package database

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

	"git.eeqj.de/sneak/routewatch/internal/routetable"
)

// TestOriginChangesWriteThenRead writes three origin changes and reads them
// back newest first, honouring the limit.
func TestOriginChangesWriteThenRead(t *testing.T) {
	t.Parallel()

	db := newRoutesTestDatabase(t)
	prefix := netip.MustParsePrefix(tablePrefixV4)

	changes := []routetable.OriginChange{
		{Prefix: prefix, OriginASN: asA, Announced: true, PeerCount: 1,
			Time: tableTime(10)},
		{Prefix: prefix, OriginASN: asA, Announced: false, PeerCount: 0,
			Time: tableTime(20)},
		{Prefix: prefix, OriginASN: asB, Announced: true, PeerCount: 1,
			Time: tableTime(30)},
	}

	err := db.WriteOriginChanges(changes)
	if err != nil {
		t.Fatalf("WriteOriginChanges: %v", err)
	}

	got, err := db.GetOriginChanges(t.Context(), prefix, 2)
	if err != nil {
		t.Fatalf("GetOriginChanges: %v", err)
	}

	want := []routetable.OriginChange{
		{Prefix: prefix, OriginASN: asB, Announced: true, PeerCount: 1,
			Time: tableTime(30)},
		{Prefix: prefix, OriginASN: asA, Announced: false, PeerCount: 0,
			Time: tableTime(20)},
	}

	if !reflect.DeepEqual(got, want) {
		t.Errorf("GetOriginChanges = %+v, want %+v", got, want)
	}
}

// TestOriginChangesPrune checks that the prune keeps, for a prefix with more
// than 500 rows, its newest 500 rows and every row newer than 72 hours, and
// deletes the rest. It checks which rows survive by their times, not only how
// many.
func TestOriginChangesPrune(t *testing.T) {
	t.Parallel()

	db := newRoutesTestDatabase(t)
	oldPrefix := netip.MustParsePrefix(tablePrefixV4)
	straddling := netip.MustParsePrefix(tablePrefixShortV4)
	busy := netip.MustParsePrefix(tablePrefixBusyV4)
	other := netip.MustParsePrefix("10.20.0.0/16")

	// Whole seconds, so the stored times round-trip exactly.
	now := time.Now().Truncate(time.Second)

	// 600 rows for oldPrefix, all older than 72 hours, oldest first. The
	// prune keeps the newest 500 and deletes the oldest 100.
	changes := rows(oldPrefix, now.Add(-100*time.Hour), 600)
	// 600 rows for straddling: 400 older than 72 hours, then 200 newer. The
	// prune keeps all 200 newer and the newest 300 of the 400 older.
	changes = append(changes, rows(straddling, now.Add(-100*time.Hour), 400)...)
	changes = append(changes, rows(straddling, now.Add(-71*time.Hour), 200)...)
	// 100 rows older than 72 hours and minOriginChangesPerPrefix+100 newer
	// rows for busy. The prune keeps all the newer rows and none of the older,
	// because the newer rows alone are more than minOriginChangesPerPrefix.
	changes = append(changes, rows(busy, now.Add(-100*time.Hour), 100)...)
	changes = append(changes, rows(busy, now.Add(-71*time.Hour),
		minOriginChangesPerPrefix+100)...)
	// One row for other, which the prune leaves alone.
	changes = append(changes, rows(other, now.Add(-100*time.Hour), 1)...)

	err := db.WriteOriginChanges(changes)
	if err != nil {
		t.Fatalf("WriteOriginChanges: %v", err)
	}

	err = db.PruneOriginChanges(t.Context())
	if err != nil {
		t.Fatalf("PruneOriginChanges: %v", err)
	}

	// The newest row survives, and the oldest survivor is the 100th oldest,
	// so a prune that kept the oldest 500 instead would fail.
	checkSurvivors(t, db, oldPrefix, 500,
		now.Add(-100*time.Hour).Add(599*time.Minute),
		now.Add(-100*time.Hour).Add(100*time.Minute))

