//
//  WrapBox.swift
//
//  Copyright 2026 Brendan Szymanski <hello@bscubed.dev>
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
//  SPDX-License-Identifier: GPL-3.0-or-later
//

import Adwaita
import CAdw

// MARK: - Swift Enum Wrappers for C Enums

/// Controls how children are justified within each line.
public enum JustifyMode {

    /// No justification.
    case none
    /// Children are stretched to fill the line.
    case fill
    /// Extra space is distributed evenly between children.
    case spread

    var cValue: AdwJustifyMode {
        switch self {
        case .none: ADW_JUSTIFY_NONE
        case .fill: ADW_JUSTIFY_FILL
        case .spread: ADW_JUSTIFY_SPREAD
        }
    }

}

/// Controls the packing direction.
public enum PackDirection {

    /// Children are packed from start to end.
    case startToEnd
    /// Children are packed from end to start.
    case endToStart

    var cValue: AdwPackDirection {
        switch self {
        case .startToEnd: ADW_PACK_START_TO_END
        case .endToStart: ADW_PACK_END_TO_START
        }
    }

}

/// Controls the wrapping policy.
public enum WrapPolicy {

    /// Wrapping occurs at the minimum size.
    case minimum
    /// Wrapping occurs at the natural size.
    case natural

    var cValue: AdwWrapPolicy {
        switch self {
        case .minimum: ADW_WRAP_MINIMUM
        case .natural: ADW_WRAP_NATURAL
        }
    }

}

/// Units for spacing and length properties.
public enum LengthUnit {

    /// Pixels.
    case px
    /// Points.
    case pt
    /// Scale-independent pixels.
    case sp

    var cValue: AdwLengthUnit {
        switch self {
        case .px: ADW_LENGTH_UNIT_PX
        case .pt: ADW_LENGTH_UNIT_PT
        case .sp: ADW_LENGTH_UNIT_SP
        }
    }

}

// MARK: - WrapBox Widget

/// A responsive wrapping container that arranges children in a reflowing grid.
///
/// `WrapBox` places its children in a horizontal flow, wrapping to the next
/// line when the available width is exhausted. It is backed by `AdwWrapBox` from libadwaita.
///
/// Use inside a `ScrollView` to allow shrinking in both axes.
///
/// ```swift
/// ScrollView {
///     WrapBox(items) { item in
///         ItemCell(item: item)
///     }
///     .childSpacing(12)
///     .lineSpacing(12)
///     .lineHomogeneous(true)
/// }
/// ```
public struct WrapBox<Element, Identifier>: AdwaitaWidget where Identifier: Hashable {

    #if exposeGeneratedAppearUpdateFunctions
        /// Additional update functions for type extensions.
        public var updateFunctions: [(ViewStorage, WidgetData, Bool) -> Void] = []
        /// Additional appear functions for type extensions.
        public var appearFunctions: [(ViewStorage, WidgetData) -> Void] = []
    #else
        /// Additional update functions for type extensions.
        var updateFunctions: [(ViewStorage, WidgetData, Bool) -> Void] = []
        /// Additional appear functions for type extensions.
        var appearFunctions: [(ViewStorage, WidgetData) -> Void] = []
    #endif

    /// The amount of space between children.
    var childSpacing: Int?
    /// The unit for `childSpacing`.
    var childSpacingUnit: LengthUnit?
    /// The packing direction.
    var packDirection: PackDirection?
    /// The alignment of children within each line (0.0 to 1.0).
    var align: Float?
    /// The justification mode.
    var justify: JustifyMode?
    /// Whether to justify the last line.
    var justifyLastLine: Bool?
    /// The amount of space between lines.
    var lineSpacing: Int?
    /// The unit for `lineSpacing`.
    var lineSpacingUnit: LengthUnit?
    /// Whether all lines should be the same size.
    var lineHomogeneous: Bool?
    /// The natural length of each line.
    var naturalLineLength: Int?
    /// The unit for `naturalLineLength`.
    var naturalLineLengthUnit: LengthUnit?
    /// Whether to reverse the wrapping direction.
    var wrapReverse: Bool?
    /// The wrapping policy.
    var wrapPolicy: WrapPolicy?

