# Nimbus
# Copyright (c) 2018 Status Research & Development GmbH
# Licensed under either of
#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
#  * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed except according to those terms.

import
  std/[sequtils, algorithm],
  stew/[byteutils], eth/trie/[hexary, db],
  eth/[common, rlp], chronicles,
  ".."/[errors, constants, utils, chain_config],
  "."/storage_types

type
  BaseChainDB* = ref object
    db*       : TrieDatabaseRef
    pruneTrie*: bool
    networkId*: NetworkId
    config*   : ChainConfig
    genesis*  : Genesis

    # startingBlock, currentBlock, and highestBlock
    # are progress indicator
    startingBlock*: BlockNumber
    currentBlock*: BlockNumber
    highestBlock*: BlockNumber

  TransactionKey = tuple
    blockNumber: BlockNumber
    index: int

proc newBaseChainDB*(
       db: TrieDatabaseRef,
       pruneTrie: bool = true,
       id: NetworkId = MainNet,
       params = networkParams(MainNet)): BaseChainDB =

  new(result)
  result.db = db
  result.pruneTrie = pruneTrie
  result.networkId = id
  result.config    = params.config
  result.genesis   = params.genesis

proc newBaseChainDB*(
       db: TrieDatabaseRef,
       config: ChainConfig,
       pruneTrie: bool = true,
       id: NetworkId = MainNet): BaseChainDB =

  new(result)
  result.db = db
  result.pruneTrie = pruneTrie
  result.networkId = id
  result.config    = config

proc `$`*(db: BaseChainDB): string =
  result = "BaseChainDB"

proc ttd*(db: BaseChainDB): DifficultyInt =
  if db.config.terminalTotalDifficulty.isSome:
    db.config.terminalTotalDifficulty.get()
  else:
    high(DifficultyInt)

proc networkParams*(db: BaseChainDB): NetworkParams =
  NetworkParams(config: db.config, genesis: db.genesis)

proc exists*(self: BaseChainDB, hash: Hash256): bool =
  self.db.contains(hash.data)

proc getBlockHeader*(self: BaseChainDB; blockHash: Hash256, output: var BlockHeader): bool =
  let data = self.db.get(genericHashKey(blockHash).toOpenArray)
  if data.len != 0:
    try:
      output = rlp.decode(data, BlockHeader)
      true
    except RlpError:
      false
  else:
    false

proc getBlockHeader*(self: BaseChainDB, blockHash: Hash256): BlockHeader =
  ## Returns the requested block header as specified by block hash.
  ##
  ## Raises BlockNotFound if it is not present in the db.
  if not self.getBlockHeader(blockHash, result):
    raise newException(BlockNotFound, "No block with hash " & blockHash.data.toHex)

proc getHash(self: BaseChainDB, key: DbKey, output: var Hash256): bool {.inline.} =
  let data = self.db.get(key.toOpenArray)
  if data.len != 0:
    output = rlp.decode(data, Hash256)
    result = true

proc getCanonicalHead*(self: BaseChainDB): BlockHeader =
  var headHash: Hash256
  if not self.getHash(canonicalHeadHashKey(), headHash) or
      not self.getBlockHeader(headHash, result):
    raise newException(CanonicalHeadNotFound,
                      "No canonical head set for this chain")

proc getCanonicalHeaderHash*(self: BaseChainDB): Hash256 =
  discard self.getHash(canonicalHeadHashKey(), result)

proc populateProgress*(self: BaseChainDB) =
  try:
    self.startingBlock = self.getCanonicalHead().blockNumber
  except CanonicalHeadNotFound:
    self.startingBlock = toBlockNumber(0)

  self.currentBlock = self.startingBlock
  self.highestBlock = self.startingBlock

proc getBlockHash*(self: BaseChainDB, n: BlockNumber, output: var Hash256): bool {.inline.} =
  ## Return the block hash for the given block number.
  self.getHash(blockNumberToHashKey(n), output)

proc getBlockHash*(self: BaseChainDB, n: BlockNumber): Hash256 {.inline.} =
  ## Return the block hash for the given block number.
  if not self.getHash(blockNumberToHashKey(n), result):
    raise newException(BlockNotFound, "No block hash for number " & $n)

proc getHeadBlockHash*(self: BaseChainDB): Hash256 =
  if not self.getHash(canonicalHeadHashKey(), result):
    result = Hash256()

