Elaborate the link preview tests.

SignalServiceKit/src/Messages/Interactions/OWSLinkPreview.swift

@@ -17,6 +17,21 @@ public enum LinkPreviewError: Int, Error {
 
 // MARK: - OWSLinkPreviewDraft
 
+public class OWSLinkPreviewContents: NSObject {
+    @objc
+    public var title: String?
+
+    @objc
+    public var imageUrl: String?
+
+    public init(title: String?, imageUrl: String? = nil) {
+        self.title = title
+        self.imageUrl = imageUrl
+
+        super.init()
+    }
+}
+
 // This contains the info for a link preview "draft".
 public class OWSLinkPreviewDraft: NSObject {
     @objc
@@ -310,10 +325,6 @@ public class OWSLinkPreview: MTLModel {
             owsFailDebug("Invalid url.")
             return nil
         }
-        guard url.path.count > 0 else {
-            owsFailDebug("Invalid url (empty path).")
-            return nil
-        }
         guard let result = whitelistedDomain(forUrl: url,
                                              domainWhitelist: OWSLinkPreview.linkDomainWhitelist) else {
                                                 owsFailDebug("Missing domain.")
@@ -360,13 +371,11 @@ public class OWSLinkPreview: MTLModel {
         guard let domain = url.host?.lowercased() else {
             return nil
         }
-        // TODO: We need to verify:
+        guard url.path.count > 1 else {
-        //
+            // URL must have non-empty path.
-        // * The final domain whitelist.
+            return nil
-        // * The relationship between the "link" whitelist and the "media" whitelist.
+        }
-        // * Exact match or suffix-based?
+
-        // * Case-insensitive?
-        // * Protocol?
         for whitelistedDomain in domainWhitelist {
             if domain == whitelistedDomain.lowercased() ||
                 domain.hasSuffix("." + whitelistedDomain.lowercased()) {
@@ -491,7 +500,7 @@ public class OWSLinkPreview: MTLModel {
         }
         return downloadLink(url: previewUrl)
             .then(on: DispatchQueue.global()) { (data) -> Promise<OWSLinkPreviewDraft> in
-                return parse(linkData: data, linkUrlString: previewUrl)
+                return parseLinkDataAndBuildDraft(linkData: data, linkUrlString: previewUrl)
                     .then(on: DispatchQueue.global()) { (linkPreviewDraft) -> Promise<OWSLinkPreviewDraft> in
                         guard linkPreviewDraft.isValid() else {
                             return Promise(error: LinkPreviewError.noPreview)
@@ -629,49 +638,30 @@ public class OWSLinkPreview: MTLModel {
         return false
     }
 
-    // Example:
+    class func parseLinkDataAndBuildDraft(linkData: Data,
-    //
-    //    <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) -> Promise<OWSLinkPreviewDraft> {
-        guard let linkText = String(bytes: linkData, encoding: .utf8) else {
+        do {
-            owsFailDebug("Could not parse link text.")
+            let contents = try parse(linkData: linkData)
-            return Promise(error: LinkPreviewError.invalidInput)
-        }
-
-        var title: String?
-        if let rawTitle = NSRegularExpression.parseFirstMatch(pattern: "<meta\\s+property\\s*=\\s*\"og:title\"\\s+content\\s*=\\s*\"(.*?)\"\\s*/?>", text: linkText) {
-            if let decodedTitle = decodeHTMLEntities(inString: rawTitle) {
-                let normalizedTitle = OWSLinkPreview.normalizeTitle(title: decodedTitle)
-                if normalizedTitle.count > 0 {
-                    title = normalizedTitle
-                }
-            }
-        }
-
-        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 {
+            let title = contents.title
+            guard let imageUrl = contents.imageUrl else {
                 return Promise.value(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
             }
-        guard let imageUrlString = decodeHTMLEntities(inString: rawImageUrlString)?.ows_stripped() else {
+
-            return Promise.value(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
+            guard isValidMediaUrl(imageUrl) else {
-        }
-        guard isValidMediaUrl(imageUrlString) else {
                 Logger.error("Invalid image URL.")
                 return Promise.value(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
             }
-        guard let imageFileExtension = fileExtension(forImageUrl: imageUrlString) else {
+            guard let imageFileExtension = fileExtension(forImageUrl: imageUrl) else {
-            Logger.error("Image URL has unknown or invalid file extension: \(imageUrlString).")
+                Logger.error("Image URL has unknown or invalid file extension: \(imageUrl).")
                 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).")
+                Logger.error("Image URL has unknown or invalid content type: \(imageUrl).")
                 return Promise.value(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
             }
 
