baseTrie.js

const assert = require('assert')
const levelup = require('levelup')
const memdown = require('memdown')
const async = require('async')
const rlp = require('rlp')
const ethUtil = require('ethereumjs-util')
const semaphore = require('semaphore')
const TrieNode = require('./trieNode')
const ReadStream = require('./readStream')
const matchingNibbleLength = require('./util').matchingNibbleLength
const doKeysMatch = require('./util').doKeysMatch
const callTogether = require('./util').callTogether
const asyncFirstSeries = require('./util').asyncFirstSeries

module.exports = Trie

/**
 * Use `require('merkel-patricia-tree')` for the base interface. In Ethereum applications stick with the Secure Trie Overlay `require('merkel-patricia-tree/secure')`. The API for the raw and the secure interface are about the same
 * @class Trie
 * @param {Object} [db] An instance of [levelup](https://github.com/rvagg/node-levelup/) or a compatible API. If the db is `null` or left undefined, then the trie will be stored in memory via [memdown](https://github.com/rvagg/memdown)
 * @param {Buffer|String} [root]` A hex `String` or `Buffer` for the root of a previously stored trie
 * @prop {Buffer} root The current root of the `trie`
 * @prop {Boolean} isCheckpoint  determines if you are saving to a checkpoint or directly to the db
 * @prop {Buffer} EMPTY_TRIE_ROOT the Root for an empty trie
 */
function Trie (db, root) {
  var self = this
  this.EMPTY_TRIE_ROOT = ethUtil.SHA3_RLP
  this.sem = semaphore(1)

  // setup dbs
  this.db = db ||
    levelup('', {
      db: memdown
    })

  this._getDBs = [this.db]
  this._putDBs = [this.db]

  Object.defineProperty(this, 'root', {
    set: function (value) {
      if (value) {
        value = ethUtil.toBuffer(value)
        assert(value.length === 32, 'Invalid root length. Roots are 32 bytes')
      } else {
        value = self.EMPTY_TRIE_ROOT
      }

      this._root = value
    },
    get: function () {
      return this._root
    }
  })

  this.root = root
}

/**
 * Gets a value given a `key`
 * @method get
 * @param {Buffer|String} key - the key to search for
 * @param {Function} cb A callback `Function` which is given the arguments `err` - for errors that may have occured and `value` - the found value in a `Buffer` or if no value was found `null`
 */
Trie.prototype.get = function (key, cb) {
  var self = this

  key = ethUtil.toBuffer(key)

  self._findPath(key, function (err, node, remainder, stack) {
    var value = null
    if (node && remainder.length === 0) {
      value = node.value
    }

    cb(err, value)
  })
}

/**
 * Stores a given `value` at the given `key`
 * @method put
 * @param {Buffer|String} key
 * @param {Buffer|String} Value
 * @param {Function} cb A callback `Function` which is given the argument `err` - for errors that may have occured
 */
Trie.prototype.put = function (key, value, cb) {
  var self = this

  key = ethUtil.toBuffer(key)
  value = ethUtil.toBuffer(value)

  if (!value || value.toString() === '') {
    self.del(key, cb)
  } else {
    cb = callTogether(cb, self.sem.leave)

    self.sem.take(function () {
      if (self.root.toString('hex') !== ethUtil.SHA3_RLP.toString('hex')) {
        // first try to find the give key or its nearst node
        self._findPath(key, function (err, foundValue, keyRemainder, stack) {
          if (err) {
            return cb(err)
          }
          // then update
          self._updateNode(key, value, keyRemainder, stack, cb)
        })
      } else {
        self._createInitialNode(key, value, cb) // if no root initialize this trie
      }
    })
  }
}

/**
 * deletes a value given a `key`
 * @method del
 * @param {Buffer|String} key
 * @param {Function} callback the callback `Function`
 */
Trie.prototype.del = function (key, cb) {
  var self = this

  key = ethUtil.toBuffer(key)
  cb = callTogether(cb, self.sem.leave)

  self.sem.take(function () {
    self._findPath(key, function (err, foundValue, keyRemainder, stack) {
      if (err) {
        return cb(err)
      }
      if (foundValue) {
        self._deleteNode(key, stack, cb)
      } else {
        cb()
      }
    })
  })
}

