import SwiftUI
import CoreImage.CIFilterBuiltins

struct WeekPlanShareView: View {
    let plan: WeekPlan
    let settings: AppSettings
    let dishes: [Dish]
    let tags: [Tag]
    let exportStyleOverride: WeekExportStyle?

    static let a4LandscapeWidth: CGFloat = 3508
    static let a4LandscapeHeight: CGFloat = 2480
    static let a4PortraitWidth: CGFloat = 2480
    static let a4PortraitHeight: CGFloat = 3508

    private let shareURL = "https://mealmood.app"
    private let qrContext = CIContext()
    private let qrFilter = CIFilter.qrCodeGenerator()

    init(
        plan: WeekPlan,
        settings: AppSettings,
        dishes: [Dish],
        tags: [Tag],
        exportStyleOverride: WeekExportStyle? = nil
    ) {
        self.plan = plan
        self.settings = settings
        self.dishes = dishes
        self.tags = tags
        self.exportStyleOverride = exportStyleOverride
    }

    static func canvasSize(for style: WeekExportStyle) -> CGSize {
        switch style {
        case .vertical:
            return CGSize(width: a4PortraitWidth, height: a4PortraitHeight)
        case .defaultStyle, .schoolTimetable:
            return CGSize(width: a4LandscapeWidth, height: a4LandscapeHeight)
        }
    }

    private var dayRange: ClosedRange<Int> {
        settings.includeWeekends ? 0...6 : 0...4
    }

    private var mealTypes: [MealType] {
        settings.activeMealTypes
    }

    private var exportStyle: WeekExportStyle {
        exportStyleOverride ?? settings.weekExportStyleEnum
    }

    private var canvasSize: CGSize {
        Self.canvasSize(for: exportStyle)
    }

    private var locale: Locale {
        Locale(identifier: settings.languageEnum.resolved().localeIdentifier)
    }

    private var exportDateString: String {
        Date.now.formatted(date: .abbreviated, time: .omitted)
    }

    private var qrImage: UIImage? {
        qrFilter.setValue(Data(shareURL.utf8), forKey: "inputMessage")
        qrFilter.setValue("M", forKey: "inputCorrectionLevel")
        guard let outputImage = qrFilter.outputImage else { return nil }
        let transformed = outputImage.transformed(by: CGAffineTransform(scaleX: 10, y: 10))
        guard let cgImage = qrContext.createCGImage(transformed, from: transformed.extent) else { return nil }
        return UIImage(cgImage: cgImage)
    }

    var body: some View {
        ZStack {
            switch exportStyle {
            case .defaultStyle:
                defaultBackground
            case .schoolTimetable:
                schoolBackground
            case .vertical:
                verticalBackground
            }

            VStack(spacing: 24) {
                headerBlock

                Group {
                    switch exportStyle {
                    case .defaultStyle:
                        defaultGridLayout
                    case .schoolTimetable:
                        schoolTimetableLayout
                    case .vertical:
                        verticalLayout
                    }
                }
                .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .top)

                footerBlock
            }
            .padding(.horizontal, exportStyle == .vertical ? 72 : 84)
            .padding(.vertical, exportStyle == .vertical ? 58 : 70)
        }
        .frame(width: canvasSize.width, height: canvasSize.height)
    }

    private var defaultBackground: some View {
        ZStack {
            LinearGradient(
                colors: [Color(hex: "#FFEFE6"), Color(hex: "#F1FBF5")],
                startPoint: .topLeading,
                endPoint: .bottomTrailing
            )

            Circle()
                .fill(Color(hex: "#FFD6E2").opacity(0.55))
                .frame(width: 760, height: 760)
                .blur(radius: 20)
                .offset(x: -980, y: -760)

            Circle()
                .fill(Color(hex: "#CFF2E8").opacity(0.55))
                .frame(width: 680, height: 680)
                .blur(radius: 20)
                .offset(x: 1050, y: 760)
        }
    }

    private var schoolBackground: some View {
        ZStack {
            Color(hex: "#FFF9F5")

