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package main

import (
	"fmt"
	"math/rand"
	"time"
)

type Philo struct {
	Name     string
	Left     Fork
	Right    Fork
	Bites    int
	MaxDelay time.Duration
	TimeOut  time.Duration
}

func (p Philo) Delay() {
	n := rand.Intn(int(p.MaxDelay))
	time.Sleep(time.Duration(n))
}

func (p Philo) Print(s string) {
	fmt.Printf("%10s %s\n", p.Name, s)
}

func (p *Philo) Arrive() stateFn {
	p.Print("arrives")

	return p.Hungry
}

func (p *Philo) Hungry() stateFn {
	p.Print("is hungry")

	p.Left.Grab()
	if ok := p.Right.TryGrab(p.TimeOut); ok {
		return p.Eat
	}
	p.Left.Put()

	return p.Starve
}

func (p *Philo) Starve() stateFn {
	p.Print("is starving")
	p.Delay()

	return p.Hungry
}

func (p *Philo) Eat() stateFn {
	p.Print("is eating")
	p.Delay()

	p.Left.Put()
	p.Right.Put()

	if p.Bites--; p.Bites <= 0 {
		return p.Leave
	}

	return p.Think
}

func (p *Philo) Think() stateFn {
	p.Print("is thinking")
	p.Delay()

	return p.Hungry
}

func (p *Philo) Leave() stateFn {
	p.Print("leaves")

	return nil
}

type stateFn func() stateFn

func (p *Philo) Dine() {
	for state := p.Arrive; state != nil; {
		state = state()
	}
}