package server_test

import (
	"net"
	"net/http"
	"strconv"
	"testing"
	"time"

	"sneak.berlin/go/neoirc/internal/server"
)

const (
	testTimeout = 5 * time.Second

	// listenCheckStep is how often waitUntilListening tries
	// to connect.
	listenCheckStep = 10 * time.Millisecond

	// stopHoldTime is how long a test waits to see that Stop
	// has not returned.
	stopHoldTime = 200 * time.Millisecond
)

// TestStopWaitsForRequestInProgress checks that stopping the
// server waits for a request it is serving to finish, and
// that the request gets its response.
func TestStopWaitsForRequestInProgress(t *testing.T) {
	t.Parallel()

	started := make(chan struct{})
	release := make(chan struct{})

	port := freePort(t)
	addr := net.JoinHostPort("127.0.0.1", strconv.Itoa(port))

	srv := server.NewTestHTTPServer(
		port,
		func(writer http.ResponseWriter, _ *http.Request) {
			close(started)
			<-release
			writer.WriteHeader(http.StatusNoContent)
		},
	)
	srv.Start()

	waitUntilListening(t, addr)

	statuses := make(chan int, 1)

	go func() {
		statuses <- get(t, "http://"+addr+"/")
	}()

	<-started

	stopped := make(chan struct{})

	go func() {
		srv.Stop(t.Context())
		close(stopped)
	}()

	select {
	case <-stopped:
		t.Error("Stop returned while a request was in progress")
	case <-time.After(stopHoldTime):
	}

	close(release)

	status := <-statuses
	if status != http.StatusNoContent {
		t.Errorf("status %d, want %d", status, http.StatusNoContent)
	}

	select {
	case <-stopped:
	case <-time.After(testTimeout):
		t.Fatal("Stop did not return after the request finished")
	}
}

// freePort returns a TCP port that nothing was listening on a
// moment ago.
func freePort(t *testing.T) int {
	t.Helper()

	var listenConfig net.ListenConfig

	listener, err := listenConfig.Listen(
		t.Context(), "tcp", "127.0.0.1:0",
	)
	if err != nil {
		t.Fatalf("listen: %v", err)
	}

	tcpAddr, ok := listener.Addr().(*net.TCPAddr)
	if !ok {
		t.Fatalf("listener address %v is not TCP", listener.Addr())
	}

	err = listener.Close()
	if err != nil {
		t.Fatalf("close listener: %v", err)
	}

	return tcpAddr.Port
}

// waitUntilListening waits until addr accepts connections,
// and fails the test if it does not within testTimeout.
func waitUntilListening(t *testing.T, addr string) {
	t.Helper()

	var dialer net.Dialer

	deadline := time.Now().Add(testTimeout)

	for {
		conn, err := dialer.DialContext(t.Context(), "tcp", addr)
		if err == nil {
			_ = conn.Close()

			return
		}

		if time.Now().After(deadline) {
			t.Fatalf("nothing listening on %s: %v", addr, err)
		}

		time.Sleep(listenCheckStep)
	}
}

// get sends a GET request to url and returns the response
// status, or 0 if there was no response.
func get(t *testing.T, url string) int {
	t.Helper()

	request, err := http.NewRequestWithContext(
		t.Context(), http.MethodGet, url, nil,
	)
	if err != nil {
		t.Errorf("new request: %v", err)

		return 0
	}

	client := http.Client{Timeout: testTimeout}

	response, err := client.Do(request)
	if err != nil {
		t.Errorf("get %s: %v", url, err)

		return 0
	}

	_ = response.Body.Close()

	return response.StatusCode
}