package bans_test

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

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

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

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

	wantChanged(t, ledger, false)

	ledger.BanForLimit(netblock, midnight(), bans.Notes{})
	wantChanged(t, ledger, true)

	// A limit broken during the ban makes no other, and a refusal changes
	// only the counts in the notes, which wait for the interval's write.
	ledger.BanForLimit(netblock, midnight().Add(time.Minute), bans.Notes{})
	ledger.Check(netblock.Addr(), midnight().Add(time.Minute))
	wantChanged(t, ledger, false)

	// Two bans before the value is read leave one.
	ledger.BanForLimit(netip.MustParsePrefix("203.0.113.10/32"), midnight(), bans.Notes{})
	ledger.BanForLimit(netip.MustParsePrefix("203.0.113.11/32"), midnight(), bans.Notes{})
	wantChanged(t, ledger, true)
	wantChanged(t, ledger, false)
}

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

	ledger := bans.New(defaultRules())
	v6 := netip.MustParsePrefix("2001:db8::/64")
	high := netip.MustParsePrefix("203.0.113.10/32")
	low := netip.MustParsePrefix("203.0.113.9/32")

	first := ledger.BanForLimit(v6, midnight(), bans.Notes{})
	ledger.BanForLimit(high, midnight(), bans.Notes{})
	ledger.BanForLimit(low, midnight(), bans.Notes{})
	ledger.BanForLimit(v6, first.Expires, bans.Notes{})

	snapshot := ledger.Snapshot()

	got := make([]string, 0, len(snapshot))
	for _, ban := range snapshot {
		got = append(got, ban.Netblock.String()+" "+ban.Start.Format(time.Kitchen))
	}

	want := []string{
		"203.0.113.9/32 12:00AM", "203.0.113.10/32 12:00AM",
		"2001:db8::/64 12:00AM", "2001:db8::/64 1:00AM",
	}
	if !slices.Equal(got, want) {
		t.Errorf("snapshot %v, want %v", got, want)
	}
}

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

	before := bans.New(defaultRules())
	netblock := netip.MustParsePrefix("203.0.113.9/32")
	ban := before.BanForLimit(netblock, midnight(), bans.Notes{Limit: 1})

	// Loaded into a new ledger, as across a restart, the ban still refuses
	// while it lasts, and once it has ended a broken limit bans for three
	// times as long, with the loaded ban counted among the earlier ones.
	after := bans.New(defaultRules())
	after.Load(before.Snapshot())

	_, banned := after.Check(netblock.Addr(), ban.Expires.Add(-time.Second))
	if !banned {
		t.Error("the loaded ban does not refuse")
	}

	again := after.BanForLimit(netblock, ban.Expires, bans.Notes{})
	if again.Expires.Sub(again.Start) != 3*time.Hour || again.Notes.EarlierBans != 1 {
		t.Errorf("the next ban lasts %s with %d earlier bans, want 3h and 1",
			again.Expires.Sub(again.Start), again.Notes.EarlierBans)
	}
}

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

	// Two entries as an admin might write them, with addresses not masked
	// to their lengths, the IPv6 one shorter than the /64 an IPv6 client's
	// ban covers, beside a ban the ledger makes on one IPv4 address.
	ledger := bans.New(defaultRules())
	ledger.Load([]bans.Ban{
		{Netblock: netip.MustParsePrefix("203.0.113.9/24"), Start: midnight()},
		{Netblock: netip.MustParsePrefix("2001:db8::1/48"), Start: midnight()},
	})
	ledger.BanForLimit(netip.MustParsePrefix("198.51.100.7/32"), midnight(), bans.Notes{})

	for client, want := range map[string]bool{
		"203.0.113.0":     true,
		"203.0.113.200":   true,
		"203.0.114.1":     false,
		"2001:db8:0:5::1": true,
		"2001:db8:1::1":   false,
		"198.51.100.7":    true,
		"198.51.100.8":    false,
	} {
		_, banned := ledger.Check(netip.MustParseAddr(client), midnight())
		if banned != want {
			t.Errorf("%s is refused: %t, want %t", client, banned, want)
		}
	}

	// The loaded netblocks are written back masked.
	snapshot := ledger.Snapshot()

	got := make([]string, 0, len(snapshot))
	for _, ban := range snapshot {
		got = append(got, ban.Netblock.String())
	}

	want := []string{"198.51.100.7/32", "203.0.113.0/24", "2001:db8::/48"}
	if !slices.Equal(got, want) {
		t.Errorf("the ledger holds bans on %v, want %v", got, want)
	}
}

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

	// bans.json lists the bans by netblock, not in the order they began.
	later := bans.Ban{Netblock: netip.MustParsePrefix("203.0.113.1/32"), Start: midnight()}
	earlier := bans.Ban{
		Netblock: netip.MustParsePrefix("203.0.113.2/32"),
		Start:    midnight().Add(-time.Hour),
	}

	rules := defaultRules()
	rules.MaxBans = 1
	ledger := bans.New(rules)
	ledger.Load([]bans.Ban{later, earlier})

	held := ledger.Snapshot()
	if len(held) != 1 || held[0] != later {
		t.Errorf("the ledger holds %+v, want only the ban that began later", held)
	}
}

func TestLoadCutsTheTextsTo256Bytes(t *testing.T) {
	t.Parallel()

	long := strings.Repeat("a", 300)
	ban := bans.Ban{
		Netblock: netip.MustParsePrefix("203.0.113.9/32"),
		Start:    midnight(),
		Notes: bans.Notes{Request: bans.Request{
			Method: long, Host: long, Path: long, UserAgent: long,
		}},
	}

	ledger := bans.New(defaultRules())
	ledger.Load([]bans.Ban{ban})

	cut := long[:256]
	want := bans.Request{Method: cut, Host: cut, Path: cut, UserAgent: cut}

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

// wantChanged checks whether the ledger's Changed has a value to read.
func wantChanged(t *testing.T, ledger *bans.Ledger, want bool) {
	t.Helper()

	got := false

	select {
	case <-ledger.Changed():
		got = true
	default:
	}

	if got != want {
		t.Errorf("Changed has a value: %t, want %t", got, want)
	}
}