proc getBlockHeader*(self: BaseChainDB; n: BlockNumber, output: var BlockHeader): bool =
  ## Returns the block header with the given number in the canonical chain.
  var blockHash: Hash256
  if self.getBlockHash(n, blockHash):
    result = self.getBlockHeader(blockHash, output)

proc getBlockHeaderWithHash*(self: BaseChainDB; n: BlockNumber): Option[(BlockHeader, Hash256)] =
  ## Returns the block header and its hash, with the given number in the canonical chain.
  ## Hash is returned to avoid recomputing it
  var hash: Hash256
  if self.getBlockHash(n, hash):
    # Note: this will throw if header is not present.
    var header: BlockHeader
    if self.getBlockHeader(hash, header):
      return some((header, hash))
    else:
      # this should not happen, but if it happen lets fail laudly as this means
      # something is super wrong
      raiseAssert("Corrupted database. Mapping number->hash present, without header in database")
  else:
    return none[(BlockHeader, Hash256)]()

proc getBlockHeader*(self: BaseChainDB; n: BlockNumber): BlockHeader =
  ## Returns the block header with the given number in the canonical chain.
  ## Raises BlockNotFound error if the block is not in the DB.
  self.getBlockHeader(self.getBlockHash(n))

proc getScore*(self: BaseChainDB; blockHash: Hash256): UInt256 =
  rlp.decode(self.db.get(blockHashToScoreKey(blockHash).toOpenArray), UInt256)

proc setScore*(self: BaseChainDB; blockHash: Hash256, score: UInt256) =
  ## for testing purpose
  self.db.put(blockHashToScoreKey(blockHash).toOpenArray, rlp.encode(score))

proc getTd*(self: BaseChainDB; blockHash: Hash256, td: var UInt256): bool =
  let bytes = self.db.get(blockHashToScoreKey(blockHash).toOpenArray)
  if bytes.len == 0: return false
  try:
    td = rlp.decode(bytes, UInt256)
  except RlpError:
    return false
  return true

proc headTotalDifficulty*(self: BaseChainDB): UInt256 =
  # this is actually a combination of `getHash` and `getScore`
  const key = canonicalHeadHashKey()
  let data = self.db.get(key.toOpenArray)
  if data.len == 0:
    return 0.u256

  let blockHash = rlp.decode(data, Hash256)
  rlp.decode(self.db.get(blockHashToScoreKey(blockHash).toOpenArray), UInt256)

proc isBlockAfterTtd*(self: BaseChainDB, header: BlockHeader): bool =
  let
    ttd = self.ttd
    ptd = self.getScore(header.parentHash)
    td  = ptd + header.difficulty
  ptd >= ttd and td >= ttd

proc getAncestorsHashes*(self: BaseChainDB, limit: UInt256, header: BlockHeader): seq[Hash256] =
  var ancestorCount = min(header.blockNumber, limit).truncate(int)
  var h = header

  result = newSeq[Hash256](ancestorCount)
  while ancestorCount > 0:
    h = self.getBlockHeader(h.parentHash)
    result[ancestorCount - 1] = h.hash
    dec ancestorCount

iterator findNewAncestors(self: BaseChainDB; header: BlockHeader): BlockHeader =
  ##         Returns the chain leading up from the given header until the first ancestor it has in
  ##         common with our canonical chain.
  var h = header
  var orig: BlockHeader
  while true:
    if self.getBlockHeader(h.blockNumber, orig) and orig.hash == h.hash:
      break

    yield h

    if h.parentHash == GENESIS_PARENT_HASH:
      break
    else:
      h = self.getBlockHeader(h.parentHash)

proc addBlockNumberToHashLookup*(self: BaseChainDB; header: BlockHeader) =
  self.db.put(blockNumberToHashKey(header.blockNumber).toOpenArray,
              rlp.encode(header.hash))

proc persistTransactions*(self: BaseChainDB, blockNumber:
                          BlockNumber, transactions: openArray[Transaction]): Hash256 =
  var trie = initHexaryTrie(self.db)
  for idx, tx in transactions:
    let
      encodedTx = rlp.encode(tx)
      txHash = keccakHash(encodedTx)
      txKey: TransactionKey = (blockNumber, idx)
    trie.put(rlp.encode(idx), encodedTx)
    self.db.put(transactionHashToBlockKey(txHash).toOpenArray, rlp.encode(txKey))
  trie.rootHash