    /// The dynamic widget elements.
    var elements: [Element]
    /// The dynamic widget content.
    var content: (Element) -> Body
    /// The dynamic widget identifier key path.
    var id: KeyPath<Element, Identifier>

    /// Initialize `WrapBox`.
    /// - Parameters:
    ///   - elements: The elements to display.
    ///   - id: The key path to the element's identifier.
    ///   - content: A view builder for rendering each element.
    public init(
        _ elements: [Element],
        id: KeyPath<Element, Identifier>,
        @ViewBuilder content: @escaping (Element) -> Body
    ) {
        self.elements = elements
        self.content = content
        self.id = id
    }

    // MARK: - AdwaitaWidget

    public func container<Data>(data: WidgetData, type: Data.Type) -> ViewStorage
    where Data: ViewRenderData {
        let storage = ViewStorage(adw_wrap_box_new()?.opaque())
        for function in appearFunctions {
            function(storage, data)
        }
        return storage
    }

    public func update<Data>(
        _ storage: ViewStorage,
        data: WidgetData,
        updateProperties: Bool,
        type: Data.Type
    ) where Data: ViewRenderData {
        storage.modify { widget in

            // --- Apply property changes ---
            if let childSpacing, updateProperties,
                (storage.previousState as? Self)?.childSpacing != childSpacing
            {
                adw_wrap_box_set_child_spacing(widget, childSpacing.cInt)
            }
            if let childSpacingUnit, updateProperties,
                (storage.previousState as? Self)?.childSpacingUnit != childSpacingUnit
            {
                adw_wrap_box_set_child_spacing_unit(widget, childSpacingUnit.cValue)
            }
            if let packDirection, updateProperties,
                (storage.previousState as? Self)?.packDirection != packDirection
            {
                adw_wrap_box_set_pack_direction(widget, packDirection.cValue)
            }
            if let align, updateProperties,
                (storage.previousState as? Self)?.align != align
            {
                adw_wrap_box_set_align(widget, align)
            }
            if let justify, updateProperties,
                (storage.previousState as? Self)?.justify != justify
            {
                adw_wrap_box_set_justify(widget, justify.cValue)
            }
            if let justifyLastLine, updateProperties,
                (storage.previousState as? Self)?.justifyLastLine != justifyLastLine
            {
                adw_wrap_box_set_justify_last_line(widget, justifyLastLine.cBool)
            }
            if let lineSpacing, updateProperties,
                (storage.previousState as? Self)?.lineSpacing != lineSpacing
            {
                adw_wrap_box_set_line_spacing(widget, lineSpacing.cInt)
            }
            if let lineSpacingUnit, updateProperties,
                (storage.previousState as? Self)?.lineSpacingUnit != lineSpacingUnit
            {
                adw_wrap_box_set_line_spacing_unit(widget, lineSpacingUnit.cValue)
            }
            if let lineHomogeneous, updateProperties,
                (storage.previousState as? Self)?.lineHomogeneous != lineHomogeneous
            {
                adw_wrap_box_set_line_homogeneous(widget, lineHomogeneous.cBool)
            }
            if let naturalLineLength, updateProperties,
                (storage.previousState as? Self)?.naturalLineLength != naturalLineLength
            {
                adw_wrap_box_set_natural_line_length(widget, naturalLineLength.cInt)
            }
            if let naturalLineLengthUnit, updateProperties,
                (storage.previousState as? Self)?.naturalLineLengthUnit != naturalLineLengthUnit
            {
                adw_wrap_box_set_natural_line_length_unit(widget, naturalLineLengthUnit.cValue)
            }
            if let wrapReverse, updateProperties,
                (storage.previousState as? Self)?.wrapReverse != wrapReverse
            {
                adw_wrap_box_set_wrap_reverse(widget, wrapReverse.cBool)
            }
            if let wrapPolicy, updateProperties,
                (storage.previousState as? Self)?.wrapPolicy != wrapPolicy
            {
                adw_wrap_box_set_wrap_policy(widget, wrapPolicy.cValue)
            }

            // --- Child management ---
            var contentStorage: [ViewStorage] = storage.content[.mainContent] ?? []
            let oldElements = storage.fields["element"] as? [Element] ?? []

            var oldByID: [Identifier: ViewStorage] = [:]
            for (i, oldElement) in oldElements.enumerated() where i < contentStorage.count {
                oldByID[oldElement[keyPath: id]] = contentStorage[i]
            }

            var newContentStorage: [ViewStorage] = []
            var lastChild: OpaquePointer?

