notes/Notes/NotesPageViewController.swift

//
//  NotesPageViewController.swift
//  Notes
//
//  Created by Laurent Morvillier on 16/10/2022.
//

import Foundation
import UIKit

class NotesPageViewController : UIPageViewController, UIPageViewControllerDelegate, UIPageViewControllerDataSource {
    
    fileprivate var _notes: [Note] = []
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        self._loadNotes()
        
        let shareButton = UIBarButtonItem(barButtonSystemItem: .action, target: self, action: #selector(shareHandler))
        let addButton = UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(addHandler))
        self.navigationItem.rightBarButtonItems = [addButton, shareButton]
        
        self.dataSource = self
        self.delegate = self
        
        if let note = self._notes.last {
            let vc = self.viewController(note: note, index: self._notes.count - 1)
            self.setViewControllers([vc], direction: .forward, animated: false)
        }
                
    }
    
    fileprivate func _displayNote(note: Note) {
        if let index = self._notes.firstIndex(of: note) {
            let vc = self.viewController(note: note, index: index)
            self.setViewControllers([vc], direction: .forward, animated: false)
        } else {
            print("note not found")
        }
    }
    
    fileprivate func viewController(note: Note, index: Int) -> NoteViewController {
        if let vc = self.storyboard?.instantiateViewController(withIdentifier: "note") as? NoteViewController {
            vc.note = note
            vc.index = index
            return vc
        } else {
            fatalError("error with storyboard")
        }
    }
    
    fileprivate func _loadNotes() {
        
        do {
            self._notes = try Note.fetchByDate()
            if self._notes.isEmpty {
                self._createNote()
                self._loadNotes()
            }
        } catch {
            print("error = \(error)")
        }
        
    }
    
    // MARK: - UIPageViewControllerDataSource
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        
        guard let vc = viewController as? NoteViewController else {
            return nil
        }
        
        let previousIndex = vc.index - 1
        if previousIndex < 0 {
            return nil
        }

        let note = self._notes[previousIndex]
        return self.viewController(note: note, index: previousIndex)
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        
        guard let vc = viewController as? NoteViewController else {
            return nil
        }
        
        let nextIndex = vc.index + 1
        if nextIndex == self._notes.count {
            return nil
        }

        let note = self._notes[nextIndex]
        return self.viewController(note: note, index: nextIndex)
    }

    // MARK: - Business
    
    @objc func shareHandler() {
        
        guard let vc = self.presentedViewController as? NoteViewController, let text = vc.note?.content else {
            return
        }
        
        let activityViewController = UIActivityViewController(activityItems: [text], applicationActivities: nil)
        self.present(activityViewController, animated: true)
    }
    
    @objc func addHandler() {
        self._createNote()
    }
    
    fileprivate func _createNote() {
        let note = Note(context: AppDelegate.viewContext)
        self._loadNotes()
        self._displayNote(note: note)
    }
    
}