//
//  FilterView.swift
//  Feels
//
//  Created by Trey Tartt on 1/12/22.
//

import SwiftUI
import CoreData

class DataHolder: ObservableObject {
    // year, month, items
    @Published var data = [Int: [Int: [DayChartView]]]()
    @Published var numberOfRatings: Int = 0
    var uncategorizedData = [MoodEntry]() {
        didSet {
            self.numberOfRatings = uncategorizedData.count
        }
    }
}


struct FilterView: View {
    typealias Year = Int
    typealias Month = Int
    
    let weekdays = [("Sun", 1), ("mon", 2), ("tue", 3), ("wed", 4), ("thur", 5), ("fri", 6), ("sat", 7)]
    let months = [(0, "J"), (1, "F"), (2,"M"), (3,"A"), (4,"M"), (5, "J"), (6,"J"), (7,"A"), (8,"S"), (9,"O"), (10, "N"), (11,"D")]
    
    @State private var toggle = true
    @State var selectedDays = [Int]()
    @State private var entryStartDate: Date = Date()
    @State private var entryEndDate: Date = Date()
    @State private var showFilter = false
    
    @FetchRequest(
        sortDescriptors: [NSSortDescriptor(keyPath: \MoodEntry.forDate, ascending: false)],
        animation: .spring())
    private var items: FetchedResults<MoodEntry>
    
    @StateObject private var dataHolder = DataHolder()
    //[
    //  2001: [0: [], 1: [], 2: []],
    //  2002: [0: [], 1: [], 2: []]
    // ]
    let columns = [
        GridItem(.flexible(minimum: 5, maximum: 50)),
        GridItem(.flexible(minimum: 5, maximum: 50)),
        GridItem(.flexible(minimum: 5, maximum: 50)),
        GridItem(.flexible(minimum: 5, maximum: 50)),
        GridItem(.flexible(minimum: 5, maximum: 50)),
        GridItem(.flexible(minimum: 5, maximum: 50)),
        GridItem(.flexible(minimum: 5, maximum: 50)),
        GridItem(.flexible(minimum: 5, maximum: 50)),
        GridItem(.flexible(minimum: 5, maximum: 50)),
        GridItem(.flexible(minimum: 5, maximum: 50)),
        GridItem(.flexible(minimum: 5, maximum: 50)),
        GridItem(.flexible(minimum: 5, maximum: 50)),
    ]
    
    private func filterEntries(startDate: Date, endDate: Date) {
        let filteredEntries = PersistenceController.shared.getData(startDate: startDate, endDate: endDate, includedDays: selectedDays)
        self.dataHolder.data.removeAll()
        let filledOutData = buildGridData(withData: filteredEntries)
        self.dataHolder.data = filledOutData
        self.dataHolder.uncategorizedData = filteredEntries
    }
    
    private func buildGridData(withData data: [MoodEntry]) -> [Year: [Month: [DayChartView]]] {
        var returnData = [Year: [Month: [DayChartView]]]()
        
        if let earliestEntry = data.first,
           let lastEntry = data.last {
            
            let calendar = Calendar.current
            let components = calendar.dateComponents([.year], from: earliestEntry.forDate!)
            let earliestYear = components.year!
            
            let latestComponents = calendar.dateComponents([.year], from: lastEntry.forDate!)
            let latestYear = latestComponents.year!
            
            for year in earliestYear...latestYear {
                var allMonths = [Int: [DayChartView]]()
                
                // add back in if months header has leading (-1, ""),
                // and add back gridItem
//                var dayViews = [DayChartView]()
//                for day in 0...32 {
//                    let view = DayChartView(color: Mood.missing.color,
//                                           weekDay: 2,
//                                           viewType: .text(String(day+1)))
//                    dayViews.append(view)
//                }
//                allMonths[0] = dayViews
                
                for month in (1...12) {
                    var components = DateComponents()
                    components.month = month
                    components.year = year
                    let startDateOfMonth = Calendar.current.date(from: components)!
                    
