package conditions

import (
	"context"
	"encoding/json"
	"errors"
	"strings"
	"testing"
	"time"
)

// clock is a time a test moves by hand.
type clock struct{ at time.Time }

func (c *clock) now() time.Time       { return c.at }
func (c *clock) pass(d time.Duration) { c.at = c.at.Add(d) }
func newClock() *clock                { return &clock{at: time.Date(2026, 10, 6, 12, 0, 0, 0, time.UTC)} }
func keeper(t *testing.T) (*Keeper, *InMemory, *Told, *clock) {
	t.Helper()
	store, told, c := NewInMemory(), &Told{}, newClock()
	k := NewKeeper(t.Context(), Options{Store: store, History: store, Teller: told, Now: c.now,
		Say: func(f string, a ...any) { t.Logf(f, a...) }})
	t.Cleanup(func() { k.Close(context.Background()) })
	return k, store, told, c
}

// settled waits until the teller has been told n events.
func settled(t *testing.T, told *Told, n int) []Event {
	t.Helper()
	deadline := time.Now().Add(5 * time.Second)
	for {
		said := told.Said()
		if len(said) >= n {
			return said
		}
		if time.Now().After(deadline) {
			t.Fatalf("told %d event(s), want %d: %+v", len(said), n, said)
		}
		time.Sleep(5 * time.Millisecond)
	}
}

func silent(node string) Observation {
	return Observation{Scope: ScopeMachine, ID: node, Kind: "silent", Machine: node, Severity: Warning,
		Summary: node + " has not been heard from", Source: "S1"}
}

// **A condition is raised once, observed many times, and said on the bus only when it changes**
// (to-be 45 §2): an observation that changes nothing is written and said nowhere, or the operator's
// channel would hear the same fault every thirty seconds.
func TestAConditionIsSaidWhenItChangesNotWhenItIsSeenAgain(t *testing.T) {
	k, _, told, c := keeper(t)
	ctx := t.Context()
	for i := 0; i < 3; i++ {
		if _, err := k.Observe(ctx, silent("ace")); err != nil {
			t.Fatal(err)
		}
		c.pass(time.Minute)
	}
	urgent := silent("ace")
	urgent.Severity = Urgent
	got, err := k.Observe(ctx, urgent)
	if err != nil {
		t.Fatal(err)
	}
	if got.Key != "machine.ace.silent" || got.Observations != 4 || got.Count != 1 || got.Severity != Urgent {
		t.Fatalf("held %+v", got)
	}
	if len(got.Evidence) != 4 || !got.Evidence[0].At.Equal(c.at) {
		t.Fatalf("evidence is not newest first: %+v", got.Evidence)
	}
	said := settled(t, told, 2)
	if said[0].Event != EventRaised || said[0].Change != ChangeRaised || said[1].Event != EventChanged ||
		said[1].Change != ChangeSeverity || said[1].Was != string(Warning) {
		t.Fatalf("said %+v", said)
	}
	time.Sleep(50 * time.Millisecond)
	if n := len(told.Said()); n != 2 {
		t.Fatalf("said %d events for one raising and one change", n)
	}
	for i, name := range told.Names {
		if name != told.Events[i].Event {
			t.Errorf("event %d published as %s and says it is %s", i, name, told.Events[i].Event)
		}
	}
}

// **Evidence is bounded**: a condition open for a week keeps its newest ten observations, not all.
func TestEvidenceKeepsTheNewestTen(t *testing.T) {
	k, _, _, c := keeper(t)
	var got Condition
	for i := 0; i < 25; i++ {
		var err error
		if got, err = k.Observe(t.Context(), silent("ace")); err != nil {
			t.Fatal(err)
		}
		c.pass(time.Minute)
	}
	if len(got.Evidence) != KeptEvidence || got.Observations != 25 {
		t.Fatalf("kept %d evidence of %d observations", len(got.Evidence), got.Observations)
	}
}

