#!/usr/bin/python -utWall

import readline, sys, os

def my_input(prompt, default=None, completions=None):
    if default is not None:
        def pre_input_hook():
            readline.insert_text(str(default))
            readline.redisplay()
        readline.set_pre_input_hook(pre_input_hook)

    if completions:
        def complete(text, state):
            if state == 0:
                line = readline.get_line_buffer()
                begidx = readline.get_begidx()
                endidx = readline.get_endidx()
                val[:] = completions(text, line, begidx, endidx)
            return val[state]

        old_completer = readline.get_completer()
        readline.set_completer(complete)
        val = []

    return raw_input(prompt)

def get_label(filename):
    header = 'X-Label: '
    fp = file(filename, 'r')
    result = ''
    for line in fp.readlines():
        if line.startswith(header):
            result = line[len(header):].strip()
            break
    fp.close()
    return result

def write_label(filename, label):
    header = ['X-Label:']
    tmpfile = filename + '.tmp'
    if label:
        header.append(' ')
        header.append(label)
    header = '"%s"' % ((''.join(header)).replace('"', '\"'))
    cmd = ' '.join([ 'formail',
                     '-I',
                     header,
                     '<',
                     filename,
                     '>',
                     tmpfile,
                     '&&',
                     'mv',
                     tmpfile,
                     filename
                     ])
    os.system(cmd)

if "__main__" == __name__:
    infile = sys.argv[1]
    histfile = os.path.join(os.environ["HOME"], ".mutt/.label_history")

    if hasattr(readline, 'read_history_file'):
        try:
            readline.read_history_file(histfile)
        except IOError:
            pass

    label = get_label(infile)
    new_label = my_input('Label: ', label)

    if new_label != label:
        write_label(infile, new_label)
    readline.write_history_file(histfile)