ui: further style collapsible sidebar

src/components/ResourcesSidebar/styles.tsx

@@ -1,5 +1,6 @@
 import styled from "styled-components"
 import { Link } from "gatsby"
+import ChevronUp from "../../icons/chevron-up.svg"
 
 export const ResourcesSidebarWrapper = styled.div`
   box-sizing: border-box;
@@ -14,20 +15,96 @@ export const Banner = styled.img`
 
 export const TreeWrapper = styled.div`
   width: 100%;
-  padding: 12px 0;
 
   & + & {
     border-top: 1px solid #dbdbdb;
   }
 `
 
+export const Label = styled.div`
+  padding: 4px 0;
+`
+
+export const FirstLabel = styled.div`
+  display: flex;
+  align-items: center;
+  width: 100%;
+  padding: 12px 15px 12px 0;
+  font-weight: 700;
+  color: #a9a9a9;
+
+  &.active {
+    color: #000;
+  }
+
+  svg {
+    margin-left: auto;
+    transform: rotate(90deg);
+    transition: transform 0.3s;
+
+    path {
+      fill: #a9a9a9;
+    }
+  }
+
+  &.active svg {
+    transform: rotate(0);
+
+    path {
+      fill: #000;
+    }
+  }
+`
+
+export const CollapseToggler = styled(ChevronUp)``
+
 export const Inner = styled.div`
   padding-top: 30px;
   padding-left: 20px;
 
-  /* TODO: change this.. */
-  & > ${TreeWrapper} > .tree-view > .tree-view_item > div {
-    font-weight: 700;
+  .tree-view {
+    overflow-y: hidden;
+  }
+
+  .tree-view_item {
+    display: flex;
+    cursor: pointer;
+  }
+
+  .tree-view_children {
+    margin-left: 16px;
+    display: flex;
+    flex-direction: column;
+    align-items: flex-start;
+  }
+
+  .tree-view_children-collapsed {
+    height: 0px;
+  }
+
+  .tree-view_arrow {
+    cursor: pointer;
+    margin-right: 6px;
+    display: inline-block;
+    -webkit-user-select: none;
+    -moz-user-select: none;
+    -ms-user-select: none;
+    user-select: none;
+  }
+
+  .tree-view_arrow:after {
+    content: "▾";
+  }
+
+  .tree-view_arrow.firstLevel {
+    display: none;
+  }
+
+  .tree-view_arrow-collapsed {
+    -webkit-transform: rotate(-90deg);
+    -moz-transform: rotate(-90deg);
+    -ms-transform: rotate(-90deg);
+    transform: rotate(-90deg);
   }
 `