package ipld_eth_statedb

import (
	"fmt"
	"math/big"
	"sort"
	"time"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/state"
	"github.com/ethereum/go-ethereum/core/state/snapshot"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/core/vm"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/metrics"
	"github.com/ethereum/go-ethereum/rlp"
	"github.com/ethereum/go-ethereum/trie"
)

/*
The portions of the EVM we want to leverage only use the following methods:

GetBalance
Snapshot
Exist
CreateAccount
SubBalance
AddBalance
GetCode
GetCodeHash
RevertToSnapshot
GetNonce
SetNonce
AddAddressToAccessList
SetCode

The rest can be left with panics for now
*/

var _ vm.StateDB = &StateDB{}

type revision struct {
	id           int
	journalIndex int
}

var (
	// emptyRoot is the known root hash of an empty trie.
	emptyRoot = common.HexToHash("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")
)

// StateDB structs within the ethereum protocol are used to store anything
// within the merkle trie. StateDBs take care of caching and storing
// nested states. It's the general query interface to retrieve:
// * Contracts
// * Accounts
type StateDB struct {
	db         Database
	prefetcher *triePrefetcher
	trie       state.Trie
	hasher     crypto.KeccakState

	// originalRoot is the pre-state root, before any changes were made.
	// It will be updated when the Commit is called.
	originalRoot common.Hash

	snaps         *snapshot.Tree
	snap          snapshot.Snapshot
	snapDestructs map[common.Hash]struct{}
	snapAccounts  map[common.Hash][]byte
	snapStorage   map[common.Hash]map[common.Hash][]byte

	// This map holds 'live' objects, which will get modified while processing a state transition.
	stateObjects        map[common.Address]*stateObject
	stateObjectsPending map[common.Address]struct{} // State objects finalized but not yet written to the trie
	stateObjectsDirty   map[common.Address]struct{} // State objects modified in the current execution

	// DB error.
	// State objects are used by the consensus core and VM which are
	// unable to deal with database-level errors. Any error that occurs
	// during a database read is memoized here and will eventually be returned
	// by StateDB.Commit.
	dbErr error

	// The refund counter, also used by state transitioning.
	refund uint64

	thash   common.Hash
	txIndex int
	logs    map[common.Hash][]*types.Log
	logSize uint

	preimages map[common.Hash][]byte

	// Per-transaction access list
	accessList *accessList

	// Journal of state modifications. This is the backbone of
	// Snapshot and RevertToSnapshot.
	journal        *journal
	validRevisions []revision
	nextRevisionId int

	// Measurements gathered during execution for debugging purposes
	AccountReads         time.Duration
	AccountHashes        time.Duration
	AccountUpdates       time.Duration
	AccountCommits       time.Duration
	StorageReads         time.Duration
	StorageHashes        time.Duration
	StorageUpdates       time.Duration
	StorageCommits       time.Duration
	SnapshotAccountReads time.Duration
	SnapshotStorageReads time.Duration
	SnapshotCommits      time.Duration

	AccountUpdated int
	StorageUpdated int
	AccountDeleted int
	StorageDeleted int
}

// New creates a new state from a given trie.
func New(root common.Hash, db Database, snaps *snapshot.Tree) (*StateDB, error) {
	tr, err := db.OpenTrie(root)
	if err != nil {
		return nil, err
	}
	sdb := &StateDB{
		db:                  db,
		trie:                tr,
		originalRoot:        root,
		snaps:               snaps,
		stateObjects:        make(map[common.Address]*stateObject),
		stateObjectsPending: make(map[common.Address]struct{}),
		stateObjectsDirty:   make(map[common.Address]struct{}),
		logs:                make(map[common.Hash][]*types.Log),
		preimages:           make(map[common.Hash][]byte),
		journal:             newJournal(),
		accessList:          newAccessList(),
		hasher:              crypto.NewKeccakState(),
	}
	if sdb.snaps != nil {
		if sdb.snap = sdb.snaps.Snapshot(root); sdb.snap != nil {
			sdb.snapDestructs = make(map[common.Hash]struct{})
			sdb.snapAccounts = make(map[common.Hash][]byte)
			sdb.snapStorage = make(map[common.Hash]map[common.Hash][]byte)
		}
	}
	return sdb, nil
}