            RoundedRectangle(cornerRadius: 220)
                .fill(Color.mealMoodMint.opacity(0.22))
                .frame(width: 1500, height: 520)
                .offset(x: 920, y: -920)

            RoundedRectangle(cornerRadius: 220)
                .fill(Color.mealMoodCoral.opacity(0.18))
                .frame(width: 1600, height: 560)
                .offset(x: -920, y: 940)
        }
    }

    private var verticalBackground: some View {
        ZStack {
            LinearGradient(
                colors: [Color(hex: "#FFF7F4"), Color(hex: "#FFF3F7"), Color(hex: "#F6FFF8")],
                startPoint: .topLeading,
                endPoint: .bottomTrailing
            )

            Circle()
                .fill(Color(hex: "#FFD0DF").opacity(0.6))
                .frame(width: 1100, height: 1100)
                .blur(radius: 90)
                .offset(x: 950, y: -1100)

            Circle()
                .fill(Color(hex: "#C0EAD8").opacity(0.55))
                .frame(width: 1000, height: 1000)
                .blur(radius: 80)
                .offset(x: -900, y: 1300)

            Circle()
                .fill(Color(hex: "#FFE0C0").opacity(0.4))
                .frame(width: 700, height: 700)
                .blur(radius: 100)
                .offset(x: 100, y: 200)
        }
    }

    @ViewBuilder
    private var headerBlock: some View {
        switch exportStyle {
        case .defaultStyle:
            defaultHeader
        case .schoolTimetable, .vertical:
            elegantHeader
        }
    }

    private var defaultHeader: some View {
        HStack(alignment: .center, spacing: 24) {
            AppIconPlaceholder(size: 104)

            VStack(alignment: .leading, spacing: 6) {
                Text(exportHeaderTitle)
                    .font(.system(size: 52, weight: .bold, design: .rounded))
                    .foregroundStyle(
                        LinearGradient(
                            colors: [Color.mealMoodCoral, Color(hex: "#3F7A64")],
                            startPoint: .leading, endPoint: .trailing
                        )
                    )
                Text(plan.weekStartDate.formattedWeekRange())
                    .font(.system(size: 28, weight: .semibold, design: .rounded))
                    .foregroundColor(Color(hex: "#5D645F"))
            }

            Spacer()

            Text(exportDateString)
                .font(.system(size: 24, weight: .medium, design: .rounded))
                .foregroundColor(.mealMoodTextSecondary)
        }
        .padding(.horizontal, 30)
        .padding(.vertical, 24)
        .background(Color.white.opacity(0.8))
        .clipShape(RoundedRectangle(cornerRadius: 24))
        .overlay(
            RoundedRectangle(cornerRadius: 24)
                .stroke(Color.mealMoodCoral.opacity(0.5), lineWidth: 1)
        )
    }

    private var elegantHeader: some View {
        VStack(spacing: 10) {
            MealMoodLogoMark(size: 96)

            Text(plan.weekStartDate.formattedWeekRange())
                .font(.custom("Didot", size: exportStyle == .vertical ? 126 : 108))
                .foregroundColor(Color(hex: "#30473F"))
                .multilineTextAlignment(.center)
                .lineLimit(1)
                .minimumScaleFactor(0.45)
                .frame(maxWidth: .infinity)

            Text(exportHeaderTitle)
                .font(.system(size: exportStyle == .vertical ? 58 : 54, weight: .semibold, design: .serif))
                .foregroundColor(.mealMoodTextPrimary)

