//
//  BudgetView.swift
//  ydnab
//
//  Created by Andrea Franceschini on 23/09/2020.
//

import SwiftUI
import Combine

/// Shows the budget values for the selected budget, month, and year.
struct BudgetView: View {
    @State var budget: BudgetInfo
    @Binding var currentBudgetId: UUID?
    @State private var month: Int = 0
    @State private var monthName: String
    @State private var year: Int = Calendar(identifier: .gregorian).component(.year, from: Date())
    @State private var showMonthPicker: Bool = false
    @State private var showNotImplemented: Bool = false
    @State private var showQuickBudget: Bool = false
    @State private var showEditCategoryEntry: Bool = false
    @State private var editingCategoryEntry: BudgetCategoryEntry? = nil

    @AppStorage("lastLoadedBudgetId") private var lastLoadedBudgetId = ""

    @Environment(\.managedObjectContext) var managedObjectContext

//    private var budgetEntriesRequest: FetchRequest<BudgetCategoryEntry>
//    private var budgetEntries: FetchedResults<BudgetCategoryEntry> { budgetEntriesRequest.wrappedValue }

    @FetchRequest<BudgetCategoryEntry> private var budgetEntries: FetchedResults<BudgetCategoryEntry>

    init(budget: BudgetInfo, currentBudgetId: Binding<UUID?>) {
        _budget = .init(initialValue: budget)
        _currentBudgetId = currentBudgetId
        var cal = Calendar(identifier: .gregorian)
        cal.locale = Locale(identifier: self._budget.wrappedValue.localeIdentifier)
        let now = Date()
        _month = .init(initialValue: cal.component(.month, from: now))
        _monthName = .init(initialValue: cal.monthSymbols[self._month.wrappedValue])
        _year = .init(initialValue: cal.component(.year, from: now))

        _budgetEntries = FetchRequest<BudgetCategoryEntry>(entity: BudgetCategoryEntry.entity(),
                                                           sortDescriptors: [],
                                                           predicate: NSPredicate(format: "(budgetId == %@) AND (month == %d) AND (year == %d)",
                                                                                  budget.id as CVarArg, _month.wrappedValue, _year.wrappedValue))

//        budgetEntriesRequest = FetchRequest<BudgetCategoryEntry>(entity: BudgetCategoryEntry.entity(),
//                                                                 sortDescriptors: [],
//                                                                 predicate: NSCompoundPredicate(andPredicateWithSubpredicates: [
//                                                                    NSPredicate(format: "budgetId == %@", budget.id as CVarArg),
//                                                                    NSPredicate(format: "month == %i", month),
//                                                                    NSPredicate(format: "year == %i", year)
//                                                                 ])
//        )
    }

    func formatAmount(_ amount: NSNumber) -> String? {
        let f = NumberFormatter()
        f.locale = Locale(identifier: budget.localeIdentifier)
        f.numberStyle = .currency
        return f.string(from: amount)
    }

    private func findBudgetCategoryEntry(withId: UUID) -> BudgetCategoryEntry? {
        return budgetEntries.first(where: { $0.budgetCategoryId == withId })
    }

    private func zeroBudgetEntries() -> Void {
        for section in budget.sections {
            for category in section.categories {
                if let entry = findBudgetCategoryEntry(withId: category.id) {
                    entry.amount = 0
                } else {
                    let newEntry = BudgetCategoryEntry(context: managedObjectContext)
                    newEntry.budgetId = budget.id
                    newEntry.budgetCategoryId = category.id
                    newEntry.month = Int64(month)
                    newEntry.year = Int64(year)
                    newEntry.amount = 0
                }

                do {
                    try managedObjectContext.save()
                } catch {
                    print(error)
                }
            }
        }
    }

    var body: some View {
        VStack {
            HStack {
                Button(action: { withAnimation() { showMonthPicker.toggle() } } ) {
                    Text("\(monthName) \(String(year))")
                    Image(systemName: showMonthPicker ? "chevron.up" : "chevron.down")
                }
                Spacer()
                Button(action: { showQuickBudget.toggle() }) { // TODO: Implement this
                    Image(systemName: "bolt.fill")
                }
                Button(action: { showNotImplemented.toggle() }) { // TODO: Implement this
                    Image(systemName: "gearshape.fill")
                }.padding(.leading, 11)
            }
            .padding(11)

            if showMonthPicker {
                YearAndMonthPicker(month: $month,
                                   monthName: $monthName,
                                   year: $year,
                                   locale: Locale(identifier: budget.localeIdentifier)
                )
            }
            
