import AppKit
import SwiftUI

@MainActor
final class MenuContextCardInjector: NSObject, NSMenuDelegate {
    static let shared = MenuContextCardInjector()

    private let tag = 9_415_227
    private let fallbackCardWidth: CGFloat = 320
    private weak var originalDelegate: NSMenuDelegate?
    private var loadTask: Task<Void, Never>?
    private let activeWindowSeconds: TimeInterval = 24 * 60 * 60

    func install(into statusItem: NSStatusItem) {
        // SwiftUI owns the menu, but we can inject a custom NSMenuItem.view right before display.
        guard let menu = statusItem.menu else { return }
        // Preserve SwiftUI's internal NSMenuDelegate, otherwise it may stop populating menu items.
        if menu.delegate !== self {
            self.originalDelegate = menu.delegate
            menu.delegate = self
        }
    }

    func menuWillOpen(_ menu: NSMenu) {
        self.originalDelegate?.menuWillOpen?(menu)

        // Remove any previous injected card items.
        for item in menu.items where item.tag == self.tag {
            menu.removeItem(item)
        }

        guard let insertIndex = self.findInsertIndex(in: menu) else { return }

        self.loadTask?.cancel()

        let placeholder = AnyView(ContextMenuCardView(
            rows: [],
            statusText: "Loading sessions…"))

        let hosting = NSHostingView(rootView: placeholder)
        let size = hosting.fittingSize
        hosting.frame = NSRect(origin: .zero, size: NSSize(width: self.initialCardWidth(for: menu), height: size.height))

        let item = NSMenuItem()
        item.tag = self.tag
        item.view = hosting
        item.isEnabled = false

        menu.insertItem(item, at: insertIndex)

        // After the menu attaches the view to its window, adopt the menu's computed width.
        DispatchQueue.main.async { [weak self, weak hosting] in
            guard let self, let hosting else { return }
            self.adoptMenuWidthIfAvailable(for: menu, hosting: hosting)
        }

        self.loadTask = Task { [weak hosting] in
            let view = await self.makeCardView()
            await MainActor.run {
                hosting?.rootView = view
                hosting?.invalidateIntrinsicContentSize()
                if let hosting {
                    self.adoptMenuWidthIfAvailable(for: menu, hosting: hosting)
                    let size = hosting.fittingSize
                    hosting.frame.size.height = size.height
                }
            }
        }
    }

    func menuDidClose(_ menu: NSMenu) {
        self.originalDelegate?.menuDidClose?(menu)
        self.loadTask?.cancel()
    }

    func menuNeedsUpdate(_ menu: NSMenu) {
        self.originalDelegate?.menuNeedsUpdate?(menu)
    }

    func confinementRect(for menu: NSMenu, on screen: NSScreen?) -> NSRect {
        if let rect = self.originalDelegate?.confinementRect?(for: menu, on: screen) {
            return rect
        }
        return NSRect.zero
    }

    private func makeCardView() async -> AnyView {
        let hints = SessionLoader.configHints()
        let store = SessionLoader.resolveStorePath(override: hints.storePath)
        let defaults = SessionDefaults(
            model: hints.model ?? SessionLoader.fallbackModel,
            contextTokens: hints.contextTokens ?? SessionLoader.fallbackContextTokens)

        do {
            let loaded = try await SessionLoader.loadRows(at: store, defaults: defaults)
            let now = Date()
            let current = loaded.filter { row in
                if row.key == "main" { return true }
                guard let updatedAt = row.updatedAt else { return false }
                return now.timeIntervalSince(updatedAt) <= self.activeWindowSeconds
            }

            let sorted = current.sorted { lhs, rhs in
                if lhs.key == "main" { return true }
                if rhs.key == "main" { return false }
                return (lhs.updatedAt ?? .distantPast) > (rhs.updatedAt ?? .distantPast)
            }

            return AnyView(ContextMenuCardView(rows: sorted))
        } catch {
            return AnyView(ContextMenuCardView(rows: [], statusText: "Could not load sessions"))
        }
    }

    private func findInsertIndex(in menu: NSMenu) -> Int? {
        // Prefer inserting before the "Send Heartbeats" toggle item.
        if let idx = menu.items.firstIndex(where: { $0.title == "Send Heartbeats" }) {
            return idx
        }
        // Fallback: insert after the first two rows (active toggle + status).
        if menu.items.count >= 2 { return 2 }
        return menu.items.count
    }

    private func initialCardWidth(for menu: NSMenu) -> CGFloat {
        let width = menu.minimumWidth
        if width > 0 { return max(300, width) }
        return 300
    }

    private func adoptMenuWidthIfAvailable(for menu: NSMenu, hosting: NSHostingView<AnyView>) {
        let targetWidth: CGFloat? = {
            if let contentWidth = hosting.window?.contentView?.bounds.width, contentWidth > 0 { return contentWidth }
            if let superWidth = hosting.superview?.bounds.width, superWidth > 0 { return superWidth }
            let minimumWidth = menu.minimumWidth
            if minimumWidth > 0 { return minimumWidth }
            return nil
        }()

        guard let targetWidth else {
            if hosting.frame.width <= 0 {
                hosting.frame.size.width = self.fallbackCardWidth
            }
            return
        }

        let clamped = max(300, targetWidth)
        if abs(hosting.frame.width - clamped) < 1 { return }
        hosting.frame.size.width = clamped
    }
}