Restructured project

src/assets/javascripts/components/sidebar/index.ts

@@ -0,0 +1,150 @@
+/*
+ * Copyright (c) 2016-2019 Martin Donath <martin.donath@squidfunk.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+import { equals } from "ramda"
+import {
+  MonoTypeOperatorFunction,
+  Observable,
+  animationFrameScheduler,
+  combineLatest,
+  pipe
+} from "rxjs"
+import {
+  distinctUntilChanged,
+  finalize,
+  map,
+  observeOn,
+  shareReplay,
+  tap
+} from "rxjs/operators"
+
+import {
+  resetSidebarHeight,
+  resetSidebarLock,
+  setSidebarHeight,
+  setSidebarLock
+} from "../../actions"
+import { ViewportOffset } from "../../utilities"
+import { Main } from "../main"
+
+/* ----------------------------------------------------------------------------
+ * Types
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Sidebar
+ */
+export interface Sidebar {
+  height: number                       /* Sidebar height */
+  lock: boolean                        /* Sidebar lock */
+}
+
+/* ----------------------------------------------------------------------------
+ * Function types
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Options
+ */
+interface Options {
+  offset$: Observable<ViewportOffset>  /* Viewport offset observable */
+  main$: Observable<Main>              /* Main area observable */
+}
+
+/* ----------------------------------------------------------------------------
+ * Functions
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Watch sidebar
+ *
+ * This function returns an observable that computes the visual parameters of
+ * the given element (a sidebar) from the vertical viewport offset, as well as
+ * the height of the main area. When the page is scrolled beyond the header,
+ * the sidebar is locked and fills the remaining space.
+ *
+ * @param el - Sidebar element
+ * @param options - Options
+ *
+ * @return Sidebar observable
+ */
+export function watchSidebar(
+  el: HTMLElement, { offset$, main$ }: Options
+): Observable<Sidebar> {
+
+  /* Adjust for internal main area offset */
+  const adjust = parseFloat(
+    getComputedStyle(el.parentElement!)
+      .getPropertyValue("padding-top")
+  )
+
+  /* Compute the sidebar's available height */
+  const height$ = combineLatest([offset$, main$])
+    .pipe(
+      map(([{ y }, { offset, height }]) => {
+        return height - adjust + Math.min(adjust, Math.max(0, y - offset))
+      })
+    )
+
+  /* Compute whether the sidebar should be locked */
+  const lock$ = combineLatest([offset$, main$])
+    .pipe(
+      map(([{ y }, { offset }]) => y >= offset + adjust)
+    )
+
+  /* Combine into single hot observable */
+  return combineLatest([height$, lock$])
+    .pipe(
+      map(([height, lock]) => ({ height, lock })),
+      distinctUntilChanged<Sidebar>(equals),
+      shareReplay(1)
+    )
+}
+
+/* ------------------------------------------------------------------------- */
+
+/**
+ * Paint sidebar from source observable
+ *
+ * @param el - Sidebar element
+ *
+ * @return Operator function
+ */
+export function paintSidebar(
+  el: HTMLElement
+): MonoTypeOperatorFunction<Sidebar> {
+  return pipe(
+
+    /* Defer repaint to next animation frame */
+    observeOn(animationFrameScheduler),
+    tap(({ height, lock }) => {
+      setSidebarHeight(el, height)
+      setSidebarLock(el, lock)
+    }),
+
+    /* Reset on complete or error */
+    finalize(() => {
+      resetSidebarHeight(el)
+      resetSidebarLock(el)
+    })
+  )
+}