Merge branch 'charlesmchen/linkPreviewImageMaxSize'

Pods

@@ -1 +1 @@
-Subproject commit db7ec4663cdd5d9615f182dcc51731f82df4b297
+Subproject commit a1c073c81d62ae5b6e7dcd54f0d41b0cd0c254cd

Signal.xcodeproj/project.pbxproj

@@ -60,7 +60,6 @@
 		343A65981FC4CFE7000477A1 /* ConversationScrollButton.m in Sources */ = {isa = PBXBuildFile; fileRef = 343A65961FC4CFE6000477A1 /* ConversationScrollButton.m */; };
 		3441FD9F21A3604F00BB9542 /* BackupRestoreViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3441FD9E21A3604F00BB9542 /* BackupRestoreViewController.swift */; };
 		34480B361FD0929200BC14EF /* ShareAppExtensionContext.m in Sources */ = {isa = PBXBuildFile; fileRef = 34480B351FD0929200BC14EF /* ShareAppExtensionContext.m */; };
-		34480B491FD0A60200BC14EF /* OWSMath.h in Headers */ = {isa = PBXBuildFile; fileRef = 34480B481FD0A60200BC14EF /* OWSMath.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		34480B551FD0A7A400BC14EF /* DebugLogger.h in Headers */ = {isa = PBXBuildFile; fileRef = 34480B4D1FD0A7A300BC14EF /* DebugLogger.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		34480B561FD0A7A400BC14EF /* DebugLogger.m in Sources */ = {isa = PBXBuildFile; fileRef = 34480B4E1FD0A7A300BC14EF /* DebugLogger.m */; };
 		34480B571FD0A7A400BC14EF /* OWSScrubbingLogFormatter.h in Headers */ = {isa = PBXBuildFile; fileRef = 34480B4F1FD0A7A300BC14EF /* OWSScrubbingLogFormatter.h */; };
@@ -710,7 +709,6 @@
 		34480B351FD0929200BC14EF /* ShareAppExtensionContext.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = ShareAppExtensionContext.m; sourceTree = "<group>"; };
 		34480B371FD092A900BC14EF /* SignalShareExtension-Bridging-Header.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "SignalShareExtension-Bridging-Header.h"; sourceTree = "<group>"; };
 		34480B381FD092E300BC14EF /* SignalShareExtension-Prefix.pch */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "SignalShareExtension-Prefix.pch"; sourceTree = "<group>"; };
-		34480B481FD0A60200BC14EF /* OWSMath.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = OWSMath.h; sourceTree = "<group>"; };
 		34480B4D1FD0A7A300BC14EF /* DebugLogger.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = DebugLogger.h; sourceTree = "<group>"; };
 		34480B4E1FD0A7A300BC14EF /* DebugLogger.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = DebugLogger.m; sourceTree = "<group>"; };
 		34480B4F1FD0A7A300BC14EF /* OWSScrubbingLogFormatter.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = OWSScrubbingLogFormatter.h; sourceTree = "<group>"; };
@@ -1564,7 +1562,6 @@
 				346129AA1FD1F0EE00532771 /* OWSFormat.m */,
 				45666EC71D994C0D008FE134 /* OWSGroupAvatarBuilder.h */,
 				45666EC81D994C0D008FE134 /* OWSGroupAvatarBuilder.m */,
-				34480B481FD0A60200BC14EF /* OWSMath.h */,
 				346129371FD1B47200532771 /* OWSPreferences.h */,
 				346129381FD1B47200532771 /* OWSPreferences.m */,
 				34641E172088D7E900E2EDE5 /* OWSScreenLock.swift */,
@@ -2606,7 +2603,6 @@
 			isa = PBXHeadersBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				34480B491FD0A60200BC14EF /* OWSMath.h in Headers */,
 				346129E71FD5C0C600532771 /* OWSDatabaseMigrationRunner.h in Headers */,
 				34AC09F9211B39B100997B47 /* CountryCodeViewController.h in Headers */,
 				34ABB2C52090C59700C727A6 /* OWSResaveCollectionDBMigration.h in Headers */,

