# -*- mode: python; coding: utf-8 -*-
# Re2o est un logiciel d'administration développé initiallement au Rézo Metz. Il
# se veut agnostique au réseau considéré, de manière à être installable en
# quelques clics.
#
# Copyright © 2017  Maël Kervella
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

"""
Templatetag used to write a URL (specified or current one) and adding
or inserting specific parameters into the query part without deleting
the other parameters.
"""

from django import template

register = template.Library()


@register.simple_tag
def url_insert_param(url="", **kwargs):
    """
    Return the URL with some specific parameters inserted into the query
    part. If a URL has already some parameters, those requested will be
    modified if already exisiting or will be added and the other parameters
    will stay unmodified. If parameters with the same name are already in the
    URL and a value is specified for this parameter, it will replace all
    existing parameters.

    **Tag name**::

        url_insert_param

    **Parameters**:

        url (optional)
            The URL to use as a base. The parameters will be added to this URL.
            If not specified, it will only return the query part of the URL
            ("?a=foo&b=bar" for example).
            Example : "https://example.com/bar?foo=0&thing=abc"

        other arguments
            Any other key-value argument will be used. The key is considered as
            the name of the parameter to insert/modify and the value is the one
            used.
            Example : q="foo" search="bar" name="johnDoe"
                will return as ?<existing_param>&q=foo&search=bar&name=johnDoe

        **Usage**::

            {% url_insert_param [URL] [param1=val1 [param2=val2 [...]]] %}

        **Example**::

            {% url_insert_param a=0 b="bar" %}
                return "?a=0&b=bar"

            {% url_insert_param "url.net/foo.html" a=0 b="bar" %}
                return "url.net/foo.html?a=0&b=bar"

            {% url_insert_param "url.net/foo.html?c=keep" a=0 b="bar" %}
                return "url.net/foo.html?c=keep&a=0&b=bar"

            {% url_insert_param "url.net/foo.html?a=del" a=0 b="bar" %}
                return "url.net/foo.html?a=0&b=bar"

            {% url_insert_param "url.net/foo.html?a=del&c=keep" a=0 b="bar" %}
                return "url.net/foo.hmtl?a=0&c=keep&b=bar"
    """

    # Get existing parameters in the url
    params = {}
    if "?" in url:
        url, parameters = url.split("?", maxsplit=1)
        for parameter in parameters.split("&"):
            p_name, p_value = parameter.split("=", maxsplit=1)
            if p_name not in params:
                params[p_name] = []
            params[p_name].append(p_value)

    # Add the request parameters to the list of parameters
    for key, value in kwargs.items():
        params[key] = [value]

    # Write the url
    url += "?"
    for param, value_list in params.items():
        for value in value_list:
            url += str(param) + "=" + str(value) + "&"

    # Remove the last '&' (or '?' if no parameters)
    return url[:-1]