add backend functionality

games/views/session.py

@@ -1,12 +1,19 @@
-from typing import Any
+import operator
+from functools import reduce
+from json import dumps as json_dumps
+from json import loads as json_loads
+from typing import Any, NotRequired, TypeAlias, TypedDict, TypeGuard
 
 from django.contrib.auth.decorators import login_required
 from django.core.paginator import Paginator
+from django.db.models.query import QuerySet
+from django.db.models.query_utils import Q
 from django.http import HttpRequest, HttpResponse
 from django.shortcuts import get_object_or_404, redirect, render
 from django.template.loader import render_to_string
 from django.urls import reverse
 from django.utils import timezone
+from typing_extensions import TypeGuard
 
 from common.components import A, Button, Div, Icon, LinkedNameWithPlatformIcon, Popover
 from common.time import (
@@ -23,11 +30,279 @@ from games.models import Purchase, Session
 from games.views.general import use_custom_redirect
 
 
+class Filter(TypedDict):
+    filter_id: str
+    filter_display: str
+    filter_string: str
+
+
+def is_filter(obj: dict[Any, Any]) -> TypeGuard[Filter]:
+    return (
+        isinstance(obj, dict)
+        and "filter_id" in obj
+        and isinstance(obj["filter_id"], str)
+        and "filter_display" in obj
+        and isinstance(obj["filter_display"], str)
+        and "filter_string" in obj
+        and isinstance(obj["filter_string"], str)
+    )
+
+
+FilterList: TypeAlias = list[Filter]
+
+
+def is_filterlist(obj: list[Any]) -> TypeGuard[FilterList]:
+    return isinstance(obj, list) and all([is_filter(item) for item in obj])
+
+
+ModelFilterSet: TypeAlias = list[dict[str, FilterList]]
+
+
+class FieldFilter(TypedDict):
+    filtered_field: str
+    filtered_value: str
+    negated: NotRequired[bool]
+    filter: Filter
+
+
+def is_fieldfilter(obj: dict) -> TypeGuard[FieldFilter]:
+    return (
+        isinstance(obj, dict)
+        and "filtered_field" in obj
+        and isinstance(obj["filtered_field"], str)
+        and "filtered_value" in obj
+        and isinstance(obj["filtered_value"], str)
+        and "filter" in obj
+        and is_filter(obj["filter"])
+    )
+
+
+FilterSet: TypeAlias = list[FieldFilter]
+
+
+def is_filterset(obj: list) -> TypeGuard[FilterSet]:
+    return isinstance(obj, list) and all([is_fieldfilter(item) for item in obj])
+
+
+iexact_filter: Filter = {
+    "filter_id": "IEXACT",
+    "filter_display": "Equals (case-insensitive)",
+    "filter_string": "__iexact",
+}
+exact_filter: Filter = {
+    "filter_id": "EXACT",
+    "filter_display": "Equals (case-sensitive)",
+    "filter_string": "__exact",
+}
+isnull_filter: Filter = {
+    "filter_id": "ISNULL",
+    "filter_display": "Is null",
+    "filter_string": "__isnull",
+}
+contains_filter: Filter = {
+    "filter_id": "CONTAINS",
+    "filter_display": "Contains",
+    "filter_string": "__contains",
+}
+startswith_filter: Filter = {
+    "filter_id": "STARTSWITH",
+    "filter_display": "Starts with",
+    "filter_string": "__startswith",
+}
+endswith_filter: Filter = {
+    "filter_id": "ENDSWITH",
+    "filter_display": "Ends with",
+    "filter_string": "__endswith",
+}
+gt_filter: Filter = {
+    "filter_id": "GT",
+    "filter_display": "Greater than",
+    "filter_string": "__gt",
+}
+lt_filter: Filter = {
+    "filter_id": "LT",
+    "filter_display": "Lesser than",
+    "filter_string": "__lt",
+}
+year_gt_filter: Filter = {
+    "filter_id": "YEARGT",
+    "filter_display": "Greater than",
+    "filter_string": "__year__gt",
+}
+year_lt_filter: Filter = {
+    "filter_id": "YEARLT",
+    "filter_display": "Lesser than",
+    "filter_string": "__year__lt",
+}
+year_exact_filter: Filter = {
+    "filter_id": "YEAREXACT",
+    "filter_display": "Equals (case-sensitive)",
+    "filter_string": "__year__exact",
+}
+
+defined_filters = [
+    iexact_filter,
+    exact_filter,
+    isnull_filter,
+    contains_filter,
+    startswith_filter,
+    endswith_filter,
+    gt_filter,
+    lt_filter,
+    year_gt_filter,
+    year_lt_filter,
+    year_exact_filter,
+]
+
+defined_filters_list = {list["filter_id"]: list for list in defined_filters}
+
+char_filter: FilterList = [
+    iexact_filter,
+    isnull_filter,
+    contains_filter,
+    startswith_filter,
+    endswith_filter,
+]
+text_filter: FilterList = [
+    isnull_filter,
+    contains_filter,
+]
+num_filter: FilterList = [exact_filter, gt_filter, lt_filter]
