package game

import (
	"context"
	"encoding/json"
	"sync"
	"testing"
	"time"

	"github.com/golang-jwt/jwt/v5"

	"github.com/ruby-sea-battle/game-server/internal/auth"
	"github.com/ruby-sea-battle/game-server/internal/protocol"
)

type fakeConn struct {
	mu        sync.Mutex
	sent      [][]byte
	closed    bool
	closeCode int
}

func (f *fakeConn) Send(_ context.Context, data []byte) error {
	f.mu.Lock()
	defer f.mu.Unlock()
	cp := make([]byte, len(data))
	copy(cp, data)
	f.sent = append(f.sent, cp)
	return nil
}

func (f *fakeConn) Close(code int, _ string) error {
	f.mu.Lock()
	defer f.mu.Unlock()
	f.closed = true
	f.closeCode = code
	return nil
}

func (f *fakeConn) messages() [][]byte {
	f.mu.Lock()
	defer f.mu.Unlock()
	out := make([][]byte, len(f.sent))
	copy(out, f.sent)
	return out
}

func (f *fakeConn) isClosed() (bool, int) {
	f.mu.Lock()
	defer f.mu.Unlock()
	return f.closed, f.closeCode
}

func claims(exp time.Time) *auth.GameClaims {
	return &auth.GameClaims{
		MatchID:    "match-1",
		Player1ID:  10,
		Player2ID:  20,
		GameServer: "ws://game.example.com/ws",
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(exp),
		},
	}
}

func parseMsg(t *testing.T, data []byte) []any {
	t.Helper()
	var v []any
	if err := json.Unmarshal(data, &v); err != nil {
		t.Fatalf("unmarshal %s: %v", data, err)
	}
	return v
}

func TestJoinFirstPlayerWaits(t *testing.T) {
	m := NewManager(time.Minute)
	c1 := &fakeConn{}
	gc := claims(time.Now().Add(time.Hour))

	_, idx, err := m.Join(context.Background(), c1, gc, gc.Player1ID)
	if err != nil {
		t.Fatalf("join: %v", err)
	}
	if idx != 0 {
		t.Fatalf("slot = %d, want 0", idx)
	}
	if got := len(c1.messages()); got != 0 {
		t.Fatalf("first player got %d messages, want 0", got)
	}
}

func TestSecondJoinStartsMatch(t *testing.T) {
	m := NewManager(time.Minute)
	gc := claims(time.Now().Add(time.Hour))
	c1, c2 := &fakeConn{}, &fakeConn{}

	if _, _, err := m.Join(context.Background(), c1, gc, gc.Player1ID); err != nil {
		t.Fatalf("join p1: %v", err)
	}
	if _, idx, err := m.Join(context.Background(), c2, gc, gc.Player2ID); err != nil {
		t.Fatalf("join p2: %v", err)
	} else if idx != 1 {
		t.Fatalf("slot = %d, want 1", idx)
	}

	for i, c := range []*fakeConn{c1, c2} {
		msgs := c.messages()
		if len(msgs) != 1 {
			t.Fatalf("player %d got %d messages, want 1", i, len(msgs))
		}
		v := parseMsg(t, msgs[0])
		// [3, seq, StatePlacingShips]
		if v[0] != float64(protocol.OpState) || v[1] != float64(1) || v[2] != float64(protocol.StatePlacingShips) {
			t.Fatalf("player %d got unexpected message: %v", i, v)
		}
	}
}

func TestJoinTimeoutEndsMatch(t *testing.T) {
	m := NewManager(50 * time.Millisecond)
	gc := claims(time.Now().Add(time.Hour))
	c1 := &fakeConn{}

	if _, _, err := m.Join(context.Background(), c1, gc, gc.Player1ID); err != nil {
		t.Fatalf("join: %v", err)
	}

	deadline := time.Now().Add(2 * time.Second)
	for {
		if closed, _ := c1.isClosed(); closed {
			break
		}
		if time.Now().After(deadline) {
			t.Fatal("timed out waiting for the match to end")
		}
		time.Sleep(10 * time.Millisecond)
	}

	msgs := c1.messages()
	if len(msgs) != 1 {
		t.Fatalf("got %d messages, want 1", len(msgs))
	}
	v := parseMsg(t, msgs[0])
	// [2, seq, -1, "join timeout exceeded"]
	if v[0] != float64(protocol.OpEnd) || v[1] != float64(1) || v[2] != float64(protocol.EndCodeJoinTimeout) || v[3] != "join timeout exceeded" {
		t.Fatalf("unexpected END message: %v", v)
	}
	if closed, code := c1.isClosed(); !closed || code != protocol.CloseCodeNormal {
		t.Fatalf("conn closed=%v code=%d, want closed with %d", closed, code, protocol.CloseCodeNormal)
	}
}

func TestJoinAfterFinishReplaysEnd(t *testing.T) {
	m := NewManager(50 * time.Millisecond)
	gc := claims(time.Now().Add(time.Hour))
	c1 := &fakeConn{}

	if _, _, err := m.Join(context.Background(), c1, gc, gc.Player1ID); err != nil {
		t.Fatalf("join: %v", err)
	}
	time.Sleep(200 * time.Millisecond) // let the join timer fire