            Text(exportDateString)
                .font(.system(size: 34, weight: .medium, design: .serif))
                .foregroundColor(.mealMoodTextSecondary)
        }
        .padding(.horizontal, 24)
        .padding(.vertical, 24)
        .background(Color.white.opacity(0.88))
        .clipShape(RoundedRectangle(cornerRadius: 24))
        .overlay(
            RoundedRectangle(cornerRadius: 24)
                .stroke(Color.mealMoodCoral.opacity(0.45), lineWidth: 1)
        )
    }

    private var exportHeaderTitle: String {
        switch exportStyle {
        case .defaultStyle:
            return String(localized: "share_week_title")
        case .schoolTimetable:
            return String(localized: "share_export_school_title")
        case .vertical:
            return String(localized: "share_export_vertical_title")
        }
    }

    private var defaultGridLayout: some View {
        ZStack {
            RoundedRectangle(cornerRadius: 30)
                .fill(Color.white.opacity(0.62))
            RoundedRectangle(cornerRadius: 30)
                .stroke(Color.white.opacity(0.75), lineWidth: 2)

            Grid(horizontalSpacing: 10, verticalSpacing: 10) {
                GridRow {
                    gridHeaderCell("", day: nil)
                        .frame(minWidth: 220)
                    ForEach(Array(dayRange), id: \.self) { day in
                        gridHeaderCell(dayShortTitle(for: day), day: day)
                    }
                }

                ForEach(mealTypes, id: \.self) { mealType in
                    GridRow {
                        gridMealCell(mealTypeLabel(mealType), icon: mealType.icon, mealType: mealType)
                            .frame(minWidth: 220)
                        ForEach(Array(dayRange), id: \.self) { day in
                            gridDishCell(dishName(day: day, mealType: mealType), day: day)
                        }
                    }
                }
            }
            .padding(18)
        }
        .shadow(color: Color(hex: "#DDAA99").opacity(0.18), radius: 26, x: 0, y: 16)
    }

    private var schoolTimetableLayout: some View {
        ZStack {
            RoundedRectangle(cornerRadius: 28)
                .fill(Color.white)
                .shadow(color: Color.black.opacity(0.06), radius: 20, x: 0, y: 10)

            VStack(spacing: 18) {
                Text(String(localized: "share_export_school_subtitle"))
                    .font(.custom("Didot", size: 48))
                    .foregroundColor(.mealMoodTextSecondary)

                Grid(horizontalSpacing: 12, verticalSpacing: 12) {
                    GridRow {
                        Text(" ")
                            .frame(width: 280)
                        ForEach(mealTypes, id: \.self) { mealType in
                            Text(mealTypeLabel(mealType).uppercased(with: locale))
                                .font(.system(size: 34, weight: .bold, design: .serif))
                                .foregroundColor(Color(hex: "#355548"))
                                .frame(maxWidth: .infinity, minHeight: 88)
                                .background(Color.mealMoodMint.opacity(0.3))
                                .clipShape(RoundedRectangle(cornerRadius: 12))
                        }
                    }

                    ForEach(Array(dayRange), id: \.self) { day in
                        GridRow {
                            Text(dayHeaderTitle(for: day).uppercased(with: locale))
                                .font(.system(size: 30, weight: .bold, design: .serif))
                                .foregroundColor(.mealMoodTextPrimary)
                                .multilineTextAlignment(.center)
                                .frame(width: 280)
                                .frame(minHeight: 138)
                                .background(dayHeaderBackground(day: day))
                                .clipShape(RoundedRectangle(cornerRadius: 12))

                            ForEach(mealTypes, id: \.self) { mealType in
                                Text(dishName(day: day, mealType: mealType))
                                    .font(.system(size: 31, weight: .medium, design: .serif))
                                    .foregroundColor(.mealMoodTextPrimary)
                                    .multilineTextAlignment(.leading)
                                    .lineLimit(3)
                                    .frame(maxWidth: .infinity, minHeight: 138, alignment: .leading)
                                    .padding(.horizontal, 16)
                                    .background(Color(hex: "#FFFDFB"))
                                    .overlay(
                                        RoundedRectangle(cornerRadius: 12)
                                            .stroke(Color(hex: "#ECDDD5"), lineWidth: 1)
                                    )
                                    .clipShape(RoundedRectangle(cornerRadius: 12))
                            }
                        }
                    }
                }
            }
            .padding(.horizontal, 24)
            .padding(.vertical, 22)
        }
    }

    private var verticalLayout: some View {
        ZStack {
            RoundedRectangle(cornerRadius: 32)
                .fill(Color.white.opacity(0.88))
                .overlay(
                    RoundedRectangle(cornerRadius: 32)
                        .stroke(
                            LinearGradient(
                                colors: [Color(hex: "#F0C0CC").opacity(0.7), Color(hex: "#B8E8D4").opacity(0.7)],
                                startPoint: .topLeading,
                                endPoint: .bottomTrailing
                            ),
                            lineWidth: 3
                        )
                )

