// Copyright 2019 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 snapshot

import (
	"encoding/binary"
	"fmt"
	"math/big"
	"math/rand"
	"testing"

	"github.com/VictoriaMetrics/fastcache"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/rawdb"
	"github.com/ethereum/go-ethereum/rlp"
)

// randomHash generates a random blob of data and returns it as a hash.
func randomHash() common.Hash {
	var hash common.Hash
	if n, err := rand.Read(hash[:]); n != common.HashLength || err != nil {
		panic(err)
	}
	return hash
}

// randomAccount generates a random account and returns it RLP encoded.
func randomAccount() []byte {
	root := randomHash()
	a := Account{
		Balance:  big.NewInt(rand.Int63()),
		Nonce:    rand.Uint64(),
		Root:     root[:],
		CodeHash: emptyCode[:],
	}
	data, _ := rlp.EncodeToBytes(a)
	return data
}

// randomAccountSet generates a set of random accounts with the given strings as
// the account address hashes.
func randomAccountSet(hashes ...string) map[common.Hash][]byte {
	accounts := make(map[common.Hash][]byte)
	for _, hash := range hashes {
		accounts[common.HexToHash(hash)] = randomAccount()
	}
	return accounts
}

// randomStorageSet generates a set of random slots with the given strings as
// the slot addresses.
func randomStorageSet(accounts []string, hashes [][]string, nilStorage [][]string) map[common.Hash]map[common.Hash][]byte {
	storages := make(map[common.Hash]map[common.Hash][]byte)
	for index, account := range accounts {
		storages[common.HexToHash(account)] = make(map[common.Hash][]byte)

		if index < len(hashes) {
			hashes := hashes[index]
			for _, hash := range hashes {
				storages[common.HexToHash(account)][common.HexToHash(hash)] = randomHash().Bytes()
			}
		}
		if index < len(nilStorage) {
			nils := nilStorage[index]
			for _, hash := range nils {
				storages[common.HexToHash(account)][common.HexToHash(hash)] = nil
			}
		}
	}
	return storages
}

// Tests that if a disk layer becomes stale, no active external references will
// be returned with junk data. This version of the test flattens every diff layer
// to check internal corner case around the bottom-most memory accumulator.
func TestDiskLayerExternalInvalidationFullFlatten(t *testing.T) {
	// Create an empty base layer and a snapshot tree out of it
	base := &diskLayer{
		diskdb: rawdb.NewMemoryDatabase(),
		root:   common.HexToHash("0x01"),
		cache:  fastcache.New(1024 * 500),
	}
	snaps := &Tree{
		layers: map[common.Hash]snapshot{
			base.root: base,
		},
	}
	// Retrieve a reference to the base and commit a diff on top
	ref := snaps.Snapshot(base.root)

	accounts := map[common.Hash][]byte{
		common.HexToHash("0xa1"): randomAccount(),
	}
	if err := snaps.update(common.HexToHash("0x02"), common.HexToHash("0x01"), nil, accounts, nil, nil); err != nil {
		t.Fatalf("failed to create a diff layer: %v", err)
	}
	if n := len(snaps.layers); n != 2 {
		t.Errorf("pre-cap layer count mismatch: have %d, want %d", n, 2)
	}
	// Commit the diff layer onto the disk and ensure it's persisted
	if err := snaps.Cap(common.HexToHash("0x02"), 0); err != nil {
		t.Fatalf("failed to merge diff layer onto disk: %v", err)
	}
	// Since the base layer was modified, ensure that data retrieval on the external reference fail
	if acc, err := ref.Account(common.HexToHash("0x01")); err != ErrSnapshotStale {
		t.Errorf("stale reference returned account: %#x (err: %v)", acc, err)
	}
	if slot, err := ref.Storage(common.HexToHash("0xa1"), common.HexToHash("0xb1")); err != ErrSnapshotStale {
		t.Errorf("stale reference returned storage slot: %#x (err: %v)", slot, err)
	}
	if n := len(snaps.layers); n != 1 {
		t.Errorf("post-cap layer count mismatch: have %d, want %d", n, 1)
		fmt.Println(snaps.layers)
	}
}