	// The newest of the newer-than-72-hours rows survives, and the oldest
	// survivor is the 100th oldest of the older-than-72-hours rows.
	checkSurvivors(t, db, straddling, 500,
		now.Add(-71*time.Hour).Add(199*time.Minute),
		now.Add(-100*time.Hour).Add(100*time.Minute))

	// Every newer-than-72-hours row survives, so the oldest survivor is the
	// first of them and the newest is minOriginChangesPerPrefix+99 minutes
	// after it.
	checkSurvivors(t, db, busy, minOriginChangesPerPrefix+100,
		now.Add(-71*time.Hour).
			Add(time.Duration(minOriginChangesPerPrefix+99)*time.Minute),
		now.Add(-71*time.Hour))

	gotOther, err := db.GetOriginChanges(t.Context(), other, 10)
	if err != nil {
		t.Fatalf("GetOriginChanges: %v", err)
	}

	if len(gotOther) != 1 {
		t.Errorf("GetOriginChanges(other) = %d rows, want 1", len(gotOther))
	}
}

// rows returns n origin changes for prefix, at times from plus one minute per
// step, oldest first.
func rows(prefix netip.Prefix, from time.Time, n int) []routetable.OriginChange {
	changes := make([]routetable.OriginChange, 0, n)

	for i := range n {
		changes = append(changes, routetable.OriginChange{
			Prefix: prefix, OriginASN: asA, Announced: true, PeerCount: 1,
			Time: from.Add(time.Duration(i) * time.Minute),
		})
	}

	return changes
}

// survivorTimes returns the times of prefix's rows after the prune, newest
// first.
func survivorTimes(
	t *testing.T, db *Database, prefix netip.Prefix, limit int,
) []time.Time {
	t.Helper()

	rows, err := db.GetOriginChanges(t.Context(), prefix, limit)
	if err != nil {
		t.Fatalf("GetOriginChanges: %v", err)
	}

	times := make([]time.Time, len(rows))
	for i, row := range rows {
		times[i] = row.Time
	}

	return times
}

// checkSurvivors checks that prefix kept exactly wantCount rows, with the
// newest survivor at wantNewest and the oldest at wantOldest.
func checkSurvivors(
	t *testing.T, db *Database, prefix netip.Prefix,
	wantCount int, wantNewest, wantOldest time.Time,
) {
	t.Helper()

	times := survivorTimes(t, db, prefix, wantCount+1)
	if len(times) != wantCount {
		t.Errorf("GetOriginChanges(%s) = %d rows, want %d",
			prefix, len(times), wantCount)

		return
	}

	if !times[0].Equal(wantNewest) {
		t.Errorf("the newest surviving row's time = %v, want %v",
			times[0], wantNewest)
	}

	if !times[wantCount-1].Equal(wantOldest) {
		t.Errorf("the oldest surviving row's time = %v, want %v",
			times[wantCount-1], wantOldest)
	}
}

// TestOriginChangesSurviveRouteDeletion checks that deleting a routes row
// leaves the prefix's origin_changes rows.
func TestOriginChangesSurviveRouteDeletion(t *testing.T) {
	t.Parallel()

	db := newRoutesTestDatabase(t)
	prefix := netip.MustParsePrefix(tablePrefixV4)

	err := db.WriteOriginChanges([]routetable.OriginChange{{
		Prefix: prefix, OriginASN: asA, Announced: true, PeerCount: 1,
		Time: tableTime(10),
	}})
	if err != nil {
		t.Fatalf("WriteOriginChanges: %v", err)
	}

	// Write a route, then delete it.
	table := routetable.New(routetable.Params{})
	announceTo(table, tablePrefixV4, asA, peerA, 10)
	writeTableChanges(t, db, table)

	table.Withdraw(prefix, peerA)
	writeTableChanges(t, db, table)

	got, err := db.GetOriginChanges(t.Context(), prefix, 10)
	if err != nil {
		t.Fatalf("GetOriginChanges: %v", err)
	}

	if len(got) != 1 {
		t.Errorf("GetOriginChanges = %d rows, want 1", len(got))
	}
}