package bans_test

import (
	"net/netip"
	"strings"
	"testing"
	"time"

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

const day = 24 * time.Hour

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	now := midnight()

	// Each ban is followed by another as soon as it ends: 1, 3, 9, 27 and
	// 81 hours.
	for i, hours := range []int{1, 3, 9, 27, 81} {
		ban := ledger.BanForLimit(netblock, now, bans.Notes{})

		length := time.Duration(hours) * time.Hour
		if !ban.Expires.Equal(now.Add(length)) || ban.Notes.EarlierBans != i {
			t.Fatalf("ban %d lasts %s with %d earlier bans, want %d hours and %d",
				i+1, ban.Expires.Sub(now), ban.Notes.EarlierBans, hours, i)
		}

		now = ban.Expires
	}

	// The sixth would last 243 hours, more than seven days: it is
	// permanent, and never ends.
	ban := ledger.BanForLimit(netblock, now, bans.Notes{})
	if !ban.Permanent() {
		t.Fatalf("sixth ban ends at %s, want a permanent one", ban.Expires)
	}

	_, banned := ledger.Check(netblock.Addr(), now.Add(100*365*day))
	if !banned {
		t.Error("a permanent ban ended")
	}
}

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

	for _, tc := range []struct {
		name string
		// gap is the time between the end of the first ban and the second.
		gap  time.Duration
		want time.Duration
	}{
		{"broken again as the window ends", day, 3 * time.Hour},
		{"broken again after the window", day + time.Nanosecond, time.Hour},
	} {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			ledger := bans.New(defaultRules())
			netblock := netip.MustParsePrefix("203.0.113.9/32")

			first := ledger.BanForLimit(netblock, midnight(), bans.Notes{})
			second := ledger.BanForLimit(netblock, first.Expires.Add(tc.gap), bans.Notes{})

			if second.Expires.Sub(second.Start) != tc.want || second.Notes.EarlierBans != 1 {
				t.Errorf("second ban lasts %s with %d earlier bans, want %s and 1",
					second.Expires.Sub(second.Start), second.Notes.EarlierBans, tc.want)
			}
		})
	}
}

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

	rules := defaultRules()
	rules.LimitBanDuration = rules.MaxBanDuration + time.Hour
	ledger := bans.New(rules)

	ban := ledger.BanForLimit(netip.MustParsePrefix("203.0.113.9/32"), midnight(),
		bans.Notes{})
	if !ban.Permanent() {
		t.Errorf("first ban ends at %s, want a permanent one", ban.Expires)
	}
}

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

	// With bans of up to 100,000 days, the 14th ban in a row, of 3^13
	// hours, is within the maximum, and three times as long would not fit
	// in a time.Duration. The 15th is permanent.
	rules := defaultRules()
	rules.MaxBanDuration = 100000 * day
	ledger := bans.New(rules)
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	now := midnight()

	for i := range 14 {
		ban := ledger.BanForLimit(netblock, now, bans.Notes{})
		if !ban.Expires.After(ban.Start) {
			t.Fatalf("ban %d starts at %s and ends at %s", i+1, ban.Start, ban.Expires)
		}

		now = ban.Expires
	}

	ban := ledger.BanForLimit(netblock, now, bans.Notes{})
	if !ban.Permanent() {
		t.Errorf("15th ban ends at %s, want a permanent one", ban.Expires)
	}
}

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")

	first := ledger.BanForLimit(netblock, midnight(), bans.Notes{})
	again := ledger.BanForLimit(netblock, midnight().Add(time.Minute), bans.Notes{})

	if again != first || len(ledger.Bans(netblock)) != 1 {
		t.Errorf("a limit broken during a ban gave %+v and %d bans, want %+v and 1",
			again, len(ledger.Bans(netblock)), first)
	}
}

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	ban := ledger.BanForLimit(netblock, midnight(), bans.Notes{Requests: 5})

	for range 3 {
		got, banned := ledger.Check(netblock.Addr(), ban.Expires.Add(-time.Nanosecond))
		if !banned || got.Start != ban.Start {
			t.Fatalf("check during the ban gives %+v and %t", got, banned)
		}
	}

	_, banned := ledger.Check(netip.MustParseAddr("203.0.113.10"), midnight())
	if banned {
		t.Error("another netblock is banned")
	}

	_, banned = ledger.Check(netblock.Addr(), ban.Expires)
	if banned {
		t.Error("the ban did not end")
	}

	// The netblock's requests went from 5 to 8 with the three refused.
	notes := ledger.Bans(netblock)[0].Notes
	if notes.Refused != 3 || notes.Requests != 8 {
		t.Errorf("the notes count %d refused requests of %d, want 3 of 8",
			notes.Refused, notes.Requests)
	}
}

