//
//  QuantityScheduleEditor.swift
//  LoopKitUI
//
//  Created by Michael Pangburn on 4/24/20.
//  Copyright © 2020 LoopKit Authors. All rights reserved.
//

import SwiftUI
import HealthKit
import LoopKit


struct QuantityScheduleEditor<ActionAreaContent: View>: View {
    enum QuantitySelectionMode {
        /// A single picker for selecting quantity values.
        case whole
        // A two-component picker for selecting the whole and fractional quantity values independently.
        case fractional
    }

    @Environment(\.guidanceColors) var guidanceColors
    
    var title: Text
    var description: Text
    var initialScheduleItems: [RepeatingScheduleValue<HKQuantity>]
    @State var scheduleItems: [RepeatingScheduleValue<HKQuantity>]
    var unit: HKUnit
    var selectableValues: [Double]
    var quantitySelectionMode: QuantitySelectionMode
    var guardrail: Guardrail<HKQuantity>
    var defaultFirstScheduleItemValue: HKQuantity
    var scheduleItemLimit: Int
    var confirmationAlertContent: AlertContent
    var guardrailWarning: (_ crossedThresholds: [SafetyClassification.Threshold]) -> ActionAreaContent
    var savingMechanism: SavingMechanism<DailyQuantitySchedule<Double>>
    var mode: SettingsPresentationMode
    var settingType: TherapySetting
    
    @State private var userDidTap: Bool = false

    var body: some View {
        ScheduleEditor(
            title: title,
            description: description,
            scheduleItems: $scheduleItems,
            initialScheduleItems: initialScheduleItems,
            defaultFirstScheduleItemValue: defaultFirstScheduleItemValue,
            scheduleItemLimit: scheduleItemLimit,
            saveConfirmation: saveConfirmation,
            valueContent: { value, isEditing in
                GuardrailConstrainedQuantityView(
                    value: value,
                    unit: unit,
                    guardrail: guardrail,
                    isEditing: isEditing
                )
            },
            valuePicker: { item, availableWidth in
                if quantitySelectionMode == .whole {
                    QuantityPicker(
                        value: item.value.animation(),
                        unit: unit,
                        guardrail: guardrail,
                        selectableValues: selectableValues,
                        guidanceColors: guidanceColors
                    )
                    .frame(width: availableWidth / 2)
                    // Ensure overlaid unit label is not clipped
                    .padding(.trailing, unitLabelWidth + unitLabelSpacing)
                    .clipped()
                    .compositingGroup()
                } else {
                    FractionalQuantityPicker(
                        value: item.value.animation(),
                        unit: unit,
                        guardrail: guardrail,
                        selectableValues: selectableValues,
                        usageContext: .component(availableWidth: availableWidth)
                    )
                }
            },
            actionAreaContent: {
                instructionalContentIfNecessary
                guardrailWarningIfNecessary
            },
            savingMechanism: savingMechanism.pullback { quantities in
                DailyQuantitySchedule(unit: unit, dailyQuantities: quantities)!
            },
            mode: mode,
            therapySettingType: settingType
        )
        .simultaneousGesture(TapGesture().onEnded {
            withAnimation {
                userDidTap = true
            }
        })
    }

    private var saveConfirmation: SaveConfirmation {
        crossedThresholds.isEmpty ? .notRequired : .required(confirmationAlertContent)
    }

    private var unitLabelWidth: CGFloat {
        let attributedUnitString = NSAttributedString(
            string: unit.shortLocalizedUnitString(),
            attributes: [.font: UIFont.preferredFont(forTextStyle: .body)]
        )
        return attributedUnitString.size().width
    }

    private var unitLabelSpacing: CGFloat { 8 }
    
    private var instructionalContentIfNecessary: some View {
        return Group {
            if mode == .acceptanceFlow && !userDidTap {
                instructionalContent
            }
        }
    }

