		enabled := c.activity.enabled
		c.activity.Unlock()
		if !enabled {
			break
		}
		time.Sleep(time.Millisecond)
	}
	select {
	case <-stopped:
		t.Fatal("stop returned before admitted read finished")
	default:
	}
	close(resume)
	<-finished
	<-stopped
	if got := wireCommands(p); !reflect.DeepEqual(got, []string{"AP"}) {
		t.Errorf("stop commands=%v want AP only", got)
	}
	c.StopMaintenance()
	c.Close()
	c.Close()
}

func TestMaintenanceWorkerTimerWake(t *testing.T) {
	c := NewClient(nil, 1)
	c.StartMaintenance()
	release := c.BeginForeground()
	// An immediate obsolete timer is harmless while foreground is registered.
	c.activity.Lock()
	c.activity.next = time.Now().Add(-time.Second)
	c.activity.Unlock()
	c.wakeWorker()
	release()
	if delay, enabled := c.maintenanceDelay(); !enabled || delay <= 59*time.Second {
		t.Errorf("worker schedule delay=%v enabled=%t", delay, enabled)
	}
	c.Close()
	if r := c.doResponse(context.Background(), cmdStatus); r.err == nil {
		t.Fatal("closed client accepted a request")
	}
}

func TestMaintenanceWorkerTimerDispatch(t *testing.T) {
	transportAddress(t)
	p := &scriptedTransport{chunks: [][]byte{vendorACK, apReply(status(0x30)), vendorACK}}
	c := &Client{port: p, reqCh: make(chan cmdReq, 1), done: make(chan struct{}), activityWake: make(chan struct{}, 1), sequenceTiming: sequenceTiming{now: time.Now, wait: waitForSequence}}
	c.StartMaintenance()
	c.activity.Lock()
	c.activity.next = time.Now().Add(-time.Second)
	c.activity.Unlock()
	workerDone := make(chan struct{})
	go func() { defer close(workerDone); c.loop() }()
	t.Cleanup(func() { c.Close(); <-workerDone })
	dispatched := make(chan struct{})
	// Observe completion through the activity guard, without touching the transport concurrently.
	go func() {
		for {
			c.activity.Lock()
			next := c.activity.next
			c.activity.Unlock()
			if time.Until(next) > 50*time.Second {
				close(dispatched)
				return
			}
			select {
			case <-c.done:
				return
			case <-time.After(time.Millisecond):
			}
		}
	}()
	select {
	case <-dispatched:
	case <-time.After(4 * time.Second):
		t.Fatal("worker timer did not finish maintenance")
	}
	c.StopMaintenance()
	if got := wireCommands(p); !reflect.DeepEqual(got, []string{"AP", "FC7"}) {
		t.Errorf("timer commands=%v", got)
	}
}

func TestForegroundEncoderClearanceCharacterization(t *testing.T) {
	for _, movement := range []bool{false, true} {
		st := status(0x33)
		if movement {
			st[0] = 0x31
		}
		p := &scriptedTransport{chunks: [][]byte{vendorACK, apReply(st), vendorACK, apReply(st), vendorACK, apReply(st), vendorACK}}
		c, now := maintenanceClient(t, p)
		c.deliveryPending = true
		c.deliveryStarted = now.Add(-time.Minute)
		c.sequenceTiming.wait = func(context.Context, time.Duration) error { *now = now.Add(2 * time.Second); return nil }
		r := workerRequest(c, context.Background(), cmdToEncoder)
		want := []string{"AP", "AP", "AP"}
		if movement {
			if !errors.Is(r.err, context.DeadlineExceeded) || !c.deliveryPending {
				t.Errorf("movement err=%v pending=%t", r.err, c.deliveryPending)
			}
		} else {
			want = append(want, "FC7")
			if r.err != nil || c.deliveryPending {
				t.Errorf("internal fallback err=%v pending=%t", r.err, c.deliveryPending)
			}
		}
		if got := wireCommands(p); !reflect.DeepEqual(got, want) {
			t.Errorf("movement=%t commands=%v want %v", movement, got, want)
		}
	}
}

func TestForegroundEncoderClearanceCallerDeadline(t *testing.T) {
	p := &scriptedTransport{chunks: [][]byte{vendorACK, apReply(status(0x33)), vendorACK, apReply(status(0x33)), vendorACK, apReply(status(0x33))}}
	c, now := maintenanceClient(t, p)
	c.deliveryPending = true
	c.deliveryStarted = *now
	start := *now
	samples := 0
	p.afterRead = func() {
		if len(p.chunks)%2 == 0 { // Only complete frame reads advance the observation clock.
			if len(p.chunks) == 4 || len(p.chunks) == 2 || len(p.chunks) == 0 {
				samples++
				*now = now.Add(time.Second)
			}
		}
	}
	ctx, cancel := context.WithTimeout(context.Background(), 4*time.Second)
	defer cancel()
	c.sequenceTiming.wait = func(context.Context, time.Duration) error {
		if samples == 3 {
			<-ctx.Done()
			return ctx.Err()
		}
		*now = now.Add(time.Second)
		return nil
	}
	r := workerRequest(c, ctx, cmdToEncoder)
	if !errors.Is(r.err, context.DeadlineExceeded) || !c.deliveryPending {
		t.Errorf("caller deadline err=%v pending=%t", r.err, c.deliveryPending)
	}
	if got := wireCommands(p); !reflect.DeepEqual(got, []string{"AP", "AP", "AP"}) {
		t.Errorf("caller deadline commands=%v want AP only", got)
	}
	if elapsed := now.Sub(start); elapsed != 5*time.Second {
		t.Errorf("last observation elapsed=%v want 5s", elapsed)
	}
}

func TestMaintenanceFailuresAreQuietAndRetryLater(t *testing.T) {
	for _, mechanical := range []bool{false, true} {
		p := &scriptedTransport{chunks: [][]byte{{0x10, 0x06, 0x30}}}
		if mechanical {
			p.chunks = [][]byte{vendorACK, apReply(status(0x30))}
		}
		c, now := maintenanceClient(t, p)
		c.StartMaintenance()
		*now = now.Add(time.Minute)
		callbacks := 0
		c.OnStockUpdate(func(string) { callbacks++ })
		c.maintainIdleCard()
		want := []string{"AP"}
		if mechanical {
			want = append(want, "FC7")
		}
		if got := wireCommands(p); !reflect.DeepEqual(got, want) {
			t.Errorf("mechanical=%t commands=%v want %v", mechanical, got, want)
		}
		if callbacks != 0 {
			t.Errorf("maintenance failure callbacks=%d", callbacks)
		}
		if delay, enabled := c.maintenanceDelay(); !enabled || delay != time.Minute {
			t.Errorf("retry delay=%v enabled=%t", delay, enabled)
		}
	}
}