HabitTracker.swift

//
//  ContentView.swift
//  HabitTracker
//
//  Created by Montasar on 05/05/2020.
//  Copyright © 2020 Montasar. All rights reserved.
//

import SwiftUI

struct Activity: Identifiable, Codable {
    let id = UUID()
    let name: String
    let description: String
    var count: Int
    
    
    //    init(name: String, description: String, count: Int) {
    //        self.id = UUID()
    //        self.name = name
    //        self.description = description
    //        self.count = count
    //    }
}

class Activities: ObservableObject {
    @Published var items = [Activity]() {
        didSet {
            let encoder = JSONEncoder()
            if let encoded = try? encoder.encode(items) {
                UserDefaults.standard.set(encoded, forKey: "activities")
            }
        }
    }
    
    init() {
        let decoder = JSONDecoder()
        if let activities = UserDefaults.standard.data(forKey: "activities") {
            if let decoded = try? decoder.decode([Activity].self, from: activities) {
                self.items = decoded
                return
            }
        }
        self.items = []
    }
}

struct AddActivity: View {
    @Environment (\.presentationMode) var presentationMode
    @ObservedObject var activities: Activities
    @State private var name = ""
    @State private var description = ""
    
    func createActivity() {
        let activity = Activity(name: name, description: description, count: 1)
        activities.items.append(activity)
    }
    
    var body: some View {
        NavigationView {
            VStack {
                TextField("Activity name", text: $name)        .multilineTextAlignment(TextAlignment.center).padding(10)
                
                TextField("Description", text: $description)        .multilineTextAlignment(TextAlignment.center).padding(10)
                
                Button(action: {
                    self.createActivity()
                    self.presentationMode.wrappedValue.dismiss()
                }) {
                    Text("Create").padding( .vertical, 5).padding(.horizontal, 15).foregroundColor(.white)
                        .background(Color.blue).cornerRadius(20)
                }
                
                
            }
            .navigationBarItems(trailing: Button("Cancel") {
                self.presentationMode.wrappedValue.dismiss()
            })
        }
    }
}

struct ActivityDetail: View {
    @State var activity: Activity
    @ObservedObject var activities: Activities
    
    func incrementCount() {
        // here is the ugly part where I would have preferred to use an ObservedObject and mutate it directly
        if let index = activities.items.firstIndex(where: { $0.id == activity.id }) {
            var newActivity = activities.items[index]
            newActivity.count += 1
            activities.items[index] = newActivity
            activity = newActivity
        }
    }
    
    var body: some View {
        VStack {
            Text(activity.name)
            Text(activity.description)
            Text("Completed \(activity.count) times")
            
            Button(action: {
                self.incrementCount()
            }) {
                Text("Increment").padding( .vertical, 5).padding(.horizontal, 15).foregroundColor(.white)
                    .background(Color.blue).cornerRadius(20)
            }
        }
    }
}

struct ContentView: View {
    
    @State private var showingAddActivity = false
    @ObservedObject var activities = Activities()
    
    func removeActivity(at offsets: IndexSet) {
        activities.items.remove(atOffsets: offsets)
    }
    
    var body: some View {
        NavigationView {
            List {
                ForEach(activities.items) { item in
                    NavigationLink(destination: ActivityDetail(activity: item, activities: self.activities)) {
                        Text("\(item.name) (\(item.count))")
                    }
                }.onDelete(perform: removeActivity)
            }
            .navigationBarTitle("HabitTracker")
            .navigationBarItems(trailing: Button(action: {
                self.showingAddActivity.toggle()
            }) {
                HStack {
                    Image(systemName: "plus")
                    Text("Add an activity")
                }
            })
                .sheet(isPresented: $showingAddActivity) {
                    AddActivity(activities: self.activities)
            }
            
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}