#!/usr/bin/python2.5

#

# Copyright 2008 the Melange authors.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

#   http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

"""Helpers used to render lists.

"""

__authors__ = [

  '"Chen Lunpeng" <forever.clp@gmail.com>',

  '"Sverre Rabbelier" <sverre@rabbelier.nl>',

  '"Pawel Solyga" <pawel.solyga@gmail.com>',

  ]

from soc.logic import dicts

from soc.logic.models.user import logic as user_logic

import soc.views.helper.forms

DEF_DEFAULT_PAGINATION = 50

DEF_MAX_PAGINATION = 100

DEF_MAX_DEV_PAGINATION = 1000

DEF_PAGINATION_CHOICES = [

    ('10', '10 items per page'),

    ('25', '25 items per page'),

    ('50', '50 items per page'),

    ('100', '100 items per page'),

]

DEF_DEVELOPER_CHOICES = [

    ('500', '500 items per page'),

    ('1000', '1000 items per page'),

    ]

def getPreferredListPagination(user=None):

  """Returns User's preferred list pagination limit.

  Args:

    user: User entity containing the list pagination preference;

      default is None, to use the current logged-in User

  """

  # TODO: eventually this limit should be a User profile preference

  #   (stored in the site-wide User Model) preference

  return DEF_DEFAULT_PAGINATION

OFFSET_KEY = 'offset_%d'

LIMIT_KEY = 'limit_%d'

def makeOffsetKey(limit_idx):

  return OFFSET_KEY % limit_idx

def makeLimitKey(limit_idx):

  return LIMIT_KEY % limit_idx

def getListParameters(request, list_index):

  """Retrieves, converts and validates values for one list

  Args:

    list_index, int: which list to get the values for.

      (there may be multiple lists on one page, which are multiplexed

       by an integer.)

  Returns:

    a dictionary of str -> str.  field name -> field value.

  """

  offset = request.GET.get(makeOffsetKey(list_index))

  limit = request.GET.get(makeLimitKey(list_index))

  if offset is None:

    offset = ''

  if limit is None:

    limit = ''

  try:

    offset = int(offset)

  except ValueError:

    offset = 0

  try:

    limit = int(limit)

  except ValueError:

    limit = getPreferredListPagination()

  offset = max(0, offset)

  limit = max(1, limit)

  if user_logic.isDeveloper():

    limit = min(DEF_MAX_DEV_PAGINATION, limit)

  else:

    limit = min(DEF_MAX_PAGINATION, limit)

  return dict(limit=limit, offset=offset)

def generateLinkFromGetArgs(request, offset_and_limits):

  """Constructs the get args for the url.

  """

  args = ["%s=%s" % (k, v) for k, v in offset_and_limits.iteritems()]

  link_suffix = '?' + '&'.join(args)

  return request.path + link_suffix

def generateLinkForRequest(request, base_params, updated_params):

  """Create a link to the same page as request but with different params

  Params:

    request: the request for the page

    base_params: the base parameters

    updated_params: the parameters to update

  """

  params = base_params.copy()

  params.update(updated_params)

  return generateLinkFromGetArgs(request, params)

def getListContent(request, params, filter=None, order=None,

                   idx=0, need_content=False, prefetch=None):

  """Returns a dict with fields used for rendering lists.

  TODO(dbentley): we need better terminology. List, in this context, can have

    one of two meanings.

    Meaning 1:  the underlying list, which may be very large.

    Meaning 2:  the returned list, which is at most 'limit' items.

  Args:

    request: the Django HTTP request object

    params: a dict with params for the View this list belongs to

    filter: a filter for this list

    order: the order which should be used for the list (in getForFields format)

    idx: the index of this list

    need_content: iff True will return None if there is no data

    prefetch: the fields of the data that should be pre-fetched

  Returns:

    A dictionary with the following values set:

    {

      'data': list data to be displayed

      'main': url to list main template

      'pagination': url to list pagination template

      'row': url to list row template

      'heading': url to list heading template

      'limit': max amount of items per page,

      'newest': url to first page of the list

      'prev': url to previous page

      'next': url to next page

      'first': offset of the first item in the list

      'last': offset of the last item in the list

    }

  """