                    let items = data.filter({ entry in
                        let components = calendar.dateComponents([.month, .year], from: startDateOfMonth)
                        let entryComponents = calendar.dateComponents([.month, .year], from: entry.forDate!)
                        return (components.month == entryComponents.month && components.year == entryComponents.year)
                    })
                    
                    allMonths[month] = createViewFor(monthEntries: items, forMonth: startDateOfMonth)
                }
                returnData[year] = allMonths
            }
        }
        return returnData
    }
    
    private func createViewFor(monthEntries: [MoodEntry], forMonth month: Date) -> [DayChartView] {
        var filledOutArray = [DayChartView]()
        
        let calendar = Calendar.current
        let range = calendar.range(of: .day, in: .month, for: month)!
        let numDays = range.count
        
        for day in 1...numDays {
            if let item = monthEntries.filter({ entry in
                let components = calendar.dateComponents([.day], from: entry.forDate!)
                let date = components.day
                return day == date
            }).first {
                let view = DayChartView(color: item.mood.color,
                                       weekDay: Int(item.weekDay),
                                       viewType: .cicle)
                filledOutArray.append(view)
            } else {
                let thisDate = Calendar.current.date(bySetting: .day, value: day, of: month)!
                let view = DayChartView(color: Mood.missing.color,
                                       weekDay:  Calendar.current.component(.weekday, from: thisDate),
                                       viewType: .cicle)
                filledOutArray.append(view)
            }
        }
        
        for _ in filledOutArray.count...32 {
            let view = DayChartView(color: Mood.missing.color,
                                   weekDay: 2,
                                   viewType: .cicle)
            filledOutArray.append(view)
        }
        
        return filledOutArray
    }
    
    var body: some View {
        VStack {
            filterButon
                .padding([.leading, .trailing, .top])
            
            statsView
                .frame(minWidth: 0, maxWidth: .infinity, minHeight: 120, maxHeight: 120)
                .cornerRadius(25)
                .padding([.leading, .trailing])
            
            Text("Total: \(self.dataHolder.numberOfRatings)")
                .font(.title2)
            
            if showFilter {
                filterView
            }
            
            gridView
                .onAppear(perform: {
                    let monthEntries = PersistenceController.shared.getData(startDate: Date(timeIntervalSince1970: 0), endDate: Date(), includedDays: selectedDays)
                    entryStartDate = monthEntries.first!.forDate!
                    entryEndDate = monthEntries.last!.forDate!
                    self.dataHolder.data = buildGridData(withData: monthEntries)
                    self.dataHolder.uncategorizedData = monthEntries
                    //                    filterEntries(startDate: entryStartDate, endDate: entryEndDate)
                })
        }
    }
    
    private var filterButon: some View {
       Button(action: {
            withAnimation{
                showFilter.toggle()
            }
        }, label: {
            Text(showFilter ? "Close Filters" : "Show Filters")
                .frame(maxWidth: .infinity)
                .frame(height: 44)
                .foregroundColor(Color(UIColor.label))
                .background(Color(UIColor.secondarySystemBackground))
                .cornerRadius(25)
        }).frame(maxWidth: .infinity)
    }
    
    struct StatsSubView: View {
        let data: [MoodEntry]
        let mood: Mood
        
        var body: some View {
            VStack {
                Text(String(Stats.getCountFor(moodType: mood,
                                              inData: data)))
                    .font(.title)
                Text(mood.strValue)
                    .foregroundColor(mood.color)
            }
        }
    }
    
    private var statsView: some View {
        ZStack {
            Color(UIColor.secondarySystemBackground)
            