-        return downloadImage(url: imageUrlString, imageMimeType: imageMimeType)
+            return downloadImage(url: imageUrl, imageMimeType: imageMimeType)
                 .then(on: DispatchQueue.global()) { (imageData: Data) -> Promise<OWSLinkPreviewDraft> in
                     let imageFilePath = OWSFileSystem.temporaryFilePath(withFileExtension: imageFileExtension)
                     do {
@@ -697,19 +687,63 @@ public class OWSLinkPreview: MTLModel {
                 .recover(on: DispatchQueue.global()) { (_) -> Promise<OWSLinkPreviewDraft> in
                     return Promise.value(OWSLinkPreviewDraft(urlString: linkUrlString, title: title))
             }
+        } catch {
+            owsFailDebug("Could not parse link data: \(error).")
+            return Promise(error: error)
+        }
+    }
+
+    // Example:
+    //
+    //    <meta property="og:title" content="Randomness is Random - Numberphile">
+    //    <meta property="og:image" content="https://i.ytimg.com/vi/tP-Ipsat90c/maxresdefault.jpg">
+    class func parse(linkData: Data) throws -> OWSLinkPreviewContents {
+        guard let linkText = String(bytes: linkData, encoding: .utf8) else {
+            owsFailDebug("Could not parse link text.")
+            throw LinkPreviewError.invalidInput
         }
 
-    private class func fileExtension(forImageUrl urlString: String) -> String? {
+        Logger.verbose("linkText: \(linkText)")
+
+        var title: String?
+        if let rawTitle = NSRegularExpression.parseFirstMatch(pattern: "<meta\\s+property\\s*=\\s*\"og:title\"\\s+content\\s*=\\s*\"(.*?)\"\\s*/?>", text: linkText) {
+            if let decodedTitle = decodeHTMLEntities(inString: rawTitle) {
+                let normalizedTitle = OWSLinkPreview.normalizeTitle(title: decodedTitle)
+                if normalizedTitle.count > 0 {
+                    title = normalizedTitle
+                }
+            }
+        }
+
+        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 OWSLinkPreviewContents(title: title)
+        }
+        guard let imageUrlString = decodeHTMLEntities(inString: rawImageUrlString)?.ows_stripped() else {
+            return OWSLinkPreviewContents(title: title)
+        }
+
+        return OWSLinkPreviewContents(title: title, imageUrl: imageUrlString)
+    }
+
+    class func fileExtension(forImageUrl urlString: String) -> String? {
         guard let imageUrl = URL(string: urlString) else {
             Logger.error("Could not parse image URL.")
             return nil
         }
         let imageFilename = imageUrl.lastPathComponent
         let imageFileExtension = (imageFilename as NSString).pathExtension.lowercased()
+        guard imageFileExtension.count > 0 else {
+            return nil
+        }
         return imageFileExtension
     }
 
-    private class func mimetype(forImageFileExtension imageFileExtension: String) -> String? {
+    class func mimetype(forImageFileExtension imageFileExtension: String) -> String? {
+        guard imageFileExtension.count > 0 else {
+            return nil
+        }
         guard let imageMimeType = MIMETypeUtil.mimeType(forFileExtension: imageFileExtension) else {
             Logger.error("Image URL has unknown content type: \(imageFileExtension).")
             return nil

SignalServiceKit/tests/Messages/OWSLinkPreviewTest.swift

@@ -3,7 +3,7 @@
 //
 
 import Foundation
-import SignalServiceKit
+@testable import SignalServiceKit
 import XCTest
 
 class OWSLinkPreviewTest: SSKBaseTestSwift {
@@ -92,7 +92,9 @@ class OWSLinkPreviewTest: SSKBaseTestSwift {
     func testIsValidLinkUrl() {
         XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://www.youtube.com/watch?v=tP-Ipsat90c"))
         XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://youtube.com/watch?v=tP-Ipsat90c"))
-        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://www.youtube.com"))
+
+        // Case shouldn't matter.
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://WWW.YOUTUBE.COM/watch?v=tP-Ipsat90c"))
 
         // Allow arbitrary subdomains.
         XCTAssertTrue(OWSLinkPreview.isValidMediaUrl("https://some.random.subdomain.youtube.com/watch?v=tP-Ipsat90c"))
@@ -112,12 +114,30 @@ class OWSLinkPreviewTest: SSKBaseTestSwift {
 
         // Don't allow media domains.
         XCTAssertFalse(OWSLinkPreview.isValidLinkUrl("https://i.ytimg.com/vi/tP-Ipsat90c/maxresdefault.jpg"))
+
+        // Allow all whitelisted domains.
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://www.youtube.com/watch?v=tP-Ipsat90c"))
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://youtu.be/tP-Ipsat90c"))
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://www.reddit.com/r/androiddev/comments/a7gctz/androidx_release_notes_this_is_the_first_release/"))
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://www.reddit.com/r/WhitePeopleTwitter/comments/a7j3mm/why/"))
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://imgur.com/gallery/KFCL8fm"))
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://imgur.com/gallery/FMdwTiV"))
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://www.instagram.com/p/BrgpsUjF9Jo/?utm_source=ig_web_button_share_sheet"))
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://www.instagram.com/p/BrgpsUjF9Jo/?utm_source=ig_share_sheet&igshid=94c7ihqjfmbm"))
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://imgur.com/gallery/igHOwDM"))
+
+        // Strip trailing commas.
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://imgur.com/gallery/igHOwDM,"))
+
+        // Ignore URLs with an empty path.
+        XCTAssertFalse(OWSLinkPreview.isValidLinkUrl("https://imgur.com"))
+        XCTAssertFalse(OWSLinkPreview.isValidLinkUrl("https://imgur.com/"))
+        XCTAssertTrue(OWSLinkPreview.isValidLinkUrl("https://imgur.com/X"))
     }
 
