package querylog

import (
	"fmt"
	"math/rand"
	"net"
	"sort"
	"testing"
	"time"

	"github.com/AdguardTeam/AdGuardHome/internal/aghtest"
	"github.com/AdguardTeam/AdGuardHome/internal/dnsfilter"
	"github.com/AdguardTeam/dnsproxy/proxyutil"
	"github.com/miekg/dns"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

func TestMain(m *testing.M) {
	aghtest.DiscardLogOutput(m)
}

// TestQueryLog tests adding and loading (with filtering) entries from disk and
// memory.
func TestQueryLog(t *testing.T) {
	l := newQueryLog(Config{
		Enabled:     true,
		FileEnabled: true,
		Interval:    1,
		MemSize:     100,
		BaseDir:     aghtest.PrepareTestDir(t),
	})

	// Add disk entries.
	addEntry(l, "example.org", net.IPv4(1, 1, 1, 1), net.IPv4(2, 2, 2, 1))
	// Write to disk (first file).
	require.Nil(t, l.flushLogBuffer(true))
	// Start writing to the second file.
	require.Nil(t, l.rotate())
	// Add disk entries.
	addEntry(l, "example.org", net.IPv4(1, 1, 1, 2), net.IPv4(2, 2, 2, 2))
	// Write to disk.
	require.Nil(t, l.flushLogBuffer(true))
	// Add memory entries.
	addEntry(l, "test.example.org", net.IPv4(1, 1, 1, 3), net.IPv4(2, 2, 2, 3))
	addEntry(l, "example.com", net.IPv4(1, 1, 1, 4), net.IPv4(2, 2, 2, 4))

	type tcAssertion struct {
		num            int
		host           string
		answer, client net.IP
	}

	testCases := []struct {
		name string
		sCr  []searchCriteria
		want []tcAssertion
	}{{
		name: "all",
		sCr:  []searchCriteria{},
		want: []tcAssertion{
			{num: 0, host: "example.com", answer: net.IPv4(1, 1, 1, 4), client: net.IPv4(2, 2, 2, 4)},
			{num: 1, host: "test.example.org", answer: net.IPv4(1, 1, 1, 3), client: net.IPv4(2, 2, 2, 3)},
			{num: 2, host: "example.org", answer: net.IPv4(1, 1, 1, 2), client: net.IPv4(2, 2, 2, 2)},
			{num: 3, host: "example.org", answer: net.IPv4(1, 1, 1, 1), client: net.IPv4(2, 2, 2, 1)},
		},
	}, {
		name: "by_domain_strict",
		sCr: []searchCriteria{{
			criteriaType: ctDomainOrClient,
			strict:       true,
			value:        "TEST.example.org",
		}},
		want: []tcAssertion{{
			num: 0, host: "test.example.org", answer: net.IPv4(1, 1, 1, 3), client: net.IPv4(2, 2, 2, 3),
		}},
	}, {
		name: "by_domain_non-strict",
		sCr: []searchCriteria{{
			criteriaType: ctDomainOrClient,
			strict:       false,
			value:        "example.ORG",
		}},
		want: []tcAssertion{
			{num: 0, host: "test.example.org", answer: net.IPv4(1, 1, 1, 3), client: net.IPv4(2, 2, 2, 3)},
			{num: 1, host: "example.org", answer: net.IPv4(1, 1, 1, 2), client: net.IPv4(2, 2, 2, 2)},
			{num: 2, host: "example.org", answer: net.IPv4(1, 1, 1, 1), client: net.IPv4(2, 2, 2, 1)},
		},
	}, {
		name: "by_client_ip_strict",
		sCr: []searchCriteria{{
			criteriaType: ctDomainOrClient,
			strict:       true,
			value:        "2.2.2.2",
		}},
		want: []tcAssertion{{
			num: 0, host: "example.org", answer: net.IPv4(1, 1, 1, 2), client: net.IPv4(2, 2, 2, 2),
		}},
	}, {
		name: "by_client_ip_non-strict",
		sCr: []searchCriteria{{
			criteriaType: ctDomainOrClient,
			strict:       false,
			value:        "2.2.2",
		}},
		want: []tcAssertion{
			{num: 0, host: "example.com", answer: net.IPv4(1, 1, 1, 4), client: net.IPv4(2, 2, 2, 4)},
			{num: 1, host: "test.example.org", answer: net.IPv4(1, 1, 1, 3), client: net.IPv4(2, 2, 2, 3)},
			{num: 2, host: "example.org", answer: net.IPv4(1, 1, 1, 2), client: net.IPv4(2, 2, 2, 2)},
			{num: 3, host: "example.org", answer: net.IPv4(1, 1, 1, 1), client: net.IPv4(2, 2, 2, 1)},
		},
	}}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			params := newSearchParams()
			params.searchCriteria = tc.sCr

