// Copyright 2016-present the Material Components for iOS authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import Foundation
import MaterialComponents.MaterialPageControl

class PageControlSwiftExampleViewController: UIViewController, UIScrollViewDelegate {

  static let pageColors = [
    UIColor(white: 0.3, alpha: 1),
    UIColor(white: 0.2, alpha: 1),
    UIColor(white: 0.3, alpha: 1),
    UIColor(white: 0.2, alpha: 1),
    UIColor(white: 0.3, alpha: 1),
    UIColor(white: 0.2, alpha: 1),
  ]

  let pageControl: MDCPageControl = {
    let pageControl = MDCPageControl()
    pageControl.currentPageIndicatorTintColor = .white
    pageControl.pageIndicatorTintColor = .lightGray
    return pageControl
  }()

  let scrollView = UIScrollView()
  let pageLabels: [UILabel] = PageControlSwiftExampleViewController.pageColors.enumerated().map {
    enumeration in
    let (i, pageColor) = enumeration
    let pageLabel = UILabel()
    pageLabel.text = "Page \(i + 1)"
    pageLabel.font = pageLabel.font.withSize(50)
    pageLabel.textColor = UIColor(white: 1, alpha: 0.8)
    pageLabel.backgroundColor = pageColor
    pageLabel.textAlignment = NSTextAlignment.center
    pageLabel.autoresizingMask = [.flexibleTopMargin, .flexibleBottomMargin]
    return pageLabel
  }

  override func viewDidLoad() {
    super.viewDidLoad()
    view.backgroundColor = UIColor.white

    scrollView.frame = self.view.bounds
    scrollView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    scrollView.delegate = self
    scrollView.isPagingEnabled = true
    scrollView.contentSize = CGSize(
      width: view.bounds.width * CGFloat(pageLabels.count),
      height: view.bounds.height)
    scrollView.showsHorizontalScrollIndicator = false
    view.addSubview(scrollView)

    // Add pages to scrollView.
    for (i, pageLabel) in pageLabels.enumerated() {
      let pageFrame = view.bounds.offsetBy(dx: CGFloat(i) * view.bounds.width, dy: 0)
      pageLabel.frame = pageFrame
      scrollView.addSubview(pageLabel)
    }

    pageControl.numberOfPages = pageLabels.count

    pageControl.addTarget(self, action: #selector(didChangePage), for: .valueChanged)
    pageControl.autoresizingMask = [.flexibleTopMargin, .flexibleWidth]
    view.addSubview(pageControl)
  }

  // MARK: - Frame changes

  override func viewWillLayoutSubviews() {
    super.viewWillLayoutSubviews()
    let pageBeforeFrameChange = pageControl.currentPage
    for (i, pageLabel) in pageLabels.enumerated() {
      pageLabel.frame = view.bounds.offsetBy(dx: CGFloat(i) * view.bounds.width, dy: 0)
    }
    scrollView.contentSize = CGSize(
      width: view.bounds.width * CGFloat(pageLabels.count),
      height: view.bounds.height)
    var offset = scrollView.contentOffset
    offset.x = CGFloat(pageBeforeFrameChange) * view.bounds.width
    // This non-anmiated change of offset ensures we keep the same page
    scrollView.contentOffset = offset

    var edgeInsets = UIEdgeInsets.zero
    edgeInsets = self.view.safeAreaInsets
    let pageControlSize = pageControl.sizeThatFits(view.bounds.size)
    let yOffset = self.view.bounds.height - pageControlSize.height - 8 - edgeInsets.bottom
    pageControl.frame =
      CGRect(x: 0, y: yOffset, width: view.bounds.width, height: pageControlSize.height)
  }

  // MARK: - UIScrollViewDelegate

  func scrollViewDidScroll(_ scrollView: UIScrollView) {
    pageControl.scrollViewDidScroll(scrollView)
  }

  func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
    pageControl.scrollViewDidEndDecelerating(scrollView)
  }

  func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
    pageControl.scrollViewDidEndScrollingAnimation(scrollView)
  }

  // MARK: - User events

  @objc func didChangePage(_ sender: MDCPageControl) {
    var offset = scrollView.contentOffset
    offset.x = CGFloat(sender.currentPage) * scrollView.bounds.size.width
    scrollView.setContentOffset(offset, animated: true)
  }

  // MARK: - CatalogByConvention

  @objc class func catalogMetadata() -> [String: Any] {
    return [
      "breadcrumbs": ["Page Control", "Swift example"],
      "primaryDemo": false,
      "presentable": false,
    ]
  }
}