Danmaku/server/main.go

package main

/*
#cgo CFLAGS: -I ${SRCDIR}/lib
#cgo LDFLAGS: -L ${SRCDIR}/lib -l ffi_wrapper
#include "ffi-wrapper.h"
#include <stdlib.h>
*/
import "C"

import (
	"context"
	"database/sql"
	"encoding/json"
	"math"
	"math/rand"
	"slices"

	"github.com/heroiclabs/nakama-common/runtime"
)

const (
	MATCH_LOADING = iota
	MATCH_START
	STATE_UPDATE
	FINAL_PHASE
	MATCH_END
)

const (
	BULLET_LINEAR = 0
)

const (
	STAGE_WIDTH              float64 = 90.0
	STAGE_HEIGHT             float64 = 160.0
	BULLET_KILL_BUFFER_WIDTH float64 = 16.0
)

// Interface for registering match handlers
type BattleRoyaleMatch struct{}

type Position struct {
	X float64 `json:"x"`
	Y float64 `json:"y"`
}

type PlayerStageState struct {
	pos             Position
	bullets         []*C.Bullet
	updatePlayerPos bool
}

type GameTickUpdate struct {
	Tick           int64                    `json:"tick"`
	PlayerPos      Position                 `json:"playerPos"`
	NewBullets     []map[string]interface{} `json:"newBullets"`
	ForcePlayerPos bool                     `json:"forcePlayerPos"`
}

type PresenceState struct { // present time! hahahahahahahah!
	presence   runtime.Presence
	stageState PlayerStageState
}

type BattleRoyaleMatchState struct {
	tickRate          int
	currentMatchPhase int
	presences         map[string]*PresenceState
	emptyTicks        int
}

// Run on match start, initializes game state and sets tick rate
func (m *BattleRoyaleMatch) MatchInit(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule, params map[string]interface{}) (interface{}, int, string) {
	tickRate := 20 // MatchLoop invocations per second
	state := &BattleRoyaleMatchState{
		tickRate:          tickRate,
		presences:         map[string]*PresenceState{},
		emptyTicks:        0,
		currentMatchPhase: MATCH_LOADING,
	}
	label := ""

	return state, tickRate, label
}

// Run when a user attempts to join or rejoin a match. Responsible for deciding whether or not to let them in.
func (m *BattleRoyaleMatch) MatchJoinAttempt(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule, dispatcher runtime.MatchDispatcher, tick int64, state interface{}, presence runtime.Presence, metadata map[string]string) (interface{}, bool, string) {
	lobbyState, ok := state.(*BattleRoyaleMatchState)
	if !ok {
		logger.Error("State is not a valid lobby state object for MatchJoin.")
		return nil, false, "Failed to join match: match does not exist."
	}
	accepted := true
	rejectedMessage := ""

	return lobbyState, accepted, rejectedMessage
}

// Run when a user successfully joins a match, registers their presence in the game state
func (m *BattleRoyaleMatch) MatchJoin(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule, dispatcher runtime.MatchDispatcher, tick int64, state interface{}, presences []runtime.Presence) interface{} {
	lobbyState, ok := state.(*BattleRoyaleMatchState)
	if !ok {
		logger.Error("State is not a valid lobby state object for MatchJoin.")
		return nil
	}

	for i := 0; i < len(presences); i++ {
		lobbyState.presences[presences[i].GetSessionId()] = &PresenceState{
			presence: presences[i],
			stageState: PlayerStageState{
				pos: Position{
					X: STAGE_WIDTH * 0.5,
					Y: STAGE_HEIGHT - STAGE_HEIGHT*0.1,
				},
				bullets:         []*C.Bullet{},
				updatePlayerPos: false,
			},
		}
	}

	return lobbyState
}

// Run when a user successfully leaves a match, de-registers their presence in the game state
func (m *BattleRoyaleMatch) MatchLeave(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule, dispatcher runtime.MatchDispatcher, tick int64, state interface{}, presences []runtime.Presence) interface{} {
	lobbyState, ok := state.(*BattleRoyaleMatchState)
	if !ok {
		logger.Error("State is not a valid lobby state object for MatchLeave.")
		return nil
	}

	for i := 0; i < len(presences); i++ {
		sessionID := presences[i].GetSessionId()

		playerState, exists := lobbyState.presences[sessionID]
		if exists {
			for _, bullet := range playerState.stageState.bullets {
				C.destroy_bullet(bullet)
			}

			delete(lobbyState.presences, sessionID)
		}
	}

	return lobbyState
}

// Run when a match gets an arbitrary signal from the Nakama runtime (probably from the matchmaker/match lister APIs)
func (m *BattleRoyaleMatch) MatchSignal(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule, dispatcher runtime.MatchDispatcher, tick int64, state interface{}, data string) (interface{}, string) {
	lobbyState, ok := state.(*BattleRoyaleMatchState)
	if !ok {
		logger.Error("State is not a valid lobby state object for MatchSignal.")
		return nil, "Failed to get valid state for return signal"
	}

	returnMessage := ""
	return lobbyState, returnMessage
}

// Run when the server enters the graceful shutdown flow. Gives the match a chance to shutdown cleanly within graceSeconds.
func (m *BattleRoyaleMatch) MatchTerminate(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule, dispatcher runtime.MatchDispatcher, tick int64, state interface{}, graceSeconds int) interface{} {
	lobbyState, ok := state.(*BattleRoyaleMatchState)
	if !ok {
		logger.Error("State is not a valid lobby state object for MatchTerminate.")
		return nil
	}

	return lobbyState
}

// Main game loop, executed at tickRate per second specified in MatchInit
func (m *BattleRoyaleMatch) MatchLoop(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule, dispatcher runtime.MatchDispatcher, tick int64, state interface{}, messages []runtime.MatchData) interface{} {
	lobbyState, ok := state.(*BattleRoyaleMatchState)
	if !ok {
		logger.Error("State is not a valid lobby state object for MatchLoop.")
		return nil
	}