Signal/src/AppDelegate.m

@@ -24,7 +24,6 @@
 #import <SignalMessaging/AppSetup.h>
 #import <SignalMessaging/Environment.h>
 #import <SignalMessaging/OWSContactsManager.h>
-#import <SignalMessaging/OWSMath.h>
 #import <SignalMessaging/OWSNavigationController.h>
 #import <SignalMessaging/OWSPreferences.h>
 #import <SignalMessaging/OWSProfileManager.h>
@@ -38,6 +37,7 @@
 #import <SignalServiceKit/OWSFailedAttachmentDownloadsJob.h>
 #import <SignalServiceKit/OWSFailedMessagesJob.h>
 #import <SignalServiceKit/OWSIncompleteCallsJob.h>
+#import <SignalServiceKit/OWSMath.h>
 #import <SignalServiceKit/OWSMessageManager.h>
 #import <SignalServiceKit/OWSMessageSender.h>
 #import <SignalServiceKit/OWSPrimaryStorage+Calling.h>

Signal/src/ViewControllers/ConversationView/ConversationInputToolbar.m

@@ -11,6 +11,7 @@
 #import "UIColor+OWS.h"
 #import "UIFont+OWS.h"
 #import "ViewControllerUtils.h"
+#import <PromiseKit/AnyPromise.h>
 #import <SignalMessaging/OWSFormat.h>
 #import <SignalMessaging/SignalMessaging-Swift.h>
 #import <SignalMessaging/UIView+OWS.h>
@@ -739,27 +740,24 @@ const CGFloat kMaxTextViewHeight = 98;
     [self ensureLinkPreviewViewWithState:[LinkPreviewLoading new]];
 
     __weak ConversationInputToolbar *weakSelf = self;
-    [OWSLinkPreview tryToBuildPreviewInfoWithPreviewUrl:previewUrl
+    [[OWSLinkPreview tryToBuildPreviewInfoObjcWithPreviewUrl:previewUrl]
-                                          callbackQueue:dispatch_get_main_queue()
+            .then(^(OWSLinkPreviewDraft *linkPreviewDraft) {
-                                             completion:^(OWSLinkPreviewDraft *_Nullable linkPreviewDraft) {
+                ConversationInputToolbar *_Nullable strongSelf = weakSelf;
-                                                 ConversationInputToolbar *_Nullable strongSelf = weakSelf;
+                if (!strongSelf) {
-                                                 if (!strongSelf) {
+                    return;
-                                                     return;
+                }
-                                                 }
+                if (strongSelf.inputLinkPreview != inputLinkPreview) {
-                                                 if (strongSelf.inputLinkPreview != inputLinkPreview) {
+                    // Obsolete callback.
-                                                     // Obsolete callback.
+                    return;
-                                                     return;
+                }
-                                                 }
+                inputLinkPreview.linkPreviewDraft = linkPreviewDraft;
-                                                 if (!linkPreviewDraft) {
+                LinkPreviewDraft *viewState = [[LinkPreviewDraft alloc] initWithLinkPreviewDraft:linkPreviewDraft];
-                                                     // The link preview could not be loaded.
+                [strongSelf ensureLinkPreviewViewWithState:viewState];
-                                                     [strongSelf clearLinkPreviewView];
+            })
-                                                     return;
+            .catch(^(id error) {
-                                                 }
+                // The link preview could not be loaded.
-                                                 inputLinkPreview.linkPreviewDraft = linkPreviewDraft;
+                [weakSelf clearLinkPreviewView];
-                                                 LinkPreviewDraft *viewState = [[LinkPreviewDraft alloc]
+            }) retainUntilComplete];
-                                                     initWithLinkPreviewDraft:linkPreviewDraft];
-                                                 [strongSelf ensureLinkPreviewViewWithState:viewState];
-                                             }];
 }
 
