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

import Foundation
import UIKit

final class DiskManager {

    enum LocalDirectory: String {
        /// Folder for new images to upload
        case upload = "Upload"

        /// Folder for downloaded images
        case images = "Images"

        /// Folder for downloaded images
        case thumbnails = "Thumbnails"

        /// Directory for name file
        case files = "Files"

        private static let fm = FileManager.default

        /// The url to the file sstem
        var url: URL {
            return URL(fileURLWithPath: self.rawValue, isDirectory: true, relativeTo: DiskManager.documentsDirectory)
        }

        fileprivate func create() -> Bool {
            return DiskManager.create(directory: url)
        }

        var content: [URL]? {
            do {
                return try LocalDirectory.fm.contentsOfDirectory(at: url, includingPropertiesForKeys: nil, options: [])
            } catch {
                print("[LocalDirectory] Could not read directory \(self.rawValue): \(error)")
                return nil
            }
        }
    }

    /// The folder where images and name list are stored
    static let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!

    private static let fm = FileManager.default

    // MARK: - First launch

    @discardableResult static func setupOnFirstLaunch() -> Bool {
        return LocalDirectory.files.create() &&
            LocalDirectory.images.create() &&
            LocalDirectory.thumbnails.create() &&
            LocalDirectory.upload.create()
    }

    private static func create(directory: URL) -> Bool {
         do {
            if !fm.fileExists(atPath: directory.path) {
                try fm.createDirectory(at: directory, withIntermediateDirectories: true, attributes: nil)
            }
            return true
        } catch {
            event("Could not create \(directory): \(error)")
            return false
        }
    }

    // MARK: - Image retrieval

    /**
     Check if an image exists for a cap
     - parameter cap: The id of the cap
     - returns: True, if an image exists
     */
    static func hasImage(for cap: Int) -> Bool {
        let url = localUrl(for: cap)
        return fm.fileExists(atPath: url.path)
    }

    private static func localUrl(for cap: Int) -> URL {
        return URL(fileURLWithPath: "\(cap).jpg", isDirectory: true, relativeTo: LocalDirectory.images.url)
    }
    
    private static func thumbnailUrl(for cap: Int) -> URL {
        return URL(fileURLWithPath: "\(cap).jpg", isDirectory: true, relativeTo: LocalDirectory.thumbnails.url)
    }

    /**
     Get the image for a cap.
     If the image exists on disk, it is returned.
     If no image exists locally, then this function returns nil.
     - parameter cap: The id of the cap
     - returns: The image data, or `nil`
     */
    static func image(for cap: Int) -> Data? {
        // If the image exists on disk, get it
        let url = localUrl(for: cap)
        return readData(from: url)
    }
    
    private static let mosaicURL: URL = documentsDirectory.appendingPathComponent("mosaic.png")
    
    
    static var mosaicExists: Bool {
        return fm.fileExists(atPath: mosaicURL.path)
    }
    
    static func saveMosaicData(_ data: Data) -> Bool {
        return write(data, to: mosaicURL)
    }
    
    static var mosaicData: Data? {
        return readData(from: mosaicURL)
    }
    
    /**
     Get the thumbnail for a cap.
     If the image exists on disk, it is returned.
     If no image exists locally, then this function returns nil.
     - parameter cap: The id of the cap
     - returns: The image data, or `nil`
     */
    static func thumbnail(for cap: Int) -> Data? {
        // If the image exists on disk, get it
        let url = thumbnailUrl(for: cap)
        return readData(from: url)
    }
    
    private static func readData(from url: URL) -> Data? {
        guard fm.fileExists(atPath: url.path) else {
            return nil
        }
        do {
            return try Data(contentsOf: url)
        } catch {
            self.error("Could not read data from \(url): \(error)")
            return nil
        }
    }
    
    /**
     Save an image to the download folder
     - parameter imageData: The data of the image
     - parameter cap: The cap id
     - returns: True, if the image was saved
     */
    static func save(imageData: Data, for cap: Int) -> Bool {
        let url = localUrl(for: cap)
        return write(imageData, to: url)
    }
    
    /**
     Save a thumbnail to the download folder
     - parameter thumbnailData: The data of the image
     - parameter cap: The cap id
     - returns: True, if the image was saved
     */
    static func save(thumbnailData: Data, for cap: Int) -> Bool {
        let url = thumbnailUrl(for: cap)
        return write(thumbnailData, to: url)
    }

    private static func write(_ data: Data, to url: URL) -> Bool {
        do {
            try data.write(to: url)
        } catch {
            self.error("Could not write data to \(url): \(error)")
            return false
        }
        return true
    }

    static func removeFromUpload(url: URL) -> Bool {
        guard fm.fileExists(atPath: url.path) else {
            return true
        }
        do {
            try fm.removeItem(at: url)
            return true
        } catch {
            self.error("Could not delete file \(url.path)")
            return false
        }
    }

    static var pendingUploads: [URL]? {
        return LocalDirectory.upload.content
    }

    static var availableImages: [Int]? {
        return LocalDirectory.images.content?.compactMap {
            Int($0.lastPathComponent.components(separatedBy: ".").first ?? "")
        }
    }

    /**
     Save an image to the uploads folder for later
     */
    static func saveForUpload(imageData: Data, name: String) -> URL?  {
        let url = LocalDirectory.upload.url.appendingPathComponent(name)
        return write(imageData, to: url) ? url : nil
    }
}

extension DiskManager: Logger {

    static let logToken = "[DiskManager]"
}