#!/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>',

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

  ]

from soc.views import helper

import soc.views.helper.forms

DEF_PAGINATION = 10

MAX_PAGINATION = 100

DEF_PAGINATION_CHOICES = (

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

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

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

  ('100', '100 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_PAGINATION

def cleanListParameters(offset=None, limit=None):

  """Converts and validates offset and limit values of the list.

  Args:

    offset: offset in list which defines first item to return

    limit: max amount of items per page

  Returns:

    updated offset and limit values

  """

  # update offset value

  try:

    offset = int(offset)

  except:

    # also catches offset=None case where offset not supplied

    offset = 0

  # update limit value

  try:

    limit = int(limit)

  except:

    # also catches limit=None case where limit not supplied

    limit = getPreferredListPagination()

  return max(0, offset), max(1, min(limit, MAX_PAGINATION))

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

  Args:

    request: the Django HTTP request object

  Returns:

    A 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': offest of the lst item in the list

    }

  """

  if not data:

    data = []

  more = bool(data[limit:])

  if more:

    del data[limit:]

  if more:

    next = request.path + '?offset=%d&limit=%d' % (offset+limit, limit)

  if offset > 0:

    prev = request.path + '?offset=%d&limit=%d' % (max(0, offset-limit), limit)

  if offset > limit:

    newest = request.path + '?limit=%d' % limit

  content = {

      'data': data,

      'first': offset+1,

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

      'limit': limit,

      'newest': newest, 

      'next': next,

      'prev': prev, 

      }

  return content

def makePaginationForm(

  request, limit, arg_name='limit', choices=DEF_PAGINATION_CHOICES,

  field_name_fmt=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 helper.forms.makeSelectQueryArgForm(); default is 'limit'

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

      DEF_PAGINATION_CHOICES

    field_name_fmt: see helper.forms.makeSelectQueryArgForm()

  """

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

  return helper.forms.makeSelectQueryArgForm(

      request, arg_name, limit, choices)

def makeNewPaginationChoices(limit=DEF_PAGINATION,

                             choices=DEF_PAGINATION_CHOICES):

  """Updates the pagination limit selection form.

  Args:

    limit: the initial value of the selection control;

      default is DEF_PAGINATION

    choices: see 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

  """

  # determine where to insert the new limit into choices

  new_choices = []

  for index, (pagination, label) in enumerate(choices):

    items = int(pagination)

    if limit == items:

      # limit is already present, so just return existing choices

      return choices

    if limit < items:

      # limit needs to be inserted before the current pagination,

      # so assemble a new choice tuple and append it 

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

      new_choices.append(choice)

      # append the remainder of the original list and exit early

      # (avoiding unnecessary remaining type conversions, etc.)

      new_choices.extend(choices[index:])

      return new_choices

    # append the existing choice

    new_choices.append((pagination, label))

  # new choice must go last, past all other existing choices

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

  new_choices.append(choice)

  return new_choices