// **Cleared and raised again within ten minutes is the same condition again** (to-be 45 §2): its
// count goes up and it is said as reopened, not as news; a person's silence of it still holds.
func TestRaisedAgainSoonAfterClearingReopens(t *testing.T) {
	k, store, told, c := keeper(t)
	ctx := t.Context()
	if _, err := k.Observe(ctx, silent("ace")); err != nil {
		t.Fatal(err)
	}
	if _, err := k.Silence(ctx, "machine.ace.silent", time.Hour, "jochen", "the laptop is on the train"); err != nil {
		t.Fatal(err)
	}
	if cleared, err := k.Clear(ctx, "machine.ace.silent", "heard again"); err != nil || !cleared {
		t.Fatalf("cleared %v: %v", cleared, err)
	}
	c.pass(5 * time.Minute)
	again, err := k.Observe(ctx, silent("ace"))
	if err != nil {
		t.Fatal(err)
	}
	if again.Count != 2 || again.Silenced == nil {
		t.Fatalf("reopened as %+v", again)
	}
	said := settled(t, told, 4)
	if said[3].Event != EventRaised || said[3].Change != ChangeReopened {
		t.Fatalf("the reopening was said as %+v", said[3])
	}
	// And from a new keeper — the controller restarted between — reading what cleared from history.
	if _, err := k.Clear(ctx, "machine.ace.silent", "heard again"); err != nil {
		t.Fatal(err)
	}
	settled(t, told, 5)
	k.Close(context.Background())
	next := NewKeeper(ctx, Options{Store: store, History: store, Now: c.now})
	defer next.Close(context.Background())
	c.pass(time.Minute)
	third, err := next.Observe(ctx, silent("ace"))
	if err != nil {
		t.Fatal(err)
	}
	if third.Count != 3 {
		t.Fatalf("a controller restarted between cleared and raised said it as new: %+v", third)
	}
	// Past the window it is news.
	if _, err := next.Clear(ctx, "machine.ace.silent", "heard again"); err != nil {
		t.Fatal(err)
	}
	c.pass(ReopenWithin + time.Minute)
	fourth, err := next.Observe(ctx, silent("ace"))
	if err != nil {
		t.Fatal(err)
	}
	if fourth.Count != 1 || fourth.Silenced != nil {
		t.Fatalf("raised past the window as %+v", fourth)
	}
}

// **A source's whole observation clears what it no longer observes, and only its own.** A watchdog
// that stops seeing a fault says it is resolved; it does not clear what another raised.
func TestReconcileClearsOnlyTheSourcesOwn(t *testing.T) {
	k, _, told, _ := keeper(t)
	ctx := t.Context()
	other := Observation{Scope: ScopeProbe, ID: "D3", Kind: "probe-failed", Token: "failed", Severity: Warning,
		Summary: "D3 did not answer", Source: "doctor"}
	if _, err := k.Observe(ctx, other); err != nil {
		t.Fatal(err)
	}
	if err := k.Reconcile(ctx, "S1", []Observation{silent("ace"), silent("g14")}); err != nil {
		t.Fatal(err)
	}
	if err := k.Reconcile(ctx, "S1", []Observation{silent("g14")}); err != nil {
		t.Fatal(err)
	}
	open, err := k.Open(ctx)
	if err != nil {
		t.Fatal(err)
	}
	var keys []string
	for _, c := range open {
		keys = append(keys, c.Key)
	}
	if strings.Join(keys, ",") != "machine.g14.silent,probe.D3.failed" {
		t.Fatalf("open after the second observation: %v", keys)
	}
	said := settled(t, told, 4)
	last := said[3]
	if last.Event != EventCleared || last.Key != "machine.ace.silent" || last.Why == "" {
		t.Fatalf("the clearing was said as %+v", last)
	}
}