 - (void)ensureLinkPreviewViewWithState:(id<LinkPreviewState>)state

Signal/src/ViewControllers/HomeView/HomeViewCell.m

@@ -6,9 +6,9 @@
 #import "OWSAvatarBuilder.h"
 #import "Signal-Swift.h"
 #import <SignalMessaging/OWSFormat.h>
-#import <SignalMessaging/OWSMath.h>
 #import <SignalMessaging/OWSUserProfile.h>
 #import <SignalMessaging/SignalMessaging-Swift.h>
+#import <SignalServiceKit/OWSMath.h>
 #import <SignalServiceKit/OWSMessageManager.h>
 #import <SignalServiceKit/TSContactThread.h>
 #import <SignalServiceKit/TSGroupThread.h>

Signal/src/views/OWSProgressView.m

@@ -1,10 +1,10 @@
 //
-//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
 #import "OWSProgressView.h"
-#import <SignalMessaging/OWSMath.h>
 #import <SignalMessaging/UIView+OWS.h>
+#import <SignalServiceKit/OWSMath.h>
 
 NS_ASSUME_NONNULL_BEGIN
 

SignalMessaging/SignalMessaging.h

@@ -31,7 +31,6 @@ FOUNDATION_EXPORT const unsigned char SignalMessagingVersionString[];
 #import <SignalMessaging/OWSDatabaseMigration.h>
 #import <SignalMessaging/OWSFormat.h>
 #import <SignalMessaging/OWSGroupAvatarBuilder.h>
-#import <SignalMessaging/OWSMath.h>
 #import <SignalMessaging/OWSNavigationController.h>
 #import <SignalMessaging/OWSPreferences.h>
 #import <SignalMessaging/OWSProfileManager.h>

SignalMessaging/categories/UIView+OWS.h

@@ -2,8 +2,8 @@
 //  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
-#import "OWSMath.h"
 #import <PureLayout/PureLayout.h>
+#import <SignalServiceKit/OWSMath.h>
 #import <UIKit/UIKit.h>
 
 NS_ASSUME_NONNULL_BEGIN

SignalServiceKit/src/Messages/Interactions/OWSLinkPreview.swift

@@ -3,11 +3,16 @@
 //
 
 import Foundation
+import PromiseKit
 
 @objc
 public enum LinkPreviewError: Int, Error {
     case invalidInput
     case noPreview
+    case assertionFailure
+    case couldNotDownload
+    case featureDisabled
+    case invalidContent
 }
 
 // MARK: - OWSLinkPreviewDraft
@@ -424,70 +429,57 @@ public class OWSLinkPreview: MTLModel {
     // This cache should only be accessed on serialQueue.
     private static var linkPreviewDraftCache: NSCache<AnyObject, OWSLinkPreviewDraft> = NSCache()
 
-    // Completion will always be invoked exactly once.
+    private class func cachedLinkPreview(forPreviewUrl previewUrl: String) -> OWSLinkPreviewDraft? {
-    //
+        var result: OWSLinkPreviewDraft?
-    // The completion is called with a link preview if one can be built for
+        serialQueue.sync {
-    // the message body.  It building the preview fails, completion will be
+            result = linkPreviewDraftCache.object(forKey: previewUrl as AnyObject)
-    // called with nil to avoid failing the message send.
-    @objc
-    public class func tryToBuildPreviewInfo(previewUrl: String?,
-                                            callbackQueue: DispatchQueue,
-                                            completion completionParam: @escaping (OWSLinkPreviewDraft?) -> Void) {
-
-        // Ensure we invoke completion on the callback queue.
-        let completion = { (linkPreviewDraft) in
-            callbackQueue.async {
-                completionParam(linkPreviewDraft)
-            }
         }
+        return result
+    }
+
+    private class func setCachedLinkPreview(_ linkPreviewDraft: OWSLinkPreviewDraft,
+                                            forPreviewUrl previewUrl: String) {
+        serialQueue.sync {
+            previewUrlCache.setObject(linkPreviewDraft, forKey: previewUrl as AnyObject)
+        }
+    }
+
+    @objc
+    public class func tryToBuildPreviewInfoObjc(previewUrl: String?) -> AnyPromise {
+        return AnyPromise(tryToBuildPreviewInfo(previewUrl: previewUrl))
+    }
+
+    public class func tryToBuildPreviewInfo(previewUrl: String?) -> Promise<OWSLinkPreviewDraft> {
 
