package proxy_test

import (
	"bufio"
	"errors"
	"io"
	"maps"
	"net/http"
	"net/netip"
	"slices"
	"sync"
	"testing"
	"time"

	"sneak.berlin/go/smallwebwaf/internal/bans"
	"sneak.berlin/go/smallwebwaf/internal/proxy"
	"sneak.berlin/go/smallwebwaf/internal/requestlog"
)

const (
	// otherClient is a client next to client.
	otherClient = "203.0.113.10"
	// userAgent is the user agent of every request a sender sends.
	userAgent = "ban-test/1.0"
	// permanent is the log line's ban_expires for a permanent ban.
	permanent = "permanent"
)

func TestBrokenLimitBansTheClient(t *testing.T) {
	t.Parallel()

	s, clk, _ := startWithClock(t, "", map[string]string{rateLimitPerMinute: "1"})
	expires := requestlog.FormatTime(clk.Now().Add(time.Hour))

	// The request over the limit of one a minute is refused, and bans the
	// client for an hour, the default.
	s.get(client, http.StatusOK, requestlog.ActionForward)

	line := s.get(client, http.StatusForbidden, requestlog.ActionRateLimited)
	if line.LimitHit != minute || line.Offence != requestlog.OffenceLimit ||
		line.BanExpires != expires {
		t.Errorf("log line has limit_hit %q, offence %q and ban_expires %q, "+
			"want minute, limit and %s", line.LimitHit, line.Offence, line.BanExpires,
			expires)
	}

	// Every request while the ban lasts is refused.
	clk.advance(time.Hour - time.Second)

	line = s.get(client, http.StatusForbidden, requestlog.ActionBanned)
	if line.BanExpires != expires || line.Offence != "" || line.LimitHit != "" {
		t.Errorf("log line has ban_expires %q, offence %q and limit_hit %q, "+
			"want %s and neither of the others", line.BanExpires, line.Offence,
			line.LimitHit, expires)
	}

	// Once it ends, the client is let through.
	clk.advance(time.Second)
	s.get(client, http.StatusOK, requestlog.ActionForward)
}

func TestBanLengthsFollowTheSettings(t *testing.T) {
	t.Parallel()

	s, clk, _ := startWithClock(t, "", map[string]string{
		rateLimitPerMinute:   "1",
		limitBanDuration:     "10m",
		limitBanRepeatWindow: "1h",
		maxBanDuration:       "1h",
	})

	// breakLimit has client go over the limit of one a minute, and
	// returns when the ban that makes ends.
	breakLimit := func() string {
		s.get(client, http.StatusOK, requestlog.ActionForward)

		return s.get(client, http.StatusForbidden, requestlog.ActionRateLimited).BanExpires
	}
	wantExpires := func(got string, length time.Duration) {
		t.Helper()

		want := requestlog.FormatTime(clk.Now().Add(length))
		if got != want {
			t.Errorf("ban ends at %s, want %s", got, want)
		}
	}

	// A first ban lasts SWWAF_LIMIT_BAN_DURATION; one within
	// SWWAF_LIMIT_BAN_REPEAT_WINDOW after it ended, three times as long.
	wantExpires(breakLimit(), 10*time.Minute)
	clk.advance(10*time.Minute + time.Hour)
	wantExpires(breakLimit(), 30*time.Minute)

	// Later than that, SWWAF_LIMIT_BAN_DURATION again.
	clk.advance(30*time.Minute + time.Hour + time.Second)
	wantExpires(breakLimit(), 10*time.Minute)
	clk.advance(10 * time.Minute)
	wantExpires(breakLimit(), 30*time.Minute)

	// 90 minutes would be longer than SWWAF_MAX_BAN_DURATION: the ban is
	// permanent.
	clk.advance(30 * time.Minute)

	got := breakLimit()
	if got != permanent {
		t.Errorf("ban ends at %s, want a permanent one", got)
	}

	clk.advance(365 * 24 * time.Hour)
	s.get(client, http.StatusForbidden, requestlog.ActionBanned)
}

func TestBanIsNotCountedAndResetsTheCounters(t *testing.T) {
	t.Parallel()

	s, clk, server := startWithClock(t, "", map[string]string{rateLimitPerDay: "2"})

