Added page break methods

src/__tests__/index.test.ts

@@ -4,20 +4,20 @@
 
 import { CacheInterface, HTMLPagination } from "../index";
 
-describe("HTMLPagination", () => {
-  let hp: HTMLPagination;
+let hp: HTMLPagination;
 
-  const content = document.createElement("div");
-  const container = document.createElement("div");
-  class Cache extends CacheInterface {
-    g(key: string) {
-      return localStorage.getItem(key);
-    }
-    s(key: string, value: string) {
-      localStorage.setItem(key, value);
-    }
+const content = document.createElement("div");
+const container = document.createElement("div");
+class Cache extends CacheInterface {
+  g(key: string) {
+    return localStorage.getItem(key);
   }
+  s(key: string, value: string) {
+    localStorage.setItem(key, value);
+  }
+}
 
+describe("Text position stuff", () => {
   beforeEach(() => {
     content.innerHTML = "";
     content.innerHTML = "<div><p>aa</p><p>bb<span>cc</span>dd</p></div>";
@@ -27,22 +27,42 @@ describe("HTMLPagination", () => {
     hp = new HTMLPagination(content, container, new Cache());
   });
 
-  test("Computes positions for each text node", () => {
+  it("computes positions for each text node", () => {
     expect(hp.elementPositions.map((el) => el[0])).toEqual([0, 2, 4, 6]);
   });
 
-  test("Gets element by position", () => {
+  it("gets element by position", () => {
     expect(hp.getElementForPosition(0)[0]).toBe(0);
     expect(hp.getElementForPosition(1)[0]).toBe(0);
     expect(hp.getElementForPosition(2)[0]).toBe(2);
     expect(hp.getElementForPosition(3)[0]).toBe(2);
   });
 
-  test("Gets html content for range of text", () => {
-    expect(hp.getFromRange(0, 8)).toEqual(
+  it("gets html content for range of text", () => {
+    expect(hp.getContentFromRange(0, 8)).toEqual(
       "<p>aa</p><p>bb<span>cc</span>dd</p>"
     );
-    expect(hp.getFromRange(0, 3)).toEqual("<p>aa</p><p>b</p>");
-    expect(hp.getFromRange(5, 7)).toEqual("<span>c</span>d");
+    expect(hp.getContentFromRange(0, 3)).toEqual("<p>aa</p><p>b</p>");
+    expect(hp.getContentFromRange(5, 7)).toEqual("<span>c</span>d");
   });
 });
+
+// TODO: Add pagination tests using puppeteer
+
+// let browser: puppeteer.Browser, page: puppeteer.Page;
+
+// describe("Page splitting stuff", () => {
+//   beforeAll(async () => {
+//     browser = await puppeteer.launch({
+//       defaultViewport: {
+//         height: 150,
+//         width: 150,
+//       },
+//     });
+//     page = await browser.newPage();
+//   });
+
+//   it("Inserts page break to prevent scroll", async () => {
+//     await page.goto("localhost:5000");
+//   });
+// });

src/index.ts

@@ -1,12 +1,13 @@
 import { CacheInterface } from "./cache";
 import { isElementNode, isTextNode, TextNode } from "./types";
+import { binSearch } from "./utils";
 
 class HTMLPagination {
   content: HTMLElement;
   container: HTMLElement;
   cache: CacheInterface;
 
-  elementPositions: [number, TextNode][];
+  elementPositions: [number, Node][];
   idPositions: Map<string, number>;
 
   /**
@@ -33,7 +34,7 @@ class HTMLPagination {
     const from = 0;
     const to = 1;
 
-    return this.getFromRange(from, to);
+    return this.getContentFromRange(from, to);
   }
 
   /**
@@ -57,27 +58,106 @@ class HTMLPagination {
     recursive(0, this.content);
   }
 
