Minor updates

src/utils/swipeable.js

@@ -0,0 +1,76 @@
+import { NEXT, PREV } from '../direction'
+import {
+  addStartEventListener,
+  removeStartEventListener,
+  addMoveEventListener,
+  removeMoveEventListener,
+  addEndEventListener,
+  removeEndEventListener,
+  createDispatcher
+} from './event'
+
+function getCoords(event) {
+  if (event instanceof TouchEvent) {
+    const touch = event.touches[0]
+    return {
+      x: touch ? touch.clientX : 0,
+      y: touch ? touch.clientY : 0
+    }
+  }
+  return {
+    x: event.clientX,
+    y: event.clientY
+  }
+}
+
+export function swipeable(node, { thresholdProvider }) {
+  const dispatch = createDispatcher(node)
+  let x
+  let y
+  let moved = 0
+
+  function handleMousedown(event) {
+    moved = 0
+    const coords = getCoords(event)
+    x = coords.x
+    y = coords.y
+    dispatch('start', { x, y })
+    addMoveEventListener(window, handleMousemove)
+    addEndEventListener(window, handleMouseup)
+  }
+
+  function handleMousemove(event) {
+    const coords = getCoords(event)
+    const dx = coords.x - x
+    const dy = coords.y - y
+    x = coords.x
+    y = coords.y
+    dispatch('move', { x, y, dx, dy })
+
+    if (dx !== 0 && Math.sign(dx) !== Math.sign(moved)) {
+      moved = 0
+    }
+    moved += dx
+    if (Math.abs(moved) > thresholdProvider()) {
+      dispatch('threshold', { direction: moved > 0 ? PREV : NEXT })
+      removeEndEventListener(window, handleMouseup)
+      removeMoveEventListener(window, handleMousemove)
+    } 
+  }
+
+  function handleMouseup(event) {
+    const coords = getCoords(event)
+    x = coords.x
+    y = coords.y
+    dispatch('end', { x, y })
+    removeEndEventListener(window, handleMouseup)
+    removeMoveEventListener(window, handleMousemove)
+  }
+
+  addStartEventListener(node, handleMousedown)
+  return {
+    destroy() {
+      removeStartEventListener(node, handleMousedown)
+    }
+  }
+}