            HStack {
                Spacer()
                ForEach(Mood.allValues, id: \.self) { mood in
                    StatsSubView(data: self.dataHolder.uncategorizedData, mood: mood)
                    Spacer()
                }
            }
        }
        .cornerRadius(25)
        .padding()
    }
    
    private var filterView: some View {
        VStack {
            VStack {
                ZStack {
                    Color(UIColor.secondarySystemBackground)
                    DatePicker(
                        "Start Date",
                        selection: $entryStartDate,
                        displayedComponents: [.date]
                    ).onChange(of: entryStartDate, perform: { value in
                        filterEntries(startDate: self.entryStartDate, endDate: self.entryEndDate)
                    })
                        .padding()
                }
                .frame(minWidth: 0, maxWidth: .infinity, minHeight: 44, maxHeight: 44)
                .cornerRadius(25)
                .padding([.leading, .trailing])
                
                ZStack {
                    Color(UIColor.secondarySystemBackground)
                    DatePicker(
                        "End Date",
                        selection: $entryEndDate,
                        displayedComponents: [.date]
                    ).onChange(of: entryStartDate, perform: { value in
                        filterEntries(startDate: self.entryStartDate, endDate: self.entryEndDate)
                    })
                        .padding()
                }
                .frame(minWidth: 0, maxWidth: .infinity, minHeight: 44, maxHeight: 44)
                .cornerRadius(25)
                .padding([.leading, .trailing])
                
                ZStack {
                    Color(UIColor.secondarySystemBackground)
                    HStack {
                        Spacer()
                        ForEach(weekdays.indices, id: \.self) { dayIdx in
                            let day = String(weekdays[dayIdx].0)
                            let value = weekdays[dayIdx].1
                            
                            Button(day.capitalized, action: {
                                if let index = selectedDays.firstIndex(of: value) {
                                    selectedDays.remove(at: index)
                                } else {
                                    selectedDays.append(value)
                                }
                                filterEntries(startDate: entryStartDate, endDate: entryEndDate)
                            })
                                .frame(maxWidth: .infinity)
                                .foregroundColor(selectedDays.contains(value) || selectedDays.isEmpty ? .green : .red)
                        }
                        Spacer()
                    }
                }
                .frame(minWidth: 0, maxWidth: .infinity, minHeight: 44, maxHeight: 44)
                .cornerRadius(25)
                .padding([ .leading, .trailing])
            }
            filterButon
                .padding([.leading, .trailing, .top])
        }
    }
    
    private var monthsHeader: some View {
        LazyVGrid(columns: columns, spacing: 0) {
            ForEach(months, id: \.self.0) { item in
                Text(item.1)
                    .textCase(.uppercase)
            }
        }.padding([.leading, .trailing, .top])
    }
    
    private var gridView: some View {
        VStack {
            monthsHeader
                .cornerRadius(25)
                .padding([.leading, .trailing])
            
            VStack {
                ScrollView {
                    ForEach(Array(self.dataHolder.data.keys.sorted(by: >)), id: \.self) { yearKey in
                        let yearData = self.dataHolder.data[yearKey]!
                        Text(String(yearKey))
                            .font(.title)
                        yearGridView(yearData: yearData, columns: columns)
                    }
                }
                .padding()
            }
        }
    }
    
    private struct yearGridView: View {
        let yearData: [Int: [DayChartView]]
        let columns: [GridItem]
        
        var body: some View {
            ZStack {
                Color(UIColor.secondarySystemBackground)
                
                VStack {
                    LazyVGrid(columns: columns, spacing: 0) {
                        ForEach(Array(yearData.keys.sorted(by: <)), id: \.self) { monthKey in
                            let monthData = yearData[monthKey]!
                            VStack {
                                monthGridView(monthData: monthData)
                            }
                        }
                    }
                    .padding([.leading, .trailing, .top, .bottom])
                }
            }
            .cornerRadius(25)
        }
    }
    
    private struct monthGridView: View {
        let monthData: [DayChartView]
        
        var body: some View {
            VStack {
                ForEach(monthData, id: \.self) { view in
                    view
                }
            }
        }
    }
}

struct FilterView_Previews: PreviewProvider {
    static var previews: some View {
        Group {
            FilterView()
            
            FilterView()
                .preferredColorScheme(.dark)
        }
    }
}