From ee2e2799d9ade4ff345293d40317469800163839 Mon Sep 17 00:00:00 2001
From: Andrew Kingston <aptkingston@ssl-mail.com>
Date: Tue, 21 Sep 2021 08:36:02 +0100
Subject: [PATCH] Enable left/right side targetting for DND

---
 .../src/components/preview/DNDHandler.svelte  | 83 ++++++++++++++++---
 .../preview/DNDPositionIndicator.svelte       | 36 +++++---
 .../src/components/preview/Indicator.svelte   |  8 +-
 3 files changed, 103 insertions(+), 24 deletions(-)

diff --git a/packages/client/src/components/preview/DNDHandler.svelte b/packages/client/src/components/preview/DNDHandler.svelte
index 7d83e0998c..8a824f6131 100644
--- a/packages/client/src/components/preview/DNDHandler.svelte
+++ b/packages/client/src/components/preview/DNDHandler.svelte
@@ -1,3 +1,12 @@
+<script context="module">
+  export const Sides = {
+    Top: "Top",
+    Right: "Right",
+    Bottom: "Bottom",
+    Left: "Left",
+  }
+</script>
+
 <script>
   import { onMount } from "svelte"
   import { get } from "svelte/store"
@@ -8,6 +17,22 @@
   let dragInfo
   let dropInfo
 
+  const getEdges = (bounds, mousePoint) => {
+    const { width, height, top, left } = bounds
+    return {
+      [Sides.Top]: [mousePoint[0], top],
+      [Sides.Right]: [left + width, mousePoint[1]],
+      [Sides.Bottom]: [mousePoint[0], top + height],
+      [Sides.Left]: [left, mousePoint[1]],
+    }
+  }
+
+  const calculatePointDelta = (point1, point2) => {
+    const deltaX = Math.abs(point1[0] - point2[0])
+    const deltaY = Math.abs(point1[1] - point2[1])
+    return Math.sqrt(deltaX * deltaX + deltaY * deltaY)
+  }
+
   const getDOMNodeForComponent = component => {
     const parent = component.closest(".component")
     const children = Array.from(parent.childNodes)
@@ -61,23 +86,57 @@
 
     e.preventDefault()
     const { droppableInside, bounds } = dropInfo
-    const { top, height } = bounds
+    const { top, left, height, width } = bounds
     const mouseY = e.clientY
+    const mouseX = e.clientX
     const snapFactor = droppableInside ? 0.33 : 0.5
-    const snapLimit = Math.min(40, height * snapFactor)
-    const edgeLimits = [
-      Math.round(top + snapLimit),
-      Math.round(top + height - snapLimit),
-    ]
+    const snapLimitV = Math.min(40, height * snapFactor)
+    const snapLimitH = Math.min(40, width * snapFactor)
 
-    if (mouseY <= edgeLimits[0]) {
+    // Determine all sies we are within snap range of
+    let sides = []
+    if (mouseY <= top + snapLimitV) {
+      sides.push(Sides.Top)
+    } else if (mouseY >= top + height - snapLimitV) {
+      sides.push(Sides.Bottom)
+    }
+    if (mouseX < left + snapLimitH) {
+      sides.push(Sides.Left)
+    } else if (mouseX > left + width - snapLimitH) {
+      sides.push(Sides.Right)
+    }
+
+    // When no edges match, drop inside if possible
+    if (!sides.length) {
+      dropInfo.mode = droppableInside ? "inside" : null
+      dropInfo.side = null
+      return
+    }
+
+    // When one edge matches, use that edge
+    if (sides.length === 1) {
+      dropInfo.side = sides[0]
+      if ([Sides.Top, Sides.Left].includes(sides[0])) {
+        dropInfo.mode = "above"
+      } else {
+        dropInfo.mode = "below"
+      }
+      return
+    }
+
+    // When 2 edges match, work out which is closer
+    const mousePoint = [mouseX, mouseY]
+    const edges = getEdges(bounds, mousePoint)
+    const edge1 = edges[sides[0]]
+    const delta1 = calculatePointDelta(mousePoint, edge1)
+    const edge2 = edges[sides[1]]
+    const delta2 = calculatePointDelta(mousePoint, edge2)
+    const edge = delta1 < delta2 ? sides[0] : sides[1]
+    dropInfo.side = edge
+    if ([Sides.Top, Sides.Left].includes(edge)) {
       dropInfo.mode = "above"
-    } else if (mouseY >= edgeLimits[1]) {
-      dropInfo.mode = "below"
-    } else if (droppableInside) {
-      dropInfo.mode = "inside"
     } else {
-      dropInfo.mode = null
+      dropInfo.mode = "below"
     }
   }
 