         guard OWSLinkPreview.featureEnabled else {
-            completion(nil)
+            return Promise(error: LinkPreviewError.featureDisabled)
-            return
         }
         guard SSKPreferences.areLinkPreviewsEnabled() else {
-            completion(nil)
+            return Promise(error: LinkPreviewError.featureDisabled)
-            return
         }
         guard let previewUrl = previewUrl else {
-            completion(nil)
+            return Promise(error: LinkPreviewError.invalidInput)
-            return
         }
-        serialQueue.async {
+        if let cachedInfo = cachedLinkPreview(forPreviewUrl: previewUrl) {
-            if let cachedInfo = linkPreviewDraftCache.object(forKey: previewUrl as AnyObject) {
+            Logger.verbose("Link preview info cache hit.")
-                Logger.verbose("Link preview info cache hit.")
+            return Promise.value(cachedInfo)
-                completion(cachedInfo)
+        }
-                return
+        return downloadLink(url: previewUrl)
-            }
+            .then(on: DispatchQueue.global()) { (data) -> Promise<OWSLinkPreviewDraft> in
-            downloadLink(url: previewUrl, completion: { (data) in
+                return parse(linkData: data, linkUrlString: previewUrl)
-                DispatchQueue.global().async {
+                    .then(on: DispatchQueue.global()) { (linkPreviewDraft) -> Promise<OWSLinkPreviewDraft> in
-                    guard let data = data else {
-                        completion(nil)
-                        return
-                    }
-                    parse(linkData: data, linkUrlString: previewUrl) { (linkPreviewDraft) in
-                        guard let linkPreviewDraft = linkPreviewDraft else {
-                            completion(nil)
-                            return
-                        }
                         guard linkPreviewDraft.isValid() else {
-                            completion(nil)
+                            return Promise(error: LinkPreviewError.noPreview)
-                            return
                         }
-                        serialQueue.async {
+                        setCachedLinkPreview(linkPreviewDraft, forPreviewUrl: previewUrl)
-                            previewUrlCache.setObject(linkPreviewDraft, forKey: previewUrl as AnyObject)
 
-                            completion(linkPreviewDraft)
+                        return Promise.value(linkPreviewDraft)
-                        }
-                    }
                 }
-            })
         }
     }
 
     private class func downloadLink(url: String,
-                                    completion: @escaping (Data?) -> Void,
+                                    remainingRetries: UInt = 3) -> Promise<Data> {
-                                    remainingRetries: UInt = 3) {
 
         Logger.verbose("url: \(url)")
 
@@ -507,6 +499,7 @@ public class OWSLinkPreview: MTLModel {
             sessionManager.requestSerializer.setValue(nil, forHTTPHeaderField: headerField)
         }
 
+        let (promise, resolver) = Promise<Data>.pending()
         sessionManager.get(url,
                            parameters: [String: AnyObject](),
                            progress: nil,
@@ -514,64 +507,91 @@ public class OWSLinkPreview: MTLModel {
 
                             guard let data = value as? Data else {
                                 Logger.warn("Result is not data: \(type(of: value)).")
-                                completion(nil)
+                                resolver.reject( LinkPreviewError.assertionFailure)
                                 return
                             }
-                            completion(data)
+                            resolver.fulfill(data)
         },
                            failure: { _, error in
                             Logger.verbose("Error: \(error)")
 