+  /**
+   * Finds position for next page break
+   * initialJump may be computed in a clever way
+   */
+  getPageBreak(start: number, initialJump: number) {
+    let previousEnd = this.getMaxPosition();
+    let end = this.getNextSpaceForPosition(start + initialJump);
+
+    this.getContentFromRange(start, end);
+    while (!this.scrollNecessary() && end < this.getMaxPosition()) {
+      previousEnd = end;
+      end = this.getNextSpaceForPosition(end + 1);
+      this.getContentFromRange(start, end);
+    }
+
+    while (this.scrollNecessary() && end > start) {
+      previousEnd = end;
+      end = this.getPreviousSpaceForPosition(end - 1);
+      this.getContentFromRange(start, end);
+    }
+
+    if (start === end) return previousEnd;
+    else return end;
+  }
+
+  /**
+   * Gets next space or gap between elements for position
+   */
+  getNextSpaceForPosition(startPos: number): number {
+    const nodeIndex = this.getElementIndexForPosition(startPos);
+    const [nodePosition, node] = this.elementPositions[nodeIndex];
+
+    let nodeOffset = startPos - nodePosition;
+    const str = node.nodeValue || "";
+    while (nodeOffset < str.length && str.charAt(nodeOffset) !== " ")
+      nodeOffset++;
+
+    if (nodeOffset === str.length) {
+      if (nodeIndex === this.elementPositions.length - 1)
+        return this.getMaxPosition();
+      else return this.elementPositions[nodeIndex + 1][0];
+    } else {
+      return this.elementPositions[nodeIndex][0] + nodeOffset;
+    }
+  }
+
+  /**
+   * Gets previous space or gap between elements for position
+   */
+  getPreviousSpaceForPosition(startPos: number): number {
+    const nodeIndex = this.getElementIndexForPosition(startPos);
+    const [nodePosition, node] = this.elementPositions[nodeIndex];
+
+    let nodeOffset = startPos - nodePosition;
+    const str = node.nodeValue || "";
+    while (nodeOffset > 0 && str.charAt(nodeOffset) !== " ") nodeOffset--;
+
+    return this.elementPositions[nodeIndex][0] + nodeOffset;
+  }
+
+  /**
+   * Checks if container is overflowing with content
+   */
+  scrollNecessary(): boolean {
+    return this.container.clientHeight < this.container.scrollHeight;
+  }
+
+  /**
+   * Returns end position of content
+   */
+  getMaxPosition(): number {
+    const [offset, element] =
+      this.elementPositions[this.elementPositions.length - 1];
+    return offset + (element.nodeValue?.length || 0);
+  }
+
+  /**
+   * Wrapper for `binSearch` util to find index of element for position
+   */
+  getElementIndexForPosition(pos: number): number {
+    return binSearch(
+      this.elementPositions,
+      pos,
+      (i) => this.elementPositions[i][0]
+    );
+  }
+
   /**
    * Finds node inside which `pos` is located. Returns node positions and itself
    */
   getElementForPosition(pos: number): [number, Node] {
-    let s = 0,
-      e = this.elementPositions.length - 1;
+    const elementIndex = this.getElementIndexForPosition(pos);
 
-    while (s <= e) {
-      const c = (s + e) >> 1;
-      if (pos > this.elementPositions[c][0]) s = c + 1;
-      else if (pos < this.elementPositions[c][0]) e = c - 1;
-      else return this.elementPositions[c];
-    }
-
-    return this.elementPositions[s - 1];
+    return this.elementPositions[elementIndex];
   }
 
   /**
    * Sets `container` element content and return as string html content between `from` and `to`
    */
-  getFromRange(from: number, to: number): string {
+  getContentFromRange(from: number, to: number): string {
     this.container.innerHTML = "";
     const range = new Range();
 

src/utils.ts

@@ -0,0 +1,21 @@
+/**
+ * Binarycally searches element in array or last element lower than searched
+ * @param getter Function to convert array element to comparable with searched element
+ */
+export const binSearch = <T>(
+  arr: T[],
+  el: number,
+  getter: (i: number) => number
+): number => {
+  let s = 0,
+    e = arr.length - 1;
+
+  while (s <= e) {
+    const c = (s + e) >> 1;
+    if (el > getter(c)) s = c + 1;
+    else if (el < getter(c)) e = c - 1;
+    else return c;
+  }
+
+  return s - 1;
+};