//
//  ExtensionFeedAddRequestFile.swift
//  NetNewsWire-iOS
//
//  Created by Maurice Parker on 2/11/20.
//  Copyright © 2020 Ranchero Software. All rights reserved.
//

import Foundation
import os.log
import Account

final class ExtensionFeedAddRequestFile: NSObject, NSFilePresenter, Sendable {

	nonisolated(unsafe) private static let log = OSLog(subsystem: Bundle.main.bundleIdentifier!, category: "extensionFeedAddRequestFile")

	private static let filePath: String = {
		let appGroup = Bundle.main.object(forInfoDictionaryKey: "AppGroup") as! String
		let containerURL = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: appGroup)
		return containerURL!.appendingPathComponent("extension_feed_add_request.plist").path
	}()
	
	private let operationQueue: OperationQueue
	
	var presentedItemURL: URL? {
		return URL(fileURLWithPath: ExtensionFeedAddRequestFile.filePath)
	}
	
	var presentedItemOperationQueue: OperationQueue {
		return operationQueue
	}
	
	@MainActor override init() {
		operationQueue = OperationQueue()
		operationQueue.maxConcurrentOperationCount = 1
		
		super.init()
		
		NSFileCoordinator.addFilePresenter(self)
		process()
	}

	func presentedItemDidChange() {
		Task { @MainActor in
			self.process()
		}
	}

	func resume() {
		NSFileCoordinator.addFilePresenter(self)
		Task { @MainActor in
			process()
		}
	}
	
	func suspend() {
		NSFileCoordinator.removeFilePresenter(self)
	}
	
	static func save(_ feedAddRequest: ExtensionFeedAddRequest) {
		
		let decoder = PropertyListDecoder()
		let encoder = PropertyListEncoder()
		encoder.outputFormat = .binary

		let errorPointer: NSErrorPointer = nil
		let fileCoordinator = NSFileCoordinator()
		let fileURL = URL(fileURLWithPath: ExtensionFeedAddRequestFile.filePath)
		
		fileCoordinator.coordinate(writingItemAt: fileURL, options: [.forMerging], error: errorPointer, byAccessor: { url in
			do {
				
				var requests: [ExtensionFeedAddRequest]
				if let fileData = try? Data(contentsOf: url),
					let decodedRequests = try? decoder.decode([ExtensionFeedAddRequest].self, from: fileData) {
					requests = decodedRequests
				} else {
					requests = [ExtensionFeedAddRequest]()
				}
				
				requests.append(feedAddRequest)

				let data = try encoder.encode(requests)
				try data.write(to: url)
				
			} catch let error as NSError {
				os_log(.error, log: Self.log, "Save to disk failed: %@.", error.localizedDescription)
			}
		})
		
		if let error = errorPointer?.pointee {
			os_log(.error, log: Self.log, "Save to disk coordination failed: %@.", error.localizedDescription)
		}
	}
	
}

private extension ExtensionFeedAddRequestFile {
	
	@MainActor func process() {

		let decoder = PropertyListDecoder()
		let encoder = PropertyListEncoder()
		encoder.outputFormat = .binary

		let errorPointer: NSErrorPointer = nil
		let fileCoordinator = NSFileCoordinator(filePresenter: self)
		let fileURL = URL(fileURLWithPath: ExtensionFeedAddRequestFile.filePath)

		var requests: [ExtensionFeedAddRequest]? = nil

		fileCoordinator.coordinate(writingItemAt: fileURL, options: [.forMerging], error: errorPointer, byAccessor: { url in
			do {

				if let fileData = try? Data(contentsOf: url),
				   let decodedRequests = try? decoder.decode([ExtensionFeedAddRequest].self, from: fileData) {
					requests = decodedRequests
				}

				let data = try encoder.encode([ExtensionFeedAddRequest]())
				try data.write(to: url)

			} catch let error as NSError {
				os_log(.error, log: Self.log, "Save to disk failed: %@.", error.localizedDescription)
			}
		})

		if let error = errorPointer?.pointee {
			os_log(.error, log: Self.log, "Save to disk coordination failed: %@.", error.localizedDescription)
		}

		if let requests {
			for request in requests {
				processRequest(request)
			}
		}
	}
	
	@MainActor func processRequest(_ request: ExtensionFeedAddRequest) {
		var destinationAccountID: String? = nil
		switch request.destinationContainerID {
		case .account(let accountID):
			destinationAccountID = accountID
		case .folder(let accountID, _):
			destinationAccountID = accountID
		default:
			break
		}
		
		guard let accountID = destinationAccountID, let account = AccountManager.shared.existingAccount(with: accountID) else {
			return
		}
		
		var destinationContainer: Container? = nil
		if account.containerID == request.destinationContainerID {
			destinationContainer = account
		} else {
			destinationContainer = account.folders?.first(where: { $0.containerID == request.destinationContainerID })
		}
		
		guard let container = destinationContainer else { return }
		
		Task { @MainActor in
			try? await account.createFeed(url: request.feedURL.absoluteString, name: request.name, container: container, validateFeed: true)
		}
	}	
}