#! /usr/bin/python3
# -*- coding: UTF-8 -*-

"""Make the fillpdf program available on this computer."""

import os
import os.path
import argparse
import shutil
import sys
import subprocess  # for cloning
from constants import (CONFIGFILE, CONFIG_INSTALLDIR,
                       CONFIG_FORMDIR, CONFIG_SEPARATOR)

FORMS_DIRNAME = "TU-Dokumente"
FORMS_URL = ("https://gitlab.math.tu-dresden.de/s1140568/" + FORMS_DIRNAME +
             ".git")


def getPath():
    """Get list of directories that are in the PATH environment variable.

    Returns:
        List of directories as strings.
        If loading path variable did not work, this list is empty.

    """
    return os.environ.get('PATH', "").split(':')  # "" is the default value


def checkLinkAccess(dir):
    """Tell if I can create a link there.

    Try to create a link. If there was no error and indeed there
    is a link, remove the link and return True.
    Otherwise return False.

    """
    # find a filename that is not used yet:
    linkloc = os.path.join(dir, "z")
    while os.path.lexists(linkloc):
        linkloc = linkloc + "z"
        if len(linkloc) > len(dir) + 100:
            print("Found files with names with 1 to 100 z's in "  +
                  "directory " + dir +
                  " Probably error.")
            return False
    try:
        # try to create a link to the arbitrary position .
        os.symlink(os.curdir, linkloc)
    except FileNotFoundError as fnfe:
        # the directory dir does not exist
        return False
    except PermissionError as pe:
        # a cannot create a link there
        return False
    else:
        try:
            os.remove(linkloc)
        except FileNotFoundError as fnfe:
            print("In order to check if I have write access to the " +
                  "directory " + dir + " I created a link " + linkloc +
                  " there." +
                  " I cannot remove it so do it yourself.")
        except PermissionError as pe:
            print("In order to check if I have write access to the " +
                  "directory " + dir + " I created a link " + linkloc +
                  " there." +
                  " I cannot remove it so do it yourself.")
        return True


def defaultPath():
    """Choose a suitable default directory for installing.

    Try to access the path variable.
    If possible use first entry where I can create a symlink and is of the form:
        /usr/local/bin
        ~/bin
        ~/.config/bin

    If not possible use first where I can create a link.

    """
    pathdirs = getPath()
    # check if sudo/ root:
    rootdir = os.path.join("/", "usr", "local", "bin")
    if rootdir in pathdirs and checkLinkAccess(rootdir):
        return rootpath
    for userdir in [os.path.join(os.environ.get("HOME", ""), ".local", "bin"),
                    os.path.join(os.environ.get("HOME", ""), "bin")]:
        if userdir in pathdirs:
            if checkLinkAccess(userdir):
                return userdir
            try:
                os.mkdirs(userdir)
            except OSError:
                # already exists
                # some other error, do not use this
                # print("Debug: userdir link creation failed")
                pass
            else:
                if checkLinkAccess(userdir):
                    return userdir
                else:
                    # something did not work
                    print("Debug: userdir link creation check failed " +
                          "after creating dir")
        else:
            print("Debug: " + userdir + " is not in the path. It should be" +
                  " on a typical system.")
    # print("Debug: non of the typical directories worked. " +
          # "Use the first possible.")
    for directory in pathdirs:
        if checkLinkAccess(directory):
            return directory
    print("""No suitable path for installing was found. Do one of the following:
          • execute this script as sudo/ root
          • add a directory where you have write access in the path
          • specify a directory via the --path option and add this directory"""
          + " to the path.")
    raise FileNotFoundError("No directory for installation found.")


def createProgramSymlinks(where):
    """Create symlinks to some of scripts in this project.

    Arguments:
        where: the directory where to create the symlinks.