    private var instructionalContent: some View {
        HStack { // to align with guardrail warning, if present
            VStack (alignment: .leading, spacing: 20) {
                Text(LocalizedString("You can edit a setting by tapping into any line item.", comment: "Description of how to edit setting"))
                Text(LocalizedString("You can add entries for different times of day by using the ➕.", comment: "Description of how to add a range"))
            }
            .foregroundColor(.secondary)
            .font(.subheadline)
            Spacer()
        }
    }

    private var guardrailWarningIfNecessary: some View {
        let crossedThresholds = self.crossedThresholds
        return Group {
            if !crossedThresholds.isEmpty && (userDidTap || mode == .settings) {
                guardrailWarning(crossedThresholds)
            }
        }
    }

    private var crossedThresholds: [SafetyClassification.Threshold] {
        scheduleItems.lazy
            .map { $0.value }
            .compactMap { quantity in
                switch guardrail.classification(for: quantity) {
                case .withinRecommendedRange:
                    return nil
                case .outsideRecommendedRange(let threshold):
                    return threshold
                }
        }
    }
}

// MARK: - Initializers

extension QuantityScheduleEditor {
    init(
        title: Text,
        description: Text,
        schedule: DailyQuantitySchedule<Double>?,
        unit: HKUnit,
        selectableValues: [Double],
        guardrail: Guardrail<HKQuantity>,
        quantitySelectionMode: QuantitySelectionMode = .whole,
        defaultFirstScheduleItemValue: HKQuantity,
        scheduleItemLimit: Int = 48,
        confirmationAlertContent: AlertContent,
        @ViewBuilder guardrailWarning: @escaping (_ thresholds: [SafetyClassification.Threshold]) -> ActionAreaContent,
        onSave savingMechanism: SavingMechanism<DailyQuantitySchedule<Double>>,
        mode: SettingsPresentationMode = .settings,
        settingType: TherapySetting = .none
    ) {
        self.title = title
        self.description = description
        self.initialScheduleItems = schedule?.quantities(using: unit) ?? []
        self._scheduleItems = State(initialValue: schedule?.quantities(using: unit) ?? [])
        self.unit = unit
        self.quantitySelectionMode = quantitySelectionMode
        self.selectableValues = selectableValues
        self.guardrail = guardrail
        self.defaultFirstScheduleItemValue = defaultFirstScheduleItemValue
        self.scheduleItemLimit = scheduleItemLimit
        self.confirmationAlertContent = confirmationAlertContent
        self.guardrailWarning = guardrailWarning
        self.savingMechanism = savingMechanism
        self.mode = mode
        self.settingType = settingType
    }

    init(
        title: Text,
        description: Text,
        schedule: DailyQuantitySchedule<Double>?,
        unit: HKUnit,
        guardrail: Guardrail<HKQuantity>,
        selectableValueStride: HKQuantity,
        quantitySelectionMode: QuantitySelectionMode = .whole,
        defaultFirstScheduleItemValue: HKQuantity,
        scheduleItemLimit: Int = 48,
        confirmationAlertContent: AlertContent,
        @ViewBuilder guardrailWarning: @escaping (_ thresholds: [SafetyClassification.Threshold]) -> ActionAreaContent,
        onSave save: @escaping (DailyQuantitySchedule<Double>) -> Void,
        mode: SettingsPresentationMode = .settings,
        settingType: TherapySetting = .none
    ) {
        let selectableValues = guardrail.allValues(stridingBy: selectableValueStride, unit: unit)
        self.init(
            title: title,
            description: description,
            schedule: schedule,
            unit: unit,
            selectableValues: selectableValues,
            guardrail: guardrail,
            quantitySelectionMode: quantitySelectionMode,
            defaultFirstScheduleItemValue: defaultFirstScheduleItemValue,
            scheduleItemLimit: scheduleItemLimit,
            confirmationAlertContent: confirmationAlertContent,
            guardrailWarning: guardrailWarning,
            onSave: .synchronous(save),
            mode: mode,
            settingType: settingType
        )
    }
}