            VStack(spacing: 20) {
                ForEach(Array(dayRange), id: \.self) { day in
                    HStack(spacing: 0) {
                        VStack(spacing: 12) {
                            Text(dayLongTitle(for: day).uppercased(with: locale))
                                .font(.custom("Didot", size: 68))
                                .foregroundColor(Color(hex: "#2C3E35"))
                                .multilineTextAlignment(.center)
                                .lineLimit(1)
                                .minimumScaleFactor(0.38)
                                .frame(maxWidth: .infinity)

                            Text(dayNumberOnly(for: day))
                                .font(.system(size: 96, weight: .bold, design: .rounded))
                                .foregroundColor(Color(hex: "#2C3E35").opacity(0.6))
                        }
                        .frame(width: 420)
                        .frame(maxHeight: .infinity)
                        .padding(.vertical, 28)
                        .background(dayHeaderBackground(day: day))

                        VStack(alignment: .leading, spacing: 24) {
                            ForEach(mealTypes, id: \.self) { mealType in
                                VStack(alignment: .leading, spacing: 8) {
                                    HStack(spacing: 14) {
                                        Image(systemName: mealType.icon)
                                            .font(.system(size: 42, weight: .medium))
                                            .foregroundColor(mealTypeAccent(mealType))
                                            .frame(width: 56)
                                        Text(mealTypeLabel(mealType).uppercased(with: locale))
                                            .font(.system(size: 42, weight: .bold, design: .serif))
                                            .foregroundColor(mealTypeAccent(mealType))
                                    }
                                    Text(dishName(day: day, mealType: mealType))
                                        .font(.system(size: 62, weight: .medium, design: .serif))
                                        .foregroundColor(.mealMoodTextPrimary)
                                        .lineLimit(2)
                                        .minimumScaleFactor(0.5)
                                        .frame(maxWidth: .infinity, alignment: .leading)
                                        .padding(.leading, 70)
                                }
                            }
                        }
                        .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .leading)
                        .padding(.horizontal, 40)
                        .padding(.vertical, 28)
                        .background(Color(hex: "#FFFCF8"))
                    }
                    .frame(maxHeight: .infinity)
                    .clipShape(RoundedRectangle(cornerRadius: 20))
                    .overlay(
                        RoundedRectangle(cornerRadius: 20)
                            .stroke(Color(hex: "#EAD8D0"), lineWidth: 1.5)
                    )
                    .shadow(color: Color.black.opacity(0.04), radius: 10, x: 0, y: 4)
                }
            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)
            .padding(.horizontal, 28)
            .padding(.vertical, 26)
        }
    }

    private func dayNumberOnly(for day: Int) -> String {
        let dayDate = plan.weekStartDate.addingDays(day)
        let formatter = DateFormatter()
        formatter.locale = locale
        formatter.dateFormat = "d"
        return formatter.string(from: dayDate)
    }

    private var footerBlock: some View {
        HStack(alignment: .center, spacing: 24) {
            MealMoodLogoMark(size: 118)

            VStack(alignment: .leading, spacing: 5) {
                Text(verbatim: "MealMood")
                    .font(.system(size: 44, weight: .heavy, design: .rounded))
                    .foregroundStyle(
                        LinearGradient(
                            colors: [Color.mealMoodCoral, Color(hex: "#3F7A64")],
                            startPoint: .leading, endPoint: .trailing
                        )
                    )
                Text(String(localized: "share_footer_tagline"))
                    .font(.system(size: 26, weight: .semibold, design: .rounded))
                    .italic()
                    .foregroundColor(Color(hex: "#5D645F"))
                Text(shareURL)
                    .font(.system(size: 22, weight: .semibold, design: .rounded))
                    .foregroundColor(Color(hex: "#588A77"))
            }

