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