import Foundation
import os

/// **⚠ Retired by the one-app collapse — one-app collapse phase 2.** 12-editions.md ▸ App-side
/// state (re-ruled 2026-07-30) removes the App Group wholesale: with one app there is no sibling
/// to share a container *with*, so the registry and its peers home in the ordinary sandbox
/// container, records carry one grant and one open-now flag, and this type goes away with the
/// entitlement. Everything below still describes the shipping code, and the code still works —
/// it is simply describing a world that is being dismantled in a later phase, so the two-app
/// reasoning is left standing rather than half-rewritten into a fiction.
///
/// **The family App Group** — where every edition's app-side state lives (12-editions.md
/// § Distribution, ruled 2026-07-29; 02-architecture.md § Per-board app state).
///
/// ### Why a shared container at all
///
/// Boards are files, so they need no migration between editions — but the *app-side* state around
/// them (the recents list, per-board frames, the quick-style row, the clipboard's staged snapshot)
/// is app-private, and per-app-private means an upgrader lands on an empty home screen. So every
/// edition declares one group — `group.dev.rzen.indie.Kanban` — and homes that state in its
/// container **from day one**: base 2.0 ships with the entitlement, Pro's first release joins the
/// same group, Teams later does too, and at no point is there a migration or an ordering dependency
/// between them.
///
/// ### The one thing that cannot be shared
///
/// **Security-scoped bookmarks never cross sandboxes** — App Group or not, a bookmark is minted for
/// one app's sandbox and resolves in that one only. So the registry record is *common* except for
/// a per-edition **grant slot** keyed by bundle id (`BoardRecord.grants`), and a record whose only
/// grant another edition minted reads as unavailable-until-reopened. Open-now flags are keyed the
/// same way, for the same shape of reason: an edition restores the boards *it* had open.
///
/// ### It degrades rather than fails
///
/// `containerURL(forSecurityApplicationGroupIdentifier:)` answers `nil` when the group is not
/// provisioned for the running binary — a unit-test host without the capability, a locally signed
/// build before the group is registered on the team. Every path here falls back to the *previous*
/// per-edition Application Support home in that case, so nothing depends on provisioning to work:
/// state simply stops being shared, which is exactly the old behaviour.
public enum AppGroup {

    /// The group id every edition declares, verbatim (12-editions.md ▸ Distribution). It is
    /// deliberately the *family* name rather than an edition's: Pro and Teams declare this same
    /// string, and a future edition's bundle id joins with no further ceremony.
    public static let identifier = "group.dev.rzen.indie.Kanban"

    private static let logger = Logger(subsystem: "dev.rzen.indie.Kanban", category: "app-group")

    // MARK: - Edition identity

    /// Base's bundle id — also the fallback when `Bundle.main` has none, which is a test host's
    /// case and never a shipped app's.
    public static let baseEditionID = "dev.rzen.indie.Kanban"

    /// The bundle id the retired Pro *app* would have carried (12 ▸ Targets, ruled 2026-07-27) —
    /// **one-app collapse phase 2**: no app has ever shipped under it, and nothing will now that Pro
    /// is a subscription rather than a second binary (12 ▸ Distribution, re-ruled 2026-07-30). It
    /// stays only because the awareness line and the grant-slot keying still read it; both go in the
    /// same phase, and this constant with them.
    public static let proEditionID = "dev.rzen.indie.KanbanPro"

    /// Which edition is running — the key every per-edition slot on a shared record is stored under.
    ///
    /// Read from `Bundle.main` rather than declared per target, which is what keeps this file free of
    /// any edition conditional: the binary already knows which app it is.
    public static var editionID: String {
        Bundle.main.bundleIdentifier ?? baseEditionID
    }

    /// The user-facing name of an edition, for the popover's awareness line ("Also open in Lanework
    /// Pro"). `nil` for a bundle id this build has never heard of — a future edition's, or a stale
    /// slot left by something else — because inventing a name for it would be worse than saying
    /// nothing, and the line's whole posture is that it never lies.
    public static func editionDisplayName(_ bundleID: String) -> String? {
        switch bundleID {
        case baseEditionID: "Lanework"
        case proEditionID: "Lanework Pro"
        default: nil
        }
    }

    // MARK: - The container

    /// The group container, or `nil` when the running binary has no such capability.
    ///
    /// Not cached: the answer is a property of the process's entitlements and cannot change within
    /// a launch, but the call is a cheap lookup and a cached `nil` from an early read (before the
    /// container has been created for the first time) is the sort of staleness this file should not
    /// invent.
    public static var containerURL: URL? {
        FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: identifier)
    }

    /// Where every app-side file store lives — the registry, the clipboard's staging snapshots, and
    /// whatever joins them.
    ///
    /// In a shipped app this is `productionStateDirectory`. **In a unit-test host it is a scratch
    /// directory** (`isUnitTestHost`), which is not a nicety: the real container is shared with the
    /// sibling edition and with the developer's own running copy, so a suite that used it would be
    /// sweeping real staged clipboard copies and rewriting a real recents list.
    public static var stateDirectory: URL {
        isUnitTestHost ? unitTestStateDirectory : productionStateDirectory
    }

