/*
 * Atoll (DynamicIsland)
 * Copyright (C) 2024-2026 Atoll Contributors
 *
 * Originally from boring.notch project
 * Modified and adapted for Atoll (DynamicIsland)
 * See NOTICE for details.
 *
 * 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/>.
 */

import Foundation
import AppKit

@MainActor
final class ShelfStateViewModel: ObservableObject {
    static let shared = ShelfStateViewModel()

    @Published private(set) var items: [ShelfItem] = [] {
        didSet { ShelfPersistenceService.shared.save(items) }
    }

    @Published var isLoading: Bool = false

    var isEmpty: Bool { items.isEmpty }

    // Queue for deferred bookmark updates to avoid publishing during view updates
    private var pendingBookmarkUpdates: [ShelfItem.ID: Data] = [:]
    private var updateTask: Task<Void, Never>?

    private init() {
        items = ShelfPersistenceService.shared.load()
    }


    func add(_ newItems: [ShelfItem]) {
        guard !newItems.isEmpty else { return }
        var merged = items
        // Deduplicate by identityKey while preserving order (existing first)
        var seen: Set<String> = Set(merged.map { $0.identityKey })
        var addedIDs: [String] = []
        for it in newItems {
            let key = it.identityKey
            if !seen.contains(key) {
                merged.append(it)
                seen.insert(key)
                addedIDs.append(it.id.uuidString)
            }
        }
        items = merged
        if !addedIDs.isEmpty {
            ExtensionRPCServer.shared.notifyShelfItemsChanged(itemIDs: addedIDs, action: "added")
        }
    }

    func remove(_ item: ShelfItem) {
        item.cleanupStoredData()
        items.removeAll { $0.id == item.id }
        ExtensionRPCServer.shared.notifyShelfItemsChanged(itemIDs: [item.id.uuidString], action: "removed")
    }

    func updateBookmark(for item: ShelfItem, bookmark: Data) {
        guard let idx = items.firstIndex(where: { $0.id == item.id }) else { return }
        if case .file = items[idx].kind {
            items[idx].kind = .file(bookmark: bookmark)
        }
    }

    private func scheduleDeferredBookmarkUpdate(for item: ShelfItem, bookmark: Data) {
        pendingBookmarkUpdates[item.id] = bookmark
        
        // Cancel existing task and schedule a new one
        updateTask?.cancel()
        updateTask = Task { @MainActor [weak self] in
            await Task.yield()
            
            guard let self = self else { return }
            
            for (itemID, bookmarkData) in self.pendingBookmarkUpdates {
                if let idx = self.items.firstIndex(where: { $0.id == itemID }),
                   case .file = self.items[idx].kind {
                    self.items[idx].kind = .file(bookmark: bookmarkData)
                }
            }
            
            self.pendingBookmarkUpdates.removeAll()
        }
    }


    func load(_ providers: [NSItemProvider]) {
        guard !providers.isEmpty else { return }
        isLoading = true
        Task { [weak self] in
            let dropped = await ShelfDropService.items(from: providers)
            await MainActor.run {
                self?.add(dropped)
                self?.isLoading = false
            }
        }
    }

    func cleanupInvalidItems() {
        Task { [weak self] in
            guard let self else { return }
            var keep: [ShelfItem] = []
            for item in self.items {
                switch item.kind {
                case .file(let data):
                    let bookmark = Bookmark(data: data)
                    if await bookmark.validate() {
                        keep.append(item)
                    } else {
                        item.cleanupStoredData()
                    }
                default:
                    keep.append(item)
                }
            }
            await MainActor.run { self.items = keep }
        }
    }


    func resolveFileURL(for item: ShelfItem) -> URL? {
        guard case .file(let bookmarkData) = item.kind else { return nil }
        let bookmark = Bookmark(data: bookmarkData)
        let result = bookmark.resolve()
        if let refreshed = result.refreshedData, refreshed != bookmarkData {
            NSLog("Bookmark for \(item) stale; refreshing")
            scheduleDeferredBookmarkUpdate(for: item, bookmark: refreshed)
        }
        return result.url
    }

    func resolveAndUpdateBookmark(for item: ShelfItem) -> URL? {
        guard case .file(let bookmarkData) = item.kind else { return nil }
        let bookmark = Bookmark(data: bookmarkData)
        let result = bookmark.resolve()
        if let refreshed = result.refreshedData, refreshed != bookmarkData {
            NSLog("Bookmark for \(item) stale; refreshing")
            updateBookmark(for: item, bookmark: refreshed)
        }
        return result.url
    }

    func resolveFileURLs(for items: [ShelfItem]) -> [URL] {
        var urls: [URL] = []
        for it in items {
            if let u = resolveFileURL(for: it) { urls.append(u) }
        }
        return urls
    }
}