// ########################################################################################
// XCode
//   Version 11.5.1 (11E503a)
// Simulator
//   Version 11.4.1 (921.9)
//   SimulatorKit 581.9.1
//   CoreSimulator 704.12.1
// Device
//   iPhone SE (2nd generation) (Works as expected)
//   iPad (7th generation)      (Has the issue)
// ########################################################################################


// ########################################################################################
// You will need to create CoreDataentities as follows:
//
// Entity: SomeEntity
// @NSManaged public var date: Date?            (Attribute)
// Entity: Location
//      @NSManaged public var name: String?     (Attribute)
// ########################################################################################



//################################################################################
// the issue I am having is with the ipad only and when it is using .navigationViewStyle(DoubleColumnNavigationViewStyle())
// this is the default style when in landscape mode but I am also forcing it in portrait
//
// the iphone works as expected because it is not using DoubleColumnNavigationViewStyle() at all
// if i force StackNavigationViewStyle on the iPad, the problem is not present but the user experience suffers greatly
//
// I have now two different issues
// Issue 1) The same begavior as descibed in my previous demo where Multiple form1s get injected in the navigation Path
// Issue 2) The date Picker closes automatically when the user changes one part of the date
//
// compared to my previous Demo, in this Demo:
// 1) I select a date using a datePicker instead of a coredata record using a Picker
// 2) I never save the CoreData
// 3) since a save never occurs, I removed the NotificationCenter for NSManagedObjectContextDidSave
//
// This demo contains 4 lists.  Two works perfectly, the other two have different issues
//
// List 1 in Stack mode and List1 in DobleColumn mode
// In this case, the coredata and Date binding variables are creted in the list1 and passed along the navigation
// In the DoubleColumn version, this causes both issues when changing de CoreData DatePicker
//
// List 2 in Stack mode and List1 in DobleColumn mode
// In this case, only the coredata is creted in the list2 and passed along the navigation
// the State var is created localy in formB
// In the DoubleColumn version, this causes only the issue where the DatePicker closes prematurely when changing de CoreData DatePicker
//
// I have commented the code where I found that it had effect on the issue
// As far as I know there is nothing in there that is rocket science
// Unless I missed something, this might be a bug with the DoubleColumnNavigationViewStyle
// Everything works fine when it is no used but I would prefer to be able to use it
//################################################################################


import SwiftUI
import CoreData

extension SomeEntity {
    
    public var wrappedDate: Date{
        get{date ?? Date() }
        set{date = newValue }
    }
    
}

struct ContentView: View {
    
    @State private var selection = 0
    @Environment(\.managedObjectContext) var moc
    
    var body: some View {
        
        TabView(selection: $selection){
            Button(action: { self.addOneSomeEntityRecord() }) {
                Text("Add CoreData Record")
            }
            .font(.title)
            .tabItem {
                VStack {
                    Image(systemName: "gear")
                    Text("Setup")
                }
            }
            .tag(0)
            List1().navigationViewStyle(StackNavigationViewStyle())
                .font(.title)
                .tabItem {
                    VStack {
                        Image(systemName: "square")
                        Text("Stack(1)")
                    }
            }
            .tag(1)
            List1().navigationViewStyle(DoubleColumnNavigationViewStyle()).padding(.leading, 0.5)
                .font(.title)
                .tabItem {
                    VStack {
                        Image(systemName: "square.split.2x1")
                        Text("DoubleColumn(1)")
                    }
            }
            .tag(2)
            List2().navigationViewStyle(StackNavigationViewStyle())
                .font(.title)
                .tabItem {
                    VStack {
                        Image(systemName: "square")
                        Text("Stack(A)")
                    }
            }
            .tag(3)
            List2().navigationViewStyle(DoubleColumnNavigationViewStyle()).padding(.leading, 0.5)
                .font(.title)
                .tabItem {
                    VStack {
                        Image(systemName: "square.split.2x1")
                        Text("DoubleColumn(A)")
                    }
            }
            .tag(4)
        }
    }
    
    func addOneSomeEntityRecord() {
        let t1 =  SomeEntity(context: moc)
        t1.date = Date()
        do {
            try moc.save()
        } catch {
            fatalError("Unable to save data")
        }
    }
    
    
}

struct List1: View {
    
    @FetchRequest(entity: SomeEntity.entity(), sortDescriptors:[], predicate: nil) var entities: FetchedResults<SomeEntity>
    
    @State var someDate: Date = Date()
    
    var body: some View {
        NavigationView{
            List() {
                ForEach(entities, id: \.self) { someEntity in
                    List1Row(someEntity:someEntity, someDate : self.$someDate)
                }
            }
            .navigationBarTitle(Text("List1"), displayMode: .inline)
        }
    }
}

struct List1Row: View {
    
    @ObservedObject var someEntity:SomeEntity
    @Binding var someDate: Date
    var body: some View {
        HStack {
            Text("To Form 1")
            NavigationLink("", destination: Form1(someEntity: someEntity, someDate : $someDate))
        }
    }
}

struct Form1: View {
    @ObservedObject var someEntity:SomeEntity
    @Binding var someDate: Date
    
