#!/usr/bin/env python3
"""
core-manage: Helper tool to add, remove, or check for services, models, and
node types in a CORE installation.
"""

import ast
import optparse
import os
import re
import sys

from core import services
from core.constants import CORE_CONF_DIR


class FileUpdater:
    """
    Helper class for changing configuration files.
    """
    actions = ("add", "remove", "check")
    targets = ("service", "model", "nodetype")

    def __init__(self, action, target, data, options):
        """
        """
        self.action = action
        self.target = target
        self.data = data
        self.options = options
        self.verbose = options.verbose
        self.search, self.filename = self.get_filename(target)

    def process(self):
        """ Invoke update_file() using a helper method depending on target.
        """
        if self.verbose:
            txt = "Updating"
            if self.action == "check":
                txt = "Checking"
            sys.stdout.write(f"{txt} file: {self.filename}\n")

        if self.target == "service":
            r = self.update_file(fn=self.update_services)
        elif self.target == "model":
            r = self.update_file(fn=self.update_emane_models)
        elif self.target == "nodetype":
            r = self.update_nodes_conf()

        if self.verbose:
            txt = ""
            if not r:
                txt = "NOT "
            if self.action == "check":
                sys.stdout.write(f"String {txt} found.\n")
            else:
                sys.stdout.write(f"File {txt} updated.\n")

        return r

    def update_services(self, line):
        """ Modify the __init__.py file having this format:
        __all__ = ["quagga", "nrl", "xorp", "bird", ]
        Returns True or False when "check" is the action, a modified line
        otherwise.
        """
        line = line.strip("\n")
        key, valstr = line.split("= ")
        vals = ast.literal_eval(valstr)
        r = self.update_keyvals(key, vals)
        if self.action == "check":
            return r
        valstr = str(r)
        return "= ".join([key, valstr]) + "\n"

    def update_emane_models(self, line):
        """ Modify the core.conf file having this format:
        emane_models = RfPipe, Ieee80211abg, CommEffect, Bypass
        Returns True or False when "check" is the action, a modified line
        otherwise.
        """
        line = line.strip("\n")
        key, valstr = line.split("= ")
        vals = valstr.split(", ")
        r = self.update_keyvals(key, vals)
        if self.action == "check":
            return r
        valstr = ", ".join(r)
        return "= ".join([key, valstr]) + "\n"

    def update_keyvals(self, key, vals):
        """  Perform self.action on (key, vals).
        Returns True or False when "check" is the action, a modified line
        otherwise.
        """
        if self.action == "check":
            if self.data in vals:
                return True
            else:
                return False
        elif self.action == "add":
            if self.data not in vals:
                vals.append(self.data)
        elif self.action == "remove":
            try:
                vals.remove(self.data)
            except ValueError:
                pass
        return vals

    def get_filename(self, target):
        """ Return search string and filename based on target.
        """
        if target == "service":
            filename = os.path.abspath(services.__file__)
            search = "__all__ ="
        elif target == "model":
            filename = os.path.join(CORE_CONF_DIR, "core.conf")
            search = "emane_models ="
        elif target == "nodetype":
            if self.options.userpath is None:
                raise ValueError("missing user path")
            filename = os.path.join(self.options.userpath, "nodes.conf")
            search = self.data
        else:
            raise ValueError("unknown target")
        if not os.path.exists(filename):
            raise ValueError(f"file {filename} does not exist")
        return search, filename

    def update_file(self, fn=None):
        """ Open a file and search for self.search, invoking the supplied
        function on the matching line. Write file changes if necessary.
        Returns True if the file has changed (or action is "check" and the
        search string is found), False otherwise.
        """
        changed = False
        output = ""  # this accumulates output, assumes input is small
        with open(self.filename, "r") as f:
            for line in f:
                if line[:len(self.search)] == self.search:
                    r = fn(line)  # line may be modified by fn() here
                    if self.action == "check":
                        return r
                    else:
                        if line != r:
                            changed = True
                        line = r
                output += line
        if changed:
            with open(self.filename, "w") as f:
                f.write(output)

        return changed

    def update_nodes_conf(self):
        """ Add/remove/check entries from nodes.conf. This file
        contains a Tcl-formatted array of node types. The array index must be
        properly set for new entries. Uses self.{action, filename, search,
        data} variables as input and returns the same value as update_file().
        """
        changed = False
        output = ""  # this accumulates output, assumes input is small
        with open(self.filename, "r") as f:
            for line in f:
                # make sure data is not added twice
                if line.find(self.search) >= 0:
                    if self.action == "check":
                        return True
                    elif self.action == "add":
                        return False
                    elif self.action == "remove":
                        changed = True
                        continue
                else:
                    output += line

        if self.action == "add":
            index = int(re.match("^\d+", line).group(0))
            output += str(index + 1) + " " + self.data + "\n"
            changed = True
        if changed:
            with open(self.filename, "w") as f:
                f.write(output)

        return changed


def main():
    actions = ", ".join(FileUpdater.actions)
    targets = ", ".join(FileUpdater.targets)
    usagestr = "usage: %prog [-h] [options] <action> <target> <string>\n"
    usagestr += "\nHelper tool to add, remove, or check for "
    usagestr += "services, models, and node types\nin a CORE installation.\n"
    usagestr += "\nExamples:\n  %prog add service newrouting"
    usagestr += "\n  %prog -v check model RfPipe"
    usagestr += "\n  %prog --userpath=\"$HOME/.core\" add nodetype \"{ftp ftp.gif ftp.gif {DefaultRoute FTP} netns {FTP server} }\" \n"
    usagestr += f"\nArguments:\n  <action> should be one of: {actions}"
    usagestr += f"\n  <target> should be one of: {targets}"
    usagestr += f"\n  <string> is the text to {actions}"
    parser = optparse.OptionParser(usage=usagestr)
    parser.set_defaults(userpath=None, verbose=False, )

    parser.add_option("--userpath", dest="userpath", type="string",
                      help="use the specified user path (e.g. \"$HOME/.core" \
                           "\") to access nodes.conf")
    parser.add_option("-v", "--verbose", dest="verbose", action="store_true",
                      help="be verbose when performing action")

    def usage(msg=None, err=0):
        sys.stdout.write("\n")
        if msg:
            sys.stdout.write(msg + "\n\n")
        parser.print_help()
        sys.exit(err)

    (options, args) = parser.parse_args()

    if len(args) != 3:
        usage("Missing required arguments!", 1)

    action = args[0]
    if action not in FileUpdater.actions:
        usage(f"invalid action {action}", 1)

    target = args[1]
    if target not in FileUpdater.targets:
        usage(f"invalid target {target}", 1)

    if target == "nodetype" and not options.userpath:
        usage(f"user path option required for this target ({target})")

    data = args[2]

    try:
        up = FileUpdater(action, target, data, options)
        r = up.process()
    except Exception as e:
        sys.stderr.write(f"Exception: {e}\n")
        sys.exit(1)
    if not r:
        sys.exit(1)
    sys.exit(0)


if __name__ == "__main__":
    main()