#69 : Determine partial window content size

src/utils/math.js

@@ -4,3 +4,64 @@ export const getDistance = (p1, p2) => {
 
   return Math.sqrt((xDist * xDist) + (yDist * yDist));
 }
+
+// 3 => true
+export function getIsOdd(num) {
+  return Boolean(num % 2)
+}
+
+
+// TODO: determine when partial offset is needed and apply partial offset
+// TODO: determine how many clones should be from both sides
+
+
+// TODO: refactor pagesToShow <= pagesToScroll
+// TODO: think about case if pagesCount < pagesToShow and pagesCount < pagesToScroll
+export function getPartialPageSize({
+  pagesToScroll,
+  pagesToShow,
+  pagesCount
+}) {
+
+  if (pagesToShow <= pagesToScroll) {
+    const overlap = pagesToShow - pagesToScroll
+
+    const d = (Math.max(pagesToShow-pagesToScroll), pagesToShow)
+    // console.log('overlap', overlap)
+    let _pages = d
+    // console.log('pages', _pages)
+  
+    while(true) {
+      // let fp = _pages - overlap
+      _pages = _pages - overlap + d
+      // console.log('pages', _pages)
+      const diff = pagesCount - _pages
+      if (diff < pagesToShow) {
+        // console.log('diff', diff)
+        // console.log('pagesToShow - diff', pagesToShow - Math.abs(diff) - overlap)
+        const res = diff + overlap
+        if (res < 0) {
+          return pagesToShow - overlap + res
+        }
+        console.log(res, diff)
+        return diff !== 0 ? Math.min(res, diff) : res
+      }
+    } 
+  } else {
+    const overlap = pagesToShow - pagesToScroll
+
+    // console.log('overlap', overlap)
+    let _pages = pagesToShow
+    console.log('pages', _pages)
+  
+    while(true) {
+      const diff = pagesCount - _pages + overlap
+      if (diff < pagesToShow) {
+        return diff
+      }
+      _pages += pagesToShow - overlap
+      console.log('pages', _pages)
+    }
+  }
+ 
+}