import UIKit
import Parse

private let reuseIdentifier = "Cell"

class homeVC: UICollectionViewController {
    
    var refresher : UIRefreshControl!
        
        // size of page
        var page : Int = 12
        
        // arrays to hold server information
        var uuidArray = [String]()
        var picArray = [PFFile]()
        
        
        // default func
        override func viewDidLoad() {
            super.viewDidLoad()
            
            // always vertical scroll
            self.collectionView?.alwaysBounceVertical = true
            
            // background color
            collectionView?.backgroundColor = .white

            // title at the top
            self.navigationItem.title = PFUser.current()?.username?.uppercased()
            
            // pull to refresh
            refresher = UIRefreshControl()
            refresher.addTarget(self, action: #selector(homeVC.refresh), for: UIControl.Event.valueChanged)
            collectionView?.addSubview(refresher)
            
            // receive notification from editVC
            NotificationCenter.default.addObserver(self, selector: #selector(homeVC.reload(_:)), name: NSNotification.Name(rawValue: "reload"), object: nil)
            
            
            // load posts func
            loadPosts()
        }
        
        
        // refreshing func
        @objc func refresh() {
            
            // reload posts
            loadPosts()
            
            // stop refresher animating
            refresher.endRefreshing()
        }
        
        
        // reloading func after received notification
        @objc func reload(_ notification:Notification) {
            collectionView?.reloadData()
        }
        
            
        // load posts func
        func loadPosts() {
            
            // request infomration from server
            let query = PFQuery(className: "posts")
            query.whereKey("username", equalTo: PFUser.current()!.username!)
            query.limit = page
            query.findObjectsInBackground (block: { (objects, error) -> Void in
                if error == nil {
                    
                    // clean up
                    self.uuidArray.removeAll(keepingCapacity: false)
                    self.picArray.removeAll(keepingCapacity: false)
                    
                    // find objects related to our request
                    for object in objects! {
                        
                        // add found data to arrays (holders)
                        self.uuidArray.append(object.value(forKey: "uuid") as! String)
                        self.picArray.append(object.value(forKey: "pic") as! PFFile)
                    }
                    
                    self.collectionView?.reloadData()

                } else {
                    print(error!.localizedDescription)
                }
            })
            
        }
        
        
        // load more while scrolling down
        override func scrollViewDidScroll(_ scrollView: UIScrollView) {
            if scrollView.contentOffset.y >= scrollView.contentSize.height - self.view.frame.size.height {
                loadMore()
            }
        }
        
        
        // paging
        func loadMore() {
            
            // if there is more objects
            if page <= picArray.count {
                
                // increase page size
                page = page + 12
                
                // load more posts
                let query = PFQuery(className: "posts")
                query.whereKey("username", equalTo: PFUser.current()!.username!)
                query.limit = page
                query.findObjectsInBackground(block: { (objects, error) -> Void in
                    if error == nil {
                        
                        // clean up
                        self.uuidArray.removeAll(keepingCapacity: false)
                        self.picArray.removeAll(keepingCapacity: false)
                        
                        // find related objects
                        for object in objects! {
                            self.uuidArray.append(object.value(forKey: "uuid") as! String)
                            self.picArray.append(object.value(forKey: "pic") as! PFFile)
                        }
                        
                        self.collectionView?.reloadData()
                        
                    } else {
                        print(error?.localizedDescription ?? String())
                    }
                })

            }
            
        }
        
        
        // cell numb
        override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
            return picArray.count
        }
        
        
        // cell size
        func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: IndexPath) -> CGSize {
            let size = CGSize(width: self.view.frame.size.width / 3, height: self.view.frame.size.width / 3)
            return size
        }
        
        
        // cell config
        override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
            
            // define cell
            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! pictureCell
            
            // get picture from the picArray
            picArray[indexPath.row].getDataInBackground { (data, error) -> Void in
                if error == nil {
                    cell.picImg.image = UIImage(data: data!)
                }
            }
            
            return cell
        }

        
        // header config
        override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
            
            // define header
            let header = collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: "Header", for: indexPath) as! headerView
            
            
            // STEP 1. Get user data
            // get users data with connections to collumns of PFuser class
            header.fullnameLbl.text = (PFUser.current()?.object(forKey: "fullname") as? String)?.uppercased()
            header.webTxt.text = PFUser.current()?.object(forKey: "web") as? String
            header.webTxt.sizeToFit()
            header.bioLbl.text = PFUser.current()?.object(forKey: "bio") as? String
            header.bioLbl.sizeToFit()
            let avaQuery = PFUser.current()?.object(forKey: "ava") as! PFFile
            avaQuery.getDataInBackground { (data, error) -> Void in
                header.avaImg.image = UIImage(data: data!)
            }
            header.button.setTitle("edit profile", for: UIControl.State())
            
            
            // STEP 2. Count statistics
            // count total posts
            let posts = PFQuery(className: "posts")
            posts.whereKey("username", equalTo: PFUser.current()!.username!)
            posts.countObjectsInBackground (block: { (count, error) -> Void in
                if error == nil {
                    header.posts.text = "\(count)"
                }
            })
            
            // count total followers
            let followers = PFQuery(className: "follow")
            followers.whereKey("following", equalTo: PFUser.current()!.username!)
            followers.countObjectsInBackground (block: { (count, error) -> Void in
                if error == nil {
                    header.followers.text = "\(count)"
                }
            })
            
            // count total followings
            let followings = PFQuery(className: "follow")
            followings.whereKey("follower", equalTo: PFUser.current()!.username!)
            followings.countObjectsInBackground (block: { (count, error) -> Void in
                if error == nil {
                    header.followings.text = "\(count)"
                }
            })
            
            return header
    }