Dactyloidae iOS initial commit

mobile/ios/Storage/DiskImageStore.swift

@@ -0,0 +1,105 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import Foundation
+import Shared
+import UIKit
+import Deferred
+import XCGLogger
+
+private var log = XCGLogger.default
+
+private class DiskImageStoreErrorType: MaybeErrorType {
+    let description: String
+    init(description: String) {
+        self.description = description
+    }
+}
+
+/**
+ * Disk-backed key-value image store.
+ */
+open class DiskImageStore {
+    fileprivate let files: FileAccessor
+    fileprivate let filesDir: String
+    fileprivate let queue = DispatchQueue(label: "DiskImageStore")
+    fileprivate let quality: CGFloat
+    fileprivate var keys: Set<String>
+
+    required public init(files: FileAccessor, namespace: String, quality: Float) {
+        self.files = files
+        self.filesDir = try! files.getAndEnsureDirectory(namespace)
+        self.quality = CGFloat(quality)
+
+        // Build an in-memory set of keys from the existing images on disk.
+        var keys = [String]()
+        if let fileEnumerator = FileManager.default.enumerator(atPath: filesDir) {
+            for file in fileEnumerator {
+                keys.append(file as! String)
+            }
+        }
+        self.keys = Set(keys)
+    }
+
+    /// Gets an image for the given key if it is in the store.
+    open func get(_ key: String) -> Deferred<Maybe<UIImage>> {
+        return deferDispatchAsync(queue) { () -> Deferred<Maybe<UIImage>> in
+            if !self.keys.contains(key) {
+                return deferMaybe(DiskImageStoreErrorType(description: "Image key not found"))
+            }
+
+            let imagePath = URL(fileURLWithPath: self.filesDir).appendingPathComponent(key)
+            if let data = try? Data(contentsOf: imagePath),
+                   let image = UIImage.imageFromDataThreadSafe(data) {
+                return deferMaybe(image)
+            }
+
+            return deferMaybe(DiskImageStoreErrorType(description: "Invalid image data"))
+        }
+    }
+
+    /// Adds an image for the given key.
+    /// This put is asynchronous; the image is not recorded in the cache until the write completes.
+    /// Does nothing if this key already exists in the store.
+    @discardableResult open func put(_ key: String, image: UIImage) -> Success {
+        return deferDispatchAsync(queue) { () -> Success in
+            if self.keys.contains(key) {
+                return deferMaybe(DiskImageStoreErrorType(description: "Key already in store"))
+            }
+
+            let imageURL = URL(fileURLWithPath: self.filesDir).appendingPathComponent(key)
+            if let data = UIImageJPEGRepresentation(image, self.quality) {
+                do {
+                    try data.write(to: imageURL, options: .noFileProtection)
+                    self.keys.insert(key)
+                    return succeed()
+                } catch {
+                    log.error("Unable to write image to disk: \(error)")
+                }
+            }
+
+            return deferMaybe(DiskImageStoreErrorType(description: "Could not write image to file"))
+        }
+    }
+
+    /// Clears all images from the cache, excluding the given set of keys.
+    open func clearExcluding(_ keys: Set<String>) -> Success {
+        return deferDispatchAsync(queue) { () -> Success in
+            let keysToDelete = self.keys.subtracting(keys)
+
+            for key in keysToDelete {
+                let url = URL(fileURLWithPath: self.filesDir).appendingPathComponent(key)
+                do {
+                    try FileManager.default.removeItem(at: url)
+                } catch {
+                    log.warning("Failed to remove DiskImageStore item at \(url.absoluteString): \(error)")
+                }
+            }
+
+            self.keys = self.keys.intersection(keys)
+
+            return succeed()
+        }
+    }
+}