"""
This module is the entrypoint of the `logparse shell command and also contains
single-use functions which don't fit elsewhere. All user interaction with
logparse should be through this module.

This module provides the following methods:
    main        Set up arguments, config, logging, and execute parsers
    rotate      Rotate logs using systemd logrotate
    rotate_sim  Simulate log rotation
"""

import logging, logging.handlers
import argparse
import os
from sys import stdin, version
from subprocess import check_output
from datetime import datetime

import logparse
from logparse import formatting, mail, config, load_parsers


def main():
    """
    Initialisation and general management of logparse functionaliy.
    """

    # Get arguments

    global argparser
    argparser = argparse.ArgumentParser(description='grab logs of some common services and send them by email')
    argparser.add_argument('-t','--to', help='mail recipient (\"to\" address)', required=False)
    argparser.add_argument('-c', '--config', help='path to config file', required=False, default="/etc/logparse/logparse.conf")
    argparser.add_argument('-p', '--print', help='print HTML to stdout', required=False, dest='printout', action='store_true', default=False)
    argparser.add_argument('-d', '--destination', help='file to output HTML', required=False)
    argparser.add_argument('-f', '--overwrite', help='force overwrite an existing output file', required=False, action='store_true', default=False)
    argparser.add_argument('-v', '--verbose', help='verbose console/syslog output (for debugging)', required=False, default=False, action='store_true')
    argparser.add_argument('-r', '--rotate', help='force rotate log files using systemd logrotate (overrides --rotate and "rotate" in logparse.conf)', required=False, default=False, action='store_true')
    argparser.add_argument('-nr', '--no-rotate', help='do not rotate logfiles (overrides --rotate and logparse.conf)', required=False, default=False, action='store_true')
    argparser.add_argument('-s', '--simulate', help="test run logrotate (do not actually change files)", required=False, default=False, action="store_true")
    argparser.add_argument('-l', '--logs', help='services to analyse', required=False)
    argparser.add_argument('-nl', '--ignore-logs', help='skip these services (takes precedence over -l)', required=False)
    argparser.add_argument('-es', '--embed-styles', help='make CSS rules inline rather than linking the file', required=False, default=False, action='store_true')
    argparser.add_argument('-nh', '--plain', help='write/send plain text rather than HTML', required=False, default=False, action='store_true')
    argparser.add_argument('-q', '--quiet', help='no output to stdout', required=False, default=False, action='store_true')
    argparser.add_argument('-nm', '--no-mail', help="do not send email (overrides config file)", required=False, default=False, action="store_true")
    argparser.add_argument('-nw', '--no-write', help="do not write output file (overrides config file)", required=False, default=False, action="store_true")

    # Load config

    config.prefs = config.loadconf(argparser.parse_args().config)
    
    # Set up logging

    logger = logging.getLogger(__name__)
    loghandler = logging.handlers.SysLogHandler(address = '/dev/log')
    loghandler.setFormatter(logging.Formatter(fmt='logparse[' + str(os.getpid()) + ']: %(message)s'))
    loghandler.setLevel(logging.INFO)   # don't spam syslog with debug messages
    if argparser.parse_args().quiet or config.prefs.getboolean("logparse", "quiet"):
        logging.basicConfig(level=logging.CRITICAL)
    elif argparser.parse_args().verbose or config.prefs.getboolean("logparse", "verbose"):
        logging.basicConfig(level=logging.DEBUG)
        logger.debug("Verbose mode turned on")
    else:
        logging.basicConfig(level=logging.INFO)
    logger.addHandler(loghandler)

    # Time analysis

    global start
    start = datetime.now()
    logger.info("Beginning log analysis at {0} {1}".format(start.strftime(formatting.DATEFMT), start.strftime(formatting.TIMEFMT)))
    logger.debug("This is {0} version {1}, running on Python {2}".format(logparse.__name__, logparse.__version__, version.replace('\n', '')))
     
    # Write header

    formatting.init_var()

    if argparser.parse_args().plain:
        output = formatting.PlaintextOutput(linewidth=config.prefs.getint("plain", "linewidth"))
        output.append_header()
    else:
        output = formatting.HtmlOutput()
        output.append_header(config.prefs.get("html", "header"))

    # Find parsers
    
    parser_names = []
    ignore_logs = []
    if argparser.parse_args().logs:
        parser_names = set(argparser.parse_args().logs.split())
    elif config.prefs.get("logparse", "parsers"):
        parser_names = set(config.prefs.get("logparse", "parsers").split())

    if argparser.parse_args().ignore_logs:
        ignore_logs = argparser.parse_args().ignore_logs.split()
    elif config.prefs.get("logparse", "ignore-parsers"):
        ignore_logs = config.prefs.get("logparse", "ignore-parsers").split()

