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

import SwiftUI
import Combine
import CoreData

/// 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

    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))
    }

    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)
//                }
//            }
//        }
    }

    @State private var refreshView: Bool = false

    var body: some View {
        DynamicFetchView(predicate: NSPredicate(format: "budgetId == %@ AND month == %ld AND year == %ld", budget.id as CVarArg, month, year),
                         sortDescriptors: []) { (budgetEntries: FetchedResults<BudgetCategoryEntry>) in

            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: String(format: "= %@ =", budgetEntries.first(where: { $0.budgetCategoryId == category.id })?.amount ?? -69 ),
                                                           color: 0 < 0 ? Color("negativeAmount") : Color("positiveAmount")
                                        )
                                    }
                                }
                            }
                        }
                    }
                }
                .listStyle(PlainListStyle())
//                .onChange(of: month) { m in
//                    let entries = budgetEntries
//                    print(entries.map { $0.amount })
//                }
                .navigationBarTitle(budget.name, displayMode: .inline)
                .toolbar {
                    EditButton()
                }
                .onAppear() {
                    currentBudgetId = budget.id
                    lastLoadedBudgetId = budget.id.uuidString
                }
                .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)
    }
}