package foo

import (
	"time"

	"github.com/dimonomid/clock"
)

type Foo struct {
	nextNum int
	out     chan<- int

	clock clock.Clock
}

type FooParams struct {
	Clock clock.Clock

	// Out is the channel to deliver numbers to
	Out chan<- int
	// Interval is how often to deliver numbers to Out
	Interval time.Duration
}

// NewFoo creates and returns an instance of Foo, and also starts an internal
// goroutine which will send numbers to the provided channel params.Out.
func NewFoo(params *FooParams) *Foo {
	if params.Clock == nil {
		panic("Clock is required")
	}

	foo := &Foo{
		clock: params.Clock,
		out:   params.Out,
	}

	go foo.run(params.Interval)

	return foo
}

func (foo *Foo) run(interval time.Duration) {
	// NOTE: there is an issue with creating ticker right in this goroutine,
	// explained below.
	ticker := foo.clock.Ticker(interval)

	for {
		<-ticker.C
		foo.out <- foo.nextNum
		foo.nextNum += 1
	}
}