package main

import (
	"bytes"
	"encoding/json"
	"io"
	"log/slog"
	"net"
	"os"
	"strconv"
	"strings"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/webhooker/internal/config"
	"sneak.berlin/go/webhooker/internal/datadir"
	"sneak.berlin/go/webhooker/internal/resetpw"
	"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) {
	config.ClearEnvForTest(t)
	t.Setenv("DATA_DIR", t.TempDir())

	got := newApp().StopTimeout()

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

// freePort returns a loopback TCP port that was free a moment ago, by
// taking one and releasing it.
func freePort(t *testing.T) int {
	t.Helper()

	var listenCfg net.ListenConfig

	l, err := listenCfg.Listen(t.Context(), "tcp", "127.0.0.1:0")
	require.NoError(t, err)

	addr, ok := l.Addr().(*net.TCPAddr)
	require.True(t, ok, "listener is not TCP")
	require.NoError(t, l.Close())

	return addr.Port
}

// TestNewApp_SendsFxEventsToTheLogger starts and stops the app main
// runs, with DEBUG=true, and reads back what reached the service's
// logger. fx's own events must arrive there as structured records:
// the start at INFO, and at DEBUG the records of how the graph was
// built.
//
// fx holds its events back until its logger is built and then replays
// them all at once, so the earliest of them arriving shows the replay
// ran at DEBUG: that globals.New was provided, which fx records before
// anything is built, and the run of logger.New, which happens before
// the configuration sets the level.
func TestNewApp_SendsFxEventsToTheLogger(t *testing.T) {
	config.ClearEnvForTest(t)
	t.Setenv("DATA_DIR", t.TempDir())
	t.Setenv("PORT", strconv.Itoa(freePort(t)))
	t.Setenv("DEBUG", "true")

	// internal/logger writes to whatever os.Stdout is when it builds
	// its handler. A file is not a terminal, so that handler is the
	// JSON one the service uses in production.
	out, err := os.CreateTemp(t.TempDir(), "stdout")
	require.NoError(t, err)

	stdout := os.Stdout
	os.Stdout = out

	t.Cleanup(func() {
		os.Stdout = stdout
		_ = out.Close()
	})

	app := newApp()
	require.NoError(t, app.Start(t.Context()))
	require.NoError(t, app.Stop(t.Context()))

	_, err = out.Seek(0, io.SeekStart)
	require.NoError(t, err)

	written, err := io.ReadAll(out)
	require.NoError(t, err)

	type record struct {
		Level       string `json:"level"`
		Msg         string `json:"msg"`
		Name        string `json:"name"`
		Constructor string `json:"constructor"`
	}

	var records []record

	for line := range strings.Lines(string(written)) {
		var r record

		// The first-boot banner is plain text, not a record.
		if json.Unmarshal([]byte(line), &r) == nil {
			records = append(records, r)
		}
	}

	const pkg = "sneak.berlin/go/webhooker/internal/"

	info := slog.LevelInfo.String()
	debug := slog.LevelDebug.String()

	assert.Contains(t, records, record{Level: info, Msg: "started"})
	assert.Contains(t, records, record{
		Level: debug, Msg: "provided", Constructor: pkg + "globals.New()",
	})
	assert.Contains(t, records, record{
		Level: debug, Msg: "run", Name: pkg + "logger.New()",
	})
	assert.Contains(t, records, record{Level: debug, Msg: "invoking"})
	assert.Contains(t, records, record{
		Level: debug, Msg: "initialized custom fxevent.Logger",
	})
}

// TestRunRefusesLockedDataDir pins what an operator's second start
// does. The entry point must refuse before it builds the fx graph —
// nothing may open a database in a DATA_DIR another process holds —
// and must exit non-zero with a message naming the directory rather
// than starting a second delivery engine over the same rows.
//
// flock(2) locks descriptors independently, so holding the lock here
// is the same denial a separate process gets; internal/datadir pins
// that property and covers the real two-process case.
func TestRunRefusesLockedDataDir(t *testing.T) {
	dir := t.TempDir()
	t.Setenv("DATA_DIR", dir)

	lock, err := datadir.Acquire(dir)
	require.NoError(t, err)

	defer func() { _ = lock.Release() }()

	var stderr bytes.Buffer

	code := run(&stderr)

	require.Equal(
		t, 1, code, "a second instance must exit non-zero",
	)
	assert.Contains(
		t, stderr.String(), dir,
		"the refusal must name the directory",
	)
	assert.Contains(t, stderr.String(), "another instance")
}

// TestDispatch_NoArgumentsRunsTheServer pins the routing of a bare
// invocation, which is what the image's CMD and every deployment use.
// Adding subcommands must not move the server off the empty argument
// list, and must not move the DATA_DIR lock: this asserts the refusal
// arrives with no fx graph built, exactly as run does on its own.
func TestDispatch_NoArgumentsRunsTheServer(t *testing.T) {
	dir := t.TempDir()
	t.Setenv("DATA_DIR", dir)

	lock, err := datadir.Acquire(dir)
	require.NoError(t, err)

	defer func() { _ = lock.Release() }()

	var stdout, stderr bytes.Buffer

	code := dispatch(nil, strings.NewReader(""), &stdout, &stderr)

	require.Equal(t, 1, code)
	assert.Contains(t, stderr.String(), "another instance")
}

// TestDispatch_UnknownSubcommand keeps a mistyped subcommand from
// starting a server. Anything else would have `webhooker resetpww`
// silently take the DATA_DIR lock and serve.
func TestDispatch_UnknownSubcommand(t *testing.T) {
	t.Parallel()

	var stdout, stderr bytes.Buffer

	code := dispatch(
		[]string{"resetpww", "admin"},
		strings.NewReader(""), &stdout, &stderr,
	)

	require.Equal(t, 2, code)
	assert.Contains(t, stderr.String(), "unknown subcommand")
	assert.Contains(
		t, stderr.String(), resetpw.Name,
		"the usage must name the subcommand that does exist",
	)
}

// TestDispatch_Help answers on standard output with a zero status, so
// `webhooker help` is usable in a pipe.
func TestDispatch_Help(t *testing.T) {
	t.Parallel()

	var stdout, stderr bytes.Buffer

	code := dispatch(
		[]string{helpCommand}, strings.NewReader(""), &stdout, &stderr,
	)

	require.Equal(t, 0, code)
	assert.Empty(t, stderr.String())
	assert.Contains(t, stdout.String(), resetpw.Name)
}

// 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.
//
// Nor does the hook start on a full budget: the ArchiveSweeper and
// RetentionReaper hooks run before it, and whatever they spent is
// gone. The outer sweep walks every amount they can spend. Once they
// have eaten into the headroom themselves, the hook must spend
// nothing of what is left. A drain that starts on the full budget
// must still get all of ShutdownTimeout, so a smaller stopTimeout
// cannot silently shorten every drain.
//
// Shrinking either budget, or unbounding the drain or 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)
	require.Equal(
		t, server.ShutdownTimeout, server.DrainBudget(stopTimeout),
		"a drain that starts on the full stop budget is cut short",
	)

	const step = 10 * time.Millisecond

	for spent := time.Duration(0); spent <= stopTimeout; spent += step {
		remaining := stopTimeout - spent
		longest := max(server.DrainBudget(remaining), 0)

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

			require.GreaterOrEqual(
				t, remaining-hook, min(remaining, tailHeadroom),
				"a %s drain after %s of earlier hooks leaves "+
					"the tail hooks short", drain, spent,
			)
		}
	}
}