murphy

package main

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

type Moo struct {
    Cow   int
    Sound string
    Tube  chan bool
}

// A cow will moo until it is being fed
func cow(num int, mootube chan Moo) {
    tube := make(chan bool)
    for {
        select {
        case mootube <- Moo{num, "moo", tube}:
            fmt.Println("Cow number", num, "mooed through the mootube")
            <-tube
            fmt.Println("Cow number", num, "is being fed and stops mooing")
            mootube <- Moo{num, "mooh", nil}
            fmt.Println("Cow number", num, "moos one last time out of happyness")
            return
        default:
            fmt.Println("Cow number", num, "mooed through the mootube and was ignored")
            time.Sleep(time.Duration(rand.Int31n(1000)) * time.Millisecond)
        }
    }
}

// The farmer wants to put food in all the mootubes to stop the mooing
func farmer(numcows int, mootube chan Moo, farmertube chan string) {
    fmt.Println("Farmer starts listening to the mootube")
    for hungryCows := numcows; hungryCows > 0; {
        moo := <-mootube
        if moo.Sound == "mooh" {
            fmt.Println("Farmer heard a moo of relief from cow number", moo.Cow)
            hungryCows--
        } else {
            fmt.Println("Farmer heard a", moo.Sound, "from cow number", moo.Cow)
            time.Sleep(2e9)
            fmt.Println("Farmer starts feeding cow number", moo.Cow)
            moo.Tube <- true
        }
    }
    fmt.Println("Farmer doesn't hear a single moo anymore. All done!")
    farmertube <- "yey!"
}

// The farm starts out with mooing cows that wants to be fed
func runFarm(numcows int) {
    farmertube := make(chan string)
    mootube := make(chan Moo)
    for cownum := 0; cownum < numcows; cownum++ {
        go cow(cownum, mootube)
    }
    go farmer(numcows, mootube, farmertube)
    farmerSaid := <-farmertube
    if farmerSaid == "yey!" {
        fmt.Println("All cows are happy.")
    }
}

func main() {
    runFarm(4)
    fmt.Println("done")
}