	// A late join with the same (still valid) token must not create a new
	// match; the stored END is replayed instead. This also works for the
	// player who never connected at all.
	for _, userID := range []int64{gc.Player1ID, gc.Player2ID} {
		c := &fakeConn{}
		_, _, err := m.Join(context.Background(), c, gc, userID)
		if err != ErrMatchFinished {
			t.Fatalf("join after finish: err = %v, want ErrMatchFinished", err)
		}
		msgs := c.messages()
		if len(msgs) != 1 {
			t.Fatalf("replayed %d messages, want 1", len(msgs))
		}
		v := parseMsg(t, msgs[0])
		if v[0] != float64(protocol.OpEnd) || v[2] != float64(protocol.EndCodeJoinTimeout) {
			t.Fatalf("unexpected replayed message: %v", v)
		}
		if closed, _ := c.isClosed(); !closed {
			t.Fatal("connection was not closed after replaying END")
		}
	}
}

func TestReconnectReplacesConnection(t *testing.T) {
	m := NewManager(time.Minute)
	gc := claims(time.Now().Add(time.Hour))
	old, c2 := &fakeConn{}, &fakeConn{}

	if _, _, err := m.Join(context.Background(), old, gc, gc.Player1ID); err != nil {
		t.Fatalf("join p1: %v", err)
	}
	if _, _, err := m.Join(context.Background(), c2, gc, gc.Player2ID); err != nil {
		t.Fatalf("join p2: %v", err)
	}
	// Game started: both got STATE, nobody acknowledged it yet.

	// Player 1 reconnects: old connection must be closed, the unacknowledged
	// STATE must be replayed to the new one.
	fresh := &fakeConn{}
	if _, idx, err := m.Join(context.Background(), fresh, gc, gc.Player1ID); err != nil {
		t.Fatalf("rejoin p1: %v", err)
	} else if idx != 0 {
		t.Fatalf("slot = %d, want 0", idx)
	}

	if closed, code := old.isClosed(); !closed || code != protocol.CloseCodeReplaced {
		t.Fatalf("old conn closed=%v code=%d, want closed with %d", closed, code, protocol.CloseCodeReplaced)
	}
	msgs := fresh.messages()
	if len(msgs) != 1 {
		t.Fatalf("replayed %d messages, want 1", len(msgs))
	}
	v := parseMsg(t, msgs[0])
	if v[0] != float64(protocol.OpState) || v[2] != float64(protocol.StatePlacingShips) {
		t.Fatalf("unexpected replayed message: %v", v)
	}

	// Leave with the old connection must not detach the new one.
	m.Leave(old, mustMatch(t, m, gc.MatchID), 0)
	m.Leave(fresh, mustMatch(t, m, gc.MatchID), 0)
}

func TestAckThenReconnectResendsCurrentState(t *testing.T) {
	m := NewManager(time.Minute)
	gc := claims(time.Now().Add(time.Hour))
	c1, c2 := &fakeConn{}, &fakeConn{}

	match, _, err := m.Join(context.Background(), c1, gc, gc.Player1ID)
	if err != nil {
		t.Fatalf("join p1: %v", err)
	}
	if _, _, err := m.Join(context.Background(), c2, gc, gc.Player2ID); err != nil {
		t.Fatalf("join p2: %v", err)
	}

	// Player 1 acknowledges the STATE message, then reconnects. The queue
	// is empty, so the server re-sends the current state with a fresh seq.
	m.Ack(match, 0, 1)

	fresh := &fakeConn{}
	if _, _, err := m.Join(context.Background(), fresh, gc, gc.Player1ID); err != nil {
		t.Fatalf("rejoin p1: %v", err)
	}
	msgs := fresh.messages()
	if len(msgs) != 1 {
		t.Fatalf("got %d messages, want 1", len(msgs))
	}
	v := parseMsg(t, msgs[0])
	if v[0] != float64(protocol.OpState) || v[1] != float64(2) || v[2] != float64(protocol.StatePlacingShips) {
		t.Fatalf("unexpected message: %v", v)
	}
}

func mustMatch(t *testing.T, m *Manager, id string) *Match {
	t.Helper()
	m.mu.Lock()
	defer m.mu.Unlock()
	match, ok := m.matches[id]
	if !ok {
		t.Fatalf("match %q not found", id)
	}
	return match
}