    Raises:
        multiple possibilities of error

    """
    here = os.path.dirname(__file__)
    origloc = 0
    linkloc = 1
    # dict { script : (where it is, where the link should be) }
    # print("Debug: here: ", here)
    scripts = {script : (os.path.abspath(
        os.path.join(here, script + ".py")),
        os.path.join(where, script))
                 for script in ["fillform", "reise"]}
    # print("Debug: scripts: ", scripts)
    todoscripts = []
    # check if the scripts exist, i.e. I am at the right place
    for script in scripts:
        # F_OK = does file exist?
        if not os.access(scripts[script][origloc], os.F_OK):
            raise FileNotFoundError("I cannot find the script " + script +
                                    " in " + scripts[script][origloc] + ".")
        if os.access(scripts[script][linkloc], os.F_OK, follow_symlinks=False):
            if os.path.islink(scripts[script][linkloc]):
                if not os.path.exists(scripts[script][linkloc]):
                    # os.path.exists says False on broken symlinks
                    raise FileExistsError("The symlink " +
                                          scripts[script][linkloc] +
                                          " already exists." +
                                          " It is a broken symlink." +
                                          " You may like to delete it " +
                                          "and start " +
                                          " this install script again.")
                elif os.path.samefile(os.readlink(scripts[script][linkloc]),
                                      scripts[script][origloc]):
                    # print("Debug: link " + script +
                          # " already links correctly.")
                    # nothing to do: link already links correctly
                    pass
                else:
                    raise FileExistsError("The symlink "
                                          + scripts[script][linkloc] +
                                          " already exists and points " +
                                          "somewhere else.")
            else:
                raise FileExistsError("The file "
                                      + scripts[script][linkloc] +
                                      " already exists.")
        else:
            todoscripts.append(script)
    for script in todoscripts:
        try:
            os.symlink(scripts[script][origloc], scripts[script][linkloc])
        except NotImplementedError:
            print("The python doc says this happens only on Windows" +
                  " previous to Windows 6.0 (Vista). You should really " +
                  "know better than using Windows.")
            raise
        except OSError as e:
            print("Apparently you do not have the permissions to create" +
                  " a symlink in the directory " + where +
                  ". Call this install script with --path <dir>" +
                  " with a <dir> where you have the permissions and" +
                  " that is in the path.")
            raise


def writeConfig(installdir, formdir):
    """Write the config file.

    Try to write to the file $HOME/.config/.fillpdfrc.

    arguments:
        installdir: where the programs are installed
        formdir: where the form files are

    write one line per info, no line if info is None
    """
    try:
        with open(CONFIGFILE, "w+") as configfile:
            # w = write
            # + = create if not exist
            if installdir is not None:
                print(CONFIG_INSTALLDIR + CONFIG_SEPARATOR +
                      os.path.abspath(installdir), file=configfile)
            else:
                print("Debug: No installdir in config saved.")
            if formdir is not None:
                print(CONFIG_FORMDIR + CONFIG_SEPARATOR +
                      os.path.abspath(formdir), file=configfile)
            else:
                print("Debug: No directory for the form files " +
                      "in config saved.")
    except:
        print("Debug: Error at writing configfile:")
        raise
    else:
        pass
        # print("Debug: config file written")


def parse():
    """Create the argument parser (including the help) and parse the arguments.

    Options/ Arguments:
        --path directory
        --formdir directory

    """
    parser = argparse.ArgumentParser(
        description=("Install fillpdf on this computer " +
                     "and show help how to start using it."))
        # formatter_class=argparse.RawDescriptionHelpFormatter,
        # epilog=("To start go to the new directory and run " +
                # "'./fillform Antrag.pdf'"))
    parser.add_argument("--path", default=None,
                        help=("The directory where the scripts should " +
                              "be installed. Should be in the path. " +
                              "If not specified, you will be asked " +
                              "where to install."))
    parser.add_argument("--formdir", default=None,
                        help=("The directory where the config (form) files " +
                              "for the pdf forms are. " +
                              "If not specified, look next to the " +
                              "parent directory of this script " +
                              "and if it is not there pull from gitlab."))
    return vars(parser.parse_args())


def defaultConfig():
    """Check if ../TU-Dokumente exists.
    If not, try to clone TU-Dokumente here and return this new directory.

    """
    here = os.path.dirname(__file__)
    nextTo = os.path.join(here, "..", FORMS_DIRNAME)
    if os.path.exists(nextTo):
        return nextTo
    nextTo = os.path.join(here, "..", FORMS_DIRNAME)
    if os.path.exists(nextTo):
        # already in current dir
        return nextTo
    try:
        clone = subprocess.Popen([
            "git", "clone", FORMS_URL],
            stderr=subprocess.PIPE,
            stdout=subprocess.PIPE)
        try:
            errorcode = clone.wait(timeout=30)
        except TimeoutExpired:
            print("Cloning the form files from " +
                    FORMS_URL + " took too long.")
        else:
            if errorcode != 0:
                print("Debug: cloning the form files from " +
                        FORMS_URL + " did not work with errorcode " +
                        str(errorcode) + ".")
            else:
                # return newly cloned and created directory
                return os.path.normpath(os.path.join(here,
                                                     FORMS_DIRNAME))
    except Exception as e:
        print("Trying to clone the form file repo failed in the" +
                " following way:", e)
    # no sensible default found
    return None


if __name__ == "__main__":
    args = parse()
    installdir = args["path"]
    if installdir is None:
        installdir = defaultPath()
    formdir = args["formdir"]
    if formdir is None:
        formdir = defaultConfig()
        # getting None again is OK
    print("Chose directory " + installdir + " for installing. ",
          "(Installing is just creating symlinks to the scripts.)")
    createProgramSymlinks(installdir)
    writeConfig(installdir, formdir)
    print("Everything successfully installed. You should be able to " +
          "start fillform and reise now.")