  # TODO(dbentley): this appears to be unnecessary indirection,

  # as we only use this logic for getForFields, which is never overridden

  logic = params['logic']

  limit_key, offset_key = makeLimitKey(idx), makeOffsetKey(idx)

  list_params = getListParameters(request, idx)

  limit, offset = list_params['limit'], list_params['offset']

  pagination_form = makePaginationForm(request, list_params['limit'],

                                       limit_key)

  # Fetch one more to see if there should be a 'next' link

  data = logic.getForFields(filter=filter, limit=limit+1, offset=offset,

                            order=order, prefetch=prefetch)

  if need_content and not data:

    return None

  more = len(data) > limit

  if more:

    del data[limit:]

  newest = next = prev = export_link = ''

  base_params = dict(i for i in request.GET.iteritems() if

                     i[0].startswith('offset_') or i[0].startswith('limit_'))

  if params.get('list_key_order'):

    export_link = generateLinkForRequest(request, base_params, {'export': idx})

  if more:

    # TODO(dbentley): here we need to implement a new field "last_key"

    next = generateLinkForRequest(request, base_params, 

                                  {offset_key: offset + limit,

                                   limit_key: limit})

  if offset > 0:

    # TODO(dbentley): here we need to implement previous in the good way.

    prev = generateLinkForRequest(request, base_params,

                                  {offset_key: max(0, offset-limit),

                                   limit_key: limit})

  if offset > limit:

    # Having a link to the first doesn't make sense on the first page (we're on

    # it).  It also doesn't make sense on the second page (because the first

    # page is the previous page).

    # NOTE(dbentley): I personally disagree that it's simpler to do that way,

    # because sometimes you want to go to the first page without having to

    # consider what page you're on now.

    newest = generateLinkForRequest(request, base_params, {offset_key: 0,

                                                           limit_key: limit})

  content = {

      'idx': idx,

      'data': data,

      'export': export_link,

      'first': offset+1,

      'last': len(data) > 1 and offset+len(data) or None,

      'logic': logic,

      'limit': limit,

      'newest': newest,

      'next': next,

      'pagination_form': pagination_form,

      'prev': prev,

      }

  updates = dicts.rename(params, params['list_params'])

  content.update(updates)

  return content

def makePaginationForm(

  request, limit, arg_name, choices=DEF_PAGINATION_CHOICES,

  field_name_fmt=soc.views.helper.forms.DEF_SELECT_QUERY_ARG_FIELD_NAME_FMT):

  """Returns a customized pagination limit selection form.

  Args:

    request: the standard Django HTTP request object

    limit: the initial value of the selection control

    arg_name: see soc.views.helper.forms.makeSelectQueryArgForm(); default is 'limit'

    choices: see soc.views.helper.forms.makeSelectQueryArgForm(); default is

      DEF_PAGINATION_CHOICES

    field_name_fmt: see soc.views.helper.forms.makeSelectQueryArgForm()

  """

  choices = makeNewPaginationChoices(limit=limit, choices=choices)

  return soc.views.helper.forms.makeSelectQueryArgForm(

      request, arg_name, limit, choices)

def makeNewPaginationChoices(limit=DEF_DEFAULT_PAGINATION,

                             choices=DEF_PAGINATION_CHOICES):

  """Updates the pagination limit selection form.

  Args:

    limit: the initial value of the selection control;

      default is DEF_DEFAULT_PAGINATION

    choices: see soc.views.helper.forms.makeSelectQueryArgForm();

      default is DEF_PAGINATION_CHOICES

  Returns:

    a new pagination choices list if limit is not in

    DEF_PAGINATION_CHOICES, or DEF_PAGINATION_CHOICES otherwise

  """

  new_choices = []

  new_choice = (str(limit), '%s items per page' % limit)

  new_choices.append(new_choice)

  new_choices.extend(choices)

  if user_logic.isDeveloper():

    new_choices.extend(DEF_DEVELOPER_CHOICES)

  new_choices = set(new_choices)

  return sorted(new_choices, key=lambda (x, y): int(x))