package main

import (
	"testing"
	"time"

	"github.com/stretchr/testify/require"
	"sneak.berlin/go/webhooker/internal/server"
)

// dockerStopGrace is Docker's default `docker stop` grace period.
// The Dockerfile sets no STOPSIGNAL or grace override, so this is
// the deadline the container is actually held to, and the fx stop
// timeout has to fit inside it with room for signal delivery and
// process exit.
const dockerStopGrace = 10 * time.Second

// TestNewApp_StopTimeout pins the fx stop timeout. Without the
// explicit fx.StopTimeout option the app reads fx's 15s
// DefaultTimeout, which exceeds dockerStopGrace: the container is
// SIGKILLed before the bound fires and every shutdown hook bounded
// by it — including the operator-facing timeout log — becomes
// unreachable in the image this repo produces.
//
// fx.New applies options before it executes invokes, so the timeout
// is set whether or not the graph itself can be constructed here.
func TestNewApp_StopTimeout(t *testing.T) {
	t.Setenv("DATA_DIR", t.TempDir())

	got := newApp().StopTimeout()

	require.Equal(t, stopTimeout, got)
	require.Less(t, got, dockerStopGrace)
}

// tailHeadroom is the slack the fx stop budget must keep beyond the
// server stop hook. The hooks that run after the server — the
// delivery engine, the healthcheck, the webhook DB manager and the
// database close — are microsecond-scale in normal operation, so
// this is generous for them.
const tailHeadroom = 2 * time.Second

// TestStopTimeout_LeavesHeadroomForTailHooks pins the relationship
// between the server's stop hook and the fx stop budget. fx bounds
// the whole stop sequence, and returns without running its
// remaining hooks once the stop context has expired. If the hook
// could use the entire budget, every later hook — the database close
// included — would be skipped in exactly the case where the drain
// mattered.
//
// The hook is not just the HTTP drain: a Sentry flush follows it in
// the same hook, and sentry.Flush honours no context, so both halves
// have to be counted. The sweep walks every drain length the hook
// can produce, since a shorter drain leaves the flush more room and
// the worst case is not necessarily at either extreme.
//
// Shrinking either budget, or unbounding the flush again, must fail
// here rather than silently recreating a hook that swallows the
// whole sequence.
func TestStopTimeout_LeavesHeadroomForTailHooks(t *testing.T) {
	t.Parallel()

	require.Less(t, server.ShutdownTimeout, stopTimeout)

	const step = 10 * time.Millisecond

	for drain := time.Duration(0); drain <= server.ShutdownTimeout; drain += step {
		hook := drain + server.SentryFlushBudget(stopTimeout-drain)

		require.LessOrEqual(
			t, hook+tailHeadroom, stopTimeout,
			"a %s drain leaves the tail hooks short", drain,
		)
	}
}