//
//  NameFile.swift
//  CapFinder
//
//  Created by User on 23.04.18.
//  Copyright © 2018 User. All rights reserved.
//

import Foundation
import SwiftyDropbox

final class NameFile: Logger {

    static let logToken = "[NameFile]"

    /// The name of the file
    private static let fileName = "names.txt"
    
    private static let path = "/" + fileName
    
    /// The url of the file on disk
    private static let url = DiskManager.documentsDirectory.appendingPathComponent(fileName)

    private static let fm = FileManager.default

    // MARK: - Reading from disk

    /// Indicates if the name list was written to disk
    private static var nameFileExistsOnDisk: Bool {
        return fm.fileExists(atPath: url.path)
    }
    
    // MARK: - Public API

    @discardableResult static func save(names: String) -> Bool {
        let data = names.data(using: .utf8)!
        return save(names: data)
    }
    
    static func saveAndUpload(names: String, completion: @escaping (Bool) -> Void) {
        let data = names.data(using: .utf8)!
        guard save(names: data) else {
            return
        }
        
        let client = DropboxController.client
        client.files.upload(path: path, mode: .overwrite, input: data).response { _ , error in
            if let error = error {
                self.error("Error uploading name list: \(error)")
                completion(false)
            } else {
                self.event("Uploaded name list")
                completion(true)
            }
        }
    }
    
    // MARK: - Private
    
    /// The content of the name file as a String
    private static var content: String? {
        do {
            return try String(contentsOf: url, encoding: .utf8)
        } catch {
            self.error("Error reading \(url): \(error)")
            return nil
        }
    }
    
    /**
     Save the name file to disk
     - parameter names: The new name file content
     - returns: True, if the data was written to disk
     */
    @discardableResult private static func save(names: Data) -> Bool {
        do {
            try names.write(to: url, options: .atomic)
            event("Name file saved to disk")
            return true
        } catch {
            self.error("Could not save names to file: \(error)")
            return false
        }
    }
    
    
    static func makeAvailable(completion: ((String?) -> Void)? = nil) {
        if nameFileExistsOnDisk {
            completion?(self.content)
        } else {
            download() { success in
                guard success else {
                    completion?(nil)
                    return
                }
                completion?(self.content)
            }
        }
    }
    
    /// The data of the name list
    private static var data: Data? {
        guard nameFileExistsOnDisk else { return nil }
        do {
            return try Data(contentsOf: url)
        } catch {
            self.error("Could not read data from \(url): \(error)")
            return nil
        }
    }
    
    /**
     Delete the file on disk
     - returns: True, if the file no longer exists on disk
     */
    @discardableResult private static func delete() -> Bool {
        guard nameFileExistsOnDisk else {
            event("No name file to delete")
            return true
        }

        do {
            try fm.removeItem(at: url)
        } catch {
            self.error("Could not delete name file: \(error)")
            return false
        }
        event("Deleted name file on disk")
        return true
    }
    
    private static func download(completion: ((Bool) -> Void)? = nil) {
        let client = DropboxController.client
        event("Downloading names from Dropbox")
        client.files.download(path: path).response { response, error in
            guard let data = response?.1 else {
                self.error("Error downloading file: \(error!)")
                completion?(false)
                return
            }
            self.event("Downloaded name file")
            completion?(NameFile.save(names: data))
        }
    }
}