                             guard isRetryable(error: error) else {
                                 Logger.warn("Error is not retryable.")
-                                completion(nil)
+                                resolver.reject( LinkPreviewError.couldNotDownload)
                                 return
                             }
 
                             guard remainingRetries > 0 else {
                                 Logger.warn("No more retries.")
-                                completion(nil)
+                                resolver.reject( LinkPreviewError.couldNotDownload)
                                 return
                             }
-                            OWSLinkPreview.downloadLink(url: url, completion: completion, remainingRetries: remainingRetries - 1)
+                            OWSLinkPreview.downloadLink(url: url, remainingRetries: remainingRetries - 1)
+                            .done(on: DispatchQueue.global()) { (data) in
+                                resolver.fulfill(data)
+                            }.catch(on: DispatchQueue.global()) { (error) in
+                                resolver.reject( error)
+                            }.retainUntilComplete()
         })
+        return promise
     }
 
-    private class func downloadImage(url urlString: String,
+    private class func downloadImage(url urlString: String, imageMimeType: String) -> Promise<Data> {
-                                     completion: @escaping (Data?) -> Void) {
 
         Logger.verbose("url: \(urlString)")
 
         guard let url = URL(string: urlString) else {
             Logger.error("Could not parse URL.")
-            return completion(nil)
+            return Promise(error: LinkPreviewError.invalidInput)
         }
 
         guard let assetDescription = ProxiedContentAssetDescription(url: url as NSURL) else {
             Logger.error("Could not create asset description.")
-            return completion(nil)
+            return Promise(error: LinkPreviewError.invalidInput)
         }
+        let (promise, resolver) = Promise<ProxiedContentAsset>.pending()
         DispatchQueue.main.async {
             _ = ProxiedContentDownloader.defaultDownloader.requestAsset(assetDescription: assetDescription,
                                                                         priority: .high,
                                                                         success: { (_, asset) in
-                                                                            DispatchQueue.global().async {
+                                                                            resolver.fulfill(asset)
-                                                                                do {
-                                                                                    let data = try Data(contentsOf: URL(fileURLWithPath: asset.filePath))
-                                                                                    completion(data)
-                                                                                } catch {
-                                                                                    owsFailDebug("Could not load asset data: \(type(of: asset.filePath)).")
-                                                                                    completion(nil)
-                                                                                }
-                                                                            }
-
             }, failure: { (_) in
-                DispatchQueue.global().async {
+                Logger.warn("Error downloading asset")
-                    Logger.verbose("Error downloading asset")
+                resolver.reject(LinkPreviewError.couldNotDownload)
+            })
+        }
+        return promise.then(on: DispatchQueue.global()) { (asset: ProxiedContentAsset) -> Promise<Data> in
+            do {
+                let imageSize = NSData.imageSize(forFilePath: asset.filePath, mimeType: imageMimeType)
+                guard imageSize.width > 0, imageSize.height > 0 else {
+                    Logger.error("Link preview is invalid or has invalid size.")
+                    return Promise(error: LinkPreviewError.invalidContent)
+               }
+                let data = try Data(contentsOf: URL(fileURLWithPath: asset.filePath))
+
+                let maxImageSize: CGFloat = 1024
+                let shouldResize = imageSize.width > maxImageSize || imageSize.height > maxImageSize
+                guard shouldResize else {
+                    return Promise.value(data)
+                }
 