proc getTransaction*(self: BaseChainDB, txRoot: Hash256, txIndex: int, res: var Transaction): bool =
  var db = initHexaryTrie(self.db, txRoot)
  let txData = db.get(rlp.encode(txIndex))
  if txData.len > 0:
    res = rlp.decode(txData, Transaction)
    result = true

iterator getBlockTransactionData*(self: BaseChainDB, transactionRoot: Hash256): seq[byte] =
  var transactionDb = initHexaryTrie(self.db, transactionRoot)
  var transactionIdx = 0
  while true:
    let transactionKey = rlp.encode(transactionIdx)
    if transactionKey in transactionDb:
      yield transactionDb.get(transactionKey)
    else:
      break
    inc transactionIdx

iterator getBlockTransactions*(self: BaseChainDB, header: BlockHeader): Transaction =
  for encodedTx in self.getBlockTransactionData(header.txRoot):
    yield rlp.decode(encodedTx, Transaction)

iterator getBlockTransactionHashes*(self: BaseChainDB, blockHeader: BlockHeader): Hash256 =
  ## Returns an iterable of the transaction hashes from th block specified
  ## by the given block header.
  for encodedTx in self.getBlockTransactionData(blockHeader.txRoot):
    yield keccakHash(encodedTx)

proc getTransactionCount*(chain: BaseChainDB, txRoot: Hash256): int =
  var trie = initHexaryTrie(chain.db, txRoot)
  var txCount = 0
  while true:
    let txKey = rlp.encode(txCount)
    if txKey notin trie:
      break
    inc txCount
  txCount

proc getUnclesCount*(self: BaseChainDB, ommersHash: Hash256): int =
  if ommersHash != EMPTY_UNCLE_HASH:
    let encodedUncles = self.db.get(genericHashKey(ommersHash).toOpenArray)
    if encodedUncles.len != 0:
      let r = rlpFromBytes(encodedUncles)
      result = r.listLen

proc getUncles*(self: BaseChainDB, ommersHash: Hash256): seq[BlockHeader] =
  if ommersHash != EMPTY_UNCLE_HASH:
    let encodedUncles = self.db.get(genericHashKey(ommersHash).toOpenArray)
    if encodedUncles.len != 0:
      result = rlp.decode(encodedUncles, seq[BlockHeader])

proc getBlockBody*(self: BaseChainDB, header: BlockHeader, output: var BlockBody): bool =
  result = true
  output.transactions = @[]
  output.uncles = @[]
  for encodedTx in self.getBlockTransactionData(header.txRoot):
    output.transactions.add(rlp.decode(encodedTx, Transaction))

  if header.ommersHash != EMPTY_UNCLE_HASH:
    let encodedUncles = self.db.get(genericHashKey(header.ommersHash).toOpenArray)
    if encodedUncles.len != 0:
      output.uncles = rlp.decode(encodedUncles, seq[BlockHeader])
    else:
      result = false

proc getBlockBody*(self: BaseChainDB, blockHash: Hash256, output: var BlockBody): bool =
  var header: BlockHeader
  if self.getBlockHeader(blockHash, header):
    return self.getBlockBody(header, output)

proc getBlockBody*(self: BaseChainDB, hash: Hash256): BlockBody =
  if not self.getBlockBody(hash, result):
    raise newException(ValueError, "Error when retrieving block body")

proc getUncleHashes*(self: BaseChainDB, blockHashes: openArray[Hash256]): seq[Hash256] =
  for blockHash in blockHashes:
    var blockBody = self.getBlockBody(blockHash)
    for uncle in blockBody.uncles:
      result.add uncle.hash

proc getUncleHashes*(self: BaseChainDB, header: BlockHeader): seq[Hash256] =
  if header.ommersHash != EMPTY_UNCLE_HASH:
    let encodedUncles = self.db.get(genericHashKey(header.ommersHash).toOpenArray)
    if encodedUncles.len != 0:
      let uncles = rlp.decode(encodedUncles, seq[BlockHeader])
      for x in uncles:
        result.add x.hash

proc getTransactionKey*(self: BaseChainDB, transactionHash: Hash256): tuple[blockNumber: BlockNumber, index: int] {.inline.} =
  let tx = self.db.get(transactionHashToBlockKey(transactionHash).toOpenArray)

