//
//  FlashCardView.swift
//  Toki Trainer
//
//  Created by Avery Ada Pace on 11/5/21.
//

import SwiftUI
import CoreData

enum FlashCardResult {
    case Correct
    case Incorrect
    case Unanswered
}

struct FlashCardView: View {
    
    @ObservedObject var flashCardsViewModel = FlashCardsViewModel()
    
    @State var currentLesson: String
    @State var dictionary: [TokiDictEntry]
    
    @State private var resultsShown = false
    @State private var results: [String: Bool] = [:]
    
    init(lesson: String, passedDictionary: [TokiDictEntry]) {
        self.dictionary = passedDictionary
        currentLesson = lesson
    }
    
    var body: some View {
        VStack {
            if !resultsShown {
                FlashCardStack(currentLesson: currentLesson, dictionary: dictionary, resultsShown: $resultsShown, results: $results)
            } else {
                ResultsView(results: $results)
            }
        }
    }
}

extension Binding {
    func onChange(_ handler: @escaping () -> ()) -> Binding<Value> {
        Binding(
            get: { self.wrappedValue },
            set: { newValue in
                self.wrappedValue = newValue
                handler()
            })
    }
}

struct ResultsView: View {
    
    @Binding var results: [String: Bool]
    
    var body: some View {
        VStack {
            Text("Results")
                .font(.title)
            //ForEach(results.sorted(by: >), id: \.key) { key, value in
            //ForEach(results.keys, id: \.self) { word in
            List(Array(results.keys).sorted(by: <), id: \.self) { result in
                Text(result)
                    .listRowBackground(results[result]! ? Color.green : Color.red)
            }
        }
    }
}

struct FlashCardStack: View {
    @Environment(\.managedObjectContext) private var viewContext
    
    @FetchRequest(fetchRequest: K.getFlashCardAnswersFetchRequest) var flashCardAnswers: FetchedResults<FlashCardAnswer>
    @FetchRequest(fetchRequest: K.getLessonAnswersFetchRequest) var lessonAnswers: FetchedResults<LessonAnswer>
    
    var currentLesson: String
    var dictionary: [TokiDictEntry]
    @State private var shuffledDictionary: [TokiDictEntry] = []
    @State private var flashCards: [FlashCard] = []
    @State private var topFlashCard: FlashCard? = nil
    @State private var flashCardsAreInteractive: [Bool] = []
    @State private var flashCardsVertOffset: [CGFloat] = []
    @State private var flashCardsResults: [FlashCardResult] = []
    @State private var helperFadeOutOverlay = false
    @State private var deckComplete = false
    
    @Binding var resultsShown: Bool
    @Binding var results: [String: Bool]
    
    @State private var currentFlashCard = 0
    
    var body: some View {
        VStack {
            ZStack {
                if(flashCards.count > 0) {
                    ForEach(flashCards.indices, id: \.self) { index in
                        flashCards[index]
                            .offset(x: 0, y: flashCardsVertOffset[index])
                            .animation(.default, value: flashCardsVertOffset[index])
                            .zIndex(-(CGFloat(index * 10)))
                    }
                }
            }
        }
        .overlay(HStack {
            Image(systemName: "arrow.backward")
            Text("Incorrect")
            Spacer()
            Text("Correct")
            Image(systemName: "arrow.right")
        }.opacity(helperFadeOutOverlay ? 0.0 : 1.0), alignment: .top)
        .onAppear {
            initFlashCards()
        }
        Spacer()
    }
    
    func initFlashCards() {
        flashCards = []
        shuffledDictionary = dictionary
        shuffledDictionary.shuffle()
        for index in shuffledDictionary.indices {
            flashCardsAreInteractive.append(false)
            flashCardsResults.append(FlashCardResult.Unanswered)
            flashCards.append(FlashCard(isInteractive: $flashCardsAreInteractive[index], result: $flashCardsResults[index].onChange(cardAnswerReceived), dictionaryEntry: shuffledDictionary[index]))
            flashCardsVertOffset.append(370)
        }
        if flashCards.count - currentFlashCard >= 3 {
            flashCardsVertOffset[currentFlashCard + 1] = 310
            flashCardsVertOffset[currentFlashCard + 2] = 340
            flashCardsVertOffset[currentFlashCard + 3] = 370
        } else if flashCards.count - currentFlashCard == 2 {
            flashCardsVertOffset[currentFlashCard + 1] = 310
            flashCardsVertOffset[currentFlashCard + 2] = 340
        } else if flashCards.count - currentFlashCard == 1 {
            flashCardsVertOffset[currentFlashCard + 1] = 310
        }
        
