#!/usr/bin/env python

import re

from circuits.io import File
from circuits import Event, Component

SEEK_END = 2

LINESEP = re.compile("\r?\n")

def splitLines(s, buffer):
    lines = LINESEP.split(buffer + s)
    return lines[:-1], lines[-1]

class Follow(Component):

    def __init__(self, filename):
        super(Follow, self).__init__()
        fd = File(filename, "r")
        fd.seek(0, SEEK_END)
        fd.register(self)

class LineBuffer(Component):

    def __init__(self):
        super(LineBuffer, self).__init__()
        self._data = ""

    def read(self, data):
        lines, self._data = splitLines(data, self._data)
        for line in lines:
            self.push(Event(line), "line", self.channel)

class Grep(Component):

    def __init__(self, pattern):
        super(Grep, self).__init__()
        self._pattern = pattern

    def line(self, line):
        if self._pattern in line:
            print line

(Follow("/tmp/foo") + LineBuffer() + Grep("pants")).run()