kotej/FinderExtension/FinderMenu.swift

import Cocoa
import FinderSync

/// Adds Kotej to Finder's contextual menu.
///
/// Two flows, matching how comparison tools are normally used:
///   - select two items  → "Comparar los 2 elementos"
///   - select one item   → "Seleccionar para comparar", then on another item
///                         "Comparar con <lo seleccionado>"
///
/// The app is asked to do the work through its `kotej://` URL scheme, so the
/// extension stays tiny and holds no comparison logic.
final class FinderMenu: FIFinderSync {
    /// Where the first pick is remembered between two right-clicks.
    private static let pendingKey = "kotej.pendingLeft"

    private var pendingLeft: URL? {
        get {
            guard let path = UserDefaults.standard.string(forKey: Self.pendingKey) else { return nil }
            return URL(fileURLWithPath: path)
        }
        set {
            if let path = newValue?.path {
                UserDefaults.standard.set(path, forKey: Self.pendingKey)
            } else {
                UserDefaults.standard.removeObject(forKey: Self.pendingKey)
            }
        }
    }

    override init() {
        super.init()
        // Watch every mounted volume so the menu is available anywhere, which is
        // what a comparison tool needs (FinderSync only offers menus for the
        // directories it monitors).
        FIFinderSyncController.default().directoryURLs = Set(
            FileManager.default.mountedVolumeURLs(includingResourceValuesForKeys: nil,
                                                  options: [.skipHiddenVolumes]) ?? [URL(fileURLWithPath: "/")]
        )
    }

    override func menu(for menuKind: FIMenuKind) -> NSMenu? {
        guard menuKind == .contextualMenuForItems else { return nil }
        let selected = FIFinderSyncController.default().selectedItemURLs() ?? []
        guard !selected.isEmpty else { return nil }

        let menu = NSMenu(title: "Kotej")

        if selected.count >= 2 {
            let item = NSMenuItem(title: String(localized: "Compare the 2 items with Kotej"),
                                  action: #selector(compareSelection(_:)), keyEquivalent: "")
            item.target = self
            menu.addItem(item)
            return menu
        }

        if let pending = pendingLeft, pending != selected[0] {
            let item = NSMenuItem(title: String(localized: "Compare with “\(pending.lastPathComponent)”"),
                                  action: #selector(compareWithPending(_:)), keyEquivalent: "")
            item.target = self
            menu.addItem(item)

            let forget = NSMenuItem(title: String(localized: "Forget “\(pending.lastPathComponent)”"),
                                    action: #selector(forgetPending(_:)), keyEquivalent: "")
            forget.target = self
            menu.addItem(forget)
        } else {
            let item = NSMenuItem(title: String(localized: "Select for comparison"),
                                  action: #selector(markForComparison(_:)), keyEquivalent: "")
            item.target = self
            menu.addItem(item)
        }
        return menu
    }

    // MARK: Actions

    @objc private func compareSelection(_ sender: AnyObject?) {
        let selected = FIFinderSyncController.default().selectedItemURLs() ?? []
        guard selected.count >= 2 else { return }
        open(left: selected[0], right: selected[1])
    }

    @objc private func markForComparison(_ sender: AnyObject?) {
        pendingLeft = FIFinderSyncController.default().selectedItemURLs()?.first
    }

    @objc private func compareWithPending(_ sender: AnyObject?) {
        guard let left = pendingLeft,
              let right = FIFinderSyncController.default().selectedItemURLs()?.first else { return }
        pendingLeft = nil
        open(left: left, right: right)
    }

    @objc private func forgetPending(_ sender: AnyObject?) {
        pendingLeft = nil
    }

    private func open(left: URL, right: URL) {
        var components = URLComponents()
        components.scheme = "kotej"
        components.host = "compare"
        components.queryItems = [
            URLQueryItem(name: "left", value: left.path),
            URLQueryItem(name: "right", value: right.path),
        ]
        guard let url = components.url else { return }
        NSWorkspace.shared.open(url)
    }
}