            Spacer()

            if let qrImage {
                VStack(spacing: 6) {
                    Image(uiImage: qrImage)
                        .interpolation(.none)
                        .resizable()
                        .scaledToFit()
                        .frame(width: 162, height: 162)
                        .padding(10)
                        .background(Color.white)
                        .clipShape(RoundedRectangle(cornerRadius: 18))
                        .overlay(
                            RoundedRectangle(cornerRadius: 18)
                                .stroke(Color.mealMoodCoral.opacity(0.35), lineWidth: 1)
                        )
                    Text(String(localized: "share_footer_scan"))
                        .font(.system(size: 18, weight: .semibold, design: .rounded))
                        .foregroundColor(.mealMoodTextSecondary)
                }
            }
        }
        .padding(.horizontal, 26)
        .padding(.vertical, 18)
        .background(Color.white.opacity(0.82))
        .clipShape(RoundedRectangle(cornerRadius: 22))
        .overlay(
            RoundedRectangle(cornerRadius: 22)
                .stroke(Color(hex: "#DDEEE6"), lineWidth: 1)
        )
    }

    private func dayShortTitle(for day: Int) -> String {
        let dayDate = plan.weekStartDate.addingDays(day)
        let formatter = DateFormatter()
        formatter.locale = locale
        formatter.setLocalizedDateFormatFromTemplate("EEE d")
        return formatter.string(from: dayDate).capitalized(with: locale)
    }

    private func dayLongTitle(for day: Int) -> String {
        let dayDate = plan.weekStartDate.addingDays(day)
        let formatter = DateFormatter()
        formatter.locale = locale
        formatter.setLocalizedDateFormatFromTemplate("EEEE")
        return formatter.string(from: dayDate).capitalized(with: locale)
    }

    private func dayHeaderTitle(for day: Int) -> String {
        let dayDate = plan.weekStartDate.addingDays(day)
        let formatter = DateFormatter()
        formatter.locale = locale
        formatter.setLocalizedDateFormatFromTemplate("EEEE d")
        return formatter.string(from: dayDate).capitalized(with: locale)
    }

    private func mealTypeLabel(_ mealType: MealType) -> String {
        String(localized: String.LocalizationValue(mealType.localizedKey))
    }

    /// Accent color per meal row in the vertical/school styles.
    private func mealTypeAccent(_ mealType: MealType) -> Color {
        switch mealType {
        case .breakfast: return Color(hex: "#B07C2B")
        case .lunch: return Color(hex: "#C85E2A")
        case .snack: return Color(hex: "#7B5EA7")
        case .dinner: return Color(hex: "#27604A")
        }
    }

    private func dishName(day: Int, mealType: MealType) -> String {
        let slot = plan.slotList.first { $0.dayOfWeek == day && $0.mealType == mealType.rawValue }
        guard let slot else { return String(localized: "share_slot_empty") }
        if slot.isEatingOut { return String(localized: "slot_eating_out") }
        guard let dishId = slot.dishId, let dish = dishes.first(where: { $0.id == dishId }) else {
            return String(localized: "share_slot_empty")
        }
        if let secondaryId = slot.secondaryDishId,
           let secondary = dishes.first(where: { $0.id == secondaryId }) {
            return "\(dish.name) + \(secondary.name)"
        }
        return dish.name
    }

    private func gridHeaderCell(_ title: String, day: Int?) -> some View {
        let background = dayHeaderBackground(day: day)
        return Text(title)
            .font(.system(size: 25, weight: .bold, design: .rounded))
            .foregroundColor(.mealMoodTextPrimary)
            .frame(maxWidth: .infinity, minHeight: 92)
            .padding(.horizontal, 10)
            .background(background)
            .clipShape(RoundedRectangle(cornerRadius: 14))
            .overlay(
                RoundedRectangle(cornerRadius: 14)
                    .stroke(Color.white.opacity(0.6), lineWidth: 1)
            )
    }

