/// <reference path="../_ref.d.ts" />

class PagerViewModel {
  constructor(skip: number, take: number, total: number) {
    this.skip = skip;
    this.take = take;
    this.total = total;
    this.UpdateState();
  }
  skip: number;
  take: number;
  total: number;
  hasNext: boolean;
  hasPrev: boolean;
  totalPages: number;
  currentPage: number;

  displayPages: Array<any>;

  screenPageLimitPerSide: number = 4;
  screenPageLimitTotal: number = this.screenPageLimitPerSide * 2 + 1;

  public next() {
    if (!this.hasNext)
      return;
    this.skip = this.skip + this.take;
    this.UpdateState();
  }

  public prev() {
    if (!this.hasPrev)
      return;
    this.skip = this.skip - this.take;
    this.UpdateState();
  }
  public changeTotal(total: number) {
    this.total = total;
    this.UpdateState();
  }

  public goToPage(page: number) {
    var newSkip = page * this.take - this.take;
    if (newSkip >= 0 && newSkip <= this.total && page != this.currentPage) {
      this.skip = newSkip;
      this.UpdateState();
    }
  }

  private UpdateState() {
    console.log("Skip:", this.skip, " Take:", this.take);
    this.totalPages = this.calculateNumberOfPages();
    this.currentPage = this.calculateCurrentPage();
    this.hasNext = this.calculateHasNext();
    this.hasPrev = this.calculateHasPrev();
    this.buildPagerNavigation();
  }

  buildPagerNavigation() {
    var top = this;
    this.displayPages = [];
    this.displayPages.push({ text: "<", goToPage: () => { this.prev() }, isDisabled: this.hasPrev == false });
    var addPefix = true;
    var addSufix = true;
    var from = this.currentPage - this.screenPageLimitPerSide;
    var to = this.currentPage + this.screenPageLimitPerSide;

    if (this.currentPage - this.screenPageLimitPerSide <= 2) {
      var curr = 1 + this.screenPageLimitPerSide;
      from = curr - this.screenPageLimitPerSide;
      to = curr + this.screenPageLimitPerSide;
      addPefix = false;
    } else if (this.currentPage + this.screenPageLimitPerSide > this.totalPages - 2) {
      var curr = this.totalPages - this.screenPageLimitPerSide;
      from = curr - this.screenPageLimitPerSide;
      to = curr + this.screenPageLimitPerSide;
      addSufix = false;
    }

    if (this.totalPages <= this.screenPageLimitTotal) {
      addPefix = false;
      addSufix = false;
    }

    from = Math.max(from, 1);
    to = Math.min(to, this.totalPages);

    if (addPefix) {
      this.displayPages.push({ text: "1", goToPage: () => { this.goToPage(1) } });
      this.displayPages.push({ text: "...", goToPage: () => { this.goToCustomPage() } });
    }


    for (var i = from; i <= to; i++) {
      (function (i, t) { t.displayPages.push({ text: i, goToPage: () => { t.goToPage(i) } }); })(i, top);
    }

    if (addSufix) {
      this.displayPages.push({ text: "...", goToPage: () => { this.goToCustomPage() } });
      this.displayPages.push({ text: this.totalPages, goToPage: () => { this.goToPage(this.totalPages) } });
    }

    this.displayPages.push({ text: ">", goToPage: () => { this.next() }, isDisabled: this.hasNext == false });
  }

  calculateHasNext(): boolean {
    return (this.skip + this.take <= this.total) && this.total - this.take !== this.skip;
  }
  calculateHasPrev(): boolean {
    return this.skip - this.take >= 0 && this.totalPages > 1;
  }

  calculateNumberOfPages(): number {
    if (this.total > 0 && this.take > 0)
      return Math.ceil(this.total / this.take);

    return 0;
  }

  calculateCurrentPage(): number {
    if (this.skip > 0) {
      return Math.ceil(this.skip / this.take) + 1;
    }
    return 1;
  }

  goToCustomPage() {
    var num = parseInt(prompt('Enter page number'));
    if (!(1 <= num && num <= this.totalPages))
      return;

    this.goToPage(num);
  }
}