// **A store that cannot be read is never an empty one** (ADR 0227 rule 4): reconciling against it
// clears nothing and says why.
func TestAnUnreadableStoreClearsNothing(t *testing.T) {
	k, store, _, _ := keeper(t)
	ctx := t.Context()
	if _, err := k.Observe(ctx, silent("ace")); err != nil {
		t.Fatal(err)
	}
	store.Fail = errors.New("the bus is away")
	if err := k.Reconcile(ctx, "S1", nil); err == nil {
		t.Fatal("reconciled against a store it could not read")
	}
	if _, err := k.Open(ctx); err == nil {
		t.Fatal("an unreadable store answered as read")
	}
	store.Fail = nil
	store.values["machine.g14.silent"] = Entry{Value: []byte("{not a condition"), Revision: 99}
	if _, err := k.Open(ctx); err == nil || !strings.Contains(err.Error(), "machine.g14.silent") {
		t.Fatalf("an unreadable condition was left out rather than said: %v", err)
	}
	if cleared, err := k.Clear(ctx, "machine.g14.silent", "x"); err == nil || cleared {
		t.Fatal("an unreadable condition was cleared unread")
	}
}

// **A silence is bounded, says why, and ends on its own** (to-be 45 §2): the condition stays open
// through it, and its messages start again when it ends.
func TestASilenceIsBoundedAndEnds(t *testing.T) {
	k, _, told, c := keeper(t)
	ctx := t.Context()
	if _, err := k.Observe(ctx, silent("ace")); err != nil {
		t.Fatal(err)
	}
	if _, err := k.Silence(ctx, "machine.ace.silent", 8*24*time.Hour, "jochen", "away"); err == nil {
		t.Fatal("silenced for longer than a week")
	}
	if _, err := k.Silence(ctx, "machine.ace.silent", time.Hour, "jochen", " "); err == nil {
		t.Fatal("silenced without a reason")
	}
	if _, err := k.Silence(ctx, "machine.nothing.silent", time.Hour, "jochen", "x"); err == nil {
		t.Fatal("silenced a condition that is not open")
	}
	held, err := k.Silence(ctx, "machine.ace.silent", time.Hour, "jochen", "on the train")
	if err != nil {
		t.Fatal(err)
	}
	if !held.SilencedAt(c.at) || held.Silenced.By != "jochen" {
		t.Fatalf("silenced as %+v", held.Silenced)
	}
	c.pass(30 * time.Minute)
	if err := k.EndSilences(ctx); err != nil {
		t.Fatal(err)
	}
	c.pass(31 * time.Minute)
	if err := k.EndSilences(ctx); err != nil {
		t.Fatal(err)
	}
	got, _, _ := k.Get(ctx, "machine.ace.silent")
	if got.Silenced != nil {
		t.Fatalf("a silence past its end still held: %+v", got.Silenced)
	}
	said := settled(t, told, 3)
	if said[1].Change != ChangeSilenced || said[2].Change != ChangeUnsilenced || said[2].Event != EventChanged {
		t.Fatalf("said %+v", said)
	}
}

// **Two writers never lose each other's word.** The serving controller observes while a person's
// command silences: the write that lost the compare-and-set reads again and redoes itself.
func TestAWriteThatLostTheRaceRedoesItself(t *testing.T) {
	k, store, _, _ := keeper(t)
	ctx := t.Context()
	if _, err := k.Observe(ctx, silent("ace")); err != nil {
		t.Fatal(err)
	}
	racing := &racingStore{InMemory: store, before: func() {
		// Another process silences between this keeper's read and its write.
		other := NewKeeper(ctx, Options{Store: store})
		defer other.Close(context.Background())
		if _, err := other.Silence(ctx, "machine.ace.silent", time.Hour, "jochen", "known"); err != nil {
			t.Error(err)
		}
	}}
	k.store = racing
	got, err := k.Observe(ctx, silent("ace"))
	if err != nil {
		t.Fatal(err)
	}
	if got.Silenced == nil || got.Observations != 2 {
		t.Fatalf("the observation overwrote the silence: %+v", got)
	}
}