-                    completion(nil)
+                guard let srcImage = UIImage(data: data) else {
+                    Logger.error("Could not parse image.")
+                    return Promise(error: LinkPreviewError.invalidContent)
                 }
-            })
+                guard let dstImage = srcImage.resized(withMaxDimensionPoints: maxImageSize) else {
+                    Logger.error("Could not resize image.")
+                    return Promise(error: LinkPreviewError.invalidContent)
+                }
+                guard let dstData = UIImageJPEGRepresentation(dstImage, 0.8) else {
+                    Logger.error("Could not write resized image.")
+                    return Promise(error: LinkPreviewError.invalidContent)
+                }
+                return Promise.value(dstData)
+            } catch {
+                owsFailDebug("Could not load asset data: \(type(of: asset.filePath)).")
+                return Promise(error: LinkPreviewError.assertionFailure)
+            }
         }
     }
 
@@ -589,12 +609,10 @@ public class OWSLinkPreview: MTLModel {
     //    <meta property="og:title" content="Randomness is Random - Numberphile">
     //    <meta property="og:image" content="https://i.ytimg.com/vi/tP-Ipsat90c/maxresdefault.jpg">
     private class func parse(linkData: Data,
-                             linkUrlString: String,
+                             linkUrlString: String) -> Promise<OWSLinkPreviewDraft> {
-                             completion: @escaping (OWSLinkPreviewDraft?) -> Void) {
         guard let linkText = String(bytes: linkData, encoding: .utf8) else {
             owsFailDebug("Could not parse link text.")
-            completion(nil)
+            return Promise(error: LinkPreviewError.invalidInput)
-            return
         }
 
         var title: String?
@@ -610,25 +628,66 @@ public class OWSLinkPreview: MTLModel {
         Logger.verbose("title: \(String(describing: title))")
 
