import ftplib
import codecs
import re

import wimcollect.common.logger as logger


def ftp_connect(ftp_config: dict, log: logger.Logger, object_id: str) -> ftplib.FTP:
    """Connect to FTP server according to parameters read from settings.ini file.

    Parameters
    ----------
    ftp_config: dict
        Dict containing FTP connection information: `host`, `user` and `password`.
    log: wimcollect.logger
        Logger to record debug/info/error messages.
    object_id: str
        Object identifier, used as marker for log messages.

    Returns
    -------
    ftplib.FTP
        FTP session.
    """
    host = ftp_config["host"]
    user = ftp_config["user"]
    passwd = codecs.decode(ftp_config["password"], "rot_13")

    try:
        session = ftplib.FTP(host=host, user=user, passwd=passwd)
    except ftplib.error_perm as e:
        log.write(object_id, "Failed to connect to " + host + " as " + user + ": " + str(e))
        raise
    except BlockingIOError as e:
        log.write(object_id, "Host [" + host + "] seems to be unreachable.")
        raise
    else:
        log.write(object_id, "Connected to [" + host + "] as user: " + user)

    return session


def ftp_list_files(ftp_session: ftplib.FTP, distant_directory_path: str, log: logger.Logger, object_id: str) -> list:
    """List the files in the distant FTP directory.

    Parameters
    ----------
    ftp_session: ftplib.FTP
        FTP session.
    distant_directory_path: str
        Full path of the directory whose content should be listed.
    log: wimcollect.logger
        Logger to record debug/info/error messages.
    object_id: str
        Object identifier, used as marker for log messages.

    Returns
    -------
    list
        List of files in the FTP directory given in parameter.
    """
    filepaths = []

    try:
        filepaths = ftp_session.nlst(distant_directory_path)
    except ftplib.error_perm as resp:
        if str(resp) == "550 No files found":
            log.write(object_id, "No files in directory " + distant_directory_path)
        else:
            raise

    return filepaths


def ftp_download_file(source_filepath: str, dest_filepath: str,
                      log: logger.Logger, object_id: str,
                      ftp_config: dict = None, ftp_session: ftplib.FTP = None,
                      delete_if_success: bool = False) -> bool:
    """Download a file from the FTP server.

    Parameters
    ----------
    source_filepath: str
        Full path of the distant to-be_downloaded file.
    dest_filepath: str
        Full path where the downloaded file should be stored.
    log: wimcollect.logger
        Logger to record debug/info/error messages.
    object_id: str
        Object identifier, used as marker for log messages.
    ftp_config: dict, optional
        Dict containing FTP connection information: `host`, `user` and `password`. If not set, `ftp_session` must be
        provided.
    ftp_session: ftplib.FTP, optional
        FTP session. If not set, a session will be created using `ftp_config` parameters. Specifying a
        custom ftp_session is useful when multiple tasks should be performed before/after downloading a single file.
    delete_if_success: bool, optional
        If `True`, the distant FTP file will be deleted from the server, once the transfer is successfully done.

    Returns
    -------
    bool
        `True` if everything went well, otherwise raises Exception.
    """
    # Open FTP session if missing
    if ftp_session is None:
        close_session = True
        ftp_session = ftp_connect(ftp_config, log, object_id)
    else:
        close_session = False

    # Try to download file
    log.write(object_id, "Downloading " + source_filepath + " ...")
    with open(dest_filepath, 'wb') as file:
        try:
            response = ftp_session.retrbinary('RETR %s' % source_filepath, file.write)
        except (ftplib.error_perm, ftplib.error_temp) as e:
            response = str(e)

    # Analyse FTP's response and emit messages accordingly
    response_code = int(re.sub("[^0-9]", "", response))
    if response_code == 226:
        if delete_if_success:
            ftp_session.delete(source_filepath)
        log.write(object_id, "Done. Destination file: " + dest_filepath)
    else:
        log.write(object_id, "FAILED. Destination file: " + dest_filepath)
        raise Exception("Failed to download [" + source_filepath + "] in [" + dest_filepath + "]."
                        " FTP response: [" + response + "]")

    # Close the FTP session if it has been opened at the beginning of this function.
    if close_session:
        ftp_session.quit()

    return True