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

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	ban := ledger.BanForLimit(netblock, midnight(), bans.Notes{Requests: 5})

	got, banned := ledger.Find(netblock.Addr(), ban.Expires.Add(-time.Nanosecond))
	if !banned || got != ban {
		t.Errorf("find during the ban gives %+v and %t, want %+v", got, banned, ban)
	}

	_, banned = ledger.Find(netblock.Addr(), ban.Expires)
	if banned {
		t.Error("the ban did not end")
	}

	if notes := ledger.Bans(netblock)[0].Notes; notes != ban.Notes {
		t.Errorf("the notes are %+v, want them unchanged, %+v", notes, ban.Notes)
	}
}

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

	rules := defaultRules()
	rules.MaxBans = 3
	ledger := bans.New(rules)
	a := netip.MustParsePrefix("203.0.113.1/32")
	b := netip.MustParsePrefix("203.0.113.2/32")
	c := netip.MustParsePrefix("203.0.113.3/32")
	d := netip.MustParsePrefix("2001:db8::/64")
	now := midnight()

	first := ledger.BanForLimit(a, now, bans.Notes{})
	ledger.BanForLimit(b, now, bans.Notes{})
	ledger.BanForLimit(c, now, bans.Notes{})

	// A request from a makes b the netblock seen longest ago, and its ban
	// goes to make room for d's.
	ledger.Check(a.Addr(), now)
	ledger.BanForLimit(d, now, bans.Notes{})
	wantBans(t, ledger, map[netip.Prefix]int{a: 1, b: 0, c: 1, d: 1})

	// a is banned again once its ban has ended; c, seen longest ago, goes.
	ledger.BanForLimit(a, first.Expires, bans.Notes{})
	wantBans(t, ledger, map[netip.Prefix]int{a: 2, c: 0, d: 1})

	// With d seen since, a is seen longest ago, and its earlier ban goes
	// first.
	ledger.Check(d.Addr(), first.Expires)
	ledger.BanForLimit(b, first.Expires, bans.Notes{})
	wantBans(t, ledger, map[netip.Prefix]int{a: 1, b: 1, d: 1})

	if !ledger.Bans(a)[0].Start.Equal(first.Expires) {
		t.Errorf("a kept its ban of %s, want the later one", ledger.Bans(a)[0].Start)
	}
}

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

	// With room for one ban, the netblock's ended ban goes to make room for
	// its new one, whose notes still count it.
	rules := defaultRules()
	rules.MaxBans = 1
	ledger := bans.New(rules)
	netblock := netip.MustParsePrefix("203.0.113.9/32")

	first := ledger.BanForLimit(netblock, midnight(), bans.Notes{})
	second := ledger.BanForLimit(netblock, first.Expires, bans.Notes{})

	held := ledger.Bans(netblock)
	if len(held) != 1 || held[0] != second || held[0].Notes.EarlierBans != 1 {
		t.Errorf("the ledger holds %+v, want only the second ban, with 1 earlier ban",
			held)
	}
}

func TestRequestTextsAreCutTo256Bytes(t *testing.T) {
	t.Parallel()

	ledger := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	long := strings.Repeat("a", 300)
	request := bans.Request{
		Time: midnight(), Method: long, Host: long, Path: long, Status: 403, UserAgent: long,
	}

	ban := ledger.BanForLimit(netblock, midnight(), bans.Notes{Request: request})

	cut := long[:256]
	want := bans.Request{
		Time: midnight(), Method: cut, Host: cut, Path: cut, Status: 403, UserAgent: cut,
	}

	if ban.Notes.Request != want || ledger.Bans(netblock)[0].Notes.Request != want {
		t.Errorf("the notes keep %+v, want each text cut to 256 bytes", ban.Notes.Request)
	}
}

// defaultRules are the rules at the settings' defaults.
func defaultRules() bans.Rules {
	return bans.Rules{
		LimitBanDuration:     time.Hour,
		LimitBanRepeatWindow: day,
		MaxBanDuration:       7 * day,
		MaxBans:              5000,
	}
}

// midnight is when the tests' first bans are made.
func midnight() time.Time {
	return time.Date(2026, 10, 6, 0, 0, 0, 0, time.UTC)
}

// wantBans checks how many bans the ledger holds on each netblock.
func wantBans(t *testing.T, ledger *bans.Ledger, want map[netip.Prefix]int) {
	t.Helper()

	for netblock, count := range want {
		got := len(ledger.Bans(netblock))
		if got != count {
			t.Errorf("%s has %d bans, want %d", netblock, got, count)
		}
	}
}