	// The third request in a day is over the limit of two, and bans the
	// client for an hour.
	s.get(client, http.StatusOK, requestlog.ActionForward)
	s.get(client, http.StatusOK, requestlog.ActionForward)
	s.get(client, http.StatusForbidden, requestlog.ActionRateLimited)

	for range 3 {
		s.get(client, http.StatusForbidden, requestlog.ActionBanned)
	}

	// Later the same day the client has its whole allowance again: the
	// ban set its counters back to zero, and the requests it refused were
	// not counted for the rate limits, only in its notes.
	clk.advance(time.Hour)
	s.get(client, http.StatusOK, requestlog.ActionForward)
	s.get(client, http.StatusOK, requestlog.ActionForward)
	s.get(client, http.StatusForbidden, requestlog.ActionRateLimited)

	banned := server.Ledger.Bans(netip.MustParsePrefix(client + "/32"))
	if len(banned) != 2 || banned[0].Notes.Refused != 3 {
		t.Errorf("bans %+v, want two, the first with 3 requests refused", banned)
	}
}

func TestBanCoversTheClientsNetblock(t *testing.T) {
	t.Parallel()

	// In the IPv4 cases, client breaks the limit; these two are next to it.
	const (
		allowed = "203.0.113.60" // in SWWAF_ALLOW_NETS
		exempt  = "203.0.113.50" // in SWWAF_RATE_LIMIT_EXEMPT_NETS
	)

	for _, tc := range []struct {
		name    string
		env     map[string]string
		breaker string // the client that breaks the limit
		refused []string
		let     []string // let through
	}{
		{
			"an IPv4 address, by default", nil, client,
			nil, []string{otherClient, exempt},
		},
		{
			"the IPv4 netblock SWWAF_BAN_SCOPE_V4_PREFIX sets",
			map[string]string{banScopeV4Prefix: "24"}, client,
			[]string{otherClient, exempt}, []string{"203.0.112.9", allowed},
		},
		{
			"an IPv6 /64", nil, "2001:db8:5::1",
			[]string{"2001:db8:5::ffff:1"}, []string{"2001:db8:5:1::1"},
		},
	} {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			env := map[string]string{
				rateLimitPerMinute:  "1",
				allowNets:           allowed,
				rateLimitExemptNets: exempt,
			}
			maps.Copy(env, tc.env)
			s, _, _ := startWithClock(t, "", env)

			s.get(tc.breaker, http.StatusOK, requestlog.ActionForward)
			s.get(tc.breaker, http.StatusForbidden, requestlog.ActionRateLimited)

			for _, sent := range tc.refused {
				s.get(sent, http.StatusForbidden, requestlog.ActionBanned)
			}

			for _, sent := range tc.let {
				s.get(sent, http.StatusOK, requestlog.ActionForward)
			}
		})
	}
}

func TestBannedClientIsRefusedBeforeItsCountryIsLookedUp(t *testing.T) {
	t.Parallel()

	geojsURL, asked := startGeoJS(t)
	s, _, _ := startWithClock(t, geojsURL, map[string]string{
		rateLimitPerMinute: "1",
		banScopeV4Prefix:   "24",
		deniedCountries:    "kp",
	})

