package ecs

import (
	"fmt"
	"log"
	"reflect"
	"time"

	"github.com/yohamta/donburi"
	"github.com/yohamta/donburi/features/events"
)

type WorldState int

type WorldId int

const (
	Init WorldState = iota
	Running
	Pause
	Error
	Closed
)

type World interface {

	// Id returns the unique identifier for the world.
	Id() WorldId
	// Create creates a new entity with the specified components.
	Create(components ...donburi.IComponentType) *Entry
	// CreateMany creates a new entity with the specified components.
	CreateMany(n int, components ...donburi.IComponentType) []*Entry
	// Entry returns an entry for the specified entity.
	Entry(entity Entity) *Entry
	// Remove removes the specified entity.
	Remove(entity Entity)
	// Valid returns true if the specified entity is valid.
	Valid(e Entity) bool
	// Len returns the number of entities in the world.
	Len() int

	StartUp()
	Pause()
	Resume()
	SetSpeed(speed float64) error
	AddSystem(sys ...ISystem)
	Close()
}

type world struct {
	world   donburi.World
	systems []ISystem
	state   WorldState
	tick    int
	speed   float64

	quit chan struct{}
}

func NewComponentType[T any](opts ...interface{}) *ComponentType[T] {
	ct := donburi.NewComponentType[T](opts...)
	return &ComponentType[T]{ct}
}

func NewWorld(tick int) World {
	return &world{
		world:   donburi.NewWorld(),
		systems: make([]ISystem, 0),
		state:   Init,
		tick:    tick,
		speed:   1,
		quit:    make(chan struct{}),
	}
}

func (w *world) Id() WorldId {
	return WorldId(w.world.Id())
}

func (w *world) Create(components ...donburi.IComponentType) *Entry {
	entity := w.world.Create(components...)
	return &Entry{w.world.Entry(entity)}
}

func (w *world) CreateMany(n int, components ...donburi.IComponentType) []*Entry {
	entitys := w.world.CreateMany(n, components...)
	ets := make([]*Entry, len(entitys))
	for i, e := range entitys {
		ets[i] = &Entry{w.world.Entry(e)}
	}
	return ets
}

func (w *world) Entry(entity Entity) *Entry {
	return &Entry{w.world.Entry(entity.Entity)}
}

func (w *world) Remove(entity Entity) {
	w.world.Remove(entity.Entity)
}

func (w *world) Valid(e Entity) bool {
	return w.world.Valid(e.Entity)
}

func (w *world) Len() int {
	return w.world.Len()
}

// 添加系统
func (w *world) AddSystem(sys ...ISystem) {
	w.systems = append(w.systems, sys...)
}

// 执行所有事件处理
func (w *world) ProcessAllEvents() {
	events.ProcessAllEvents(w.world)
}

// 暂停世界
func (w *world) Pause() {
	if w.state == Running {
		w.state = Pause
	}
}

// 恢复世界运行
func (w *world) Resume() {
	if w.state == Pause {
		w.state = Running
	}
}

const (
	SpeedMin = 0.1
	SpeedMax = 10
)

// 设置世界运行速度
func (w *world) SetSpeed(speed float64) error {
	if speed < SpeedMin || speed > SpeedMax {
		return fmt.Errorf("速度必须在[%f, %d]之间", SpeedMin, SpeedMax)
	}
	w.speed = speed
	return nil
}

// 启动世界,世界逻辑开始执行且世界为运行状态
func (w *world) StartUp() {
	if w.state == Init { // 避免重复运行
		w.state = Running
		go w.run()
	}
}

// 关闭世界
func (w *world) Close() {
	w.quit <- struct{}{}
}

func (w *world) run() {
	for {
		select {
		case <-w.quit: // 退出信号
			log.Println("仿真退出,id:", w.world.Id())
			w.state = Closed
		default:
		}
		if w.state == Error {
			log.Println("世界错误,关闭世界,id:", w.world.Id())
			return
		}
		if w.state == Closed {
			log.Println("世界正常关闭,id:", w.world.Id())
			return
		}
		if w.state == Pause { // 暂停不更新
			log.Println("仿真暂停中,id:", w.world.Id())
			sleep := int64(float64(w.tick) / (w.speed))
			time.Sleep(time.Duration(sleep) * time.Millisecond)
			continue
		}
		start := time.Now()
		// fmt.Println("仿真更新,id:", info.id)
		for _, sys := range w.systems {
			sys.Update(w)
		}

		// 处理所有事件
		// w.ProcessAllEvents()

		// 执行逻辑花费时间，单位ms
		ot := time.Duration(time.Now().Nanosecond() - start.Nanosecond()).Milliseconds()
		// 根据间隔和速度计算休眠时间
		sleep := int64(float64(w.tick)/(w.speed)) - ot
		if sleep > 0 {
			time.Sleep(time.Duration(sleep) * time.Millisecond)
		} else {
			log.Println("仿真无休眠,id:", w.world.Id())
		}
	}
}

func NewEventType[T any](w World) *EventType[T] {
	// events.NewEventType()
	ct := NewComponentType[T]()
	var et T
	name := reflect.TypeOf(et).Name()
	return &EventType[T]{
		name,
		ct,
		w,
	}
}