From b77db5a4392963721366dfbd10cf6c6afd61ba8e Mon Sep 17 00:00:00 2001
From: Alex Zoitos <azoitos1@gmail.com>
Date: Tue, 22 Sep 2020 22:53:19 -0400
Subject: [PATCH] Horizontal scroll buttons (#100)

* feat(frontend): horizontal scroll buttons with animations

* feat(frontend): scroll + window resize events for buttons on slider
---
 src/components/Slider/index.tsx | 211 +++++++++++++++++++++++++++++---
 1 file changed, 193 insertions(+), 18 deletions(-)

diff --git a/src/components/Slider/index.tsx b/src/components/Slider/index.tsx
index 27fbfc3f..97c23191 100644
--- a/src/components/Slider/index.tsx
+++ b/src/components/Slider/index.tsx
@@ -1,4 +1,6 @@
-import React from 'react';
+import { debounce } from 'lodash';
+import React, { useCallback, useEffect, useRef, useState } from 'react';
+import { useSpring } from 'react-spring';
 import TitleCard from '../TitleCard';
 
 interface SliderProps {
@@ -8,34 +10,207 @@ interface SliderProps {
   isEmpty: boolean;
 }
 
+enum Direction {
+  RIGHT,
+  LEFT,
+}
+
 const Slider: React.FC<SliderProps> = ({
   sliderKey,
   items,
   isLoading,
   isEmpty,
 }) => {
+  const containerRef = useRef<HTMLDivElement>(null);
+  const [scrollPos, setScrollPos] = useState({ isStart: true, isEnd: false });
+
+  const handleScroll = useCallback(() => {
+    const scrollWidth = containerRef.current?.scrollWidth ?? 0;
+    const clientWidth =
+      containerRef.current?.getBoundingClientRect().width ?? 0;
+    const scrollPosition = containerRef.current?.scrollLeft ?? 0;
+
+    if (!items || items?.length === 0) {
+      setScrollPos({ isStart: true, isEnd: true });
+    } else if (clientWidth >= scrollWidth) {
+      setScrollPos({ isStart: true, isEnd: true });
+    } else if (
+      scrollPosition >=
+      (containerRef.current?.scrollWidth ?? 0) - clientWidth
+    ) {
+      setScrollPos({ isStart: false, isEnd: true });
+    } else if (scrollPosition > 0) {
+      setScrollPos({ isStart: false, isEnd: false });
+    } else {
+      setScrollPos({ isStart: true, isEnd: false });
+    }
+  }, [items]);
+
+  // eslint-disable-next-line react-hooks/exhaustive-deps
+  const debouncedScroll = useCallback(
+    debounce(() => handleScroll(), 50),
+    [handleScroll]
+  );
+
+  useEffect(() => {
+    const handleResize = () => {
+      debouncedScroll();
+    };
+
+    window.addEventListener('resize', handleResize, { passive: true });
+
+    return () => {
+      window.removeEventListener('resize', handleResize);
+    };
+  }, [debouncedScroll]);
+
+  useEffect(() => {
+    handleScroll();
+  }, [items, handleScroll]);
+
+  const onScroll = () => {
+    debouncedScroll();
+  };
+
+  const [, setX] = useSpring(() => ({
+    from: { x: 0 },
+    to: { x: 0 },
+    onFrame: (props: { x: number }) => {
+      if (containerRef.current) {
+        containerRef.current.scrollLeft = props.x;
+      }
+    },
+  }));
+
+  const slide = (direction: Direction) => {
+    const clientWidth =
+      containerRef.current?.getBoundingClientRect().width ?? 0;
+    const cardWidth =
+      containerRef.current?.firstElementChild?.getBoundingClientRect().width ??
+      0;
+    const scrollPosition = containerRef.current?.scrollLeft ?? 0;
+    const visibleItems = Math.floor(clientWidth / cardWidth);
+    const scrollOffset = scrollPosition % cardWidth;
+
+    if (direction === Direction.LEFT) {
+      const newX = Math.max(
+        scrollPosition - scrollOffset - visibleItems * cardWidth,
+        0
+      );
+      setX({
+        from: { x: scrollPosition },
+        to: {
+          x: newX,
+        },
+        onFrame: (props) => {
+          if (containerRef.current) {
+            containerRef.current.scrollLeft = props.x;
+          }
+        },
+        reset: true,
+        config: { friction: 60, tension: 500, velocity: 20 },