			entries, _ := l.search(params)
			require.Len(t, entries, len(tc.want))
			for _, want := range tc.want {
				assertLogEntry(t, entries[want.num], want.host, want.answer, want.client)
			}
		})
	}
}

func TestQueryLogOffsetLimit(t *testing.T) {
	l := newQueryLog(Config{
		Enabled:  true,
		Interval: 1,
		MemSize:  100,
		BaseDir:  aghtest.PrepareTestDir(t),
	})

	const (
		entNum           = 10
		firstPageDomain  = "first.example.org"
		secondPageDomain = "second.example.org"
	)
	// Add entries to the log.
	for i := 0; i < entNum; i++ {
		addEntry(l, secondPageDomain, net.IPv4(1, 1, 1, 1), net.IPv4(2, 2, 2, 1))
	}
	// Write them to the first file.
	require.Nil(t, l.flushLogBuffer(true))
	// Add more to the in-memory part of log.
	for i := 0; i < entNum; i++ {
		addEntry(l, firstPageDomain, net.IPv4(1, 1, 1, 1), net.IPv4(2, 2, 2, 1))
	}

	params := newSearchParams()

	testCases := []struct {
		name    string
		offset  int
		limit   int
		wantLen int
		want    string
	}{{
		name:    "page_1",
		offset:  0,
		limit:   10,
		wantLen: 10,
		want:    firstPageDomain,
	}, {
		name:    "page_2",
		offset:  10,
		limit:   10,
		wantLen: 10,
		want:    secondPageDomain,
	}, {
		name:    "page_2.5",
		offset:  15,
		limit:   10,
		wantLen: 5,
		want:    secondPageDomain,
	}, {
		name:    "page_3",
		offset:  20,
		limit:   10,
		wantLen: 0,
	}}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			params.offset = tc.offset
			params.limit = tc.limit
			entries, _ := l.search(params)

			require.Len(t, entries, tc.wantLen)

			if tc.wantLen > 0 {
				assert.Equal(t, entries[0].QHost, tc.want)
				assert.Equal(t, entries[tc.wantLen-1].QHost, tc.want)
			}
		})
	}
}

func TestQueryLogMaxFileScanEntries(t *testing.T) {
	l := newQueryLog(Config{
		Enabled:     true,
		FileEnabled: true,
		Interval:    1,
		MemSize:     100,
		BaseDir:     aghtest.PrepareTestDir(t),
	})

	const entNum = 10
	// Add entries to the log.
	for i := 0; i < entNum; i++ {
		addEntry(l, "example.org", net.IPv4(1, 1, 1, 1), net.IPv4(2, 2, 2, 1))
	}
	// Write them to disk.
	require.Nil(t, l.flushLogBuffer(true))

	params := newSearchParams()

	for _, maxFileScanEntries := range []int{5, 0} {
		t.Run(fmt.Sprintf("limit_%d", maxFileScanEntries), func(t *testing.T) {
			params.maxFileScanEntries = maxFileScanEntries
			entries, _ := l.search(params)
			assert.Len(t, entries, entNum-maxFileScanEntries)
		})
	}
}

func TestQueryLogFileDisabled(t *testing.T) {
	l := newQueryLog(Config{
		Enabled:     true,
		FileEnabled: false,
		Interval:    1,
		MemSize:     2,
		BaseDir:     aghtest.PrepareTestDir(t),
	})

	addEntry(l, "example1.org", net.IPv4(1, 1, 1, 1), net.IPv4(2, 2, 2, 1))
	addEntry(l, "example2.org", net.IPv4(1, 1, 1, 1), net.IPv4(2, 2, 2, 1))
	// The oldest entry is going to be removed from memory buffer.
	addEntry(l, "example3.org", net.IPv4(1, 1, 1, 1), net.IPv4(2, 2, 2, 1))