/**
 * Retrieves a raw value in the underlying db
 * @method getRaw
 * @param {Buffer} key
 * @param {Function} callback A callback `Function`, which is given the arguments `err` - for errors that may have occured and `value` - the found value in a `Buffer` or if no value was found `null`.
 */
Trie.prototype.getRaw = function (key, cb) {
  key = ethUtil.toBuffer(key)

  function dbGet (db, cb2) {
    db.get(key, {
      keyEncoding: 'binary',
      valueEncoding: 'binary'
    }, function (err, foundNode) {
      if (err || !foundNode) {
        cb2(null, null)
      } else {
        cb2(null, foundNode)
      }
    })
  }
  asyncFirstSeries(this._getDBs, dbGet, cb)
}

// retrieves a node from dbs by hash
Trie.prototype._lookupNode = function (node, cb) {
  if (TrieNode.isRawNode(node)) {
    cb(new TrieNode(node))
  } else {
    this.getRaw(node, function (err, value) {
      if (err) {
        throw err
      }

      if (value) {
        value = new TrieNode(rlp.decode(value))
      }

      cb(value)
    })
  }
}

// TODO: remove the proxy method when changing the caching
Trie.prototype._putRaw = function (key, val, cb) {
  function dbPut (db, cb2) {
    db.put(key, val, {
      keyEncoding: 'binary',
      valueEncoding: 'binary'
    }, cb2)
  }
  async.each(this._putDBs, dbPut, cb)
}

/**
 * Writes a value directly to the underlining db
 * @method putRaw
 * @param {Buffer|String} key The key as a `Buffer` or `String`
 * @param {Buffer} value The value to be stored
 * @param {Function} callback A callback `Function`, which is given the argument `err` - for errors that may have occured
 */
Trie.prototype.putRaw = Trie.prototype._putRaw

/**
 * Removes a raw value in the underlying db
 * @method delRaw
 * @param {Buffer|String} key
 * @param {Function} callback A callback `Function`, which is given the argument `err` - for errors that may have occured
 */
Trie.prototype.delRaw = function (key, cb) {
  function del (db, cb2) {
    db.del(key, {
      keyEncoding: 'binary'
    }, cb2)
  }
  async.each(this._putDBs, del, cb)
}

// writes a single node to dbs
Trie.prototype._putNode = function (node, cb) {
  var hash = node.hash()
  var serialized = node.serialize()
  this._putRaw(hash, serialized, cb)
}

// writes many nodes to db
Trie.prototype._batchNodes = function (opStack, cb) {
  function dbBatch (db, cb) {
    db.batch(opStack, {
      keyEncoding: 'binary',
      valueEncoding: 'binary'
    }, cb)
  }

  async.each(this._putDBs, dbBatch, cb)
}

/**
 * Trys to find a path to the node for the given key
 * It returns a `stack` of nodes to the closet node
 * @method _findPath
 * @param {String|Buffer} - key - the search key
 * @param {Function} - cb - the callback function. Its is given the following
 * arguments
 *  - err - any errors encontered
 *  - node - the last node found
 *  - keyRemainder - the remaining key nibbles not accounted for
 *  - stack - an array of nodes that forms the path to node we are searching for
 */

Trie.prototype._findPath = function (targetKey, cb) {
  var self = this
  var root = self.root
  var stack = []
  targetKey = TrieNode.stringToNibbles(targetKey)

  this._walkTrie(root, processNode, cb)

  function processNode (root, node, keyProgress, walkController) {
    var nodeKey = node.key || []
    var keyRemainder = targetKey.slice(matchingNibbleLength(keyProgress, targetKey))
    var matchingLen = matchingNibbleLength(keyRemainder, nodeKey)

    stack.push(node)

    if (node.type === 'branch') {
      if (keyRemainder.length === 0) {
        walkController.return(null, node, [], stack)
      // we exhausted the key without finding a node
      } else {
        var branchIndex = keyRemainder[0]
        var branchNode = node.getValue(branchIndex)
        if (!branchNode) {
          // there are no more nodes to find and we didn't find the key
          walkController.return(null, null, keyRemainder, stack)
        } else {
          // node found, continuing search
          walkController.only(branchIndex)
        }
      }
    } else if (node.type === 'leaf') {
      if (doKeysMatch(keyRemainder, nodeKey)) {
        // keys match, return node with empty key
        walkController.return(null, node, [], stack)
      } else {
        // reached leaf but keys dont match
        walkController.return(null, null, keyRemainder, stack)
      }
    } else if (node.type === 'extention') {
      if (matchingLen !== nodeKey.length) {
        // keys dont match, fail
        walkController.return(null, null, keyRemainder, stack)
      } else {
        // keys match, continue search
        walkController.next()
      }
    }
  }
}