        flashCardsVertOffset[currentFlashCard] = 50
        flashCardsAreInteractive[currentFlashCard] = true
        
        resetLessonAnswersCoreData()
    }
    
    func resetLessonAnswersCoreData() {
        for lessonAnswer in lessonAnswers {
            if lessonAnswer.lesson == currentLesson {
                viewContext.delete(lessonAnswer)
            }
        }
        try? viewContext.save()
    }
    
    func setFlashCardAnswersCoreData(_ correct: Bool) {
        var cardInDatabase = false
        for answer in flashCardAnswers {
            if answer.word == shuffledDictionary[currentFlashCard].word {
                print("word in database: \(answer.word ?? "nil")")
                print("tries: \(answer.triesCount)")
                print("correct`: \(answer.correctCount)")
                cardInDatabase = true
                answer.setValue((answer.triesCount + 1), forKey: "triesCount")
                if correct {
                    answer.setValue((answer.correctCount + 1), forKey: "correctCount")
                }
                print("answer found in database")
            }
        }
        
        var lessonInDatabase = false
        for lessonAnswer in lessonAnswers {
            if lessonAnswer.lesson == currentLesson {
                lessonInDatabase = true
                lessonAnswer.setValue((lessonAnswer.triesCount + 1), forKey: "triesCount")
                if correct {
                    lessonAnswer.setValue((lessonAnswer.correctCount + 1), forKey: "correctCount")
                }
                print("lesson found in database")
            }
        }
        
        if lessonInDatabase == false {
            let lessonAnswer = LessonAnswer(context: viewContext)
            lessonAnswer.lesson = currentLesson
            lessonAnswer.triesCount = 1
            if correct {
                lessonAnswer.correctCount = 1
            }
            print("lesson not found in database")
        }
        
        if cardInDatabase == false {
            let answer = FlashCardAnswer(context: viewContext)
            answer.word = shuffledDictionary[currentFlashCard].word
            answer.triesCount = 1
            if correct {
                answer.correctCount = 1
            }
            print("answer not found in database")
        }
        
        try? viewContext.save()
    }
    
    func cardAnswerReceived() {
        if flashCardsResults[currentFlashCard] == FlashCardResult.Correct {
            setFlashCardAnswersCoreData(true)
        } else if flashCardsResults[currentFlashCard] == FlashCardResult.Incorrect {
            setFlashCardAnswersCoreData(false)
        } else {
            return
        }
        nextFlashCard()
    }
    
    func nextFlashCard() {
        flashCardsVertOffset[currentFlashCard] = -1000
        if currentFlashCard == (flashCards.count - 1) {
            for (index, card) in flashCards.enumerated() {
                self.results[card.dictionaryEntry.word] = (flashCardsResults[index] == FlashCardResult.Correct) ? true : false
            }
            self.resultsShown = true
            return
        }
        currentFlashCard += 1
        flashCardsVertOffset[currentFlashCard] = 50
        flashCardsAreInteractive[currentFlashCard] = true
        
        self.helperFadeOutOverlay = true
        
        if ((flashCards.count - 1) - currentFlashCard) > 3 {
            print("flashCards: \(flashCards.count)")
            print("currentFlashCard: \(currentFlashCard)")
            flashCardsVertOffset[currentFlashCard + 1] = 310
            flashCardsVertOffset[currentFlashCard + 2] = 340
            flashCardsVertOffset[currentFlashCard + 3] = 370
        } else if (flashCards.count - 1) - currentFlashCard > 2 {
            flashCardsVertOffset[currentFlashCard + 1] = 310
            flashCardsVertOffset[currentFlashCard + 2] = 340
        } else if (flashCards.count - 1) - currentFlashCard > 1 {
            flashCardsVertOffset[currentFlashCard + 1] = 310
        }
    }
    
