//
//  AddToMealPlanSheet.swift
//  Nextcloud Cookbook iOS Client
//

import Foundation
import SwiftUI

struct AddToMealPlanSheet: View {
    @EnvironmentObject var mealPlan: MealPlanManager
    @Environment(\.dismiss) private var dismiss

    let recipeId: String
    let recipeName: String
    let prepTime: String?
    let recipeImage: UIImage?

    @State private var weekOffset: Int = 0
    @State private var selectedDays: Set<String> = []

    private var calendar: Calendar { Calendar.current }

    private var weekDates: [Date] {
        let today = calendar.startOfDay(for: Date())
        let weekday = calendar.component(.weekday, from: today)
        let daysToMonday = (weekday + 5) % 7
        guard let monday = calendar.date(byAdding: .day, value: -daysToMonday, to: today),
              let offsetMonday = calendar.date(byAdding: .weekOfYear, value: weekOffset, to: monday) else {
            return []
        }
        return (0..<7).compactMap { calendar.date(byAdding: .day, value: $0, to: offsetMonday) }
    }

    private var weekLabel: String {
        if weekOffset == 0 {
            return String(localized: "This Week")
        } else if weekOffset == 1 {
            return String(localized: "Next Week")
        } else if weekOffset == -1 {
            return String(localized: "Last Week")
        } else {
            return weekRangeString
        }
    }

    private var weekRangeString: String {
        guard let first = weekDates.first, let last = weekDates.last else { return "" }
        let formatter = DateFormatter()
        formatter.dateFormat = "dd.MM."
        return "\(formatter.string(from: first)) – \(formatter.string(from: last))"
    }

    var body: some View {
        NavigationStack {
            VStack(spacing: 0) {
                // Recipe header
                recipeHeader
                    .padding()

                Divider()

                // Week navigation
                weekNavigationHeader
                    .padding(.horizontal)
                    .padding(.vertical, 8)

                // Day rows with checkboxes
                List {
                    ForEach(weekDates, id: \.self) { date in
                        let dayStr = MealPlanDate.dayString(from: date)
                        let isAlreadyAssigned = mealPlan.isRecipeAssigned(recipeId, on: date)
                        let existingCount = mealPlan.entries(for: date).count

                        Button {
                            if !isAlreadyAssigned {
                                if selectedDays.contains(dayStr) {
                                    selectedDays.remove(dayStr)
                                } else {
                                    selectedDays.insert(dayStr)
                                }
                            }
                        } label: {
                            HStack {
                                Image(systemName: (isAlreadyAssigned || selectedDays.contains(dayStr)) ? "checkmark.circle.fill" : "circle")
                                    .foregroundStyle(isAlreadyAssigned ? Color.secondary : Color.nextcloudBlue)

                                Text(dayDisplayName(date))
                                    .foregroundStyle(isAlreadyAssigned ? .secondary : .primary)

                                Spacer()

                                if existingCount > 0 {
                                    Text("\(existingCount)")
                                        .font(.caption)
                                        .foregroundStyle(.secondary)
                                        .padding(.horizontal, 8)
                                        .padding(.vertical, 2)
                                        .background(Capsule().fill(Color(.tertiarySystemFill)))
                                }
                            }
                        }
                        .disabled(isAlreadyAssigned)
                    }
                }
                .listStyle(.plain)
            }
            .navigationTitle("Schedule Recipe")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("Cancel") { dismiss() }
                }
                ToolbarItem(placement: .confirmationAction) {
                    Button("Done") {
                        let dates = selectedDays.compactMap { MealPlanDate.dateFromDay($0) }
                        if !dates.isEmpty {
                            mealPlan.assignRecipe(recipeId: recipeId, recipeName: recipeName, toDates: dates)
                        }
                        dismiss()
                    }
                    .disabled(selectedDays.isEmpty)
                }
            }
        }
    }

    private var recipeHeader: some View {
        HStack(spacing: 12) {
            if let recipeImage {
                Image(uiImage: recipeImage)
                    .resizable()
                    .aspectRatio(contentMode: .fill)
                    .frame(width: 60, height: 60)
                    .clipShape(RoundedRectangle(cornerRadius: 10))
            } else {
                LinearGradient(
                    gradient: Gradient(colors: [.ncGradientDark, .ncGradientLight]),
                    startPoint: .topLeading,
                    endPoint: .bottomTrailing
                )
                .frame(width: 60, height: 60)
                .overlay {
                    Image(systemName: "fork.knife")
                        .foregroundStyle(.white.opacity(0.7))
                }
                .clipShape(RoundedRectangle(cornerRadius: 10))
            }

            VStack(alignment: .leading, spacing: 4) {
                Text(recipeName)
                    .font(.headline)
                    .lineLimit(2)

                if let prepTime, !prepTime.isEmpty {
                    let duration = DurationComponents.fromPTString(prepTime)
                    if duration.hourComponent > 0 || duration.minuteComponent > 0 {
                        HStack(spacing: 4) {
                            Image(systemName: "clock")
                                .font(.caption)
                            Text(duration.displayString)
                                .font(.caption)
                        }
                        .foregroundStyle(.secondary)
                    }
                }
            }

            Spacer()
        }
    }

    private var weekNavigationHeader: some View {
        HStack {
            Button {
                withAnimation { weekOffset -= 1 }
            } label: {
                Image(systemName: "chevron.left")
                    .font(.title3)
                    .foregroundStyle(Color.nextcloudBlue)
            }

            Spacer()

            VStack(spacing: 2) {
                Text(weekLabel)
                    .font(.headline)
                if weekOffset == 0 || weekOffset == 1 || weekOffset == -1 {
                    Text(weekRangeString)
                        .font(.caption)
                        .foregroundStyle(.secondary)
                }
            }

            Spacer()

            Button {
                withAnimation { weekOffset += 1 }
            } label: {
                Image(systemName: "chevron.right")
                    .font(.title3)
                    .foregroundStyle(Color.nextcloudBlue)
            }
        }
    }

    private func dayDisplayName(_ date: Date) -> String {
        let formatter = DateFormatter()
        formatter.dateFormat = "EEEE, d MMM"
        let name = formatter.string(from: date)
        if calendar.isDateInToday(date) {
            return "\(name) (\(String(localized: "Today")))"
        }
        return name
    }
}