+      });
+
+      if (newX === 0) {
+        setScrollPos({ isStart: true, isEnd: false });
+      } else {
+        setScrollPos({ isStart: false, isEnd: false });
+      }
+    } else if (direction === Direction.RIGHT) {
+      const newX = Math.min(
+        scrollPosition - scrollOffset + visibleItems * cardWidth,
+        containerRef.current?.scrollWidth ?? 0 - clientWidth
+      );
+      setX({
+        from: { x: scrollPosition },
+        to: {
+          x: newX,
+        },
+        onFrame: (props) => {
+          if (containerRef.current) {
+            containerRef.current.scrollLeft = props.x;
+          }
+        },
+        reset: true,
+        config: { friction: 60, tension: 500, velocity: 20 },
+      });
+
+      if (newX >= (containerRef.current?.scrollWidth ?? 0) - clientWidth) {
+        setScrollPos({ isStart: false, isEnd: true });
+      } else {
+        setScrollPos({ isStart: false, isEnd: false });
+      }
+    }
+  };
+
   return (
-    <div className="overflow-x-scroll whitespace-no-wrap hide-scrollbar scrolling-touch overscroll-x-contain -ml-4 -mr-4">
-      {items?.map((item, index) => (
-        <div
-          key={`${sliderKey}-${index}`}
-          className="first:pl-4 last:pr-4 px-2 inline-block"
+    <div className="relative">
+      <div className="absolute flex text-gray-400 right-0 -mt-10">
+        <button
+          className={`${
+            scrollPos.isStart ? 'cursor-not-allowed text-gray-800' : ''
+          }`}
+          onClick={() => slide(Direction.LEFT)}
+          disabled={scrollPos.isStart}
+        >
+          <svg
+            className="w-6 h-6"
+            fill="none"
+            stroke="currentColor"
+            viewBox="0 0 24 24"
+            xmlns="http://www.w3.org/2000/svg"
+          >
+            <path
+              strokeLinecap="round"
+              strokeLinejoin="round"
+              strokeWidth={2}
+              d="M15 19l-7-7 7-7"
+            />
+          </svg>
+        </button>
+        <button
+          className={`${
+            scrollPos.isEnd ? 'cursor-not-allowed text-gray-800' : ''
+          }`}
+          onClick={() => slide(Direction.RIGHT)}
+          disabled={scrollPos.isEnd}
         >
-          {item}
-        </div>
-      ))}
-      {isLoading &&
-        [...Array(10)].map((_item, i) => (
-          <div
-            key={`placeholder-${i}`}
-            className="first:pl-4 last:pr-4 px-2 inline-block"
+          <svg
+            className="w-6 h-6"
+            fill="none"
+            stroke="currentColor"
+            viewBox="0 0 24 24"
+            xmlns="http://www.w3.org/2000/svg"
           >
-            <TitleCard.Placeholder />
+            <path
+              strokeLinecap="round"
+              strokeLinejoin="round"
+              strokeWidth={2}
+              d="M9 5l7 7-7 7"
+            />
+          </svg>
+        </button>
+      </div>
+      <div
+        className="overflow-x-scroll whitespace-no-wrap hide-scrollbar scrolling-touch overscroll-x-contain -ml-4 -mr-4 px-2"
+        ref={containerRef}
+        onScroll={onScroll}
+      >
+        {items?.map((item, index) => (
+          <div key={`${sliderKey}-${index}`} className="px-2 inline-block">
+            {item}
           </div>
         ))}
-      {isEmpty && (
-        <div className="text-center text-white mt-32">No Results</div>
-      )}
+        {isLoading &&
+          [...Array(10)].map((_item, i) => (
+            <div key={`placeholder-${i}`} className="px-2 inline-block">
+              <TitleCard.Placeholder />
+            </div>
+          ))}
+        {isEmpty && (
+          <div className="text-center text-white mt-16 mb-16">No Results</div>
+        )}
+      </div>
     </div>
   );
 };