package main

import (
    "hash/fnv"
    "log"
    "math/rand"
    "os"
    "sync"
    "time"
)

var ph = []string{"Aristotle", "Kant", "Spinoza", "Marx", "Russell"}

const hunger = 3
const think = time.Second / 100
const eat = time.Second / 100

var fmt = log.New(os.Stdout, "", 0)

var dining sync.WaitGroup

func philosopher(phName string, dominantHand, otherHand *sync.Mutex) {
    fmt.Println(phName, "seated")
    h := fnv.New64a()
    h.Write([]byte(phName))
    rg := rand.New(rand.NewSource(int64(h.Sum64())))
    rSleep := func(t time.Duration) {
        time.Sleep(t/2 + time.Duration(rg.Int63n(int64(t))))
    }
    for h := hunger; h > 0; h-- {
        fmt.Println(phName, "hungry")
        dominantHand.Lock() // pick up forks
        otherHand.Lock()
        fmt.Println(phName, "eating")
        rSleep(eat)
        dominantHand.Unlock() // put down forks
        otherHand.Unlock()
        fmt.Println(phName, "thinking")
        rSleep(think)
    }
    fmt.Println(phName, "satisfied")
    dining.Done()
    fmt.Println(phName, "left the table")
}

func main() {
    fmt.Println("table empty")
    dining.Add(5)
    fork0 := &sync.Mutex{}
    forkLeft := fork0
    for i := 1; i < len(ph); i++ {
        forkRight := &sync.Mutex{}
        go philosopher(ph[i], forkLeft, forkRight)
        forkLeft = forkRight
    }
    go philosopher(ph[0], fork0, forkLeft)
    dining.Wait() // wait for philosphers to finish
    fmt.Println("table empty")
}