    /// What a shipped app uses: `<group container>/Library/Application Support/`.
    ///
    /// **No bundle-id subfolder**, unlike the per-edition home this replaces — that subfolder was
    /// exactly what kept two editions from seeing one list, and its absence is the whole feature.
    /// `Library/Application Support` is kept as the path *inside* the container for Apple's
    /// convention rather than for any behaviour: the container is the app's either way.
    ///
    /// Falls back to `perEditionSupportDirectory` when there is no group container (see the type's
    /// note): unshared, but working.
    public static var productionStateDirectory: URL {
        guard let containerURL else {
            logger.debug("no group container for \(identifier, privacy: .public); using the per-edition home")
            return perEditionSupportDirectory
        }
        return containerURL
            .appendingPathComponent("Library", isDirectory: true)
            .appendingPathComponent("Application Support", isDirectory: true)
    }

    /// The pre-2.0 home — `~/Library/Application Support/<bundle id>/`, inside this edition's own
    /// sandbox container. Kept as the fallback above and as the home of anything deliberately *not*
    /// shared.
    public static var perEditionSupportDirectory: URL {
        let support = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask).first
            ?? URL(fileURLWithPath: NSHomeDirectory(), isDirectory: true)
                .appendingPathComponent("Library/Application Support", isDirectory: true)
        return support.appendingPathComponent(editionID, isDirectory: true)
    }

    // MARK: - Keeping the suites out of it

    /// Whether this process is hosting a unit-test bundle.
    ///
    /// ### Why the app has to know
    ///
    /// The unit-test host **is the app** (`KanbanTests` is a hosted bundle), so
    /// `KanbanApp.init()` runs for real on every test launch and builds an `AppModel` over whatever
    /// the defaults resolve to. Every *object* a test constructs takes its storage by injection — that
    /// is the seam, and it is untouched — but the host's own launch has no injection point, and after
    /// the 2026-07-29 ruling the thing it would reach for is a container shared with the developer's
    /// own running copy. Its launch sweep would collect real staged
    /// clipboard trees; its `refreshRecents()` would resolve, refresh and rewrite real records.
    ///
    /// So the *default* moves for a test host, which is the one place a default can be wrong in a way
    /// injection cannot fix.
    ///
    /// ### Why this variable and not a launch flag
    ///
    /// `UITestLaunch.fixtureFlag` is the flag-shaped answer and remains the right one for the UI
    /// suites, which launch the app themselves and can pass arguments. A *unit*-test host is launched
    /// by the test runner, which passes nothing of ours — but it does set these variables, and it has
    /// set them for as long as XCTest has existed. Three spellings are checked because Apple has used
    /// each at some point and a missed one would silently mean "not a test".
    ///
    /// It cannot fire in a shipped app: nothing sets these but a test runner.
    public static var isUnitTestHost: Bool {
        let environment = ProcessInfo.processInfo.environment
        return environment["XCTestConfigurationFilePath"] != nil
            || environment["XCTestBundlePath"] != nil
            || environment["XCTestSessionIdentifier"] != nil
    }

    /// The scratch home a test host uses instead. Inside the app's own container (`NSTemporaryDirectory`
    /// sandboxes there), so nothing outside this app can see it and the OS reclaims it.
    ///
    /// One fixed folder rather than one per run: the suites do not depend on it being empty — they
    /// inject their own paths for anything they assert on — and a stable name keeps it inspectable when
    /// something writes there that should not have.
    public static var unitTestStateDirectory: URL {
        URL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true)
            .appendingPathComponent("LaneworkUnitTestState", isDirectory: true)
    }

    // MARK: - The shared defaults suite

    /// The group's shared `UserDefaults` suite — where app-side state that is a *scalar* lives
    /// (02-architecture.md § Per-board app state: "or the group's shared `UserDefaults` suite where
    /// a scalar fits").
    ///
    /// `UserDefaults(suiteName:)` answers `nil` only for a suite name equal to the app's own bundle
    /// id, which this never is; `.standard` is the fallback anyway, for the reason every fallback
    /// here exists — an unshared preference is a papercut, an unreadable one is a bug.
    ///
    /// Without the entitlement the suite is an ordinary named domain rather than a shared one, so
    /// this works unprovisioned too: the values are simply this edition's alone.
    ///
    /// A **test host gets its own suite name** for `isUnitTestHost`'s reason applied to preferences: a
    /// suite that read and wrote the real one would be reading and writing the developer's quick-style
    /// row and window size, which is the objection `StyleModelTests` already states about
    /// `UserDefaults.standard`.
    public static var defaults: UserDefaults {
        UserDefaults(suiteName: isUnitTestHost ? "\(identifier).unit-tests" : identifier) ?? .standard
    }
}