	// fromDE's ban covers otherClient, which is refused unasked about.
	s.get(fromDE, http.StatusOK, requestlog.ActionForward)
	s.get(fromDE, http.StatusForbidden, requestlog.ActionRateLimited)

	line := s.get(otherClient, http.StatusForbidden, requestlog.ActionBanned)
	if line.Country != "" {
		t.Errorf("log line has country %q, want none", line.Country)
	}

	if !slices.Equal(asked(), []string{fromDE}) {
		t.Errorf("GeoJS was asked about %v, want %s alone", asked(), fromDE)
	}
}

func TestBanResponseAnswersEveryRefusalButTheSizeLimits(t *testing.T) {
	t.Parallel()

	const denied = "192.0.2.50" // in SWWAF_DENY_NETS

	for _, tc := range []struct {
		setting string // "" leaves SWWAF_BAN_RESPONSE at its default
		status  int    // 0 is the connection closed without an answer
	}{
		{"", http.StatusForbidden},
		{"403", http.StatusForbidden},
		{"429", http.StatusTooManyRequests},
		{"close", 0},
	} {
		t.Run(banResponse+"="+tc.setting, func(t *testing.T) {
			t.Parallel()

			geojsURL, _ := startGeoJS(t)
			env := map[string]string{
				rateLimitPerMinute: "1",
				denyNets:           denied,
				deniedCountries:    "kp",
			}

			if tc.setting != "" {
				env[banResponse] = tc.setting
			}

			s, _, _ := startWithClock(t, geojsURL, env)

			s.get(denied, tc.status, requestlog.ActionDenied)
			s.get(fromKP, tc.status, requestlog.ActionCountryDenied)
			s.get(fromDE, http.StatusOK, requestlog.ActionForward)
			s.get(fromDE, tc.status, requestlog.ActionRateLimited)
			s.get(fromDE, tc.status, requestlog.ActionBanned)
		})
	}
}

func TestBanNotes(t *testing.T) {
	t.Parallel()

	geojsURL, _ := startGeoJS(t)
	s, clk, server := startWithClock(t, geojsURL, map[string]string{
		rateLimitPerMinute: "1",
		deniedCountries:    "kp",
	})
	start := clk.Now()

	s.get(fromDE, http.StatusOK, requestlog.ActionForward)
	s.request(fromDE, "/repo/commits?page=2",
		http.StatusForbidden, requestlog.ActionRateLimited)
	s.get(fromDE, http.StatusForbidden, requestlog.ActionBanned)
	s.get(fromDE, http.StatusForbidden, requestlog.ActionBanned)

	netblock := netip.MustParsePrefix(fromDE + "/32")
	want := bans.Ban{
		Netblock: netblock,
		Start:    start,
		Expires:  start.Add(time.Hour),
		Cause:    bans.CauseLimit,
		Notes: bans.Notes{
			Country: "DE",
			Limit:   1,
			Window:  minute,
			Count:   2,
			Request: bans.Request{
				Time:      start,
				Method:    http.MethodGet,
				Host:      appHost,
				Path:      "/repo/commits?page=2",
				Status:    http.StatusForbidden,
				UserAgent: userAgent,
			},
			// The one let through, the one that broke the limit and the two
			// refused under the ban.
			Requests:    4,
			Refused:     2,
			EarlierBans: bans.EarlierBans{},
		},
	}

	ledger := server.Ledger

	got := ledger.Bans(netblock)
	if len(got) != 1 || got[0] != want {
		t.Fatalf("bans\n%+v\nwant\n%+v", got, want)
	}

	// The next ban counts this one among the earlier.
	clk.advance(time.Hour)
	s.get(fromDE, http.StatusOK, requestlog.ActionForward)
	s.get(fromDE, http.StatusForbidden, requestlog.ActionRateLimited)

	got = ledger.Bans(netblock)
	if len(got) != 2 || got[1].Notes.EarlierBans != (bans.EarlierBans{Limit: 1}) {
		t.Errorf("bans %+v, want two, the second with one earlier ban for a limit", got)
	}
}

func TestMaxBansDropsTheBanOfTheNetblockSeenLongestAgo(t *testing.T) {
	t.Parallel()

	s, _, _ := startWithClock(t, "", map[string]string{
		rateLimitPerMinute: "1",
		maxBans:            "1",
	})