// Tests that if a disk layer becomes stale, no active external references will
// be returned with junk data. This version of the test retains the bottom diff
// layer to check the usual mode of operation where the accumulator is retained.
func TestDiskLayerExternalInvalidationPartialFlatten(t *testing.T) {
	// Create an empty base layer and a snapshot tree out of it
	base := &diskLayer{
		diskdb: rawdb.NewMemoryDatabase(),
		root:   common.HexToHash("0x01"),
		cache:  fastcache.New(1024 * 500),
	}
	snaps := &Tree{
		layers: map[common.Hash]snapshot{
			base.root: base,
		},
	}
	// Retrieve a reference to the base and commit two diffs on top
	ref := snaps.Snapshot(base.root)

	accounts := map[common.Hash][]byte{
		common.HexToHash("0xa1"): randomAccount(),
	}
	if err := snaps.update(common.HexToHash("0x02"), common.HexToHash("0x01"), nil, accounts, nil, nil); err != nil {
		t.Fatalf("failed to create a diff layer: %v", err)
	}
	if err := snaps.update(common.HexToHash("0x03"), common.HexToHash("0x02"), nil, accounts, nil, nil); err != nil {
		t.Fatalf("failed to create a diff layer: %v", err)
	}
	if n := len(snaps.layers); n != 3 {
		t.Errorf("pre-cap layer count mismatch: have %d, want %d", n, 3)
	}
	// Commit the diff layer onto the disk and ensure it's persisted
	defer func(memcap uint64) { aggregatorMemoryLimit = memcap }(aggregatorMemoryLimit)
	aggregatorMemoryLimit = 0

	if err := snaps.Cap(common.HexToHash("0x03"), 1); err != nil {
		t.Fatalf("failed to merge accumulator onto disk: %v", err)
	}
	// Since the base layer was modified, ensure that data retrievald on the external reference fail
	if acc, err := ref.Account(common.HexToHash("0x01")); err != ErrSnapshotStale {
		t.Errorf("stale reference returned account: %#x (err: %v)", acc, err)
	}
	if slot, err := ref.Storage(common.HexToHash("0xa1"), common.HexToHash("0xb1")); err != ErrSnapshotStale {
		t.Errorf("stale reference returned storage slot: %#x (err: %v)", slot, err)
	}
	if n := len(snaps.layers); n != 2 {
		t.Errorf("post-cap layer count mismatch: have %d, want %d", n, 2)
		fmt.Println(snaps.layers)
	}
}

// Tests that if a diff layer becomes stale, no active external references will
// be returned with junk data. This version of the test retains the bottom diff
// layer to check the usual mode of operation where the accumulator is retained.
func TestDiffLayerExternalInvalidationPartialFlatten(t *testing.T) {
	// Create an empty base layer and a snapshot tree out of it
	base := &diskLayer{
		diskdb: rawdb.NewMemoryDatabase(),
		root:   common.HexToHash("0x01"),
		cache:  fastcache.New(1024 * 500),
	}
	snaps := &Tree{
		layers: map[common.Hash]snapshot{
			base.root: base,
		},
	}
	// Commit three diffs on top and retrieve a reference to the bottommost
	accounts := map[common.Hash][]byte{
		common.HexToHash("0xa1"): randomAccount(),
	}
	if err := snaps.update(common.HexToHash("0x02"), common.HexToHash("0x01"), nil, accounts, nil, nil); err != nil {
		t.Fatalf("failed to create a diff layer: %v", err)
	}
	if err := snaps.update(common.HexToHash("0x03"), common.HexToHash("0x02"), nil, accounts, nil, nil); err != nil {
		t.Fatalf("failed to create a diff layer: %v", err)
	}
	if err := snaps.update(common.HexToHash("0x04"), common.HexToHash("0x03"), nil, accounts, nil, nil); err != nil {
		t.Fatalf("failed to create a diff layer: %v", err)
	}
	if n := len(snaps.layers); n != 4 {
		t.Errorf("pre-cap layer count mismatch: have %d, want %d", n, 4)
	}
	ref := snaps.Snapshot(common.HexToHash("0x02"))