     func testIsValidMediaUrl() {
         XCTAssertTrue(OWSLinkPreview.isValidMediaUrl("https://www.youtube.com/watch?v=tP-Ipsat90c"))
         XCTAssertTrue(OWSLinkPreview.isValidMediaUrl("https://youtube.com/watch?v=tP-Ipsat90c"))
-        XCTAssertTrue(OWSLinkPreview.isValidMediaUrl("https://www.youtube.com"))
 
         // Allow arbitrary subdomains.
         XCTAssertTrue(OWSLinkPreview.isValidMediaUrl("https://some.random.subdomain.youtube.com/watch?v=tP-Ipsat90c"))
@@ -154,4 +174,66 @@ class OWSLinkPreviewTest: SSKBaseTestSwift {
         XCTAssertEqual(OWSLinkPreview.previewUrl(forMessageBodyText: "alice bob https://www.youtube.com/watch?v=tP-Ipsat90c jim https://www.youtube.com/watch?v=other-url carol"),
                        "https://www.youtube.com/watch?v=tP-Ipsat90c")
     }
+
+    func testUtils() {
+        XCTAssertNil(OWSLinkPreview.fileExtension(forImageUrl: ""))
+        XCTAssertNil(OWSLinkPreview.fileExtension(forImageUrl: "https://www.some.host/path/imagename"))
+        XCTAssertNil(OWSLinkPreview.fileExtension(forImageUrl: "https://www.some.host/path/imagename."))
+
+        XCTAssertEqual(OWSLinkPreview.fileExtension(forImageUrl: "https://www.some.host/path/imagename.jpg"), "jpg")
+        XCTAssertEqual(OWSLinkPreview.fileExtension(forImageUrl: "https://www.some.host/path/imagename.gif"), "gif")
+        XCTAssertEqual(OWSLinkPreview.fileExtension(forImageUrl: "https://www.some.host/path/imagename.png"), "png")
+        XCTAssertEqual(OWSLinkPreview.fileExtension(forImageUrl: "https://www.some.host/path/imagename.boink"), "boink")
+
+        XCTAssertNil(OWSLinkPreview.mimetype(forImageFileExtension: ""))
+        XCTAssertNil(OWSLinkPreview.mimetype(forImageFileExtension: "boink"))
+        XCTAssertNil(OWSLinkPreview.mimetype(forImageFileExtension: "tiff"))
+        XCTAssertNil(OWSLinkPreview.mimetype(forImageFileExtension: "gif"))
+
+        XCTAssertEqual(OWSLinkPreview.mimetype(forImageFileExtension: "jpg"), OWSMimeTypeImageJpeg)
+        XCTAssertEqual(OWSLinkPreview.mimetype(forImageFileExtension: "png"), OWSMimeTypeImagePng)
+    }
+
+    func testLinkDownloadAndParsing() {
+        let expectation = self.expectation(description: "link download and parsing")
+
+        OWSLinkPreview.tryToBuildPreviewInfo(previewUrl: "https://www.youtube.com/watch?v=tP-Ipsat90c")
+            .done { (draft) in
+                XCTAssertNotNil(draft)
+
+                XCTAssertEqual(draft.title, "Randomness is Random - Numberphile")
+                XCTAssertNotNil(draft.imageFilePath)
+
+                expectation.fulfill()
+            }.catch { (error) in
+                Logger.error("error: \(error)")
+                XCTFail("Unexpected error: \(error)")
+                expectation.fulfill()
+            }.retainUntilComplete()
+
+        self.waitForExpectations(timeout: 5.0, handler: nil)
+    }
+
+    func testLinkDataParsing_Empty() {
+        let linkText = ""
+        let linkData = linkText.data(using: .utf8)!
+
+        let content = try! OWSLinkPreview.parse(linkData: linkData)
+        XCTAssertNotNil(content)
+
+        XCTAssertNil(content.title)
+        XCTAssertNil(content.imageUrl)
+    }
+
+    func testLinkDataParsing() {
+        let linkText = ("<meta property=\"og:title\" content=\"Randomness is Random - Numberphile\">" +
+                        "<meta property=\"og:image\" content=\"https://i.ytimg.com/vi/tP-Ipsat90c/maxresdefault.jpg\">")
+        let linkData = linkText.data(using: .utf8)!
+
+        let content = try! OWSLinkPreview.parse(linkData: linkData)
+        XCTAssertNotNil(content)
+
+        XCTAssertEqual(content.title, "Randomness is Random - Numberphile")
+        XCTAssertEqual(content.imageUrl, "https://i.ytimg.com/vi/tP-Ipsat90c/maxresdefault.jpg")
+    }
 }