// setError remembers the first non-nil error it is called with.
func (s *StateDB) setError(err error) {
	if s.dbErr == nil {
		s.dbErr = err
	}
}

func (s *StateDB) AddLog(log *types.Log) {
	s.journal.append(addLogChange{txhash: s.thash})

	log.TxHash = s.thash
	log.TxIndex = uint(s.txIndex)
	log.Index = s.logSize
	s.logs[s.thash] = append(s.logs[s.thash], log)
	s.logSize++
}

// AddPreimage records a SHA3 preimage seen by the VM.
func (s *StateDB) AddPreimage(hash common.Hash, preimage []byte) {
	if _, ok := s.preimages[hash]; !ok {
		s.journal.append(addPreimageChange{hash: hash})
		pi := make([]byte, len(preimage))
		copy(pi, preimage)
		s.preimages[hash] = pi
	}
}

// AddRefund adds gas to the refund counter
func (s *StateDB) AddRefund(gas uint64) {
	s.journal.append(refundChange{prev: s.refund})
	s.refund += gas
}

// SubRefund removes gas from the refund counter.
// This method will panic if the refund counter goes below zero
func (s *StateDB) SubRefund(gas uint64) {
	s.journal.append(refundChange{prev: s.refund})
	if gas > s.refund {
		panic(fmt.Sprintf("Refund counter below zero (gas: %d > refund: %d)", gas, s.refund))
	}
	s.refund -= gas
}

// Exist reports whether the given account address exists in the state.
// Notably this also returns true for suicided accounts.
func (s *StateDB) Exist(addr common.Address) bool {
	return s.getStateObject(addr) != nil
}

// Empty returns whether the state object is either non-existent
// or empty according to the EIP161 specification (balance = nonce = code = 0)
func (s *StateDB) Empty(addr common.Address) bool {
	so := s.getStateObject(addr)
	return so == nil || so.empty()
}

// GetBalance retrieves the balance from the given address or 0 if object not found
func (s *StateDB) GetBalance(addr common.Address) *big.Int {
	stateObject := s.getStateObject(addr)
	if stateObject != nil {
		return stateObject.Balance()
	}
	return common.Big0
}

func (s *StateDB) GetNonce(addr common.Address) uint64 {
	stateObject := s.getStateObject(addr)
	if stateObject != nil {
		return stateObject.Nonce()
	}

	return 0
}

func (s *StateDB) GetCode(addr common.Address) []byte {
	stateObject := s.getStateObject(addr)
	if stateObject != nil {
		return stateObject.Code(s.db)
	}
	return nil
}

func (s *StateDB) GetCodeSize(addr common.Address) int {
	stateObject := s.getStateObject(addr)
	if stateObject != nil {
		return stateObject.CodeSize(s.db)
	}
	return 0
}

func (s *StateDB) GetCodeHash(addr common.Address) common.Hash {
	stateObject := s.getStateObject(addr)
	if stateObject == nil {
		return common.Hash{}
	}
	return common.BytesToHash(stateObject.CodeHash())
}

// GetState retrieves a value from the given account's storage trie.
func (s *StateDB) GetState(addr common.Address, hash common.Hash) common.Hash {
	stateObject := s.getStateObject(addr)
	if stateObject != nil {
		return stateObject.GetState(s.db, hash)
	}
	return common.Hash{}
}

// GetCommittedState retrieves a value from the given account's committed storage trie.
func (s *StateDB) GetCommittedState(addr common.Address, hash common.Hash) common.Hash {
	stateObject := s.getStateObject(addr)
	if stateObject != nil {
		return stateObject.GetCommittedState(s.db, hash)
	}
	return common.Hash{}
}

func (s *StateDB) HasSuicided(addr common.Address) bool {
	stateObject := s.getStateObject(addr)
	if stateObject != nil {
		return stateObject.suicided
	}
	return false
}