    func setTopFlashCard(card: FlashCard?) {
        if let safeCard = card {
            self.topFlashCard?.isInteractive = false
            self.topFlashCard = safeCard
            self.topFlashCard?.isInteractive = true
        }
    }
}

struct FlashCard: View {
    let screen = UIScreen.main.bounds
    
    @State var isFaceDown = false
    @State var rotationAngle: Double = 0
    @Binding var isInteractive: Bool
    @Binding var result: FlashCardResult
    
    var dictionaryEntry: TokiDictEntry
    
    @State private var dragAmount = CGFloat(0)
    
    var drag: some Gesture {
        DragGesture()
            .onChanged { gesture in
                if isInteractive {
                    self.dragAmount = gesture.translation.width
                }
            }
            .onEnded { gesture in
                withAnimation {
                    if isInteractive {
                        if self.dragAmount < -20 {
                            self.dragAmount = -500
                            self.result = FlashCardResult.Incorrect
                        } else if self.dragAmount > 20 {
                            self.dragAmount = 500
                            self.result = FlashCardResult.Correct
                        } else {
                            self.dragAmount = 0
                        }
                    }
                }
            }
    }
    
    var body: some View {
        
        Text("")
            .modifier(CardFlipModifier(isFaceDown: isFaceDown, frontText: dictionaryEntry.word, backText: concatenateDefinitions()))
            .frame(width: 300, height: 200)
            .offset(x: isFaceDown ? -dragAmount : dragAmount, y: abs(dragAmount) / 10)
            .rotationEffect(.degrees(isFaceDown ? -(dragAmount / 50) : dragAmount / 50))
            .font(.title)
            .rotation3DEffect(self.isFaceDown ? Angle(degrees: 180) : Angle(degrees: 0), axis: (x: 0.0, y: 10.0, z: 0.0))
            .animation(.default, value: isFaceDown)
            .animation(.default, value: dragAmount)
            .onTapGesture {
                if self.isInteractive == true {
                    self.isFaceDown.toggle()
                }
            }
            .gesture(drag)
        
    }
    
    func concatenateDefinitions() -> String {
        var result = String()
        for definition in dictionaryEntry.definitions {
            result.append(contentsOf: "\(definition.definition)\n")
        }
        return result
    }
    
    func setCanBeFlipped(_ input: Bool) {
        self.isInteractive.toggle()
    }
}

struct CardFlipModifier: AnimatableModifier {
    
    var frontText: String
    var backText: String
    var isFaceDown: Bool
    var rotationAngle: Double
    
    init(isFaceDown: Bool, frontText: String, backText: String) {
        rotationAngle = isFaceDown ? 180 : 0
        self.isFaceDown = isFaceDown
        self.frontText = frontText
        self.backText = backText
    }
    
    var animatableData: Double {
        get { rotationAngle }
        set { rotationAngle = newValue }
    }
    
    func body(content: Content) -> some View {
        return ZStack {
            RoundedRectangle(cornerRadius: 20.0)
                .fill(rotationAngle < 90 ? Color("CardColor") : Color("CardColorBack"))
                .animation(.none, value: rotationAngle)
                .overlay(
                    RoundedRectangle(cornerRadius: 20)
                        .stroke(Color("CardColorBack"), lineWidth: 5))
                .animation(.none, value: rotationAngle)
            Image("CardLogoDark")
                .resizable()
                .frame(width: 180, height: 180, alignment: .center)
                .opacity(0.5)
            Text(frontText)
                .font(.title)
                .foregroundColor(.white)
                .opacity(rotationAngle < 90 ? 1.0 : 0.0)
                .animation(.none, value: rotationAngle)
            Text(backText)
                .font(.subheadline)
                .padding()
                .foregroundColor(.white)
                .opacity(rotationAngle < 90 ? 0.0 : 1.0)
                .animation(.none, value: rotationAngle)
                .scaleEffect(CGSize(width: -1.0, height: 1.0))
        }
    }
}

struct FlashCardView_Previews: PreviewProvider {
    static var lessonVM = FlashCardLessonsViewModel()
    
    static var previews: some View {
        FlashCardView(lesson: lessonVM.lessons[0].lesson, passedDictionary: lessonVM.lessons[0].words).environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
    }
}