	// If we have no presences in the match according to the match state, increment the empty ticks count
	if len(lobbyState.presences) == 0 {
		lobbyState.emptyTicks++
	}

	// If the match has been empty for more than 100 ticks, end the match by returning nil
	if lobbyState.emptyTicks > 100 {
		return nil
	}

	// Respond to player input
	for _, msg := range messages {
		// Validate player existence
		_, exists := lobbyState.presences[msg.GetSessionId()]
		if !exists {
			logger.Warn("Received input for non-existent player session ID: %v", msg.GetSessionId())
			continue
		}

		// Parse player message
		var pos Position
		if err := json.Unmarshal(msg.GetData(), &pos); err != nil {
			logger.Warn("Failed to parse input: %v", err)
			continue
		}

		// Player movement bounds detection
		clampedX := pos.X < 0 || pos.X > STAGE_WIDTH
		clampedY := pos.Y < 0 || pos.Y > STAGE_HEIGHT

		pos.X = math.Max(0, math.Min(pos.X, STAGE_WIDTH))
		pos.Y = math.Max(0, math.Min(pos.Y, STAGE_HEIGHT))

		lobbyState.presences[msg.GetSessionId()].stageState.pos.X = pos.X
		lobbyState.presences[msg.GetSessionId()].stageState.pos.Y = pos.Y

		if clampedX || clampedY {
			lobbyState.presences[msg.GetSessionId()].stageState.updatePlayerPos = true
		}
	}

	// Compute and broadcast per-presence state
	for _, v := range lobbyState.presences {
		// Clean up bullets when they pass off the board
		v.stageState.bullets = slices.DeleteFunc(v.stageState.bullets, func(b *C.Bullet) bool {
			if C.bullet_beyond_kill_boundary(b, C.int64_t(tick)) {
				C.destroy_bullet(b)
				return true
			}
			return false
		})

		var newBulletsToBroadcast = []map[string]interface{}{}

		// Test bullet spawning
		if tick%1 == 0 {
			velx := rand.Float64()*(STAGE_WIDTH/float64(lobbyState.tickRate)) + 1.0
			vely := rand.Float64()*(STAGE_WIDTH/float64(lobbyState.tickRate)) + 1.0
			vel_x_sign := 2*rand.Intn(2) - 1
			vel_y_sign := 2*rand.Intn(2) - 1

			bullet := C.new_bullet(
				C.uint8_t(BULLET_LINEAR),
				C.int64_t(tick),
				C.double(STAGE_WIDTH*rand.Float64()),
				C.double(STAGE_HEIGHT*rand.Float64()),
				C.double(float64(vel_x_sign)*velx),
				C.double(float64(vel_y_sign)*vely),
			)

			v.stageState.bullets = append(v.stageState.bullets, bullet)

			var x, y C.double
			C.bullet_get_current_pos(bullet, C.int64_t(tick), &x, &y)

			bulletData := map[string]interface{}{
				"class": BULLET_LINEAR,
				"tick":  tick,
				"x":     float64(x),
				"y":     float64(y),
				"vel_x": float64(vel_x_sign) * velx,
				"vel_y": float64(vel_y_sign) * vely,
			}

			newBulletsToBroadcast = append(newBulletsToBroadcast, bulletData)
		}

		var tickData = GameTickUpdate{
			Tick: tick,
			PlayerPos: Position{
				X: v.stageState.pos.X,
				Y: v.stageState.pos.Y,
			},
			NewBullets:     newBulletsToBroadcast,
			ForcePlayerPos: v.stageState.updatePlayerPos,
		}

		v.stageState.updatePlayerPos = false

		data, err := json.Marshal(tickData)
		if err != nil {
			logger.Error("Error marshalling bullet data", err)
		} else {
			reliable := true
			dispatcher.BroadcastMessage(STATE_UPDATE, data, nil, nil, reliable)
		}
	}

	return lobbyState
}

// RPC for force-creating a match for debugging/development, separate from the matchmaking process
func ManualForceCreateBRMatchRPC(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule, payload string) (string, error) {
	modulename := "battle-royale"

	if matchId, err := nk.MatchCreate(ctx, modulename, make(map[string]interface{})); err != nil {
		return "", err
	} else {
		return matchId, nil
	}
}

// main function for hooking into the nakama runtime, responsible for setting up all handlers
func InitModule(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule, initializer runtime.Initializer) error {
	// Register handlers for match lifecycle
	if err := initializer.RegisterMatch("battle-royale", func(ctx context.Context, logger runtime.Logger, db *sql.DB, nk runtime.NakamaModule) (runtime.Match, error) {
		return &BattleRoyaleMatch{}, nil
	}); err != nil {
		logger.Error("Unable to register match handler: %v", nil)
		return err
	}

	// Register RPCs
	if err := initializer.RegisterRpc("manual_force_create_br_match_rpc", ManualForceCreateBRMatchRPC); err != nil {
		logger.Error("Unable to register: %v", err)
		return err
	}

	return nil
}