{Mark, YAMLError} = require './errors'

class @ReaderError extends YAMLError
  constructor: (@position, @character, @reason) ->
    super()

  toString: ->
    """
    unacceptable character ##{@character.charCodeAt(0).toString 16}: #{@reason}
      position #{@position}
    """

###
Reader:
  checks if characters are within the allowed range
  add '\x00' to the end
###
class @Reader
  NON_PRINTABLE = ///
    [^\x09\x0A\x0D\x20-\x7E\x85\xA0-\uFFFD] # Invalid single characters
  | [\uD800-\uDBFF](?![\uDC00-\uDFFF])      # Missing or invalid low surrogate
  | (?:[^\uD800-\uDBFF]|^)[\uDC00-\uDFFF]   # Missing or invalid high surrogate
  ///

  constructor: @::initialise

  initialise: (@string) ->
    @line = 0
    @column = 0
    @index = 0

    @check_printable()
    @string += '\x00'

  peek: (index = 0) -> @string[@index + index]

  prefix: (length = 1) -> @string[@index...@index + length]

  forward: (length = 1) ->
    while length
      char = @string[@index]
      @index++
      if char in '\n\x85\u2082\u2029' \
          or (char == '\r' and @string[@index] != '\n')
        @line++
        @column = 0
      else
        @column++
      length--

  get_mark: ->
    new Mark @line, @column, @string, @index

  check_printable: ->
    match = NON_PRINTABLE.exec @string
    if match
      character = match[0]
      position  = (@string.length - @index) + match.index
      throw new exports.ReaderError position, character, 'special characters are not allowed'