import argparse
import re

from collections import namedtuple
from pathlib import Path


TIME_UNIT_FACTORS = {
    "s": 1,
    "m": 60,
    "h": 60 * 60,
}

ParsedDuration = namedtuple("ParsedDuration", ["value", "unit", "seconds"])

Settings = namedtuple(
    "Settings", ["duration", "interval", "directory", "port"]
)


def parse_duration(raw_value, default_unit="m"):
    """' parses a duration like 10sec, 5min or 2h

    :params raw_value: string value to parse
    :params default_unit: default unit to use, if no (known) unit is present
    :returns: ParsedTime named tuple or None
    """
    match = re.match(r"(?P<value>\d+)(?P<unit>.*)", raw_value)
    if not match:
        return None
    value = int(match["value"])
    unit = _normalize_time_unit(match["unit"], default_unit=default_unit)
    factor = TIME_UNIT_FACTORS[unit]
    return ParsedDuration(value, unit, value * factor)


def parse_cli_arguments():
    """ parses command line interface arguments """
    parser = argparse.ArgumentParser(
        description="Make time series measurements with a Sartorius scale.",
        epilog=(
            "Times can be specified as  10s, 10m, or 10h"
            "for seconds, minutes or hours respectively."
            "A relative directory path starts at the Desktop."
        ),
    )
    parser.add_argument("port", nargs="?", default="COM4", metavar="COMPORT")
    parser.add_argument("-d", "--duration", nargs="?", default="30m")
    parser.add_argument("-i", "--interval", nargs="?", default="10s")
    parser.add_argument("-o", "--output", nargs="?", metavar="DIRECTORY")
    raw_arguments = parser.parse_args()
    return _normalize_cli_arguments(raw_arguments)


def parse_gui_arguments():
    from gooey import GooeyParser
    """ parses command line interface arguments """
    parser = GooeyParser(
        description="Make time series measurements with a Sartorius scale.",
        epilog=(
            "Times can be specified as  10s, 10m, or 10h"
            "for seconds, minutes or hours respectively."
            "A relative directory path starts at the Desktop."
        ),
    )
    parser.add_argument("port", nargs="?", default="COM4", metavar="COMPORT", help="Serial Port that connects the Scale, defaults to 'COM4'")
    parser.add_argument("-d", "--duration", nargs="?", default="30m", help="Measurement duration, e.g. 10s, 30m, 2h")
    parser.add_argument("-i", "--interval", nargs="?", default="10s", help="Measurement interval, e.g. 5s, 1m, 1h")
    parser.add_argument("-o", "--output", nargs="?", metavar="DIRECTORY", widget='DirChooser', help="Select Output Directory, defaults to 'Desktop'")
    raw_arguments = parser.parse_args()
    return _normalize_cli_arguments(raw_arguments)


# helper functions


def _normalize_time_unit(raw_unit, default_unit):
    """ checks if a known time unit is present, else uses the default unit """
    known_units = "hms"
    found = [unit for unit in known_units if unit in raw_unit.lower()]
    unit = found[0] if found else default_unit
    return unit


def _normalize_cli_arguments(raw_arguments):
    """ transforms  cli arguments into a suitable form """
    # time related stuff
    duration = parse_duration(raw_arguments.duration, default_unit="m")
    interval = parse_duration(raw_arguments.interval, default_unit="s")

    # directory stuff
    dir_path = _check_output_directory_path(raw_arguments.output)

    return Settings(duration, interval, dir_path, raw_arguments.port)


def _check_output_directory_path(raw_path):
    """ returns the absolue path of the output directory

    The desktop path (~/Desktop) is considered the default directory. If a
    relative path is provided, it is considered relative to the desktop.
    """
    # the desktop path is the default output directory
    out_path = desktop_path = Path.home() / "Desktop"

    # if a relative path is provided, make it relative to the desktop
    if raw_path:
        out_path = Path(raw_path)
        if not out_path.is_absolute():
            out_path = desktop_path / out_path
            out_path = out_path.resolve()

    # if the provided path is something strange like an existing file,
    # use the default path (Desktop)
    if out_path.exists() and not out_path.is_dir():
        out_path = desktop_path

    return out_path