// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package discv5

import (
	"crypto/ecdsa"
	"fmt"
	"math/rand"

	"net"
	"reflect"
	"testing"
	"testing/quick"
	"time"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/crypto"
)

func TestBucket_bumpNoDuplicates(t *testing.T) {
	t.Parallel()
	cfg := &quick.Config{
		MaxCount: 1000,
		Rand:     rand.New(rand.NewSource(time.Now().Unix())),
		Values: func(args []reflect.Value, rand *rand.Rand) {
			// generate a random list of nodes. this will be the content of the bucket.
			n := rand.Intn(bucketSize-1) + 1
			nodes := make([]*Node, n)
			for i := range nodes {
				nodes[i] = nodeAtDistance(common.Hash{}, 200)
			}
			args[0] = reflect.ValueOf(nodes)
			// generate random bump positions.
			bumps := make([]int, rand.Intn(100))
			for i := range bumps {
				bumps[i] = rand.Intn(len(nodes))
			}
			args[1] = reflect.ValueOf(bumps)
		},
	}

	prop := func(nodes []*Node, bumps []int) (ok bool) {
		b := &bucket{entries: make([]*Node, len(nodes))}
		copy(b.entries, nodes)
		for i, pos := range bumps {
			b.bump(b.entries[pos])
			if hasDuplicates(b.entries) {
				t.Logf("bucket has duplicates after %d/%d bumps:", i+1, len(bumps))
				for _, n := range b.entries {
					t.Logf("  %p", n)
				}
				return false
			}
		}
		return true
	}
	if err := quick.Check(prop, cfg); err != nil {
		t.Error(err)
	}
}

// nodeAtDistance creates a node for which logdist(base, n.sha) == ld.
// The node's ID does not correspond to n.sha.
func nodeAtDistance(base common.Hash, ld int) (n *Node) {
	n = new(Node)
	n.sha = hashAtDistance(base, ld)
	copy(n.ID[:], n.sha[:]) // ensure the node still has a unique ID
	return n
}

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

	test := func(test *closeTest) bool {
		// for any node table, Target and N
		tab := newTable(test.Self, &net.UDPAddr{})
		tab.stuff(test.All)

		// check that doClosest(Target, N) returns nodes
		result := tab.closest(test.Target, test.N).entries
		if hasDuplicates(result) {
			t.Errorf("result contains duplicates")
			return false
		}
		if !sortedByDistanceTo(test.Target, result) {
			t.Errorf("result is not sorted by distance to target")
			return false
		}

		// check that the number of results is min(N, tablen)
		wantN := test.N
		if tab.count < test.N {
			wantN = tab.count
		}
		if len(result) != wantN {
			t.Errorf("wrong number of nodes: got %d, want %d", len(result), wantN)
			return false
		} else if len(result) == 0 {
			return true // no need to check distance
		}

		// check that the result nodes have minimum distance to target.
		for _, b := range tab.buckets {
			for _, n := range b.entries {
				if contains(result, n.ID) {
					continue // don't run the check below for nodes in result
				}
				farthestResult := result[len(result)-1].sha
				if distcmp(test.Target, n.sha, farthestResult) < 0 {
					t.Errorf("table contains node that is closer to target but it's not in result")
					t.Logf("  Target:          %v", test.Target)
					t.Logf("  Farthest Result: %v", farthestResult)
					t.Logf("  ID:              %v", n.ID)
					return false
				}
			}
		}
		return true
	}
	if err := quick.Check(test, quickcfg()); err != nil {
		t.Error(err)
	}
}

func TestTable_ReadRandomNodesGetAll(t *testing.T) {
	cfg := &quick.Config{
		MaxCount: 200,
		Rand:     rand.New(rand.NewSource(time.Now().Unix())),
		Values: func(args []reflect.Value, rand *rand.Rand) {
			args[0] = reflect.ValueOf(make([]*Node, rand.Intn(1000)))
		},
	}
	test := func(buf []*Node) bool {
		tab := newTable(NodeID{}, &net.UDPAddr{})
		for i := 0; i < len(buf); i++ {
			ld := cfg.Rand.Intn(len(tab.buckets))
			tab.stuff([]*Node{nodeAtDistance(tab.self.sha, ld)})
		}
		gotN := tab.readRandomNodes(buf)
		if gotN != tab.count {
			t.Errorf("wrong number of nodes, got %d, want %d", gotN, tab.count)
			return false
		}
		if hasDuplicates(buf[:gotN]) {
			t.Errorf("result contains duplicates")
			return false
		}
		return true
	}
	if err := quick.Check(test, cfg); err != nil {
		t.Error(err)
	}
}

type closeTest struct {
	Self   NodeID
	Target common.Hash
	All    []*Node
	N      int
}

func (*closeTest) Generate(rand *rand.Rand, size int) reflect.Value {
	t := &closeTest{
		Self:   gen(NodeID{}, rand).(NodeID),
		Target: gen(common.Hash{}, rand).(common.Hash),
		N:      rand.Intn(bucketSize),
	}
	for _, id := range gen([]NodeID{}, rand).([]NodeID) {
		t.All = append(t.All, &Node{ID: id})
	}
	return reflect.ValueOf(t)
}

func hasDuplicates(slice []*Node) bool {
	seen := make(map[NodeID]bool)
	for i, e := range slice {
		if e == nil {
			panic(fmt.Sprintf("nil *Node at %d", i))
		}
		if seen[e.ID] {
			return true
		}
		seen[e.ID] = true
	}
	return false
}

func sortedByDistanceTo(distbase common.Hash, slice []*Node) bool {
	var last common.Hash
	for i, e := range slice {
		if i > 0 && distcmp(distbase, e.sha, last) < 0 {
			return false
		}
		last = e.sha
	}
	return true
}

func contains(ns []*Node, id NodeID) bool {
	for _, n := range ns {
		if n.ID == id {
			return true
		}
	}
	return false
}

// gen wraps quick.Value so it's easier to use.
// it generates a random value of the given value's type.
func gen(typ interface{}, rand *rand.Rand) interface{} {
	v, ok := quick.Value(reflect.TypeOf(typ), rand)
	if !ok {
		panic(fmt.Sprintf("couldn't generate random value of type %T", typ))
	}
	return v.Interface()
}

func newkey() *ecdsa.PrivateKey {
	key, err := crypto.GenerateKey()
	if err != nil {
		panic("couldn't generate key: " + err.Error())
	}
	return key
}
