Django admin.ModelAdmin `list_filter` meta type classes for relative time and boolean values

filters.py

#! /usr/bin/env python
# -*- coding: utf-8 -*-
#
# >>
#   vidangel-backend, 2022
#   Blake VandeMerwe <[email protected]>
# <<

import re
from datetime import timedelta
from logging import getLogger
from typing import Any, Sequence, Type

import humanize
from django.contrib import admin
from django.utils import timezone
from toolz.functoolz import curry
from django.http import HttpRequest
from django.db.models import QuerySet
from django.utils.translation import gettext_lazy as lazy

__all__ = [
    'boolean_filter',
    'relative_filter',
    'relative_datetime_column',
]

logger = getLogger(__name__)

TIME_PAIR_RE = re.compile(r'(\d+)([mhsdw])', re.I)
REVERSE_PERIOD = {
    's': 'seconds',
    'm': 'minutes',
    'h': 'hours',
    'd': 'days',
    'w': 'weeks',
}


def boolean_filter(
    title: str,
    parameter_name: str,
    conditions: Sequence[str],
) -> Type[admin.SimpleListFilter]:
    """Creates a new dynamic type for boolean quick-sort SimpleListFilter."""

    def bool_queryset(
        this: admin.SimpleListFilter,
        request: HttpRequest,
        queryset: QuerySet,
    ) -> QuerySet:
        """Create a filter on a queryset that eliminates items based on boolean
        conditions."""

        orig_p_val = this.value()

        if not orig_p_val:
            return queryset

        p_val = orig_p_val.lower()[0]

        if p_val in ('t', 'y', '1'):
            f_val = True
        elif p_val in ('f', 'n', '0'):
            f_val = False
        else:
            raise ValueError(f'invalid value for {parameter_name}, {orig_p_val}')

        kw = {}
        for condition in conditions:
            if condition.startswith('~'):
                condition = condition[1:]
                value = not f_val
            else:
                value = f_val
            kw[condition] = value
        return queryset.filter(**kw)

    cls_name = re.sub(r'[_\-.\w]', '', title.title())

    cls_type = type(
        f'Dyn{cls_name}Filter',
        (admin.SimpleListFilter,),
        {
            'title': lazy(title),
            'parameter_name': parameter_name,
            'queryset': bool_queryset,
            'lookups': lambda *_: (
                ('t', lazy(f'is {title}')),
                ('f', lazy(f'is not {title}')),
            )
        },
    )

    assert issubclass(cls_type, admin.SimpleListFilter)
    return cls_type


def relative_filter(
    title: str,
    parameter_name: str,
    column_name: str,
    show_values: Sequence[str],
) -> Type[admin.SimpleListFilter]:
    """Creates a new dynamic type for a relative quick-sort SimpleListFilter.

    Example:

        list_filter = (
            relative_filter(
                'recently matched',
                'recent_match',
                'matched_at',
                ['10m', '30m', '1h', '3h', '12h', '1d', '3d'],
            ),
        ...,
        ...,
    )

        yields:

        > By recently matched
        >  All
        >  10 minutes ago
        >  30 minutes ago
        >  an hour ago
        >  .. etc ..
    """

    def humanize_short_periods(*vals: str) -> tuple[tuple[str, Any], ...]:
        """Turns short values into a long description, displayed in the gui."""

        def inner():
            for val in vals:
                if m := TIME_PAIR_RE.match(val):
                    a, b = m.groups()
                    diff = timedelta(**{REVERSE_PERIOD[b]: int(a)})
                    desc = humanize.naturaldelta(diff, months=False)
                    yield val, lazy(f'{desc} ago')
                else:
                    raise ValueError(f'cannot convert time definition {val}')

        return tuple(inner())

    cls_name = re.sub(r'[_\-.\w]', '', column_name.title())

    cls_type = type(
        f'Dyn{cls_name}Filter',
        (admin.SimpleListFilter,),
        {
            'title': lazy(title),
            'parameter_name': parameter_name,
            'lookups': lambda *_: humanize_short_periods(*show_values),
            'queryset': relative_datetime_column(column_name),
        },
    )

    assert issubclass(cls_type, admin.SimpleListFilter)
    return cls_type


@curry
def relative_datetime_column(
    bind_column: str,
    this: admin.SimpleListFilter,
    request: HttpRequest,
    queryset: QuerySet,
) -> QuerySet:
    """Bind a single column to be filtered by relative time, e.g. 'The last 10 minutes'.

    This is bound to a simple DSL that excepts ``NNs`` where ``s`` can be one of
    _s_econds, _m_inutes, _h_ours, _d_ays, or _w_eeks.
    """

    p_val = this.value()

    if not p_val:
        return queryset

    pairs = TIME_PAIR_RE.findall(p_val)

    if not pairs:
        return queryset

    total = {}
    for val, period in pairs:
        key = REVERSE_PERIOD[period]
        total.setdefault(key, 0)
        total[key] += int(val)
    diff = timedelta(**total)

    logger.info(f'turned {p_val} into {diff}')

    return queryset.filter(**{
        f'{bind_column}__gte': timezone.now() - diff,
    })

Usage example,

class ContentRequestAdmin(admin.ModelAdmin):
    ...
    ...
    list_filter = (
        relative_filter(
            'recently matched',  # in gui
            'recent_match',      # querystring parameter
            'matched_at',        # database column
            ['10m', '30m', '1h', '3h', '12h', '1d', '3d'],
        ),
        boolean_filter(
            'matched',
            'matched',
            ('~content_match__isnull', '~matched_at__isnull'),
        )
    )