/*
 * Finds all nodes that store k,v values
 */
Trie.prototype._findNode = function (key, root, stack, cb) {
  this._findPath(key, function () {
    cb.apply(null, arguments)
  })
}

/*
 * Finds all nodes that store k,v values
 */
Trie.prototype._findValueNodes = function (onFound, cb) {
  this._walkTrie(this.root, function (root, node, key, walkController) {
    var fullKey = key

    if (node.key) {
      fullKey = key.concat(node.key)
    }

    if (node.type === 'leaf') {
      // found leaf node!
      onFound(root, node, fullKey, walkController.next)
    } else if (node.type === 'branch' && node.value) {
      // found branch with value
      onFound(root, node, fullKey, walkController.next)
    } else {
      // keep looking for value nodes
      walkController.next()
    }
  }, cb)
}

/*
 * Finds all nodes that are stored directly in the db
 * (some nodes are stored raw inside other nodes)
 */
Trie.prototype._findDbNodes = function (onFound, cb) {
  this._walkTrie(this.root, function (root, node, key, walkController) {
    if (TrieNode.isRawNode(root)) {
      walkController.next()
    } else {
      onFound(root, node, key, walkController.next)
    }
  }, cb)
}

/**
 * Updates a node
 * @method _updateNode
 * @param {Buffer} key
 * @param {Buffer| String} value
 * @param {Array} keyRemainder
 * @param {Array} stack -
 * @param {Function} cb - the callback
 */
Trie.prototype._updateNode = function (key, value, keyRemainder, stack, cb) {
  var toSave = []
  var lastNode = stack.pop()

  // add the new nodes
  key = TrieNode.stringToNibbles(key)
  if (lastNode.type === 'branch') {
    stack.push(lastNode)
    if (keyRemainder !== 0) {
      // add an extention to a branch node
      keyRemainder.shift()
      // create a new leaf
      var newLeaf = new TrieNode('leaf', keyRemainder, value)
      stack.push(newLeaf)
    } else {
      lastNode.value = value
    }
  } else if (lastNode.type === 'leaf' && keyRemainder.length === 0) {
    // just updating a found value
    lastNode.value = value
    stack.push(lastNode)
  } else {
    // create a branch node
    var lastKey = lastNode.key
    var matchingLength = matchingNibbleLength(lastKey, keyRemainder)
    var newBranchNode = new TrieNode('branch')

    // create a new extention node
    if (matchingLength !== 0) {
      var newKey = lastNode.key.slice(0, matchingLength)
      var newExtNode = new TrieNode('extention', newKey, value)
      stack.push(newExtNode)
      lastKey.splice(0, matchingLength)
      keyRemainder.splice(0, matchingLength)
    }

    stack.push(newBranchNode)

    if (lastKey.length !== 0) {
      var branchKey = lastKey.shift()
      if (lastKey.length !== 0 || lastNode.type === 'leaf') {
        // shriking extention or leaf
        lastNode.key = lastKey
        var formatedNode = this._formatNode(lastNode, false, toSave)
        newBranchNode.setValue(branchKey, formatedNode)
      } else {
        // remove extention or attaching
        this._formatNode(lastNode, false, true, toSave)
        newBranchNode.setValue(branchKey, lastNode.value)
      }
    } else {
      newBranchNode.value = lastNode.value
    }

    if (keyRemainder.length !== 0) {
      keyRemainder.shift()
      // add a leaf node to the new branch node
      var newLeafNode = new TrieNode('leaf', keyRemainder, value)
      stack.push(newLeafNode)
    } else {
      newBranchNode.value = value
    }
  }

  this._saveStack(key, stack, toSave, cb)
}

// walk tree

Trie.prototype._walkTrie = function (root, onNode, onDone) {
  var self = this
  root = root || self.root
  onDone = onDone || function () {}
  var aborted = false
  var returnValues = []

