peasy/coffee/samples/statemachine.coffee

an easy but powerful parser

hasOwnProperty = Object.hasOwnProperty

exports.StateMachine =  class StateMachine
  constructor: (items=[]) ->
    @index = 1
    @stateMap = {}
    @stateMap[0] = {}
    @tagMap = {}
    for item in items then @add(item[0], item[1] or item[0])

  add: (word, tag=word) ->
    length = word.length
    state = 0
    i = 0
    stateMap = @stateMap
    while i<length-1
      c = word[i++]
      if hasOwnProperty.call(stateMap[state], c)
        state = stateMap[state][c]
        if state < 0 then state = -state
      else
        newState = @index++
        stateMap[state][c] = newState
        stateMap[newState] = {}
        state = newState
    c = word[i]
    if hasOwnProperty.call(stateMap[state], c)
      s = stateMap[state][c]
      if s>0
        stateMap[state][c] = -s
        @tagMap[s] = tag
    else
      newState = @index++
      stateMap[state][c] = -newState
      stateMap[newState] = {}
      @tagMap[newState] = tag

  match: (text, i=0) ->
    state = 0
    length = text.length
    stateMap = @stateMap
    while i<length
      state = stateMap[state][text[i++]]
      if state is undefined then i--; break
      else if state<0 then state = -state; succeedState = state; cursor = i
    if succeedState then return [@tagMap[succeedState], cursor]
    else return [null, i]