	// Doing a Cap operation with many allowed layers should be a no-op
	exp := len(snaps.layers)
	if err := snaps.Cap(common.HexToHash("0x04"), 2000); err != nil {
		t.Fatalf("failed to flatten diff layer into accumulator: %v", err)
	}
	if got := len(snaps.layers); got != exp {
		t.Errorf("layers modified, got %d exp %d", got, exp)
	}
	// Flatten the diff layer into the bottom accumulator
	if err := snaps.Cap(common.HexToHash("0x04"), 1); err != nil {
		t.Fatalf("failed to flatten diff layer into accumulator: %v", err)
	}
	// Since the accumulator diff layer was modified, ensure that data retrievald on the external reference fail
	if acc, err := ref.Account(common.HexToHash("0x01")); err != ErrSnapshotStale {
		t.Errorf("stale reference returned account: %#x (err: %v)", acc, err)
	}
	if slot, err := ref.Storage(common.HexToHash("0xa1"), common.HexToHash("0xb1")); err != ErrSnapshotStale {
		t.Errorf("stale reference returned storage slot: %#x (err: %v)", slot, err)
	}
	if n := len(snaps.layers); n != 3 {
		t.Errorf("post-cap layer count mismatch: have %d, want %d", n, 3)
		fmt.Println(snaps.layers)
	}
}

// TestPostCapBasicDataAccess tests some functionality regarding capping/flattening.
func TestPostCapBasicDataAccess(t *testing.T) {
	// setAccount is a helper to construct a random account entry and assign it to
	// an account slot in a snapshot
	setAccount := func(accKey string) map[common.Hash][]byte {
		return map[common.Hash][]byte{
			common.HexToHash(accKey): randomAccount(),
		}
	}
	// Create a starting base layer and a snapshot tree out of it
	base := &diskLayer{
		diskdb: rawdb.NewMemoryDatabase(),
		root:   common.HexToHash("0x01"),
		cache:  fastcache.New(1024 * 500),
	}
	snaps := &Tree{
		layers: map[common.Hash]snapshot{
			base.root: base,
		},
	}
	// The lowest difflayer
	snaps.update(common.HexToHash("0xa1"), common.HexToHash("0x01"), nil, setAccount("0xa1"), nil, nil)
	snaps.update(common.HexToHash("0xa2"), common.HexToHash("0xa1"), nil, setAccount("0xa2"), nil, nil)
	snaps.update(common.HexToHash("0xb2"), common.HexToHash("0xa1"), nil, setAccount("0xb2"), nil, nil)

	snaps.update(common.HexToHash("0xa3"), common.HexToHash("0xa2"), nil, setAccount("0xa3"), nil, nil)
	snaps.update(common.HexToHash("0xb3"), common.HexToHash("0xb2"), nil, setAccount("0xb3"), nil, nil)

	// checkExist verifies if an account exiss in a snapshot
	checkExist := func(layer *diffLayer, key string) error {
		if data, _ := layer.Account(common.HexToHash(key)); data == nil {
			return fmt.Errorf("expected %x to exist, got nil", common.HexToHash(key))
		}
		return nil
	}
	// shouldErr checks that an account access errors as expected
	shouldErr := func(layer *diffLayer, key string) error {
		if data, err := layer.Account(common.HexToHash(key)); err == nil {
			return fmt.Errorf("expected error, got data %x", data)
		}
		return nil
	}
	// check basics
	snap := snaps.Snapshot(common.HexToHash("0xb3")).(*diffLayer)

	if err := checkExist(snap, "0xa1"); err != nil {
		t.Error(err)
	}
	if err := checkExist(snap, "0xb2"); err != nil {
		t.Error(err)
	}
	if err := checkExist(snap, "0xb3"); err != nil {
		t.Error(err)
	}
	// Cap to a bad root should fail
	if err := snaps.Cap(common.HexToHash("0x1337"), 0); err == nil {
		t.Errorf("expected error, got none")
	}
	// Now, merge the a-chain
	snaps.Cap(common.HexToHash("0xa3"), 0)

	// At this point, a2 got merged into a1. Thus, a1 is now modified, and as a1 is
	// the parent of b2, b2 should no longer be able to iterate into parent.