	// One ban is held, so otherClient's ban drops client's.
	s.get(client, http.StatusOK, requestlog.ActionForward)
	s.get(client, http.StatusForbidden, requestlog.ActionRateLimited)
	s.get(otherClient, http.StatusOK, requestlog.ActionForward)
	s.get(otherClient, http.StatusForbidden, requestlog.ActionRateLimited)

	s.get(client, http.StatusOK, requestlog.ActionForward)
	s.get(otherClient, http.StatusForbidden, requestlog.ActionBanned)
}

// clock is the time a test sets, by which smallwebwaf counts requests and
// makes bans.
type clock struct {
	mu  sync.Mutex
	now time.Time
}

// Now tells the time.
func (c *clock) Now() time.Time {
	c.mu.Lock()
	defer c.mu.Unlock()

	return c.now
}

// advance moves the clock on by d.
func (c *clock) advance(d time.Duration) {
	c.mu.Lock()
	defer c.mu.Unlock()

	c.now = c.now.Add(d)
}

// startWithClock starts smallwebwaf in front of an app that answers 200,
// with the settings in env on top of trusting localhost's
// X-Forwarded-For, clients' countries looked up at geojsURL, and a clock
// set to midnight, the start of a bucket in every window.
func startWithClock(
	t *testing.T, geojsURL string, env map[string]string,
) (*sender, *clock, *proxy.Server) {
	t.Helper()

	app := startApp(t, func(http.ResponseWriter, *http.Request) {})
	clk := &clock{now: time.Date(2026, 10, 6, 0, 0, 0, 0, time.UTC)}
	settings := map[string]string{trustedProxies: trustLocalhost}
	maps.Copy(settings, env)

	addr, out, server := startProxyWithClock(t, app.URL, geojsURL, clk.Now, settings)

	return &sender{t: t, addr: addr, out: out}, clk, server
}

// sender sends requests to smallwebwaf one after another, each on a
// connection of its own, and checks each one's answer and log line. They
// must be the only requests smallwebwaf is sent, since the log lines are
// matched to them in order.
type sender struct {
	t    *testing.T
	addr string
	out  *output
	sent int
}

// get sends a GET request for / from the client at from.
func (s *sender) get(from string, status int, action string) logLine {
	s.t.Helper()

	return s.request(from, "/", status, action)
}

// request sends a GET request for path from the client at from, as
// X-Forwarded-For names it, and checks that its answer and its log line
// have status, 0 for the connection closed without an answer, and that
// the line has action. It returns the log line.
func (s *sender) request(from, path string, status int, action string) logLine {
	s.t.Helper()

	line, _ := s.requestWithHeader(from, path, "", status, action)

	return line
}

// requestWithHeader is request with header, such as "Authorization:
// Bearer x", added to the request unless it is "". It returns the body of
// the answer too.
func (s *sender) requestWithHeader(
	from, path, header string, status int, action string,
) (logLine, string) {
	s.t.Helper()

	if header != "" {
		header += "\r\n"
	}

	conn := dial(s.t, s.addr)
	send(s.t, conn, "GET "+path+" HTTP/1.1\r\nHost: "+appHost+
		"\r\nUser-Agent: "+userAgent+"\r\n"+forwardedFor+": "+from+"\r\n"+
		header+"\r\n")

	err := conn.SetReadDeadline(time.Now().Add(waitLimit))
	if err != nil {
		s.t.Fatalf("set read deadline: %v", err)
	}

	var got answer

	res, err := http.ReadResponse(bufio.NewReader(conn), nil)

	switch {
	case err == nil:
		got = readAnswer(res)
	case !errors.Is(err, io.ErrUnexpectedEOF):
		s.t.Fatalf("read response: %v", err)
	}

	_ = conn.Close()

	if got.status != status {
		s.t.Errorf("request %d, from %s: status %d, want %d", s.sent+1, from,
			got.status, status)
	}

	line := s.out.requestLines(s.t, s.sent+1)[s.sent]
	s.sent++
	wantLine(s.t, line, status, action)

	return line, string(got.body)
}