Focus trap and Modal Functionality (#145)

* Focus trap and Modal Functionality

* Changes

* Changes

* Update components/ui/Modal/Modal.tsx

Co-authored-by: Luis Alvarez D. <luis@vercel.com>

* changes

Co-authored-by: Luis Alvarez D. <luis@vercel.com>

lib/focus-trap.tsx

@@ -0,0 +1,64 @@
+import React, { useEffect, RefObject } from 'react'
+import { tabbable } from 'tabbable'
+
+interface Props {
+  children: React.ReactNode | any
+  focusFirst?: boolean
+}
+
+export default function FocusTrap({ children, focusFirst = false }: Props) {
+  const root: RefObject<any> = React.useRef()
+  const anchor: RefObject<any> = React.useRef(document.activeElement)
+
+  const returnFocus = () => {
+    // Returns focus to the last focused element prior to trap.
+    if (anchor) {
+      anchor.current.focus()
+    }
+  }
+
+  const trapFocus = () => {
+    // Focus the container element
+    if (root.current) {
+      root.current.focus()
+      if (focusFirst) {
+        selectFirstFocusableEl()
+      }
+    }
+  }
+
+  const selectFirstFocusableEl = () => {
+    // Try to find focusable elements, if match then focus
+    // Up to 6 seconds of load time threshold
+    let match = false
+    let end = 60 // Try to find match at least n times
+    let i = 0
+    const timer = setInterval(() => {
+      if (!match !== i > end) {
+        match = !!tabbable(root.current).length
+        if (match) {
+          // Attempt to focus the first el
+          tabbable(root.current)[0].focus()
+        }
+        i = i + 1
+      } else {
+        // Clear interval after n attempts
+        clearInterval(timer)
+      }
+    }, 100)
+  }
+
+  useEffect(() => {
+    setTimeout(trapFocus, 20)
+    return () => {
+      returnFocus()
+    }
+  }, [root, children])
+
+  return React.createElement('div', {
+    ref: root,
+    children,
+    className: 'outline-none focus-trap',
+    tabIndex: -1,
+  })
+}