/*
 * SETTERS
 */

// AddBalance adds amount to the account associated with addr.
func (s *StateDB) AddBalance(addr common.Address, amount *big.Int) {
	stateObject := s.getOrNewStateObject(addr)
	if stateObject != nil {
		stateObject.AddBalance(amount)
	}
}

// SubBalance subtracts amount from the account associated with addr.
func (s *StateDB) SubBalance(addr common.Address, amount *big.Int) {
	stateObject := s.getOrNewStateObject(addr)
	if stateObject != nil {
		stateObject.SubBalance(amount)
	}
}

func (s *StateDB) SetBalance(addr common.Address, amount *big.Int) {
	stateObject := s.getOrNewStateObject(addr)
	if stateObject != nil {
		stateObject.SetBalance(amount)
	}
}

func (s *StateDB) SetNonce(addr common.Address, nonce uint64) {
	stateObject := s.getOrNewStateObject(addr)
	if stateObject != nil {
		stateObject.SetNonce(nonce)
	}
}

func (s *StateDB) SetCode(addr common.Address, code []byte) {
	stateObject := s.getOrNewStateObject(addr)
	if stateObject != nil {
		stateObject.SetCode(crypto.Keccak256Hash(code), code)
	}
}

func (s *StateDB) SetState(addr common.Address, key, value common.Hash) {
	stateObject := s.getOrNewStateObject(addr)
	if stateObject != nil {
		stateObject.SetState(s.db, key, value)
	}
}

// Suicide marks the given account as suicided.
// This clears the account balance.
//
// The account's state object is still available until the state is committed,
// getStateObject will return a non-nil account after Suicide.
func (s *StateDB) Suicide(addr common.Address) bool {
	stateObject := s.getStateObject(addr)
	if stateObject == nil {
		return false
	}
	s.journal.append(suicideChange{
		account:     &addr,
		prev:        stateObject.suicided,
		prevbalance: new(big.Int).Set(stateObject.Balance()),
	})
	stateObject.markSuicided()
	stateObject.data.Balance = new(big.Int)

	return true
}

//
// Setting, updating & deleting state object methods.
//

// updateStateObject writes the given object to the trie.
// TODO:
func (s *StateDB) updateStateObject(obj *stateObject) {
	// Track the amount of time wasted on updating the account from the trie
	if metrics.EnabledExpensive {
		defer func(start time.Time) { s.AccountUpdates += time.Since(start) }(time.Now())
	}
	// Encode the account and update the account trie
	addr := obj.Address()
	if err := s.trie.TryUpdateAccount(addr[:], &obj.data); err != nil {
		s.setError(fmt.Errorf("updateStateObject (%x) error: %v", addr[:], err))
	}

	// If state snapshotting is active, cache the data til commit. Note, this
	// update mechanism is not symmetric to the deletion, because whereas it is
	// enough to track account updates at commit time, deletions need tracking
	// at transaction boundary level to ensure we capture state clearing.
	if s.snap != nil {
		s.snapAccounts[obj.addrHash] = snapshot.SlimAccountRLP(obj.data.Nonce, obj.data.Balance, obj.data.Root, obj.data.CodeHash)
	}
}

// deleteStateObject removes the given object from the state trie.
// TODO:
func (s *StateDB) deleteStateObject(obj *stateObject) {
	// Track the amount of time wasted on deleting the account from the trie
	if metrics.EnabledExpensive {
		defer func(start time.Time) { s.AccountUpdates += time.Since(start) }(time.Now())
	}
	// Delete the account from the trie
	addr := obj.Address()
	if err := s.trie.TryDeleteAccount(addr[:]); err != nil {
		s.setError(fmt.Errorf("deleteStateObject (%x) error: %v", addr[:], err))
	}
}

// getStateObject retrieves a state object given by the address, returning nil if
// the object is not found or was deleted in this execution context. If you need
// to differentiate between non-existent/just-deleted, use getDeletedStateObject.
func (s *StateDB) getStateObject(addr common.Address) *stateObject {
	if obj := s.getDeletedStateObject(addr); obj != nil && !obj.deleted {
		return obj
	}
	return nil
}