	// These should still be accessible
	if err := checkExist(snap, "0xb2"); err != nil {
		t.Error(err)
	}
	if err := checkExist(snap, "0xb3"); err != nil {
		t.Error(err)
	}
	// But these would need iteration into the modified parent
	if err := shouldErr(snap, "0xa1"); err != nil {
		t.Error(err)
	}
	if err := shouldErr(snap, "0xa2"); err != nil {
		t.Error(err)
	}
	if err := shouldErr(snap, "0xa3"); err != nil {
		t.Error(err)
	}
	// Now, merge it again, just for fun. It should now error, since a3
	// is a disk layer
	if err := snaps.Cap(common.HexToHash("0xa3"), 0); err == nil {
		t.Error("expected error capping the disk layer, got none")
	}
}

// TestSnaphots tests the functionality for retrieveing the snapshot
// with given head root and the desired depth.
func TestSnaphots(t *testing.T) {
	// setAccount is a helper to construct a random account entry and assign it to
	// an account slot in a snapshot
	setAccount := func(accKey string) map[common.Hash][]byte {
		return map[common.Hash][]byte{
			common.HexToHash(accKey): randomAccount(),
		}
	}
	makeRoot := func(height uint64) common.Hash {
		var buffer [8]byte
		binary.BigEndian.PutUint64(buffer[:], height)
		return common.BytesToHash(buffer[:])
	}
	// Create a starting base layer and a snapshot tree out of it
	base := &diskLayer{
		diskdb: rawdb.NewMemoryDatabase(),
		root:   makeRoot(1),
		cache:  fastcache.New(1024 * 500),
	}
	snaps := &Tree{
		layers: map[common.Hash]snapshot{
			base.root: base,
		},
	}
	// Construct the snapshots with 129 layers, flattening whatever's above that
	var (
		last = common.HexToHash("0x01")
		head common.Hash
	)
	for i := 0; i < 129; i++ {
		head = makeRoot(uint64(i + 2))
		snaps.update(head, last, nil, setAccount(fmt.Sprintf("%d", i+2)), nil, nil)
		last = head
		snaps.Cap(head, 128) // 130 layers (128 diffs + 1 accumulator + 1 disk)
	}
	var cases = []struct {
		headRoot     common.Hash
		limit        int
		nodisk       bool
		expected     int
		expectBottom common.Hash
	}{
		{head, 0, false, 0, common.Hash{}},
		{head, 64, false, 64, makeRoot(129 + 2 - 64)},
		{head, 128, false, 128, makeRoot(3)}, // Normal diff layers, no accumulator
		{head, 129, true, 129, makeRoot(2)},  // All diff layers, including accumulator
		{head, 130, false, 130, makeRoot(1)}, // All diff layers + disk layer
	}
	for i, c := range cases {
		layers := snaps.Snapshots(c.headRoot, c.limit, c.nodisk)
		if len(layers) != c.expected {
			t.Errorf("non-overflow test %d: returned snapshot layers are mismatched, want %v, got %v", i, c.expected, len(layers))
		}
		if len(layers) == 0 {
			continue
		}
		bottommost := layers[len(layers)-1]
		if bottommost.Root() != c.expectBottom {
			t.Errorf("non-overflow test %d: snapshot mismatch, want %v, get %v", i, c.expectBottom, bottommost.Root())
		}
	}
	// Above we've tested the normal capping, which leaves the accumulator live.
	// Test that if the bottommost accumulator diff layer overflows the allowed
	// memory limit, the snapshot tree gets capped to one less layer.
	// Commit the diff layer onto the disk and ensure it's persisted
	defer func(memcap uint64) { aggregatorMemoryLimit = memcap }(aggregatorMemoryLimit)
	aggregatorMemoryLimit = 0

	snaps.Cap(head, 128) // 129 (128 diffs + 1 overflown accumulator + 1 disk)

	cases = []struct {
		headRoot     common.Hash
		limit        int
		nodisk       bool
		expected     int
		expectBottom common.Hash
	}{
		{head, 0, false, 0, common.Hash{}},
		{head, 64, false, 64, makeRoot(129 + 2 - 64)},
		{head, 128, false, 128, makeRoot(3)}, // All diff layers, accumulator was flattened
		{head, 129, true, 128, makeRoot(3)},  // All diff layers, accumulator was flattened
		{head, 130, false, 129, makeRoot(2)}, // All diff layers + disk layer
	}
	for i, c := range cases {
		layers := snaps.Snapshots(c.headRoot, c.limit, c.nodisk)
		if len(layers) != c.expected {
			t.Errorf("overflow test %d: returned snapshot layers are mismatched, want %v, got %v", i, c.expected, len(layers))
		}
		if len(layers) == 0 {
			continue
		}
		bottommost := layers[len(layers)-1]
		if bottommost.Root() != c.expectBottom {
			t.Errorf("overflow test %d: snapshot mismatch, want %v, get %v", i, c.expectBottom, bottommost.Root())
		}
	}
}
