//
//  ContentView.swift
//  Shared
//
//  Created by Trey Tartt on 1/5/22.
//

import SwiftUI
import CoreData
import Charts

struct ContentView: View {
    @Environment(\.managedObjectContext) private var viewContext
    
    @State private var showingSheet = false
    @State private var showTodayInput = true
    
    @FetchRequest(
        sortDescriptors: [NSSortDescriptor(keyPath: \MoodEntry.forDate, ascending: false)],
        animation: .spring())
    private var items: FetchedResults<MoodEntry>
    
    init(){ }
    
    var body: some View {
        TabView {
            mainView
                .tabItem {
                    Label("Main", systemImage: "list.dash")
                }
            
            FilterView()
                .tabItem {
                    Label("Filter", systemImage: "calendar.circle")
                }
            
            GraphView()
                .tabItem {
                    Label("Stats", systemImage: "chart.line.uptrend.xyaxis")
                }

        }
    }
    
    private var settingsButtonView: some View {
        HStack {
            Spacer()
            Button(action: {
                showingSheet.toggle()
            }, label: {
                Image(systemName: "gear")
                    .foregroundColor(Color(UIColor.systemGray))
                    .font(.system(size: 20))
            }).sheet(isPresented: $showingSheet) {
                SettingsView()
            }.padding(.trailing)
        }
    }
    
    private func weekdayName(fromDate date: Date) -> String {
        let weekday = Calendar.current.component(.weekday, from: date)
        let calendar = Calendar.current
        let dayIndex = ((weekday - 1) + (calendar.firstWeekday - 1)) % 7
        return calendar.shortWeekdaySymbols[dayIndex]
    }
    
    private var listView: some View {
        List {
            ForEach(items) { item in
                HStack {
                    item.mood.icon
                        .resizable()
                        .aspectRatio(contentMode: .fit)
                        .frame(width: 40, height: 40, alignment: .center)
                        .foregroundColor(item.mood.color)
                    VStack {
                        HStack {
                            Text(weekdayName(fromDate:item.forDate!))
                                .font(.title3)
                                .foregroundColor(Color(UIColor.label))
                                .frame(maxWidth: 40, alignment: .leading)
                            Text(" - ")
                                .padding([.leading, .trailing], -10)
                            Text(item.forDate ?? Date(), style: .date)
                                .font(.title3)
                                .foregroundColor(Color(UIColor.label))
                                .frame(maxWidth: .infinity, alignment: .leading)
                        }
                        Text("\(item.moodString)")
                            .font(.body)
                            .foregroundColor(Color(UIColor.systemGray))
                            .frame(maxWidth: .infinity, alignment: .leading)
                    }
                    
                }
            }
            .onDelete(perform: deleteItems)
        }
    }
    
    private var mainView: some View {
        VStack{
            settingsButtonView
            if shouldShowTodayInput() {
                AddMoodHeaderView()
                    .frame(minHeight: 85, maxHeight: 180)
                    .frame(minWidth: 0, maxWidth: .infinity)
            } else {
                HeaderStatsView(fakeData: false, backDays: 30)
                .frame(minHeight: 85, maxHeight: 180)
                // should match backDays above
                Text("Past \(30) days")
                    .font(.body)
                    .foregroundColor(Color(UIColor.systemGray))
                    .frame(maxWidth: .infinity, alignment: .center)
            }
            listView
        }
    }
    
    private func deleteItems(offsets: IndexSet) {
        withAnimation {
            offsets.map { items[$0] }.forEach(viewContext.delete)
            
            do {
                try viewContext.save()
            } catch {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
                let nsError = error as NSError
                fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
            }
        }
    }
    
    private func shouldShowTodayInput() -> Bool {
        let fetchRequest = NSFetchRequest<MoodEntry>(entityName: "MoodEntry")
        
        var calendar = Calendar.current
        calendar.timeZone = NSTimeZone.local
        
        // Get today's beginning & end
        let dateFrom = calendar.startOfDay(for: Date()) // eg. 2016-10-10 00:00:00
        let dateTo = calendar.date(byAdding: .day, value: 1, to: dateFrom)!
        // Note: Times are printed in UTC. Depending on where you live it won't print 00:00:00 but it will work with UTC times which can be converted to local time
        
        // Set predicate as date being today's date
        let fromPredicate = NSPredicate(format: "%@ <= %K", dateFrom as NSDate, #keyPath(MoodEntry.forDate))
        let toPredicate = NSPredicate(format: "%K < %@", #keyPath(MoodEntry.forDate), dateTo as NSDate)
        let datePredicate = NSCompoundPredicate(andPredicateWithSubpredicates: [fromPredicate, toPredicate])
        fetchRequest.predicate = datePredicate
        let entries = try! self.viewContext.count(for: fetchRequest)
        
        return entries == 0
    }
}

private let itemFormatter: DateFormatter = {
    let formatter = DateFormatter()
    formatter.dateStyle = .short
    formatter.timeStyle = .medium
    return formatter
}()

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView().environment(\.managedObjectContext, PersistenceController.shared.container.viewContext)
            .onAppear(perform: {
                PersistenceController.shared.populateMemory()
            })
        
        ContentView()
            .preferredColorScheme(.dark)
            .environment(\.managedObjectContext, PersistenceController.shared.container.viewContext)
    }
}