  if tx.len > 0:
    let key = rlp.decode(tx, TransactionKey)
    result = (key.blockNumber, key.index)
  else:
    result = (0.toBlockNumber, -1)

proc removeTransactionFromCanonicalChain(self: BaseChainDB, transactionHash: Hash256) {.inline.} =
  ## Removes the transaction specified by the given hash from the canonical chain.
  self.db.del(transactionHashToBlockKey(transactionHash).toOpenArray)

proc setAsCanonicalChainHead(self: BaseChainDB; headerHash: Hash256): seq[BlockHeader] =
  ##         Sets the header as the canonical chain HEAD.
  let header = self.getBlockHeader(headerHash)

  var newCanonicalHeaders = sequtils.toSeq(findNewAncestors(self, header))
  reverse(newCanonicalHeaders)
  for h in newCanonicalHeaders:
    var oldHash: Hash256
    if not self.getBlockHash(h.blockNumber, oldHash):
      break

    let oldHeader = self.getBlockHeader(oldHash)
    for txHash in self.getBlockTransactionHashes(oldHeader):
      self.removeTransactionFromCanonicalChain(txHash)
      # TODO re-add txn to internal pending pool (only if local sender)

  for h in newCanonicalHeaders:
    self.addBlockNumberToHashLookup(h)

  self.db.put(canonicalHeadHashKey().toOpenArray, rlp.encode(headerHash))

  return newCanonicalHeaders

proc headerExists*(self: BaseChainDB; blockHash: Hash256): bool =
  ## Returns True if the header with the given block hash is in our DB.
  self.db.contains(genericHashKey(blockHash).toOpenArray)

proc markCanonicalChain(self: BaseChainDB, header: BlockHeader, headerHash: Hash256): bool =
  ## mark this chain as canonical by adding block number to hash lookup
  ## down to forking point
  var
    currHash = headerHash
    currHeader = header

  # mark current header as canonical
  let key = blockNumberToHashKey(currHeader.blockNumber)
  self.db.put(key.toOpenArray, rlp.encode(currHash))

  # it is a genesis block, done
  if currHeader.parentHash == Hash256():
    return true

  # mark ancestor blocks as canonical too
  currHash = currHeader.parentHash
  if not self.getBlockHeader(currHeader.parentHash, currHeader):
    return false

  while currHash != Hash256():
    let key = blockNumberToHashKey(currHeader.blockNumber)
    let data = self.db.get(key.toOpenArray)
    if data.len == 0:
      # not marked, mark it
      self.db.put(key.toOpenArray, rlp.encode(currHash))
    elif rlp.decode(data, Hash256) != currHash:
      # replace prev chain
      self.db.put(key.toOpenArray, rlp.encode(currHash))
    else:
      # forking point, done
      break

    if currHeader.parentHash == Hash256():
      break

    currHash = currHeader.parentHash
    if not self.getBlockHeader(currHeader.parentHash, currHeader):
      return false

  return true

proc setHead*(self: BaseChainDB, blockHash: Hash256): bool =
  var header: BlockHeader
  if not self.getBlockHeader(blockHash, header):
    return false

  if not self.markCanonicalChain(header, blockHash):
    return false

  self.db.put(canonicalHeadHashKey().toOpenArray, rlp.encode(blockHash))
  return true

proc setHead*(self: BaseChainDB, header: BlockHeader, writeHeader = false): bool =
  var headerHash = rlpHash(header)
  if writeHeader:
    self.db.put(genericHashKey(headerHash).toOpenArray, rlp.encode(header))
  if not self.markCanonicalChain(header, headerHash):
    return false
  self.db.put(canonicalHeadHashKey().toOpenArray, rlp.encode(headerHash))
  return true

proc persistReceipts*(self: BaseChainDB, receipts: openArray[Receipt]): Hash256 =
  var trie = initHexaryTrie(self.db)
  for idx, rec in receipts:
    trie.put(rlp.encode(idx), rlp.encode(rec))
  trie.rootHash

iterator getReceipts*(self: BaseChainDB; receiptRoot: Hash256): Receipt =
  var receiptDb = initHexaryTrie(self.db, receiptRoot)
  var receiptIdx = 0
  while true:
    let receiptKey = rlp.encode(receiptIdx)
    if receiptKey in receiptDb:
      let receiptData = receiptDb.get(receiptKey)
      yield rlp.decode(receiptData, Receipt)
    else:
      break
    inc receiptIdx

