#
# $Id: lineinput.rb 3723 2007-03-28 21:34:13Z aamine $
#
# Copyright (c) 2002-2007 Minero Aoki
#
# This program is free software.
# You can distribute/modify this program under the terms of
# the GNU LGPL, Lesser General Public License version 2.1.
#

require 'stringio'

# Utility class for line-wise file parsing
class LineInput

  def LineInput.for_string(s)
    new(StringIO.new(s))
  end

  def initialize(f)
    @input = f
    @buf = []
    @lineno = 0
    @eof_p = false
  end

  def inspect
    "\#<#{self.class} file=#{@input.inspect} line=#{lineno()}>"
  end

  def eof?
    @eof_p
  end

  def path
    @input.path
  end

  def lineno
    @lineno
  end

  def gets
    unless @buf.empty?
      @lineno += 1
      return @buf.pop
    end
    return nil if @eof_p   # to avoid ARGF blocking.
    line = @input.gets
    @eof_p = true unless line
    @lineno += 1
    line
  end

  def ungets(line)
    return unless line
    @lineno -= 1
    @buf.push line
    line
  end

  def peek
    line = gets()
    ungets line if line
    line
  end

  def next?
    peek() ? true : false
  end

  def skip_blank_lines
    n = 0
    while line = gets()
      unless line.strip.empty?
        ungets line
        return n
      end
      n += 1
    end
    n
  end

  def gets_if(re, index = nil)
    line = gets()
    if not line or not (re =~ line)
      ungets line
      return nil
    end
    return $~[index] if index
    line
  end

  def gets_unless(re)
    line = gets()
    if not line or re =~ line
      ungets line
      return nil
    end
    line
  end

  def each
    while line = gets()
      yield line
    end
  end

  def while_match(re)
    while line = gets()
      unless re =~ line
        ungets line
        return
      end
      yield line
    end
    nil
  end

  def getlines_while(re)
    buf = []
    while_match(re) do |line|
      buf.push line
    end
    buf
  end

  alias span getlines_while   # from Haskell

  def until_match(re)
    while line = gets()
      if re =~ line
        ungets line
        return
      end
      yield line
    end
    nil
  end

  def getlines_until(re)
    buf = []
    until_match(re) do |line|
      buf.push line
    end
    buf
  end

  alias break getlines_until   # from Haskell

  def until_terminator(re)
    while line = gets()
      return if re =~ line   # discard terminal line
      yield line
    end
    nil
  end

  def getblock(term_re)
    buf = []
    until_terminator(term_re) do |line|
      buf.push line
    end
    buf
  end

end