            for element in elements {
                let elementID = element[keyPath: id]
                if let existingStorage = oldByID.removeValue(forKey: elementID) {
                    newContentStorage.append(existingStorage)
                    if let lastPtr = lastChild {
                        adw_wrap_box_reorder_child_after(
                            widget,
                            existingStorage.opaquePointer?.cast(),
                            lastPtr.cast()
                        )
                    } else {
                        adw_wrap_box_reorder_child_after(
                            widget,
                            existingStorage.opaquePointer?.cast(),
                            nil
                        )
                    }
                    lastChild = existingStorage.opaquePointer
                } else {
                    let child = content(element).storage(data: data, type: type)
                    if let lastPtr = lastChild {
                        adw_wrap_box_insert_child_after(
                            widget,
                            child.opaquePointer?.cast(),
                            lastPtr.cast()
                        )
                    } else {
                        adw_wrap_box_prepend(widget, child.opaquePointer?.cast())
                    }
                    newContentStorage.append(child)
                    lastChild = child.opaquePointer
                }
            }

            for (_, staleStorage) in oldByID {
                adw_wrap_box_remove(widget, staleStorage.opaquePointer?.cast())
            }

            storage.fields["element"] = elements
            storage.content[.mainContent] = newContentStorage

            for (index, element) in elements.enumerated() {
                content(element).updateStorage(
                    newContentStorage[index],
                    data: data,
                    updateProperties: updateProperties,
                    type: type
                )
            }
        }

        for function in updateFunctions {
            function(storage, data, updateProperties)
        }
        if updateProperties {
            storage.previousState = self
        }
    }

}

// MARK: - Modifier Methods

extension WrapBox {

    /// The amount of space between children.
    public func childSpacing(_ childSpacing: Int?) -> Self {
        modify { $0.childSpacing = childSpacing }
    }

    /// The unit for `childSpacing`.
    public func childSpacingUnit(_ childSpacingUnit: LengthUnit?) -> Self {
        modify { $0.childSpacingUnit = childSpacingUnit }
    }

    /// The packing direction.
    public func packDirection(_ packDirection: PackDirection?) -> Self {
        modify { $0.packDirection = packDirection }
    }

    /// The alignment of children within each line (0.0 to 1.0).
    public func align(_ align: Float?) -> Self {
        modify { $0.align = align }
    }

    /// The justification mode.
    public func justify(_ justify: JustifyMode?) -> Self {
        modify { $0.justify = justify }
    }

    /// Whether to justify the last line.
    public func justifyLastLine(_ justifyLastLine: Bool? = true) -> Self {
        modify { $0.justifyLastLine = justifyLastLine }
    }

    /// The amount of space between lines.
    public func lineSpacing(_ lineSpacing: Int?) -> Self {
        modify { $0.lineSpacing = lineSpacing }
    }

    /// The unit for `lineSpacing`.
    public func lineSpacingUnit(_ lineSpacingUnit: LengthUnit?) -> Self {
        modify { $0.lineSpacingUnit = lineSpacingUnit }
    }

    /// Whether all lines should be the same size.
    public func lineHomogeneous(_ lineHomogeneous: Bool? = true) -> Self {
        modify { $0.lineHomogeneous = lineHomogeneous }
    }

    /// The natural length of each line.
    public func naturalLineLength(_ naturalLineLength: Int?) -> Self {
        modify { $0.naturalLineLength = naturalLineLength }
    }

    /// The unit for `naturalLineLength`.
    public func naturalLineLengthUnit(_ naturalLineLengthUnit: LengthUnit?) -> Self {
        modify { $0.naturalLineLengthUnit = naturalLineLengthUnit }
    }

    /// Whether to reverse the wrapping direction.
    public func wrapReverse(_ wrapReverse: Bool? = true) -> Self {
        modify { $0.wrapReverse = wrapReverse }
    }

    /// The wrapping policy.
    public func wrapPolicy(_ wrapPolicy: WrapPolicy?) -> Self {
        modify { $0.wrapPolicy = wrapPolicy }
    }

}

// MARK: - Convenience Initializer for Identifiable Elements

extension WrapBox where Element: Identifiable, Identifier == Element.ID {

    /// Initialize `WrapBox` with identifiable elements.
    /// - Parameters:
    ///   - elements: The identifiable elements to display.
    ///   - content: A view builder for rendering each element.
    public init(
        _ elements: [Element],
        @ViewBuilder content: @escaping (Element) -> Body
    ) {
        self.elements = elements
        self.content = content
        self.id = \.id
    }

}