//
//  MonthCalendarView.swift
//  Expiranner
//
//  월별 캘린더: 날짜 그리드 + 선택한 날의 아이템 목록

import SwiftUI
import SwiftData

struct MonthCalendarView: View {
    let year: Int
    let month: Int

    @Environment(\.modelContext) private var modelContext
    @Query private var items: [ProductItem]

    @State private var selectedDay: Int?
    @State private var showScanner = false
    @State private var editingItem: ProductItem?

    private let columns = Array(repeating: GridItem(.flexible()), count: 7)
    private let weekdaySymbols = ["일", "월", "화", "수", "목", "금", "토"]

    init(year: Int, month: Int) {
        self.year = year
        self.month = month
        let (start, end) = MonthCell.monthBounds(year: year, month: month)
        _items = Query(
            filter: #Predicate<ProductItem> { $0.date >= start && $0.date < end },
            sort: \ProductItem.date
        )
    }

    private var daysInMonth: Int {
        let calendar = Calendar.current
        let start = calendar.date(from: DateComponents(year: year, month: month, day: 1)) ?? Date()
        return calendar.range(of: .day, in: .month, for: start)?.count ?? 30
    }

    /// 1일의 요일 오프셋 (일요일 시작 기준)
    private var firstWeekdayOffset: Int {
        let calendar = Calendar.current
        let start = calendar.date(from: DateComponents(year: year, month: month, day: 1)) ?? Date()
        return calendar.component(.weekday, from: start) - 1
    }

    private func day(of item: ProductItem) -> Int {
        Calendar.current.component(.day, from: item.date)
    }

    private var selectedDayItems: [ProductItem] {
        guard let selectedDay else { return [] }
        return items.filter { day(of: $0) == selectedDay }
    }

    var body: some View {
        ZStack(alignment: .bottomTrailing) {
            VStack {
                LazyVGrid(columns: columns, spacing: 8) {
                    ForEach(weekdaySymbols, id: \.self) { symbol in
                        Text(symbol)
                            .font(.caption)
                            .foregroundStyle(.secondary)
                    }
                    ForEach(0..<firstWeekdayOffset, id: \.self) { _ in
                        Text("")
                    }
                    ForEach(1...daysInMonth, id: \.self) { day in
                        let count = items.filter { self.day(of: $0) == day }.count
                        Button {
                            selectedDay = day
                        } label: {
                            VStack(spacing: 2) {
                                Text("\(day)")
                                    .fontWeight(selectedDay == day ? .bold : .regular)
                                Circle()
                                    .fill(count > 0 ? .red : .clear)
                                    .frame(width: 6, height: 6)
                            }
                            .frame(maxWidth: .infinity)
                            .padding(.vertical, 4)
                            .background(
                                RoundedRectangle(cornerRadius: 6)
                                    .fill(selectedDay == day ? Color(.systemGray4) : .clear)
                            )
                        }
                        .buttonStyle(.plain)
                    }
                }
                .padding(.horizontal)

                if let selectedDay {
                    List {
                        Section("\(month)월 \(selectedDay)일 저장된 항목") {
                            if selectedDayItems.isEmpty {
                                Text("저장된 항목이 없습니다")
                                    .foregroundStyle(.secondary)
                            }
                            ForEach(selectedDayItems) { item in
                                Button {
                                    editingItem = item
                                } label: {
                                    HStack {
                                        if let data = item.imageData, let image = UIImage(data: data) {
                                            Image(uiImage: image)
                                                .resizable()
                                                .scaledToFill()
                                                .frame(width: 44, height: 44)
                                                .clipShape(RoundedRectangle(cornerRadius: 6))
                                        }
                                        Text(item.name)
                                        Spacer()
                                    }
                                }
                                .buttonStyle(.plain)
                            }
                            .onDelete(perform: deleteItems)
                        }
                    }
                    .listStyle(.insetGrouped)
                } else {
                    Spacer()
                    Text("날짜를 선택하면 저장된 항목이 표시됩니다")
                        .foregroundStyle(.secondary)
                    Spacer()
                }
            }

            FloatingScanButton {
                showScanner = true
            }
        }
        .navigationTitle("\(String(year))년 \(month)월")
        .navigationBarTitleDisplayMode(.inline)
        .fullScreenCover(isPresented: $showScanner) {
            ScannerView(year: year, month: month)
        }
        .sheet(item: $editingItem) { item in
            ItemEditView(item: item)
        }
    }

    private func deleteItems(at offsets: IndexSet) {
        let targets = offsets.map { selectedDayItems[$0] }
        for item in targets {
            print("항목 삭제: \(item.name)")
            modelContext.delete(item)
        }
    }
}

/// 저장된 항목의 날짜(연/월/일) 수정 뷰
struct ItemEditView: View {
    @Bindable var item: ProductItem
    @Environment(\.dismiss) private var dismiss

    var body: some View {
        NavigationStack {
            Form {
                Section("제품명") {
                    TextField("제품명", text: $item.name)
                }
                Section("날짜 이동") {
                    DatePicker("날짜", selection: $item.date, displayedComponents: .date)
                        .datePickerStyle(.graphical)
                }
            }
            .navigationTitle("항목 수정")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .confirmationAction) {
                    Button("완료") {
                        print("항목 수정 완료: \(item.name) → \(item.date)")
                        dismiss()
                    }
                }
            }
        }
    }
}

#Preview {
    NavigationStack {
        MonthCalendarView(year: 2026, month: 7)
    }
    .modelContainer(for: ProductItem.self, inMemory: true)
}