r"""
Functions that perform input/output. This forms a layer between the
executable itself and the more libraryish modules.
"""
from subprocess import Popen, PIPE
from typing import TextIO
from djbdns.dnscache import handle_dnscache_log
from djbdns.tinydns import handle_tinydns_log

def parse_logfile(file : TextIO):
    r"""
    Process a single log ``file``.

    Parameters
    ----------

    file : typing.TextIO
        An open log file, or stdin.

    Examples
    --------

        >>> line = "@4000000063227a320c4f3114 7f000001:9d61:be69 - 0001 www.example.com\n"
        >>> from tempfile import NamedTemporaryFile
        >>> with NamedTemporaryFile(mode="w", delete=False) as f:
        ...     _ = f.write(line)
        >>> from os import environ
        >>> environ["TZ"] = "UTC+4"
        >>> f = open(f.name, 'r')
        >>> parse_logfile(f)
        2022-09-14 21:04:40.206516500 dropped query (no authority) from 127.0.0.1:40289 (id 48745): a www.example.com
        >>> f.close()
        >>> from os import remove
        >>> remove(f.name)

    """
    # Open a pipe to tai64nlocal. We'll write lines of our input file
    # (the log file) to it, and read back the same lines but with
    # friendly timestamps in them.
    with Popen(["tai64nlocal"],
               stdin=PIPE,
               stdout=PIPE,
               text=True,
               bufsize=0) as tai:

        if not tai.stdin or not tai.stdout:
            # Mypy tells me that this can happen, based on the type
            # annotations in the standard library I guess?
            return

        for line in file:
            tai.stdin.write(line)
            line = tai.stdout.readline()

            friendly_line = handle_tinydns_log(line)
            if not friendly_line:
                friendly_line = handle_dnscache_log(line)
                if not friendly_line:
                    friendly_line = line

            try:
                print(friendly_line)
            except BrokenPipeError:
                # If our stdout is being piped to another process and if
                # that process closes the pipe, this error will be raised
                # the next time we try to write to stdout.
                break