// 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 (
	"math/rand"
	"testing"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/rawdb"
	"github.com/ethereum/go-ethereum/ethdb/memorydb"
)

// 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
}

// Tests that given a database with random data content, all parts of a snapshot
// can be crrectly wiped without touching anything else.
func TestWipe(t *testing.T) {
	// Create a database with some random snapshot data
	db := memorydb.New()

	for i := 0; i < 128; i++ {
		account := randomHash()
		rawdb.WriteAccountSnapshot(db, account, randomHash().Bytes())
		for j := 0; j < 1024; j++ {
			rawdb.WriteStorageSnapshot(db, account, randomHash(), randomHash().Bytes())
		}
	}
	rawdb.WriteSnapshotRoot(db, randomHash())

	// Add some random non-snapshot data too to make wiping harder
	for i := 0; i < 65536; i++ {
		// Generate a key that's the wrong length for a state snapshot item
		var keysize int
		for keysize == 0 || keysize == 32 || keysize == 64 {
			keysize = 8 + rand.Intn(64) // +8 to ensure we will "never" randomize duplicates
		}
		// Randomize the suffix, dedup and inject it under the snapshot namespace
		keysuffix := make([]byte, keysize)
		rand.Read(keysuffix)
		db.Put(append(rawdb.StateSnapshotPrefix, keysuffix...), randomHash().Bytes())
	}
	// Sanity check that all the keys are present
	var items int

	it := db.NewIteratorWithPrefix(rawdb.StateSnapshotPrefix)
	defer it.Release()

	for it.Next() {
		key := it.Key()
		if len(key) == len(rawdb.StateSnapshotPrefix)+32 || len(key) == len(rawdb.StateSnapshotPrefix)+64 {
			items++
		}
	}
	if items != 128+128*1024 {
		t.Fatalf("snapshot size mismatch: have %d, want %d", items, 128+128*1024)
	}
	if hash := rawdb.ReadSnapshotRoot(db); hash == (common.Hash{}) {
		t.Errorf("snapshot block marker mismatch: have %#x, want <not-nil>", hash)
	}
	// Wipe all snapshot entries from the database
	if err := wipeSnapshot(db); err != nil {
		t.Fatalf("failed to wipe snapshot: %v", err)
	}
	// Iterate over the database end ensure no snapshot information remains
	it = db.NewIteratorWithPrefix(rawdb.StateSnapshotPrefix)
	defer it.Release()

	for it.Next() {
		key := it.Key()
		if len(key) == len(rawdb.StateSnapshotPrefix)+32 || len(key) == len(rawdb.StateSnapshotPrefix)+64 {
			t.Errorf("snapshot entry remained after wipe: %x", key)
		}
	}
	if hash := rawdb.ReadSnapshotRoot(db); hash != (common.Hash{}) {
		t.Errorf("snapshot block marker remained after wipe: %#x", hash)
	}
	// Iterate over the database and ensure miscellaneous items are present
	items = 0

	it = db.NewIterator()
	defer it.Release()

	for it.Next() {
		items++
	}
	if items != 65536 {
		t.Fatalf("misc item count mismatch: have %d, want %d", items, 65536)
	}
}