         guard let rawImageUrlString = NSRegularExpression.parseFirstMatch(pattern: "<meta\\s+property\\s*=\\s*\"og:image\"\\s+content\\s*=\\s*\"(.*?)\"\\s*/?>", text: linkText) else {
-            return completion(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
+            return Promise.value(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
         }
         guard let imageUrlString = decodeHTMLEntities(inString: rawImageUrlString)?.ows_stripped() else {
-            return completion(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
+            return Promise.value(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
         }
         guard isValidMediaUrl(imageUrlString) else {
             Logger.error("Invalid image URL.")
-            return completion(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
+            return Promise.value(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
         }
-        Logger.verbose("imageUrlString: \(imageUrlString)")
+        guard let imageFileExtension = fileExtension(forImageUrl: imageUrlString) else {
-        guard let imageUrl = URL(string: imageUrlString) else {
+            Logger.error("Image URL has unknown or invalid file extension: \(imageUrlString).")
+            return Promise.value(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
+        }
+        guard let imageMimeType = mimetype(forImageFileExtension: imageFileExtension) else {
+            Logger.error("Image URL has unknown or invalid content type: \(imageUrlString).")
+            return Promise.value(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
+        }
+
+        return downloadImage(url: imageUrlString, imageMimeType: imageMimeType)
+            .then(on: DispatchQueue.global()) { (imageData: Data) -> Promise<OWSLinkPreviewDraft> in
+                let imageFilePath = OWSFileSystem.temporaryFilePath(withFileExtension: imageFileExtension)
+                do {
+                    try imageData.write(to: NSURL.fileURL(withPath: imageFilePath), options: .atomicWrite)
+                } catch let error as NSError {
+                    owsFailDebug("file write failed: \(imageFilePath), \(error)")
+                    return Promise(error: LinkPreviewError.assertionFailure)
+                }
+                // NOTE: imageSize(forFilePath:...) will call ows_isValidImage(...).
+                let imageSize = NSData.imageSize(forFilePath: imageFilePath, mimeType: imageMimeType)
+                let kMaxImageSize: CGFloat = 2048
+                guard imageSize.width > 0,
+                    imageSize.height > 0,
+                    imageSize.width < kMaxImageSize,
+                    imageSize.height < kMaxImageSize else {
+                        Logger.error("Image has invalid size: \(imageSize).")
+                        return Promise(error: LinkPreviewError.assertionFailure)
+                }
+
+                let linkPreviewDraft = OWSLinkPreviewDraft(urlString: linkUrlString, title: title, imageFilePath: imageFilePath)
+                return Promise.value(linkPreviewDraft)
+        }
+        .recover(on: DispatchQueue.global()) { (_) -> Promise<OWSLinkPreviewDraft> in
+            return Promise.value(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
+        }
+    }
+
+    private class func fileExtension(forImageUrl urlString: String) -> String? {
+        guard let imageUrl = URL(string: urlString) else {
             Logger.error("Could not parse image URL.")
-            return completion(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
+            return nil
         }
         let imageFilename = imageUrl.lastPathComponent
         let imageFileExtension = (imageFilename as NSString).pathExtension.lowercased()
+        return imageFileExtension
+    }
+
+    private class func mimetype(forImageFileExtension imageFileExtension: String) -> String? {
         guard let imageMimeType = MIMETypeUtil.mimeType(forFileExtension: imageFileExtension) else {
             Logger.error("Image URL has unknown content type: \(imageFileExtension).")
-            return completion(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
+            return nil
         }
         let kValidMimeTypes = [
             OWSMimeTypeImagePng,
@@ -636,36 +695,9 @@ public class OWSLinkPreview: MTLModel {
         ]
         guard kValidMimeTypes.contains(imageMimeType) else {
             Logger.error("Image URL has invalid content type: \(imageMimeType).")
-            return completion(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
+            return nil
         }
-
+        return imageMimeType
-        downloadImage(url: imageUrlString,
-                      completion: { (imageData) in
-                        guard let imageData = imageData else {
-                            Logger.error("Could not download image.")
-                            return completion(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
-                        }
-                        let imageFilePath = OWSFileSystem.temporaryFilePath(withFileExtension: imageFileExtension)
-                        do {
-                            try imageData.write(to: NSURL.fileURL(withPath: imageFilePath), options: .atomicWrite)
-                        } catch let error as NSError {
-                            owsFailDebug("file write failed: \(imageFilePath), \(error)")
-                            return completion(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
-                        }
-                        // NOTE: imageSize(forFilePath:...) will call ows_isValidImage(...).
-                        let imageSize = NSData.imageSize(forFilePath: imageFilePath, mimeType: imageMimeType)
-                        let kMaxImageSize: CGFloat = 2048
-                        guard imageSize.width > 0,
-                            imageSize.height > 0,
-                            imageSize.width < kMaxImageSize,
-                            imageSize.height < kMaxImageSize else {
-                                Logger.error("Image has invalid size: \(imageSize).")
-                                return completion(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
-                        }
-
-                        let linkPreviewDraft = OWSLinkPreviewDraft(urlString: linkUrlString, title: title, imageFilePath: imageFilePath)
-                        completion(linkPreviewDraft)
-        })
     }
 
     private class func decodeHTMLEntities(inString value: String) -> String? {

SignalServiceKit/src/Util/OWSMath.h

@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
 NS_ASSUME_NONNULL_BEGIN

SignalShareExtension/SignalShareExtension-Bridging-Header.h

@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
 #import <Foundation/Foundation.h>
@@ -14,7 +14,6 @@
 #import <SignalMessaging/DebugLogger.h>
 #import <SignalMessaging/Environment.h>
 #import <SignalMessaging/OWSContactsManager.h>
-#import <SignalMessaging/OWSMath.h>
 #import <SignalMessaging/OWSPreferences.h>
 #import <SignalMessaging/UIColor+OWS.h>
 #import <SignalMessaging/UIFont+OWS.h>
@@ -23,5 +22,6 @@
 #import <SignalServiceKit/AppContext.h>
 #import <SignalServiceKit/AppReadiness.h>
 #import <SignalServiceKit/AppVersion.h>
+#import <SignalServiceKit/OWSMath.h>
 #import <SignalServiceKit/OWSMessageSender.h>
 #import <SignalServiceKit/TSAccountManager.h>