    private func gridMealCell(_ title: String, icon: String, mealType: MealType) -> some View {
        let background: LinearGradient
        switch mealType {
        case .breakfast:
            background = LinearGradient(colors: [Color(hex: "#FFEFC9"), Color(hex: "#FFE5A9")], startPoint: .topLeading, endPoint: .bottomTrailing)
        case .lunch:
            background = LinearGradient(colors: [Color(hex: "#FFE2C8"), Color(hex: "#FFD4B2")], startPoint: .topLeading, endPoint: .bottomTrailing)
        case .snack:
            background = LinearGradient(colors: [Color(hex: "#EBE0F5"), Color(hex: "#DFD0EF")], startPoint: .topLeading, endPoint: .bottomTrailing)
        case .dinner:
            background = LinearGradient(colors: [Color(hex: "#D7EFE7"), Color(hex: "#C2E7DB")], startPoint: .topLeading, endPoint: .bottomTrailing)
        }
        return HStack(spacing: 8) {
            Image(systemName: icon)
            Text(title)
        }
        .font(.system(size: 25, weight: .bold, design: .rounded))
        .foregroundColor(Color(hex: "#365548"))
        .frame(maxWidth: .infinity, minHeight: 130)
        .padding(.horizontal, 14)
        .background(background)
        .clipShape(RoundedRectangle(cornerRadius: 14))
        .overlay(
            RoundedRectangle(cornerRadius: 14)
                .stroke(Color.white.opacity(0.6), lineWidth: 1)
        )
    }

    private func gridDishCell(_ title: String, day: Int) -> some View {
        let tint = dayCellTint(day: day)
        return Text(title)
            .font(.system(size: 26, weight: .medium))
            .foregroundColor(.mealMoodTextPrimary)
            .multilineTextAlignment(.center)
            .lineLimit(3)
            .minimumScaleFactor(0.6)
            .frame(maxWidth: .infinity, minHeight: 130)
            .padding(.horizontal, 10)
            .background(
                LinearGradient(
                    colors: [Color.white.opacity(0.95), tint.opacity(0.32)],
                    startPoint: .topLeading,
                    endPoint: .bottomTrailing
                )
            )
            .clipShape(RoundedRectangle(cornerRadius: 14))
            .overlay(
                RoundedRectangle(cornerRadius: 14)
                    .stroke(Color(hex: "#F2E5DE"), lineWidth: 1)
            )
    }

    private func dayHeaderBackground(day: Int?) -> LinearGradient {
        guard let day else {
            return LinearGradient(
                colors: [Color(hex: "#F6E7DE"), Color(hex: "#F2DED2")],
                startPoint: .topLeading,
                endPoint: .bottomTrailing
            )
        }
        let palettes: [(String, String)] = [
            ("#FFD5D9", "#FFC8D2"),
            ("#FFE1C8", "#FFD3AF"),
            ("#FFF0C8", "#FFE6A8"),
            ("#DFF2CC", "#CFEAB6"),
            ("#D3F0E7", "#BFE6DA"),
            ("#D9E8FF", "#C9DDFF"),
            ("#E6D9FF", "#D9C8FF")
        ]
        let index = max(0, min(day, palettes.count - 1))
        return LinearGradient(
            colors: [Color(hex: palettes[index].0), Color(hex: palettes[index].1)],
            startPoint: .topLeading,
            endPoint: .bottomTrailing
        )
    }

    private func dayCellTint(day: Int) -> Color {
        let colors = [
            Color(hex: "#FFD0D8"),
            Color(hex: "#FFE1C6"),
            Color(hex: "#FFF0C3"),
            Color(hex: "#DFF1CA"),
            Color(hex: "#D5EFE6"),
            Color(hex: "#D7E7FF"),
            Color(hex: "#E7DCFF")
        ]
        return colors[max(0, min(day, colors.count - 1))]
    }
}