#!/usr/bin/env python

import sys
import json

class I3statusHandler:
    modules = []

    def __init__(self):
        pass

    def register_module(self, module):
        """ Register a new module. """

        # check if module implemented the 
        # correct functions
        if not hasattr(module, 'output'):
            raise Exception("Module %s does not implement \
                all the needed functions!".format(module))

        self.modules.append(module)

    def print_line(self, message):
        """ Non-buffered printing to stdout. """

        sys.stdout.write(message + '\n')
        sys.stdout.flush()

    def read_line(self):
        """ Interrupted respecting reader for stdin. """

        # try reading a line, removing any extra whitespace
        try:
            line = sys.stdin.readline().strip()
            # i3status sends EOF, or an empty line
            if not line:
                sys.exit(3)
            return line
        # exit on ctrl-c
        except KeyboardInterrupt:
            sys.exit()

    def run(self):
        self.print_line(self.read_line())
        self.print_line(self.read_line())

        while True:
            line, prefix = self.read_line(), ''

            # ignore comma at start of lines
            if line.startswith(','):
                line, prefix = line[1:], ','

            j = json.loads(line)

            for module in self.modules:
                output = module.output()

                if output:
                    j.insert(0, module.output())

            # and echo back new encoded json
            self.print_line(prefix+json.dumps(j))