    //################################################################################
    // removing this also removes the issue even if it is not currently used in the code
    // in my real application i need to show a list of locations so i will need a fetch
    @FetchRequest(entity: Location.entity(), sortDescriptors:[], predicate: nil) var locations: FetchedResults<Location>
    //################################################################################
    
    var body: some View {
        Form{
            Section(header: Text("Locations"))
            {
                ForEach(1...3, id: \.self) { _ in
                    Form1Row(someEntity:self.someEntity, someDate : self.$someDate)
                }
            }
        }
        .navigationBarTitle("Form1")
    }
}



struct Form1Row: View {
    @ObservedObject var someEntity:SomeEntity
    @Binding var someDate: Date
    
    var body: some View {
        NavigationLink("To Form 2", destination: Form2(someEntity: someEntity, someDate : $someDate))
    }
}


struct Form2: View {
    
    @ObservedObject var someEntity:SomeEntity
    @Binding var someDate: Date
    
    private var coreDataSomeDateSaver:Binding<Date> {
        Binding<Date>(get: {self.someEntity.wrappedDate  }, set: {
            self.someEntity.date = $0
            //################################################################################
            // Even if I don't save here, the problem still occurs
            // in the final application, I plan to save here
            //            let moc = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
            //            do { try moc.save() } catch {}
            //################################################################################
        })
    }
    
    var body: some View {
        Form{
            //################################################################################
            // only the date picker binded to a coredata record that has been passed along from the list has the issue
            // if it would have been defined in form1 it would not have the issue
            //################################################################################
            DatePicker("CoreDate :",
                       selection: coreDataSomeDateSaver,
                       displayedComponents: .date)
            
            //################################################################################
            // I would expect the behavior to be the same as DatePicker where the selection is on a Binding
            // The binding DatePicker workds regardless of where the binding variable was first defined
            // but it has impact on the DatePicker that handles a coredata record
            // in this case, the binding was defined in list1 and passed along to here.
            // this causes the multiple Form1 bug occurs and the selection view is closed prematurely as soon as a value changed
            //################################################################################
            DatePicker("Binding :",
                       selection: $someDate,
                       displayedComponents: .date)
        }
        .navigationBarTitle("Form2")
    }
    
    
}







struct List2: View {
    
    @FetchRequest(entity: SomeEntity.entity(), sortDescriptors:[], predicate: nil) var entities: FetchedResults<SomeEntity>
    var body: some View {
        NavigationView{
            List() {
                ForEach(entities, id: \.self) { someEntity in
                    List2Row(someEntity:someEntity)
                }
            }
            .navigationBarTitle(Text("List1"), displayMode: .inline)
        }
    }
}

struct List2Row: View {
    
    @ObservedObject var someEntity:SomeEntity
    var body: some View {
        HStack {
            Text("To Form A")
            NavigationLink("", destination: FormA(someEntity: someEntity))
        }
    }
}

struct FormA: View {
    @ObservedObject var someEntity:SomeEntity
    
    //################################################################################
    // removing this also removes the issue even if it is not currently used in the code
    // in my real application i need to show a list of locations so i will need a fetch
    @FetchRequest(entity: Location.entity(), sortDescriptors:[], predicate: nil) var locations: FetchedResults<Location>
    //################################################################################
    
    var body: some View {
        Form{
            Section(header: Text("Locations"))
            {
                ForEach(1...3, id: \.self) { _ in
                    FormARow(someEntity:self.someEntity)
                }
            }
        }
        .navigationBarTitle("FormA")
    }
}



struct FormARow: View {
    @ObservedObject var someEntity:SomeEntity
    
    var body: some View {
        NavigationLink("To Form B", destination: FormB(someEntity: someEntity))
    }
}


struct FormB: View {
    
    @ObservedObject var someEntity:SomeEntity
    @State var someDate: Date = Date()
    
    private var coreDataSomeDateSaver:Binding<Date> {
        Binding<Date>(get: {self.someEntity.wrappedDate  }, set: {
            self.someEntity.date = $0
            //################################################################################
            // Even if I don't save here, the problem still occurs
            // in the final application, I plan to save here
            //            let moc = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
            //            do { try moc.save() } catch {}
            //################################################################################
        })
    }
    
    var body: some View {
        Form{
            //################################################################################
            // only the date picker binded to a coredata record that has been passed along from the list has the issue
            // if it would have been defined in formA it would not have the issue
            //################################################################################
            DatePicker("CoreDate :",
                       selection: coreDataSomeDateSaver,
                       displayedComponents: .date)
            
            //################################################################################
            // I would expect the behavior to be the same as DatePicker where the selection is on a State variable
            // Defining a State variable locally for the DatePicker works
            // but it has impact on the DatePicker that handles a coredata record
            // In this case, the Multiple form1 issue does not happend
            // but the selection view is closed prematurely as soon as a value changed
            //################################################################################
            DatePicker("State :",
                       selection: $someDate,
                       displayedComponents: .date)
        }
        .navigationBarTitle("FormB")
    }
    
    
    
}