//
//  SaveDocumentPicker.swift
//  Browse
//
//  Created by Javier Cicchelli on 17/12/2022.
//  Copyright © 2022 Röck+Cöde. All rights reserved.
//

import Foundation
import SwiftUI
import UIKit

struct SaveDocumentPicker: UIViewControllerRepresentable {

    // MARK: Type aliases

    typealias DownloadedClosure = (NSError?) -> Void
    typealias CancelledClosure = () -> Void

    // MARK: Properties

    private let fileName: String
    private let fileData: Data
    private let downloaded: DownloadedClosure
    private let cancelled: CancelledClosure?

    // MARK: Initialisers

    init(
        fileName: String,
        fileData: Data,
        downloaded: @escaping DownloadedClosure,
        cancelled: CancelledClosure? = nil
    ) {
        self.fileName = fileName
        self.fileData = fileData
        self.downloaded = downloaded
        self.cancelled = cancelled
    }

    // MARK: Functions

    func makeUIViewController(context: Context) -> UIDocumentPickerViewController {
        let controller = UIDocumentPickerViewController(
            forOpeningContentTypes: [.folder]
        )

        controller.allowsMultipleSelection = false
        controller.shouldShowFileExtensions = false
        controller.delegate = context.coordinator

        return controller
    }

    func updateUIViewController(
        _ uiViewController: UIDocumentPickerViewController,
        context: Context
    ) { }

    func makeCoordinator() -> Coordinator {
        .init(self)
    }
}

// MARK: - Coordinators

extension SaveDocumentPicker {
    class Coordinator: NSObject, UIDocumentPickerDelegate {

        // MARK: Properties

        private let parent: SaveDocumentPicker
        private let fileCoordinator: NSFileCoordinator = .init()
        private let fileManager: FileManager = .default

        // MARK: Initialisers

        init(_ parent: SaveDocumentPicker) {
            self.parent = parent
        }

        // MARK: UIDocumentPickerDelegate

        func documentPicker(
            _ controller: UIDocumentPickerViewController,
            didPickDocumentsAt urls: [URL]
        ) {
            guard
                let url = urls.first,
                url.startAccessingSecurityScopedResource()
            else {
                // TODO: Handle this error appropriately.
                return
            }
            
            var error: NSError?
            
            fileCoordinator.coordinate(
                writingItemAt: url,
                error: &error
            ) { url in
                fileManager.createFile(
                    atPath: url.appendingPathComponent(parent.fileName).relativePath,
                    contents: parent.fileData
                )
            }
            
            url.stopAccessingSecurityScopedResource()
            
            parent.downloaded(error)
        }

        func documentPickerWasCancelled(_ controller: UIDocumentPickerViewController) {
            controller.dismiss(animated: true) { [weak self] in
                self?.parent.cancelled?()
            }
        }

    }
}