package main

import (
	"context"
	"regexp"
	"testing"
	"time"
)

func makeDut() (*dispatcher, context.CancelFunc, context.Context) {
	dut := newDispatcher()

	ctx := context.Background()
	ctxC, cancelCtx := context.WithCancel(ctx)
	go dut.run(ctxC)

	return dut, cancelCtx, ctx
}

func expectReceived(t *testing.T, s *sms, data chan *sms) {
	ticker := time.NewTicker(100 * time.Millisecond)
	defer ticker.Stop()
	select {
	case d := <-data:
		if d.from != s.from {
			t.Errorf("Received SMS from %q, wanted %q", d.from, s.from)
		}
		if d.body != s.body {
			t.Errorf("Received SMS body %q, wanted %q", d.body, s.body)
		}
		if d.timestamp != s.timestamp {
			t.Errorf("Received SMS timestamp %v, wanted %v", d.timestamp, s.timestamp)
		}
	case <-ticker.C:
		t.Fatalf("Timed out waiting for message")
	}
}

func expectEmpty(t *testing.T, data chan *sms) {
	ticker := time.NewTicker(1 * time.Millisecond)
	defer ticker.Stop()
	select {
	case <-data:
		t.Fatalf("Received unwanted message")
	case <-ticker.C:
	}
}

func TestDispatcher(t *testing.T) {
	dut, cancelDut, _ := makeDut()
	defer cancelDut()

	data := make(chan *sms)
	cancel := make(chan struct{})

	dut.subscribe(&subscriber{
		re:     regexp.MustCompile(".*"),
		data:   data,
		cancel: cancel,
	})

	in := &sms{
		from:      "+4821372137",
		body:      "foo",
		timestamp: time.Now(),
	}
	dut.publish(in)

	// Make sure we ge the message.
	expectReceived(t, in, data)

	// Make sure we don't receive the message again.
	expectEmpty(t, data)

	// Publish a new message, but this time close our subscriber.
	close(cancel)
	// Hack: yield.
	time.Sleep(1 * time.Millisecond)

	dut.publish(in)
	expectEmpty(t, data)
}

type testSubscriber struct {
	re     *regexp.Regexp
	data   chan *sms
	cancel chan struct{}
}

func TestDispatcherFilters(t *testing.T) {
	dut, cancelDut, _ := makeDut()
	defer cancelDut()

	subscribers := []*testSubscriber{
		{re: regexp.MustCompile(".*")},
		{re: regexp.MustCompile("foo")},
		{re: regexp.MustCompile("bar")},
	}

	for _, s := range subscribers {
		s.data = make(chan *sms)
		s.cancel = make(chan struct{})
		dut.subscribe(&subscriber{
			re:     s.re,
			data:   s.data,
			cancel: s.cancel,
		})
		defer func(c chan struct{}) {
			close(c)
		}(s.cancel)
	}

	in := &sms{
		from:      "+4821372137",
		body:      "foo",
		timestamp: time.Now(),
	}
	dut.publish(in)
	expectReceived(t, in, subscribers[0].data)
	expectReceived(t, in, subscribers[1].data)
	expectEmpty(t, subscribers[2].data)

	in = &sms{
		from:      "+4821372137",
		body:      "bar",
		timestamp: time.Now(),
	}
	dut.publish(in)
	expectReceived(t, in, subscribers[0].data)
	expectEmpty(t, subscribers[1].data)
	expectReceived(t, in, subscribers[2].data)

	in = &sms{
		from:      "+4821372137",
		body:      "foobar",
		timestamp: time.Now(),
	}
	dut.publish(in)
	expectReceived(t, in, subscribers[0].data)
	expectReceived(t, in, subscribers[1].data)
	expectReceived(t, in, subscribers[2].data)
}

func TestDispatcherMany(t *testing.T) {
	dut, cancelDut, _ := makeDut()
	defer cancelDut()

	subscribers := make([]*testSubscriber, 10000)

	for i, _ := range subscribers {
		s := &testSubscriber{
			re:     regexp.MustCompile(".*"),
			data:   make(chan *sms),
			cancel: make(chan struct{}),
		}
		subscribers[i] = s
		dut.subscribe(&subscriber{
			re:     s.re,
			data:   s.data,
			cancel: s.cancel,
		})
		defer func(c chan struct{}) {
			close(c)
		}(s.cancel)
	}

	in := &sms{
		from:      "+4821372137",
		body:      "foo",
		timestamp: time.Now(),
	}
	dut.publish(in)

	for _, s := range subscribers {
		expectReceived(t, in, s.data)
	}
}

func TestDispatcherHammer(t *testing.T) {
	dut, cancelDut, _ := makeDut()
	defer cancelDut()

	for i := 0; i < 1000000; i += 1 {
		s := &testSubscriber{
			re:     regexp.MustCompile(".*"),
			data:   make(chan *sms),
			cancel: make(chan struct{}),
		}

		dut.subscribe(&subscriber{
			re:     s.re,
			data:   s.data,
			cancel: s.cancel,
		})

		in := &sms{
			from:      "+4821372137",
			body:      "foo",
			timestamp: time.Now(),
		}
		dut.publish(in)
		expectReceived(t, in, s.data)

		close(s.cancel)
	}
}