  if (root.toString('hex') === ethUtil.SHA3_RLP.toString('hex')) {
    return onDone()
  }

  self._lookupNode(root, function (node) {
    processNode(root, node, null, function (err) {
      if (err) {
        return onDone(err)
      }
      onDone.apply(null, returnValues)
    })
  })

  function processNode (root, node, key, cb) {
    if (!node) return cb()
    if (aborted) return cb()
    var stopped = false
    key = key || []

    var walkController = {
      stop: function () {
        stopped = true
        cb()
      },
      // end all traversal and return values to the onDone cb
      return: function () {
        aborted = true
        returnValues = arguments
        cb()
      },
      next: function () {
        if (aborted) {
          return cb()
        }
        if (stopped) {
          return cb()
        }
        var children = node.getChildren()
        async.forEachOf(children, function (data, index, cb) {
          var keyExtension = data[0]
          var childRoot = data[1]
          var childKey = key.concat(keyExtension)
          self._lookupNode(childRoot, function (node) {
            processNode(childRoot, node, childKey, cb)
          })
        }, cb)
      },
      only: function (childIndex) {
        var childRoot = node.getValue(childIndex)
        self._lookupNode(childRoot, function (node) {
          var childKey = key.slice()
          childKey.push(childIndex)
          processNode(childRoot, node, childKey, cb)
        })
      }
    }
    onNode(root, node, key, walkController)
  }
}

/**
 * saves a stack
 * @method _saveStack
 * @param {Array} key - the key. Should follow the stack
 * @param {Array} stack - a stack of nodes to the value given by the key
 * @param {Array} opStack - a stack of levelup operations to commit at the end of this funciton
 * @param {Function} cb
 */
Trie.prototype._saveStack = function (key, stack, opStack, cb) {
  var lastRoot

  // update nodes
  while (stack.length) {
    var node = stack.pop()
    if (node.type === 'leaf') {
      key.splice(key.length - node.key.length)
    } else if (node.type === 'extention') {
      key.splice(key.length - node.key.length)
      if (lastRoot) {
        node.value = lastRoot
      }
    } else if (node.type === 'branch') {
      if (lastRoot) {
        var branchKey = key.pop()
        node.setValue(branchKey, lastRoot)
      }
    }
    lastRoot = this._formatNode(node, stack.length === 0, opStack)
  }

  if (lastRoot) {
    this.root = lastRoot
  }

  this._batchNodes(opStack, cb)
}

Trie.prototype._deleteNode = function (key, stack, cb) {
  function processBranchNode (key, branchKey, branchNode, parentNode, stack) {
    // branchNode is the node ON the branch node not THE branch node
    var branchNodeKey = branchNode.key
    if (!parentNode || parentNode.type === 'branch') {
      // branch->?
      if (parentNode) {
        stack.push(parentNode)
      }

      if (branchNode.type === 'branch') {
        // create an extention node
        // branch->extention->branch
        var extentionNode = new TrieNode('extention', [branchKey], null)
        stack.push(extentionNode)
        key.push(branchKey)
      } else {
        // branch key is an extention or a leaf
        // branch->(leaf or extention)
        branchNodeKey.unshift(branchKey)
        branchNode.key = branchNodeKey

        // hackery. This is equvilant to array.concat except we need keep the
        // rerfance to the `key` that was passed in.
        branchNodeKey.unshift(0)
        branchNodeKey.unshift(key.length)
        key.splice.apply(key, branchNodeKey)
      }
      stack.push(branchNode)
    } else {
      // parent is a extention
      var parentKey = parentNode.key
      if (branchNode.type === 'branch') {
        // ext->branch
        parentKey.push(branchKey)
        key.push(branchKey)
        parentNode.key = parentKey
        stack.push(parentNode)
      } else {
        // branch node is an leaf or extention and parent node is an exstention
        // add two keys together
        // dont push the parent node
        branchNodeKey.unshift(branchKey)
        key = key.concat(branchNodeKey)
        parentKey = parentKey.concat(branchNodeKey)
        branchNode.key = parentKey
      }
      stack.push(branchNode)
    }

    return key
  }

  var lastNode = stack.pop()
  var parentNode = stack.pop()
  var opStack = []
  var self = this

  if (!Array.isArray(key)) {
    // convert key to nibbles
    key = TrieNode.stringToNibbles(key)
  }

