Kingfisher/Sources/General/ImageSource/Resource.swift

//
//  Resource.swift
//  Kingfisher
//
//  Created by Wei Wang on 15/4/6.
//
//  Copyright (c) 2019 Wei Wang <onevcat@gmail.com>
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.

import Foundation

/// Represents an image resource at a certain url and a given cache key.
/// Kingfisher will use a ``Resource`` to download a resource from network and cache it with the cache key when
/// using ``Source/network(_:)`` as its image setting source.
public protocol Resource {
    
    /// The key used in cache.
    var cacheKey: String { get }
    
    /// The target image URL.
    var downloadURL: URL { get }
}

extension Resource {

    /// Converts `self` to a valid ``Source`` based on the ``Resource/downloadURL`` scheme. A ``Source/provider(_:)``
    /// with ``LocalFileImageDataProvider`` associated will be returned if the URL points to a local file. Otherwise,
    /// ``Source/network(_:)`` is returned.
    ///
    /// - Parameter overrideCacheKey: The key should be used to override the ``Resource/cacheKey`` when performing the
    /// conversion. `nil` if not overridden and ``Resource/cacheKey`` of `self` is used.
    /// - Returns: The converted source.
    ///
    public func convertToSource(overrideCacheKey: String? = nil) -> Source {
        let key = overrideCacheKey ?? cacheKey
        return downloadURL.isFileURL ?
            .provider(LocalFileImageDataProvider(fileURL: downloadURL, cacheKey: key)) :
            .network(KF.ImageResource(downloadURL: downloadURL, cacheKey: key))
    }
}

@available(*, deprecated, message: "This type conflicts with `GeneratedAssetSymbols.ImageResource` in Swift 5.9. Renamed to avoid issues in the future.", renamed: "KF.ImageResource")
public typealias ImageResource = KF.ImageResource


extension KF {
    /// ``ImageResource`` is a simple combination of ``downloadURL`` and ``cacheKey``.
    /// When passed to image view set methods, Kingfisher will try to download the target
    /// image from the ``downloadURL``, and then store it with the ``cacheKey`` as the key in cache.
    public struct ImageResource: Resource {

        // MARK: - Initializers

        /// Creates an image resource.
        ///
        /// - Parameters:
        ///   - downloadURL: The target image URL from where the image can be downloaded.
        ///   - cacheKey: 
        ///   The cache key. If `nil`, Kingfisher will use the `absoluteString` of ``ImageResource/downloadURL`` as
        ///   the key. Default is `nil`.
        ///   
        public init(downloadURL: URL, cacheKey: String? = nil) {
            self.downloadURL = downloadURL
            self.cacheKey = cacheKey ?? downloadURL.cacheKey
        }

        // MARK: Protocol Conforming
        
        /// The key used in cache.
        public let cacheKey: String

        /// The target image URL.
        public let downloadURL: URL
    }
}

/// URL conforms to ``Resource`` in Kingfisher.
/// The `absoluteString` of this URL is used as ``cacheKey``. And the URL itself will be used as `downloadURL`.
/// If you need customize the url and/or cache key, use `ImageResource` instead.
extension URL: Resource {
    public var cacheKey: String { return isFileURL ? localFileCacheKey : absoluteString }
    public var downloadURL: URL { return self }
}

extension URL {
    static let localFileCacheKeyPrefix = "kingfisher.local.cacheKey"
    
    // The special version of cache key for a local file on disk. Every time the app is reinstalled on the disk,
    // the system assigns a new container folder to hold the .app (and the extensions, .appex) folder. So the URL for
    // the same image in bundle might be different.
    //
    // This getter only uses the fixed part in the URL (until the bundle name folder) to provide a stable cache key
    // for the image under the same path inside the bundle.
    //
    // See #1825 (https://github.com/onevcat/Kingfisher/issues/1825)
    var localFileCacheKey: String {
        var validComponents: [String] = []
        for part in pathComponents.reversed() {
            validComponents.append(part)
            if part.hasSuffix(".app") || part.hasSuffix(".appex") {
                break
            }
        }
        let fixedPath = "\(Self.localFileCacheKeyPrefix)/\(validComponents.reversed().joined(separator: "/"))"
        if let q = query {
            return "\(fixedPath)?\(q)"
        } else {
            return fixedPath
        }
    }
}