diff --git a/packages/client/src/components/preview/DNDPositionIndicator.svelte b/packages/client/src/components/preview/DNDPositionIndicator.svelte
index 19a44cfccc..e849ab0313 100644
--- a/packages/client/src/components/preview/DNDPositionIndicator.svelte
+++ b/packages/client/src/components/preview/DNDPositionIndicator.svelte
@@ -1,39 +1,53 @@
 <script>
   import Indicator from "./Indicator.svelte"
+  import { Sides } from "./DNDHandler.svelte"
 
   export let dropInfo
   export let zIndex
   export let color
   export let transition
 
-  $: dimensions = getDimensions(dropInfo?.bounds, dropInfo?.mode)
+  $: dimensions = getDimensions(dropInfo)
   $: prefix = dropInfo?.mode === "above" ? "Before" : "After"
   $: text = `${prefix} ${dropInfo?.name}`
+  $: renderKey = `${dropInfo?.target}-${dropInfo?.side}`
 
-  const getDimensions = (bounds, mode) => {
-    if (!bounds || !mode) {
+  const getDimensions = info => {
+    const { bounds, side } = info ?? {}
+    if (!bounds || !side) {
       return null
     }
     const { left, top, width, height } = bounds
-    return {
-      top: mode === "above" ? top - 4 : top + height,
-      left: left - 2,
-      width: width + 4,
+    if (side === Sides.Top || side === Sides.Bottom) {
+      return {
+        top: side === Sides.Top ? top - 4 : top + height,
+        left: left - 2,
+        width: width + 4,
+        height: 0,
+      }
+    } else {
+      return {
+        top: top - 2,
+        left: side === Sides.Left ? left - 4 : left + width,
+        width: 0,
+        height: height + 4,
+      }
     }
   }
 </script>
 
-{#key `${dropInfo?.target}-${dropInfo?.mode}`}
+{#key renderKey}
   {#if dimensions && dropInfo?.mode !== "inside"}
     <Indicator
-      left={dimensions.left}
-      top={dimensions.top}
+      left={Math.round(dimensions.left)}
+      top={Math.round(dimensions.top)}
       width={dimensions.width}
-      height={0}
+      height={dimensions.height}
       {text}
       {zIndex}
       {color}
       {transition}
+      alignRight={dropInfo?.side === Sides.Right}
       line
     />
   {/if}
diff --git a/packages/client/src/components/preview/Indicator.svelte b/packages/client/src/components/preview/Indicator.svelte
index e4082f6f7c..212cd1671d 100644
--- a/packages/client/src/components/preview/Indicator.svelte
+++ b/packages/client/src/components/preview/Indicator.svelte
@@ -10,6 +10,7 @@
   export let zIndex
   export let transition = false
   export let line = false
+  export let alignRight = false
 
   $: flipped = top < 20
 </script>
@@ -26,7 +27,7 @@
   style="top: {top}px; left: {left}px; width: {width}px; height: {height}px; --color: {color}; --zIndex: {zIndex};"
 >
   {#if text}
-    <div class="text" class:flipped class:line>
+    <div class="text" class:flipped class:line class:right={alignRight}>
       {text}
     </div>
   {/if}
@@ -34,6 +35,7 @@
 
 <style>
   .indicator {
+    right: 0;
     position: absolute;
     z-index: var(--zIndex);
     border: 2px solid var(--color);
@@ -78,4 +80,8 @@
     transform: translateY(-50%) !important;
     border-radius: 4px !important;
   }
+  .text.right {
+    right: -2px !important;
+    left: auto !important;
+  }
 </style>