            BudgetViewSummary(budget: $budget, month: $month, monthName: $monthName, year: $year)
                .padding([.leading, .trailing], 16)

            List {
                ForEach(budget.sections) { section in
                    if !section.hidden {
                        Section(header: BudgetSectionCell(section: section,
                                                          amountText: "", //formatAmount(0) ?? "--",
                                                          color: 0 < 0 ? Color("negativeAmount") : Color("positiveAmount"))
                        ) {
                            ForEach(section.categories) { category in
                                if !category.hidden {
                                    BudgetCategoryCell(category: category,
                                                       amountText: formatAmount(budgetEntries.first(where: { $0.budgetCategoryId == category.id })?.amount ?? 0) ?? "--",
                                                       color: 0 < 0 ? Color("negativeAmount") : Color("positiveAmount")
                                    )
                                    .onLongPressGesture {
                                        editingCategoryEntry = findBudgetCategoryEntry(withId: category.id)
                                        showEditCategoryEntry.toggle()
                                    }
                                }
                            }
                            .onMove { (indexSet, s) in
                                print(indexSet, s)
                            }
                        }
                    }
                }
                .onMove { (indexSet, s) in
                    print(indexSet, s)
                }
            }
            .listStyle(PlainListStyle())
            .navigationBarTitle(budget.name, displayMode: .inline)
            .toolbar {
                EditButton()
            }
            .onAppear() {
                currentBudgetId = budget.id
                lastLoadedBudgetId = budget.id.uuidString
            }
            .onChange(of: month) { e in

            }
            .onReceive(budgetEntries.publisher) { o in
                print(o.month)
            }
            .actionSheet(isPresented: $showQuickBudget) {
                ActionSheet(
                    title: Text("Quick budget"),
                    message: Text("How would you like to set up your budget for \(monthName) \(String(year))?"),
                    buttons: [
                        .cancel { print(self.showQuickBudget) },
                        .default(Text("All categories to zero"), action: zeroBudgetEntries),
                        .default(Text("Values used the previous month"), action: { print(self) })
                    ]
                )
            }
            .popover(isPresented: $showEditCategoryEntry) {
//                BudgetCategoryEntryEditor(amount: $editingCategoryEntry.wrappedValue?.amount)
            }

            .alert(isPresented: $showNotImplemented) {
                Alert(title: Text("Not Implemented!"))
            }
        }
    }
}

struct BudgetCategoryEntryEditor: View {
    @Binding var amount: Decimal?
    @Binding var locale: Locale
    @State private var amountText = ""

    var body: some View {
        VStack {
            TextField("Amount", text: $amountText)
                .keyboardType(.numbersAndPunctuation)
                .onReceive(Just(amountText)) { newValue in
                    let filtered = newValue.filter { "0123456789.,".contains($0) }
                    if filtered != newValue {
                        amount = Decimal(string: filtered, locale: locale)
                    }
                }
        }
        .onAppear {
            amountText = "\(amount ?? -69)"
        }
    }
}

struct BudgetView_Previews: PreviewProvider {
    static let budget: [BudgetSection] = [
        BudgetSection(name: "Everyday Expenses", categories: [
            BudgetCategory(name: "Groceries"),
            BudgetCategory(name: "Eating out"),
            BudgetCategory(name: "Medical"),
            BudgetCategory(name: "Clothing"),
            BudgetCategory(name: "Household goods")
        ]),
        BudgetSection(name: "Travel", categories: [
            BudgetCategory(name: "Transport"),
            BudgetCategory(name: "Fuel"),
            BudgetCategory(name: "Accommodation")
        ]),
        BudgetSection(name: "Rainy Days", categories: [
            BudgetCategory(name: "Emergencies"),
            BudgetCategory(name: "Car insurance")
        ]),
        BudgetSection(name: "Monthly Expenses", categories: [
            BudgetCategory(name: "Rent"),
            BudgetCategory(name: "Mobile")
        ]),
        BudgetSection(name: "Savings Goals", categories: [
            BudgetCategory(name: "Savings"),
            BudgetCategory(name: "Holidays")
        ])
    ]
    @State static var currentBudgetId: UUID?

    static var previews: some View {
        NavigationView {
            BudgetView(budget: BudgetInfo(name: "Default Budget", sections: budget),
                       currentBudgetId: $currentBudgetId)
        }
        .preferredColorScheme(.light)
    }
}