package matcher

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

	"github.com/cosmic-clash/cosmic-clash/server/domain"
)

type creatorSpy struct {
	calls int
	err   error
	last  domain.Proposal
	ids   map[string]string
}

func (c *creatorSpy) CreateProposal(_ context.Context, proposal domain.Proposal, ids map[string]string, _ time.Time) error {
	c.calls++
	c.last = proposal
	c.ids = ids
	return c.err
}

func candidates() []domain.Candidate {
	now := time.Unix(1000, 0).UTC()
	result := make([]domain.Candidate, 4)
	for i := range result {
		result[i] = domain.Candidate{TicketID: "ticket-" + string(rune('1'+i)), PlayerID: "player-" + string(rune('1'+i)), Playlist: domain.Casual, ProtocolVersion: 1, EnqueuedAt: now.Add(time.Duration(i) * time.Second), PredictedRTT: map[string]float64{"EU": 20}}
	}
	return result
}

func workerFor(source CandidateSource, creator ProposalCreator) Worker {
	return Worker{Source: source, Creator: creator, Playlist: domain.Casual, Size: 4, Now: func() time.Time { return time.Unix(1000, 0).UTC() }, NextID: func() string { return "proposal-1234567890123456" }, Prepare: func(id string, playlist domain.Playlist, formation domain.MatchFormation, now time.Time) (domain.PreparedProposal, error) {
		return domain.PrepareProposal(id, playlist, formation, nil, domain.RankedArena{}, now)
	}}
}

func TestRunOnceDelegatesFinalClaimAndBindsTickets(t *testing.T) {
	creator := &creatorSpy{}
	worker := workerFor(func(context.Context, time.Time, domain.Playlist, int) ([]domain.Candidate, error) {
		return candidates(), nil
	}, creator)
	formed, err := worker.RunOnce(context.Background())
	if err != nil || !formed || creator.calls != 1 {
		t.Fatalf("formed=%v err=%v calls=%d", formed, err, creator.calls)
	}
	if len(creator.ids) != 4 || creator.ids["player-1"] != "ticket-1" {
		t.Fatalf("ticket bindings=%v", creator.ids)
	}
}

func TestRunOnceFailsClosedOnSourceOrDurableClaimFailure(t *testing.T) {
	creator := &creatorSpy{err: errors.New("serialization conflict")}
	worker := workerFor(func(context.Context, time.Time, domain.Playlist, int) ([]domain.Candidate, error) {
		return nil, errors.New("redis unavailable")
	}, creator)
	if _, err := worker.RunOnce(context.Background()); err == nil {
		t.Fatal("source failure was swallowed")
	}
	worker.Source = func(context.Context, time.Time, domain.Playlist, int) ([]domain.Candidate, error) {
		return candidates(), nil
	}
	if _, err := worker.RunOnce(context.Background()); err == nil {
		t.Fatal("durable claim failure was swallowed")
	}
	if creator.calls != 1 {
		t.Fatalf("creator calls=%d", creator.calls)
	}
}

func TestRunOnceDoesNotClaimAnIncompleteBatch(t *testing.T) {
	creator := &creatorSpy{}
	worker := workerFor(func(context.Context, time.Time, domain.Playlist, int) ([]domain.Candidate, error) {
		return candidates()[:3], nil
	}, creator)
	formed, err := worker.RunOnce(context.Background())
	if err != nil || formed || creator.calls != 0 {
		t.Fatalf("formed=%v err=%v calls=%d", formed, err, creator.calls)
	}
}

func TestRunOnceRejectsMixedPlaylistAndDuplicateIdentityBatches(t *testing.T) {
	creator := &creatorSpy{}
	worker := workerFor(func(_ context.Context, _ time.Time, _ domain.Playlist, _ int) ([]domain.Candidate, error) {
		batch := candidates()
		batch[1].Playlist = domain.Ranked
		return batch, nil
	}, creator)
	if _, err := worker.RunOnce(context.Background()); err == nil {
		t.Fatal("mixed playlist was accepted")
	}
	worker.Source = func(_ context.Context, _ time.Time, _ domain.Playlist, _ int) ([]domain.Candidate, error) {
		batch := candidates()
		batch[1].PlayerID = batch[0].PlayerID
		return batch, nil
	}
	if _, err := worker.RunOnce(context.Background()); err == nil {
		t.Fatal("duplicate identity was accepted")
	}
	if creator.calls != 0 {
		t.Fatalf("creator calls=%d", creator.calls)
	}
}

// TestRunSurvivesPerPassErrorsAndKeepsRetrying reproduces a real production
// bug found via a live integration test (multiplayer-next.md 8.40): two real
// players queued with no verified common region formed exactly this
// "source succeeds, formation fails" shape, and the matcher process died
// entirely rather than waiting for a compatible batch -- silently taking
// matchmaking down for every other player behind them too, not just the
// incompatible pair. Run must survive a per-pass RunOnce error and try
// again next interval rather than returning immediately.
func TestRunSurvivesPerPassErrorsAndKeepsRetrying(t *testing.T) {
	var mu sync.Mutex
	attempts := 0
	creatorCalls := 0
	worker := workerFor(func(context.Context, time.Time, domain.Playlist, int) ([]domain.Candidate, error) {
		mu.Lock()
		defer mu.Unlock()
		attempts++
		if attempts == 1 {
			// Same failure shape as domain.FormFromQueue's "no compatible
			// candidates" -- RunOnce still returns a non-nil error here, only
			// Run's handling of it is what this test is about.
			return nil, errors.New("no common region")
		}
		return candidates(), nil
	}, ProposalCreatorFunc(func(context.Context, domain.Proposal, map[string]string, time.Time) error {
		mu.Lock()
		defer mu.Unlock()
		creatorCalls++
		return nil
	}))
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()
	done := make(chan error, 1)
	go func() { done <- worker.Run(ctx, 5*time.Millisecond) }()
	deadline := time.After(1 * time.Second)
	for {
		mu.Lock()
		calls := creatorCalls
		mu.Unlock()
		if calls > 0 {
			break
		}
		select {
		case err := <-done:
			t.Fatalf("Run returned early on a per-pass error instead of retrying: %v", err)
		case <-deadline:
			t.Fatal("Run never recovered from the first pass's error")
		default:
			time.Sleep(time.Millisecond)
		}
	}
	mu.Lock()
	defer mu.Unlock()
	if creatorCalls != 1 {
		t.Fatalf("creator calls=%d, want exactly 1 once formation finally succeeded", creatorCalls)
	}
}

// TestRunStopsImmediatelyOnConfigurationErrors is the other half of the
// fix: a genuinely static misconfiguration (true on every future pass, not
// just this one) must still stop the worker rather than spin forever.
func TestRunStopsImmediatelyOnConfigurationErrors(t *testing.T) {
	worker := workerFor(func(context.Context, time.Time, domain.Playlist, int) ([]domain.Candidate, error) {
		return candidates(), nil
	}, &creatorSpy{})
	worker.Playlist = domain.Playlist("invalid")
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()
	err := worker.Run(ctx, 5*time.Millisecond)
	if !errors.Is(err, ErrUnsupportedPlaylist) {
		t.Fatalf("Run() error = %v, want ErrUnsupportedPlaylist", err)
	}
}