#!/usr/bin/python3
"""
.. moduleauthor:: Eric Torres

Run a backup, creating a snapshot in the process.

Command-Line Arguments
======================

-c, --use-checksums   use rsync's checksum feature to detect file changes
-d, --dry-run         make this backup a dry run
--debug               show debug messages
-n, --name            name to give to the backup snapshot
-p, --port            port that ssh on the destination is listening on
-s, --run-post-sync   run sync syscall after backup
-u, --umask           umask value to use while running backup process
-v, --verbose         show info messages

On each run of this script, a new snapshot is made and any unchanged
files are hardlinked into the new snapshot.
"""
import argparse
import logging
import os
import sys

import rbackup.config.config_files as config
import rbackup.script as script
from rbackup.struct.repository import Repository

# ========== Constants ==========
LOGFORMAT = "==> %(levelname)s %(message)s"
EXTRA_RSYNC_OPTS = {
    "dry_run": "--dry-run",
    "delete": "--delete-after",
    "checksum": "--checksum",
    "update": "--update",
}

# ----- Error Codes -----
E_PERMISSION = 13


# ========== Logging Setup ==========
console_formatter = logging.Formatter(LOGFORMAT)
syslog = logging.getLogger("rbackup")
syslog.setLevel(logging.DEBUG)

stdout_handler = logging.StreamHandler(sys.stdout)
stdout_handler.setLevel(logging.INFO)
stdout_handler.setFormatter(console_formatter)
stdout_handler.addFilter(lambda record: record.levelno <= logging.INFO)

stderr_handler = logging.StreamHandler(sys.stderr)
stderr_handler.setLevel(logging.WARNING)
stderr_handler.setFormatter(console_formatter)

syslog.addHandler(stdout_handler)
syslog.addHandler(stderr_handler)


# ========== Functions ==========
def parse_cmdline_arguments(**kwargs):
    """Parse command line arguments passed to the script.
        All kwargs are passed to ArgumentParser.parse_args().

    :rtype: argparse.Namespace object
    """
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "-c",
        "--use-checksums",
        action="store_const",
        dest="extra_rsync_opts",
        const=EXTRA_RSYNC_OPTS["checksum"],
        help="use rsync's checksumming feature to look for changed files",
    )
    parser.add_argument(
        "-d",
        "--dry-run",
        action="append_const",
        dest="extra_rsync_opts",
        const=EXTRA_RSYNC_OPTS["dry_run"],
        help="pass --dry-run to rsync",
    )
    parser.add_argument("--debug", action="store_true", help="log debug messages")
    parser.add_argument(
        "-n", "--name", default=None, help="name to give to the snapshot"
    )
    parser.add_argument(
        "-p",
        "--port",
        default=22,
        help="port that ssh on the destination is listening on",
    )
    parser.add_argument(
        "-s",
        "--run-post-sync",
        action="store_true",
        help="run sync operation after backup is complete",
    )
    parser.add_argument(
        "-u",
        "--umask",
        type=int,
        default=None,
        help="umask value to use while running backup process",
    )
    parser.add_argument(
        "-v", "--verbose", action="store_true", help="log info messages"
    )
    parser.add_argument("repository", help="repository to back up to", metavar="repo")

    return parser.parse_args(**kwargs)


# ========== Main Script ==========
if __name__ == "__main__":
    args = parse_cmdline_arguments()

    try:
        parsed_config = config.parse_configfile()
        repo = Repository(args.repository)
    except PermissionError as e:
        syslog.critical(e)
        exit(E_PERMISSION)
    else:
        script.do_backup(repo, parsed_config, args)

    if args.verbose:
        stdout_handler.setLevel(logging.INFO)

    if args.debug:
        stdout_handler.setLevel(logging.DEBUG)

    if args.run_post_sync:
        syslog.info("Running sync operation")
        os.sync()