    # Set up parsers

    loader = load_parsers.ParserLoader()
    if parser_names:
        for parser_name in parser_names:
            if parser_name not in ignore_logs:
                loader.search(parser_name)
    else:
        loader.load_pkg()
        if ignore_logs:
            loader.ignore(ignore_logs)

    # Execute parsers

    for parser in loader.parsers:
        output.append_section(parser.parse_log())

    # Write footer

    output.append_footer()

    # Write output

    if (argparser.parse_args().destination or config.prefs.get("logparse", "output")) and not argparser.parse_args().no_write:
        if argparser.parse_args().destination:
            dest_path = argparser.parse_args().destination
        else:
            dest_path = config.prefs.get("logparse", "output")
        logger.debug("Outputting to {0}".format(dest_path))
        if (argparser.parse_args().embed_styles or config.prefs.getboolean("html", "embed-styles")) and not (argparser.parse_args().plain or config.prefs.getboolean("plain", "plain")):
            output.embed_css(config.prefs.get("html", "css"))
        if (not os.path.isfile(dest_path)) and not (argparser.parse_args().overwrite or config.prefs.getboolean("logparse", "overwrite")):
            output.write(dest_path)
        elif logging.root.level == logging.CRITICAL:
            pass
        else:
            logger.warning("Destination file already exists")
            if input("Would you like to overwrite {0}? (y/n) [n] ".format(dest_path)) == 'y':
                output.write(dest_path)
            else:
                logger.warning("No output written")

    # Send email if requested

    if (str(argparser.parse_args().to) or str(config.prefs.get("mail", "to"))) and not argparser.parse_args().no_mail:
        if str(argparser.parse_args().to):
            to = argparser.parse_args().to
        else:
            to = config.prefs.get("mail", "to")
        mail.sendmail(
            mailbin=config.prefs.get("mail", "mailbin"),
            body=(output.embed_css(config.prefs.get("html", "css")) if isinstance(output, formatting.HtmlOutput) else output.content),
            recipient=to,
            subject=formatting.fsubject(config.prefs.get("mail", "subject")),
            html=isinstance(output, formatting.HtmlOutput),
            sender=config.prefs.get("mail", "from"))

    # Rotate logs if requested

    if not argparser.parse_args().no_rotate:
        if argparser.parse_args().simulate or config.prefs.getboolean("logparse", "rotate"):
            rotate_sim()
        elif config.prefs.getboolean("logparse", "rotate") or argparser.parse_args().rotate:
            rotate()
        else:
            logger.debug("User doesn't want to rotate logs")
    else:
        logger.debug("User doesn't want to rotate logs")

    # Finish up

    finish = datetime.now()
    logger.info("Finished parsing logs at {0} {1} (total time: {2})".format(finish.strftime(formatting.DATEFMT), finish.strftime(formatting.TIMEFMT), finish - start))

    if argparser.parse_args().printout:
        output.print_stdout()

    return


def rotate():
    """
    Rotate logs using systemd logrotate. This requires root privileges, and a
    basic check for this is attempted below. Root password will be prompted
    for if permissions are not automatically granted.
    """

    try:
        if not os.geteuid() == 0:
            if stdin.isatty():
                logger.warning("Not running as root, using sudo (may require password to be entered)")
                rotate_shell = check_output("sudo logrotate /etc/logrotate.conf", shell=True)
            else:
                raise PermissionError("Root priviliges are required to run logrotate but are not provided")
        else:
            rotate_shell = check_output("/usr/sbin/logrotate /etc/logrotate.conf", shell=True)
        logger.info("Rotated logfiles")
        logger.debug("logrotate output: " + rotate_shell)
    except Exception as e:
        logger.warning("Failed to rotate log files: " + str(e))


def rotate_sim():   # Simulate log rotation
    """
    Simulate log rotation using logrotate's -d flag. This does not require root
    privileges, but permission errors will be shown in the output without it.
    """

    try:
        if not os.geteuid() == 0:
            logger.warning("Cannot run logrotate as root - you will see permission errors in the output below")
        sim_cmd = "logrotate -d /etc/logrotate.conf"
        logger.debug("Here is the output of `{0}` (simulated):".format(sim_cmd))
        sim = check_output(sim_cmd, shell=True)
        logger.debug(sim)
    except Exception as e:
        logger.warning("Failed to get logrotate simulation: " + str(e))