	params := newSearchParams()
	ll, _ := l.search(params)
	require.Len(t, ll, 2)
	assert.Equal(t, "example3.org", ll[0].QHost)
	assert.Equal(t, "example2.org", ll[1].QHost)
}

func addEntry(l *queryLog, host string, answerStr, client net.IP) {
	q := dns.Msg{
		Question: []dns.Question{{
			Name:   host + ".",
			Qtype:  dns.TypeA,
			Qclass: dns.ClassINET,
		}},
	}

	a := dns.Msg{
		Question: q.Question,
		Answer: []dns.RR{&dns.A{
			Hdr: dns.RR_Header{
				Name:   q.Question[0].Name,
				Rrtype: dns.TypeA,
				Class:  dns.ClassINET,
			},
			A: answerStr,
		}},
	}
	res := dnsfilter.Result{
		IsFiltered:  true,
		Reason:      dnsfilter.Rewritten,
		ServiceName: "SomeService",
		Rules: []*dnsfilter.ResultRule{{
			FilterListID: 1,
			Text:         "SomeRule",
		}},
	}
	params := AddParams{
		Question:   &q,
		Answer:     &a,
		OrigAnswer: &a,
		Result:     &res,
		ClientIP:   client,
		Upstream:   "upstream",
	}
	l.Add(params)
}

func assertLogEntry(t *testing.T, entry *logEntry, host string, answer, client net.IP) {
	t.Helper()

	require.NotNil(t, entry)

	assert.Equal(t, host, entry.QHost)
	assert.Equal(t, client, entry.IP)
	assert.Equal(t, "A", entry.QType)
	assert.Equal(t, "IN", entry.QClass)

	msg := &dns.Msg{}
	require.Nil(t, msg.Unpack(entry.Answer))
	require.Len(t, msg.Answer, 1)

	ip := proxyutil.GetIPFromDNSRecord(msg.Answer[0]).To16()
	assert.Equal(t, answer, ip)
}

func testEntries() (entries []*logEntry) {
	rsrc := rand.NewSource(time.Now().UnixNano())
	rgen := rand.New(rsrc)

	entries = make([]*logEntry, 1000)
	for i := range entries {
		min := rgen.Intn(60)
		sec := rgen.Intn(60)
		entries[i] = &logEntry{
			Time: time.Date(2020, 1, 1, 0, min, sec, 0, time.UTC),
		}
	}

	return entries
}

// logEntriesByTimeDesc is a wrapper over []*logEntry for sorting.
//
// NOTE(a.garipov): Weirdly enough, on my machine this gets consistently
// outperformed by sort.Slice, see the benchmark below.  I'm leaving this
// implementation here, in tests, in case we want to make sure it outperforms on
// most machines, but for now this is unused in the actual code.
type logEntriesByTimeDesc []*logEntry

// Len implements the sort.Interface interface for logEntriesByTimeDesc.
func (les logEntriesByTimeDesc) Len() (n int) { return len(les) }

// Less implements the sort.Interface interface for logEntriesByTimeDesc.
func (les logEntriesByTimeDesc) Less(i, j int) (less bool) {
	return les[i].Time.After(les[j].Time)
}

// Swap implements the sort.Interface interface for logEntriesByTimeDesc.
func (les logEntriesByTimeDesc) Swap(i, j int) { les[i], les[j] = les[j], les[i] }

func BenchmarkLogEntry_sort(b *testing.B) {
	b.Run("methods", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			b.StopTimer()
			entries := testEntries()
			b.StartTimer()

			sort.Stable(logEntriesByTimeDesc(entries))
		}
	})

	b.Run("reflect", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			b.StopTimer()
			entries := testEntries()
			b.StartTimer()

			sort.SliceStable(entries, func(i, j int) (less bool) {
				return entries[i].Time.After(entries[j].Time)
			})
		}
	})
}

func TestLogEntriesByTime_sort(t *testing.T) {
	entries := testEntries()
	sort.Sort(logEntriesByTimeDesc(entries))

	for i := range entries[1:] {
		assert.False(t, entries[i+1].Time.After(entries[i].Time),
			"%s %s", entries[i+1].Time, entries[i].Time)
	}
}