proc getReceipts*(self: BaseChainDB; receiptRoot: Hash256): seq[Receipt] =
  var receipts = newSeq[Receipt]()
  for r in self.getReceipts(receiptRoot):
    receipts.add(r)
  return receipts

proc readTerminalHash*(self: BaseChainDB; h: var Hash256): bool =
  let bytes = self.db.get(terminalHashKey().toOpenArray)
  if bytes.len == 0:
    return false
  try:
    h = rlp.decode(bytes, Hash256)
  except RlpError:
    return false

  true

proc writeTerminalHash*(self: BaseChainDB; h: Hash256) =
  self.db.put(terminalHashKey().toOpenArray, rlp.encode(h))

proc currentTerminalHeader*(self: BaseChainDB; header: var BlockHeader): bool =
  var terminalHash: Hash256
  if not self.readTerminalHash(terminalHash):
    return false
  if not self.getBlockHeader(terminalHash, header):
    return false
  true

proc persistHeaderToDb*(self: BaseChainDB; header: BlockHeader): seq[BlockHeader] =
  let isGenesis = header.parentHash == GENESIS_PARENT_HASH
  let headerHash = header.blockHash
  if not isGenesis and not self.headerExists(header.parentHash):
    raise newException(ParentNotFound, "Cannot persist block header " &
        $headerHash & " with unknown parent " & $header.parentHash)
  self.db.put(genericHashKey(headerHash).toOpenArray, rlp.encode(header))

  let score = if isGenesis: header.difficulty
              else: self.getScore(header.parentHash) + header.difficulty
  self.db.put(blockHashToScoreKey(headerHash).toOpenArray, rlp.encode(score))

  self.addBlockNumberToHashLookup(header)

  var headScore: UInt256
  try:
    headScore = self.getScore(self.getCanonicalHead().hash)
  except CanonicalHeadNotFound:
    return self.setAsCanonicalChainHead(headerHash)

  let ttd = self.ttd()
  if headScore < ttd and score >= ttd:
    self.writeTerminalHash(headerHash)

  if score > headScore or score >= ttd:
    result = self.setAsCanonicalChainHead(headerHash)

proc persistHeaderToDbWithoutSetHead*(self: BaseChainDB; header: BlockHeader) =
  let isGenesis = header.parentHash == GENESIS_PARENT_HASH
  let headerHash = header.blockHash
  let score = if isGenesis: header.difficulty
              else: self.getScore(header.parentHash) + header.difficulty

  self.db.put(blockHashToScoreKey(headerHash).toOpenArray, rlp.encode(score))
  self.db.put(genericHashKey(headerHash).toOpenArray, rlp.encode(header))

proc persistUncles*(self: BaseChainDB, uncles: openArray[BlockHeader]): Hash256 =
  ## Persists the list of uncles to the database.
  ## Returns the uncles hash.
  let enc = rlp.encode(uncles)
  result = keccakHash(enc)
  self.db.put(genericHashKey(result).toOpenArray, enc)

proc safeHeaderHash*(self: BaseChainDB): Hash256 =
  discard self.getHash(safeHashKey(), result)

proc safeHeaderHash*(self: BaseChainDB, headerHash: Hash256) =
  self.db.put(safeHashKey().toOpenArray, rlp.encode(headerHash))

proc finalizedHeaderHash*(self: BaseChainDB): Hash256 =
  discard self.getHash(finalizedHashKey(), result)

proc finalizedHeaderHash*(self: BaseChainDB, headerHash: Hash256) =
  self.db.put(finalizedHashKey().toOpenArray, rlp.encode(headerHash))

proc safeHeader*(self: BaseChainDB): BlockHeader =
  self.getBlockHeader(self.safeHeaderHash)

proc finalizedHeader*(self: BaseChainDB): BlockHeader =
  self.getBlockHeader(self.finalizedHeaderHash)

proc haveBlockAndState*(self: BaseChainDB, headerHash: Hash256): bool =
  var header: BlockHeader
  if not self.getBlockHeader(headerHash, header):
    return false
  # see if stateRoot exists
  self.exists(header.stateRoot)