// getDeletedStateObject is similar to getStateObject, but instead of returning
// nil for a deleted state object, it returns the actual object with the deleted
// flag set. This is needed by the state journal to revert to the correct s-
// destructed object instead of wiping all knowledge about the state object.
// TODO:
func (s *StateDB) getDeletedStateObject(addr common.Address) *stateObject {
	// Prefer live objects if any is available
	if obj := s.stateObjects[addr]; obj != nil {
		return obj
	}
	// If no live objects are available, attempt to use snapshots
	var data *types.StateAccount
	if s.snap != nil {
		start := time.Now()
		acc, err := s.snap.Account(crypto.HashData(s.hasher, addr.Bytes()))
		if metrics.EnabledExpensive {
			s.SnapshotAccountReads += time.Since(start)
		}
		if err == nil {
			if acc == nil {
				return nil
			}
			data = &types.StateAccount{
				Nonce:    acc.Nonce,
				Balance:  acc.Balance,
				CodeHash: acc.CodeHash,
				Root:     common.BytesToHash(acc.Root),
			}
			if len(data.CodeHash) == 0 {
				data.CodeHash = emptyCodeHash
			}
			if data.Root == (common.Hash{}) {
				data.Root = emptyRoot
			}
		}
	}
	// If snapshot unavailable or reading from it failed, load from the database
	if data == nil {
		start := time.Now()
		var err error
		data, err = s.trie.TryGetAccount(addr.Bytes())
		if metrics.EnabledExpensive {
			s.AccountReads += time.Since(start)
		}
		if err != nil {
			s.setError(fmt.Errorf("getDeleteStateObject (%x) error: %w", addr.Bytes(), err))
			return nil
		}
		if data == nil {
			return nil
		}
	}
	// Insert into the live set
	obj := newObject(s, addr, *data)
	s.setStateObject(obj)
	return obj
}

func (s *StateDB) setStateObject(object *stateObject) {
	s.stateObjects[object.Address()] = object
}

// getOrNewStateObject retrieves a state object or create a new state object if nil.
func (s *StateDB) getOrNewStateObject(addr common.Address) *stateObject {
	stateObject := s.getStateObject(addr)
	if stateObject == nil {
		stateObject, _ = s.createObject(addr)
	}
	return stateObject
}

// createObject creates a new state object. If there is an existing account with
// the given address, it is overwritten and returned as the second return value.
func (s *StateDB) createObject(addr common.Address) (newobj, prev *stateObject) {
	prev = s.getDeletedStateObject(addr) // Note, prev might have been deleted, we need that!

	var prevdestruct bool
	if s.snap != nil && prev != nil {
		_, prevdestruct = s.snapDestructs[prev.addrHash]
		if !prevdestruct {
			s.snapDestructs[prev.addrHash] = struct{}{}
		}
	}
	newobj = newObject(s, addr, types.StateAccount{})
	if prev == nil {
		s.journal.append(createObjectChange{account: &addr})
	} else {
		s.journal.append(resetObjectChange{prev: prev, prevdestruct: prevdestruct})
	}
	s.setStateObject(newobj)
	if prev != nil && !prev.deleted {
		return newobj, prev
	}
	return newobj, nil
}

// CreateAccount explicitly creates a state object. If a state object with the address
// already exists the balance is carried over to the new account.
//
// CreateAccount is called during the EVM CREATE operation. The situation might arise that
// a contract does the following:
//
//   1. sends funds to sha(account ++ (nonce + 1))
//   2. tx_create(sha(account ++ nonce)) (note that this gets the address of 1)
//
// Carrying over the balance ensures that Ether doesn't disappear.
func (s *StateDB) CreateAccount(addr common.Address) {
	newObj, prev := s.createObject(addr)
	if prev != nil {
		newObj.setBalance(prev.data.Balance)
	}
}

func (db *StateDB) ForEachStorage(addr common.Address, cb func(key, value common.Hash) bool) error {
	so := db.getStateObject(addr)
	if so == nil {
		return nil
	}
	it := trie.NewIterator(so.getTrie(db.db).NodeIterator(nil))

	for it.Next() {
		key := common.BytesToHash(db.trie.GetKey(it.Key))
		if value, dirty := so.dirtyStorage[key]; dirty {
			if !cb(key, value) {
				return nil
			}
			continue
		}

		if len(it.Value) > 0 {
			_, content, _, err := rlp.Split(it.Value)
			if err != nil {
				return err
			}
			if !cb(key, common.BytesToHash(content)) {
				return nil
			}
		}
	}
	return nil
}