// racingStore lets another writer in once, between a read and the write after it.
type racingStore struct {
	*InMemory
	before func()
	done   bool
}

func (r *racingStore) Update(ctx context.Context, key string, value []byte, revision uint64) error {
	if !r.done {
		r.done = true
		r.before()
	}
	return r.InMemory.Update(ctx, key, value, revision)
}

// **An observation that could not be routed is refused**, naming what it lacks.
func TestAnObservationSaysWhatItIs(t *testing.T) {
	k, _, _, _ := keeper(t)
	for _, o := range []Observation{
		{Scope: "elsewhere", ID: "x", Kind: "k", Severity: Warning, Summary: "s", Source: "S1"},
		{Scope: ScopeMachine, ID: "x", Kind: "k", Severity: "loud", Summary: "s", Source: "S1"},
		{Scope: ScopeMachine, ID: "x", Kind: "k", Severity: Warning, Source: "S1"},
		{Scope: ScopeMachine, ID: "x", Kind: "k", Severity: Warning, Summary: "s"},
	} {
		if _, err := k.Observe(t.Context(), o); err == nil {
			t.Errorf("observed %+v", o)
		}
	}
}

// **A key holds nothing the bus would refuse or read as a wildcard**, whatever the thing is called.
func TestAKeyIsSafeForTheBus(t *testing.T) {
	if got := Key(ScopeProvider, "keycloak.novox.my app*", "failing"); got != "provider.keycloak.novox.my_app_.failing" {
		t.Fatalf("key %q", got)
	}
	if got := Key(ScopeBus, "EVENTS.>", "consumer-lost"); got != "bus.EVENTS._.consumer-lost" {
		t.Fatalf("key %q", got)
	}
}

// **The event's shape is a contract** (to-be 45 §2): the operator-channel's holder is written against
// these field names. A rename here is a channel that reads nothing, so they are held still.
func TestTheEventShapeIsTheContract(t *testing.T) {
	k, _, told, _ := keeper(t)
	if _, err := k.Observe(t.Context(), silent("ace")); err != nil {
		t.Fatal(err)
	}
	said := settled(t, told, 1)
	body, err := json.Marshal(said[0])
	if err != nil {
		t.Fatal(err)
	}
	var shape map[string]any
	if err := json.Unmarshal(body, &shape); err != nil {
		t.Fatal(err)
	}
	// The condition at the top level, kebab-case, beside what happened to it.
	for _, field := range []string{"event", "at", "change", "show", "key", "kind", "subject", "severity",
		"summary", "evidence", "source", "raised", "last-observed", "observations", "count", "resolver",
		"silenced", "epoch"} {
		if _, ok := shape[field]; !ok {
			t.Errorf("the event carries no %q: %s", field, body)
		}
	}
	if shape["silenced"] != nil {
		t.Errorf("an unsilenced condition says silenced %v, not null", shape["silenced"])
	}
	subject, _ := shape["subject"].(map[string]any)
	if subject["scope"] != "machine" || subject["id"] != "ace" || subject["machine"] != "ace" {
		t.Errorf("subject %v", shape["subject"])
	}
	if said[0].Show != "mesh-controller.conditions key=machine.ace.silent" {
		t.Errorf("show is %q", said[0].Show)
	}
}

// **A transition the bus will not take is offered again**, and said lost only after TellFor.
func TestATransitionIsOfferedAgainWhileTheBusIsAway(t *testing.T) {
	store, told, c := NewInMemory(), &Told{Fail: errors.New("no responders")}, newClock()
	k := NewKeeper(t.Context(), Options{Store: store, History: store, Teller: told, Now: c.now})
	defer k.Close(context.Background())
	if _, err := k.Observe(t.Context(), silent("ace")); err != nil {
		t.Fatal(err)
	}
	time.Sleep(300 * time.Millisecond)
	told.mu.Lock()
	told.Fail = nil
	told.mu.Unlock()
	said := settled(t, told, 1)
	if said[0].Key != "machine.ace.silent" || k.Unsaid() != 0 {
		t.Fatalf("said %+v, unsaid %d", said, k.Unsaid())
	}
}