  if (!parentNode) {
    // the root here has to be a leaf.
    this.root = this.EMPTY_TRIE_ROOT
    cb()
  } else {
    if (lastNode.type === 'branch') {
      lastNode.value = null
    } else {
      // the lastNode has to be a leaf if its not a branch. And a leaf's parent
      // if it has one must be a branch.
      var lastNodeKey = lastNode.key
      key.splice(key.length - lastNodeKey.length)
      // delete the value
      this._formatNode(lastNode, false, true, opStack)
      parentNode.setValue(key.pop(), null)
      lastNode = parentNode
      parentNode = stack.pop()
    }

    // nodes on the branch
    var branchNodes = []
    // count the number of nodes on the branch
    lastNode.raw.forEach(function (node, i) {
      var val = lastNode.getValue(i)
      if (val) branchNodes.push([i, val])
    })

    // if there is only one branch node left, collapse the branch node
    if (branchNodes.length === 1) {
      // add the one remaing branch node to node above it
      var branchNode = branchNodes[0][1]
      var branchNodeKey = branchNodes[0][0]

      // look up node
      this._lookupNode(branchNode, function (foundNode) {
        key = processBranchNode(key, branchNodeKey, foundNode, parentNode, stack, opStack)
        self._saveStack(key, stack, opStack, cb)
      })
    } else {
      // simple removing a leaf and recaluclation the stack
      if (parentNode) {
        stack.push(parentNode)
      }

      stack.push(lastNode)
      self._saveStack(key, stack, opStack, cb)
    }
  }
}

// Creates the initial node from an empty tree
Trie.prototype._createInitialNode = function (key, value, cb) {
  var newNode = new TrieNode('leaf', key, value)
  this.root = newNode.hash()
  this._putNode(newNode, cb)
}

// formats node to be saved by levelup.batch.
// returns either the hash that will be used key or the rawNode
Trie.prototype._formatNode = function (node, topLevel, remove, opStack) {
  if (arguments.length === 3) {
    opStack = remove
    remove = false
  }

  var rlpNode = node.serialize()
  if (rlpNode.length >= 32 || topLevel) {
    var hashRoot = node.hash()

    if (remove && this.isCheckpoint) {
      opStack.push({
        type: 'del',
        key: hashRoot
      })
    } else {
      opStack.push({
        type: 'put',
        key: hashRoot,
        value: rlpNode
      })
    }
    return hashRoot
  }
  return node.raw
}

/**
 * The `data` event is given an `Object` hat has two properties; the `key` and the `value`. Both should be Buffers.
 * @method createReadStream
 * @return {stream.Readable} Returns a [stream](https://nodejs.org/dist/latest-v5.x/docs/api/stream.html#stream_class_stream_readable) of the contents of the `trie`
 */
Trie.prototype.createReadStream = function () {
  return new ReadStream(this)
}

// creates a new trie backed by the same db
// and starting at the same root
Trie.prototype.copy = function () {
  return new Trie(this.db, this.root)
}

/**
 * The given hash of operations (key additions or deletions) are executed on the DB
 * @method batch
 * @example
 * var ops = [
 *    { type: 'del', key: 'father' }
 *  , { type: 'put', key: 'name', value: 'Yuri Irsenovich Kim' }
 *  , { type: 'put', key: 'dob', value: '16 February 1941' }
 *  , { type: 'put', key: 'spouse', value: 'Kim Young-sook' }
 *  , { type: 'put', key: 'occupation', value: 'Clown' }
 * ]
 * trie.batch(ops)
 * @param {Array} ops
 * @param {Function} cb
 */
Trie.prototype.batch = function (ops, cb) {
  var self = this

  async.eachSeries(ops, function (op, cb2) {
    if (op.type === 'put') {
      self.put(op.key, op.value, cb2)
    } else if (op.type === 'del') {
      self.del(op.key, cb2)
    } else {
      cb2()
    }
  }, cb)
}

/**
 * Checks if a given root exists
 * @method checkRoot
 * @param {Buffer} root
 * @param {Function} cb
 */
Trie.prototype.checkRoot = function (root, cb) {
  root = ethUtil.toBuffer(root)
  this._lookupNode(root, function (value) {
    cb(null, !!value)
  })
}