Plain

  1import collections.abc
  2import inspect
  3import warnings
  4from math import ceil
  5
  6from plain.utils.functional import cached_property
  7from plain.utils.inspect import method_has_no_args
  8
  9
 10class UnorderedObjectListWarning(RuntimeWarning):
 11    pass
 12
 13
 14class InvalidPage(Exception):
 15    pass
 16
 17
 18class PageNotAnInteger(InvalidPage):
 19    pass
 20
 21
 22class EmptyPage(InvalidPage):
 23    pass
 24
 25
 26class Paginator:
 27    # Translators: String used to replace omitted page numbers in elided page
 28    # range generated by paginators, e.g. [1, 2, '…', 5, 6, 7, '…', 9, 10].
 29    ELLIPSIS = "…"
 30
 31    def __init__(self, object_list, per_page, orphans=0, allow_empty_first_page=True):
 32        self.object_list = object_list
 33        self._check_object_list_is_ordered()
 34        self.per_page = int(per_page)
 35        self.orphans = int(orphans)
 36        self.allow_empty_first_page = allow_empty_first_page
 37
 38    def __iter__(self):
 39        for page_number in self.page_range:
 40            yield self.page(page_number)
 41
 42    def validate_number(self, number):
 43        """Validate the given 1-based page number."""
 44        try:
 45            if isinstance(number, float) and not number.is_integer():
 46                raise ValueError
 47            number = int(number)
 48        except (TypeError, ValueError):
 49            raise PageNotAnInteger("That page number is not an integer")
 50        if number < 1:
 51            raise EmptyPage("That page number is less than 1")
 52        if number > self.num_pages:
 53            raise EmptyPage("That page contains no results")
 54        return number
 55
 56    def get_page(self, number):
 57        """
 58        Return a valid page, even if the page argument isn't a number or isn't
 59        in range.
 60        """
 61        try:
 62            number = self.validate_number(number)
 63        except PageNotAnInteger:
 64            number = 1
 65        except EmptyPage:
 66            number = self.num_pages
 67        return self.page(number)
 68
 69    def page(self, number):
 70        """Return a Page object for the given 1-based page number."""
 71        number = self.validate_number(number)
 72        bottom = (number - 1) * self.per_page
 73        top = bottom + self.per_page
 74        if top + self.orphans >= self.count:
 75            top = self.count
 76        return self._get_page(self.object_list[bottom:top], number, self)
 77
 78    def _get_page(self, *args, **kwargs):
 79        """
 80        Return an instance of a single page.
 81
 82        This hook can be used by subclasses to use an alternative to the
 83        standard :cls:`Page` object.
 84        """
 85        return Page(*args, **kwargs)
 86
 87    @cached_property
 88    def count(self):
 89        """Return the total number of objects, across all pages."""
 90        c = getattr(self.object_list, "count", None)
 91        if callable(c) and not inspect.isbuiltin(c) and method_has_no_args(c):
 92            return c()
 93        return len(self.object_list)
 94
 95    @cached_property
 96    def num_pages(self):
 97        """Return the total number of pages."""
 98        if self.count == 0 and not self.allow_empty_first_page:
 99            return 0
100        hits = max(1, self.count - self.orphans)
101        return ceil(hits / self.per_page)
102
103    @property
104    def page_range(self):
105        """
106        Return a 1-based range of pages for iterating through within
107        a template for loop.
108        """
109        return range(1, self.num_pages + 1)
110
111    def _check_object_list_is_ordered(self):
112        """
113        Warn if self.object_list is unordered (typically a QuerySet).
114        """
115        ordered = getattr(self.object_list, "ordered", None)
116        if ordered is not None and not ordered:
117            obj_list_repr = (
118                f"{self.object_list.model} {self.object_list.__class__.__name__}"
119                if hasattr(self.object_list, "model")
120                else f"{self.object_list!r}"
121            )
122            warnings.warn(
123                "Pagination may yield inconsistent results with an unordered "
124                f"object_list: {obj_list_repr}.",
125                UnorderedObjectListWarning,
126                stacklevel=3,
127            )
128
129
130class Page(collections.abc.Sequence):
131    def __init__(self, object_list, number, paginator):
132        self.object_list = object_list
133        self.number = number
134        self.paginator = paginator
135
136    def __repr__(self):
137        return f"<Page {self.number} of {self.paginator.num_pages}>"
138
139    def __len__(self):
140        return len(self.object_list)
141
142    def __getitem__(self, index):
143        if not isinstance(index, int | slice):
144            raise TypeError(
145                "Page indices must be integers or slices, not %s."
146                % type(index).__name__
147            )
148        # The object_list is converted to a list so that if it was a QuerySet
149        # it won't be a database hit per __getitem__.
150        if not isinstance(self.object_list, list):
151            self.object_list = list(self.object_list)
152        return self.object_list[index]
153
154    def has_next(self):
155        return self.number < self.paginator.num_pages
156
157    def has_previous(self):
158        return self.number > 1
159
160    def has_other_pages(self):
161        return self.has_previous() or self.has_next()
162
163    def next_page_number(self):
164        return self.paginator.validate_number(self.number + 1)
165
166    def previous_page_number(self):
167        return self.paginator.validate_number(self.number - 1)
168
169    def start_index(self):
170        """
171        Return the 1-based index of the first object on this page,
172        relative to total objects in the paginator.
173        """
174        # Special case, return zero if no items.
175        if self.paginator.count == 0:
176            return 0
177        return (self.paginator.per_page * (self.number - 1)) + 1
178
179    def end_index(self):
180        """
181        Return the 1-based index of the last object on this page,
182        relative to total objects found (hits).
183        """
184        # Special case for the last page because there can be orphans.
185        if self.number == self.paginator.num_pages:
186            return self.paginator.count
187        return self.number * self.paginator.per_page