+date_filter: FilterList = [
+    year_exact_filter,
+    isnull_filter,
+    year_gt_filter,
+    year_lt_filter,
+]
+
+conditions = ["and", "or"]
+session_filters: ModelFilterSet = [
+    {"name": char_filter},
+    {"timestamp_start": date_filter},
+    {"timestamp_end": date_filter},
+    {"duration_manual": num_filter},
+    {"duration_calculated": num_filter},
+    {"note": text_filter},
+    {"device": char_filter},
+    {"created_at": date_filter},
+    {"modified_at": date_filter},
+]
+name_contains_age: FieldFilter = {
+    "filtered_field": "name",
+    "filtered_value": "age",
+    "filter": contains_filter,
+}
+simple_example_filter: FilterSet = [name_contains_age]
+timestamp_start_year_2024: FieldFilter = {
+    "filtered_field": "timestamp_start",
+    "filtered_value": "2024",
+    "filter": year_exact_filter,
+}
+physical_only: FieldFilter = {
+    "filtered_field": "purchase__ownership_type",
+    "filtered_value": "ph",
+    "filter": exact_filter,
+}
+
+
+def negate_filter(filter: FieldFilter) -> FieldFilter:
+    return {**filter, "negated": True}
+
+
+without_physical: FieldFilter = negate_filter(physical_only)
+combined_example_filter: FilterSet = [name_contains_age, timestamp_start_year_2024]
+combined_with_negated_example_filter = [timestamp_start_year_2024, without_physical]
+
+
+def string_to_dict(s: str) -> dict[str, str]:
+    key, value = s.split("=")
+    return {key: value}
+
+
+def create_django_filter_dict(
+    filter: Filter, field: str, filtered_value: str
+) -> dict[str, str]:
+    """
+    Creates a dict that can be used with the Django
+    filter function by unpacking it:
+    Model.objects.filter(**return_value)
+    """
+    if not is_filter(filter):
+        raise ValueError("filter is not of type Filter")
+    return {f"{field}{filter["filter_string"]}": filtered_value}
+
+
+def join_filter_with_condition(filters: FilterSet, condition: str):
+    if not is_filterset(filters):
+        raise ValueError("filters is not FilterSet")
+    conditions = {"AND": operator.and_, "OR": operator.or_, "XOR": operator.xor}
+    condition = condition.upper()
+    if condition not in conditions:
+        raise ValueError(f"Condition '{condition}' not one of '{conditions.keys()}'.")
+    q_objects: list[Q] = []
+    for filter_item in filters:
+        q = Q(
+            **create_django_filter_dict(
+                filter_item["filter"],
+                filter_item["filtered_field"],
+                filter_item["filtered_value"],
+            )
+        )
+        if filter_item.get("negated", False):
+            q = ~q
+        q_objects.append(q)
+    return reduce(conditions[condition], q_objects)
+
+
+def apply_filters(
+    filters: FilterSet,
+    queryset: QuerySet[Any],
+) -> QuerySet[Any] | None:
+    if len(filters) == 0:
+        return queryset
+    if type(filters) is not list:
+        raise ValueError("filters argument not of type list")
+    # TODO: modify FilterSet so it includes the condition to use
+    # so we can remove the hard-coding of "AND" here
+    return queryset.filter(join_filter_with_condition(filters, "AND"))
+
+
+def filters_to_string(filters: FilterSet) -> str:
+    constructed_filters: list[dict[str, str | bool]] = []
+    for filter in filters:
+        constructed_filters.append(
+            {
+                "id": filter["filter"]["filter_id"],
+                "field": filter["filtered_field"],
+                "value": filter["filtered_value"],
+                "negated": filter.get("negated", False),
+            }
+        )
+    return json_dumps(constructed_filters)
+
+
+def string_to_filters(filter_string: str) -> FilterSet:
+    obj = json_loads(filter_string)
+    filters = [
+        {
+            "filter": defined_filters_list[item["id"]],
+            "filtered_field": item["field"],
+            "filtered_value": item["value"],
+            "negated": item.get("negated", False),
+        }
+        for item in obj
+    ]
+    if not is_filterset(filters):
+        raise ValueError("filters is not of type FilterSet")
+    return filters
+
+
 @login_required
 def list_sessions(request: HttpRequest) -> HttpResponse:
     context: dict[Any, Any] = {}
     page_number = request.GET.get("page", 1)
     limit = request.GET.get("limit", 10)
+    filters = request.GET.get("filters", "")
     sessions = Session.objects.order_by("-timestamp_start")
     last_session = sessions.latest()
     page_obj = None