Drag and drop space icons (#17) (#78)

Closes #17

Co-authored-by: Jon Staab <shtaab@gmail.com>
Reviewed-on: #78
Co-authored-by: triesap <tyson@radroots.org>
Co-committed-by: triesap <tyson@radroots.org>

src/routes/spaces/+page.svelte

@@ -1,4 +1,5 @@
 <script lang="ts">
+  import {insertAt, removeAt} from "@welshman/lib"
   import SettingsMinimalistic from "@assets/icons/settings-minimalistic.svg?dataurl"
   import AddCircle from "@assets/icons/add-circle.svg?dataurl"
   import Icon from "@lib/components/Icon.svelte"
@@ -9,9 +10,88 @@
   import MenuSpacesItem from "@app/components/MenuSpacesItem.svelte"
   import SpaceAdd from "@app/components/SpaceAdd.svelte"
   import {userSpaceUrls, loadUserGroupList, PLATFORM_RELAYS} from "@app/core/state"
+  import {setSpaceMembershipOrder} from "@app/core/commands"
   import {pushModal} from "@app/util/modal"
 
   const addSpace = () => pushModal(SpaceAdd)
+
+  const reconcileUrls = (currentUrls: string[], nextUrls: string[]) => {
+    const mergedUrls = currentUrls.filter(url => nextUrls.includes(url))
+
+    for (const url of nextUrls) {
+      if (!mergedUrls.includes(url)) {
+        mergedUrls.push(url)
+      }
+    }
+
+    return mergedUrls
+  }
+
+  const isSameOrder = (a: string[], b: string[]) =>
+    a.length === b.length && a.every((url, index) => url === b[index])
+
+  const reorderSpaceUrls = (targetUrl: string) => {
+    if (!draggedUrl) {
+      return
+    }
+
+    const sourceIndex = orderedSpaceUrls.indexOf(draggedUrl)
+    const targetIndex = orderedSpaceUrls.indexOf(targetUrl)
+
+    if (sourceIndex === -1 || targetIndex === -1 || sourceIndex === targetIndex) {
+      return
+    }
+
+    orderedSpaceUrls = insertAt(
+      targetIndex,
+      orderedSpaceUrls[sourceIndex],
+      removeAt(sourceIndex, orderedSpaceUrls),
+    )
+  }
+
+  const onDragStart = (e: DragEvent, url: string) => {
+    draggedUrl = url
+    dragStartOrder = [...orderedSpaceUrls]
+
+    if (e.dataTransfer) {
+      e.dataTransfer.effectAllowed = "move"
+      e.dataTransfer.setData("text/plain", url)
+    }
+  }
+
+  const onDragOver = (e: DragEvent, targetUrl: string) => {
+    e.preventDefault()
+    reorderSpaceUrls(targetUrl)
+  }
+
+  const onDrop = (e: DragEvent, targetUrl: string) => {
+    e.preventDefault()
+    reorderSpaceUrls(targetUrl)
+    draggedUrl = undefined
+
+    if (dragStartOrder && !isSameOrder(dragStartOrder, orderedSpaceUrls)) {
+      void setSpaceMembershipOrder(orderedSpaceUrls).catch(console.error)
+    }
+
+    dragStartOrder = undefined
+  }
+
+  const onDragEnd = () => {
+    draggedUrl = undefined
+    dragStartOrder = undefined
+  }
+
+  $effect(() => {
+    const nextUrls = reconcileUrls(orderedSpaceUrls, $userSpaceUrls)
+
+    if (!isSameOrder(nextUrls, orderedSpaceUrls)) {
+      orderedSpaceUrls = nextUrls
+    }
+  })
+
+  let orderedSpaceUrls = $state<string[]>([])
+  let draggedUrl = $state<string | undefined>()
+  let dragStartOrder = $state<string[] | undefined>()
 </script>
 
 <Page class="cw-full">
@@ -43,8 +123,17 @@
           Loading your spaces...
         </div>
       {:then}
-        {#each $userSpaceUrls as url (url)}
-          <MenuSpacesItem {url} />
+        {#each orderedSpaceUrls as url (url)}
+          <div
+            class:opacity-60={draggedUrl === url}
+            draggable="true"
+            role="listitem"
+            ondragstart={e => onDragStart(e, url)}
+            ondragover={e => onDragOver(e, url)}
+            ondrop={e => onDrop(e, url)}
+            ondragend={onDragEnd}>
+            <MenuSpacesItem {url} />
+          </div>
         {:else}
           <div class="flex flex-col gap-8 items-center py-20">
             <p>You haven't added any spaces yet!</p>