scan-subread/src/read-order.ts

src/read-order.ts (671 bytes)
1 // The order in which the reader reads the pages of a book. Pure.
2 
3 /**
4  * The next page to read: the current page, then the pages after it up to
5  * the end, then the pages before it, nearest first. The narration goes on
6  * from the current page, so the pages after it are necessary first.
7  * `pending` holds the pages that are not read yet. -1 when it is empty.
8  */
9 export function nextPage(pending: ReadonlySet<number>, current: number): number {
10   let after = Infinity;
11   let before = -1;
12   for (const page of pending) {
13     if (page >= current) after = Math.min(after, page);
14     else before = Math.max(before, page);
15   }
16   return after < Infinity ? after : before;
17 }