// Snapshot returns an identifier for the current revision of the state.
func (s *StateDB) Snapshot() int {
	id := s.nextRevisionId
	s.nextRevisionId++
	s.validRevisions = append(s.validRevisions, revision{id, s.journal.length()})
	return id
}

// RevertToSnapshot reverts all state changes made since the given revision.
func (s *StateDB) RevertToSnapshot(revid int) {
	// Find the snapshot in the stack of valid snapshots.
	idx := sort.Search(len(s.validRevisions), func(i int) bool {
		return s.validRevisions[i].id >= revid
	})
	if idx == len(s.validRevisions) || s.validRevisions[idx].id != revid {
		panic(fmt.Errorf("revision id %v cannot be reverted", revid))
	}
	snapshot := s.validRevisions[idx].journalIndex

	// Replay the journal to undo changes and remove invalidated snapshots
	s.journal.revert(s, snapshot)
	s.validRevisions = s.validRevisions[:idx]
}

// GetRefund returns the current value of the refund counter.
func (s *StateDB) GetRefund() uint64 {
	return s.refund
}

func (s *StateDB) clearJournalAndRefund() {
	if len(s.journal.entries) > 0 {
		s.journal = newJournal()
		s.refund = 0
	}
	s.validRevisions = s.validRevisions[:0] // Snapshots can be created without journal entries
}

// PrepareAccessList handles the preparatory steps for executing a state transition with
// regards to both EIP-2929 and EIP-2930:
//
// - Add sender to access list (2929)
// - Add destination to access list (2929)
// - Add precompiles to access list (2929)
// - Add the contents of the optional tx access list (2930)
//
// This method should only be called if Berlin/2929+2930 is applicable at the current number.
func (s *StateDB) PrepareAccessList(sender common.Address, dst *common.Address, precompiles []common.Address, list types.AccessList) {
	// Clear out any leftover from previous executions
	s.accessList = newAccessList()

	s.AddAddressToAccessList(sender)
	if dst != nil {
		s.AddAddressToAccessList(*dst)
		// If it's a create-tx, the destination will be added inside evm.create
	}
	for _, addr := range precompiles {
		s.AddAddressToAccessList(addr)
	}
	for _, el := range list {
		s.AddAddressToAccessList(el.Address)
		for _, key := range el.StorageKeys {
			s.AddSlotToAccessList(el.Address, key)
		}
	}
}

// AddAddressToAccessList adds the given address to the access list
func (s *StateDB) AddAddressToAccessList(addr common.Address) {
	if s.accessList.AddAddress(addr) {
		s.journal.append(accessListAddAccountChange{&addr})
	}
}

// AddSlotToAccessList adds the given (address, slot)-tuple to the access list
func (s *StateDB) AddSlotToAccessList(addr common.Address, slot common.Hash) {
	addrMod, slotMod := s.accessList.AddSlot(addr, slot)
	if addrMod {
		// In practice, this should not happen, since there is no way to enter the
		// scope of 'address' without having the 'address' become already added
		// to the access list (via call-variant, create, etc).
		// Better safe than sorry, though
		s.journal.append(accessListAddAccountChange{&addr})
	}
	if slotMod {
		s.journal.append(accessListAddSlotChange{
			address: &addr,
			slot:    &slot,
		})
	}
}

// AddressInAccessList returns true if the given address is in the access list.
func (s *StateDB) AddressInAccessList(addr common.Address) bool {
	return s.accessList.ContainsAddress(addr)
}

// SlotInAccessList returns true if the given (address, slot)-tuple is in the access list.
func (s *StateDB) SlotInAccessList(addr common.Address, slot common.Hash) (addressPresent bool, slotPresent bool) {
	return s.accessList.Contains(addr, slot)
}