Refactor FiltersService by extracting Filter model and centralising filter logic

src/app/core/models/github/filters.model.ts

@@ -0,0 +1,163 @@
+import { Sort } from '@angular/material/sort';
+import {
+  OrderOptions,
+  SortOptions,
+  StatusOptions,
+  TypeOptions
+} from '../../constants/filter-options.constants';
+
+/**
+ * Raw data shape used to construct a Filter.
+ * Kept separate from the Filter instance type for strong typing.
+ */
+export interface FilterProps {
+  title: string;
+  status: string[];
+  type: string;
+  sort: Sort;
+  labels: string[];
+  milestones: string[];
+  hiddenLabels: Set<string>;
+  deselectedLabels: Set<string>;
+  itemsPerPage: number;
+  assignees: string[];
+}
+
+/** Patch/update type for Filter props/properties (safe alternative to Partial<Filter>). */
+export type FilterUpdate = Partial<FilterProps>;
+
+/**
+ * Filter is an immutable value object.
+ * Use .clone(...) to produce a new instance with changes.
+ */
+export class Filter {
+  readonly title: string;
+  readonly status: string[];
+  readonly type: string;
+  readonly sort: Sort;
+  readonly labels: string[];
+  readonly milestones: string[];
+  readonly hiddenLabels: Set<string>;
+  readonly deselectedLabels: Set<string>;
+  readonly itemsPerPage: number;
+  readonly assignees: string[];
+
+  constructor(props: FilterProps) {
+    this.title = props.title;
+    this.status = [...props.status];
+    this.type = props.type;
+    this.sort = { ...props.sort };
+    this.labels = [...props.labels];
+    this.milestones = [...props.milestones];
+    this.hiddenLabels = new Set(props.hiddenLabels);
+    this.deselectedLabels = new Set(props.deselectedLabels);
+    this.itemsPerPage = props.itemsPerPage;
+    this.assignees = [...props.assignees];
+  }
+
+  /** Create a default Filter instance. */
+  static createDefault(itemsPerPage = 20): Filter {
+    return new Filter({
+      title: '',
+      status: [
+        StatusOptions.OpenPullRequests,
+        StatusOptions.MergedPullRequests,
+        StatusOptions.OpenIssues,
+        StatusOptions.ClosedIssues
+      ],
+      type: TypeOptions.All,
+      sort: { active: SortOptions.Status, direction: OrderOptions.Asc },
+      labels: [],
+      milestones: [],
+      hiddenLabels: new Set<string>(),
+      deselectedLabels: new Set<string>(),
+      itemsPerPage,
+      assignees: []
+    });
+  }
+
+  /**
+   * Deserialize from a plain query object (Angular-agnostic).
+   * Accepts values as string or string[] (like Router query params).
+   */
+  static fromQueryObject(query: Record<string, string | string[] | undefined>): Filter {
+    const arr = (v: string | string[] | undefined) =>
+      Array.isArray(v) ? v : v ? [v] : [];
+
+    const first = (v: string | string[] | undefined) =>
+      Array.isArray(v) ? v[0] : v;
+
+    const parseSet = (v: string | string[] | undefined) => new Set(arr(v));
+
+    const sortStr = first(query['sort']);
+    const sort = sortStr
+      ? (JSON.parse(sortStr) as Sort)
+      : { active: SortOptions.Status, direction: OrderOptions.Asc };
+
+    const itemsPerPageStr = first(query['itemsPerPage']);
+    const itemsPerPage = itemsPerPageStr ? Number(itemsPerPageStr) : 20;
+
+    return new Filter({
+      title: first(query['title']) ?? '',
+      status:
+        arr(query['status']).length > 0
+          ? arr(query['status'])
+          : [
+              StatusOptions.OpenPullRequests,
+              StatusOptions.MergedPullRequests,
+              StatusOptions.OpenIssues,
+              StatusOptions.ClosedIssues
+            ],
+      type: first(query['type']) ?? TypeOptions.All,
+      sort,
+      labels: arr(query['labels']),
+      milestones: arr(query['milestones']),
+      hiddenLabels: parseSet(query['hiddenLabels']),
+      deselectedLabels: parseSet(query['deselectedLabels']),
+      itemsPerPage,
+      assignees: arr(query['assignees'])
+    });
+  }
+
+  /** Immutable update that returns a new Filter instance. */
+  clone(update: FilterUpdate = {}): Filter {
+    return new Filter({
+      title: update.title ?? this.title,
+      status: update.status ?? this.status,
+      type: update.type ?? this.type,
+      sort: update.sort ?? this.sort,
+      labels: update.labels ?? this.labels,
+      milestones: update.milestones ?? this.milestones,
+      hiddenLabels: update.hiddenLabels ?? this.hiddenLabels,
+      deselectedLabels: update.deselectedLabels ?? this.deselectedLabels,
+      itemsPerPage: update.itemsPerPage ?? this.itemsPerPage,
+      assignees: update.assignees ?? this.assignees
+    });
+  }
+
+  /** Serialize to a plain query object suitable for Angular Router. */
+  toQueryObject(): Record<string, string | string[]> {
+    const q: Record<string, string | string[]> = {};
+
+    const entries: [string, any][] = [
+        ['title', this.title],
+        ['type', this.type],
+        ['status', this.status.length ? this.status : undefined],
+        ['labels', this.labels.length ? this.labels : undefined],
+        ['milestones', this.milestones.length ? this.milestones : undefined],
+        ['assignees', this.assignees.length ? this.assignees : undefined],
+        ['hiddenLabels', this.hiddenLabels.size ? [...this.hiddenLabels] : undefined],
+        ['deselectedLabels', this.deselectedLabels.size ? [...this.deselectedLabels] : undefined],
+        ['sort', JSON.stringify(this.sort)],
+        ['itemsPerPage', String(this.itemsPerPage)]
+    ];
+
+    for (const [key, value] of entries) {
+        if (value !== undefined) {
+        q[key] = value;
+        }
+    }
+
+    return q;
+  }
+}