package app

import (
	"context"
	"errors"
	"os"
	"sorbet/pkg/app/appkit"
)

func Init(args ...string) (err error) {
	if len(args) == 0 {
		args = os.Args[1:]
	}

	switch Status() {
	case Initialized:
		return nil
	case Starting:
		return errors.New("starting")
	case Running:
		return errors.New("running")
	case Stopping:
		return errors.New("stopping")
	case Idle, Stopped:
		// continue
	}

	initLifecycle()
	initStats(args)
	initUdp(args)
	initBus()
	initBuiltins()

	setStatus(Initialized)

	return
}

func initBuiltins() {
	// 订阅应用启动
	var sub appkit.Subscriber
	sub = Sub("start", func([]byte) []byte {
		sub.Cancel()
		return nil
	})

	// 订阅应用停止
	Sub("stop", func(bytes []byte) []byte {
		quit := exit
		if quit != nil {
			exit = nil
			quit()
		}
		return nil
	})
}

func Loop() error {
	switch Status() {
	case Starting, Running:
		return nil
	case Stopping:
		return errors.New("stopping")
	case Idle:
		return errors.New("idle, you maybe forgot call app.Init()")
	case Stopped:
		return errors.New("stopped, you maybe forgot call app.Init()")
	case Initialized:
		// nothing
	}

	// 释放内存
	defer free()

	wg.Add(1)
	setStatus(Starting)

	// In a goroutine, we wait on for all goroutines to complete (for example
	// timers). We use this to signal to the main thread to exit.
	// wg.Add(1) basically translates to uv_ref, if this was Node.
	// wg.Done() basically translates to uv_unref
	go func() {
		wg.Wait()
		setStatus(Stopping)
		stop()
	}()

	// 启动应用指令
	Pub("start", nil)

	for {
		select {
		case msg := <-pubs:
			err := dispatch(msg)
			exitOnError(err)
			wg.Done() // Corresponds to the wg.Add(1) in Pub().

		case <-ctx.Done():
			// 只有等待所有协程全部完成后，
			// 然后才可以退出主循环
			checkPubsEmpty()
			setStatus(Stopped)
			return ctx.Err()
		}

		// We don't want to exit until we've received at least one message.
		// This is so the program doesn't exit after sending the "start"
		// message.
		if Status() == Starting {
			wg.Done()
			start()
			setStatus(Running)
		}
	}
}

func Stop() {
	Pub("stop", nil)
}

func Go(fn func(context.Context)) {
	assert(fn != nil, "invalid fn")
	async(fn)
}