Test with simple swift promises

See https://shadowfacts.net/2020/simple-swift-promises/

Pachyderm/Client.swift

@@ -7,6 +7,7 @@
 //
 
 import Foundation
+import Combine
 
 /**
  The base Mastodon API client.
@@ -80,6 +81,43 @@ public class Client {
         task.resume()
     }
     
+    public func run<Result>(_ request: Request<Result>) -> Promise<(Result, Pagination?)> {
+        return Promise { (resolve, reject) in
+            self.run(request) { (response) in
+                switch response {
+                case let .success(result, pagination):
+                    resolve((result, pagination))
+                case let .failure(error):
+                    reject(error)
+                }
+            }
+        }
+    }
+    
+    public func run<Result: Decodable>(_ request: Request<Result>) -> AnyPublisher<(Result, Pagination?), Swift.Error> {
+        guard let request = createURLRequest(request: request) else {
+            return Fail(error: Error.invalidRequest).eraseToAnyPublisher()
+        }
+        return session.dataTaskPublisher(for: request)
+            .mapError { Error.urlError($0) }
+            .tryMap {
+                guard let response = $0.response as? HTTPURLResponse else {
+                    throw Error.invalidResponse
+                }
+                guard response.statusCode == 200 else {
+                    if let mastodonError = try? self.decoder.decode(MastodonError.self, from: $0.data) {
+                        throw Error.mastodonError(mastodonError.description)
+                    } else {
+                        throw Error.unknownError
+                    }
+                }
+                let result = try self.decoder.decode(Result.self, from: $0.data)
+                let pagination = response.allHeaderFields["Link"].flatMap { $0 as? String }.flatMap(Pagination.init)
+                return (result, pagination)
+            }
+            .eraseToAnyPublisher()
+    }
+    
     func createURLRequest<Result>(request: Request<Result>) -> URLRequest? {
         guard var components = URLComponents(url: baseURL, resolvingAgainstBaseURL: true) else { return nil }
         components.path = request.path
@@ -325,6 +363,6 @@ extension Client {
         case invalidResponse
         case invalidModel
         case mastodonError(String)
-        
+        case urlError(URLError)
     }
 }

Pachyderm/Promise.swift

@@ -0,0 +1,170 @@
+//
+//  Promise.swift
+//  Pachyderm
+//
+//  Created by Shadowfacts on 2/14/20.
+//  Copyright © 2020 Shadowfacts. All rights reserved.
+//
+
+import Foundation
+
+public class Promise<Result> {
+    private var handlers: [(Result) -> Void] = []
+    private var result: Result?
+    private var catchers: [(Error) -> Void] = []
+    private var error: Error?
+
+    func resolve(_ result: Result) {
+        self.result = result
+        self.handlers.forEach { $0(result) }
+    }
+    
+    func reject(_ error: Error) {
+        self.error = error
+        self.catchers.forEach { $0(error) }
+    }
+    
+    func addHandler(_ handler: @escaping (Result) -> Void) {
+        if let result = result {
+            handler(result)
+        } else {
+            handlers.append(handler)
+        }
+    }
+    
+    func addCatcher(_ catcher: @escaping (Error) -> Void) {
+        if let error = error {
+            catcher(error)
+        } else {
+            catchers.append(catcher)
+        }
+    }
+}
+
+public extension Promise {
+    static func resolve<Result>(_ value: Result) -> Promise<Result> {
+        let promise = Promise<Result>()
+        promise.resolve(value)
+        return promise
+    }
+    
+    static func reject<Result>(_ error: Error) -> Promise<Result> {
+        let promise = Promise<Result>()
+        promise.reject(error)
+        return promise
+    }
+    
+    static func all<Result>(_ promises: [Promise<Result>], queue: DispatchQueue = .main) -> Promise<[Result]> {
+        let group = DispatchGroup()
+        
+        var results = [Result?](repeating: nil, count: promises.count)
+        var firstError: Error?
+
+        for (index, promise) in promises.enumerated() {
+            group.enter()
+            promise.then { (res) in
+                queue.async {
+                    results[index] = res
+                    group.leave()
+                }
+            }.catch { (err) -> Void in
+                if firstError == nil {
+                    firstError = err
+                }
+                group.leave()
+            }
+        }
+        
+        return Promise<[Result]> { (resolve, reject) in
+            group.notify(queue: queue) {
+                if let firstError = firstError {
+                    reject(firstError)
+                } else {
+                    resolve(results.compactMap { $0 })
+                }
+            }
+        }
+    }
+    
+    convenience init(resultProvider: @escaping (_ resolve: @escaping (Result) -> Void, _ reject: @escaping (Error) -> Void) -> Void) {
+        self.init()
+        resultProvider(self.resolve, self.reject)
+    }
+    
+    convenience init<ErrorType>(_ resultProvider: @escaping ((Swift.Result<Result, ErrorType>) -> Void) -> Void) {
+        self.init { (resolve, reject) in
+            resultProvider { (result) in
+                switch result {
+                case let .success(res):
+                    resolve(res)
+                case let .failure(error):
+                    reject(error)
+                }
+            }
+        }
+    }
+
+    @discardableResult
+    func then(_ func: @escaping (Result) -> Void) -> Promise<Result> {
+        addHandler(`func`)
+        return self
+    }
+    
+    func then<Next>(_ mapper: @escaping (Result) -> Promise<Next>) -> Promise<Next> {
+        let next = Promise<Next>()
+        addHandler { (parentResult) in
+            let newPromise = mapper(parentResult)
+            newPromise.addHandler(next.resolve)
+            newPromise.addCatcher(next.reject)
+        }
+        addCatcher(next.reject)
+        return next
+    }
+    
+    func then<Next>(_ mapper: @escaping (Result) -> Next) -> Promise<Next> {
+        let next = Promise<Next>()
+        addHandler { (parentResult) in
+            let newResult = mapper(parentResult)
+            next.resolve(newResult)
+        }
+        addCatcher(next.reject)
+        return next
+    }
+    
+    @discardableResult
+    func `catch`(_ catcher: @escaping (Error) -> Void) -> Promise<Result> {
+        addCatcher(catcher)
+        return self
+    }
+    
+    func `catch`(_ catcher: @escaping (Error) -> Promise<Result>) -> Promise<Result> {
+        let next = Promise<Result>()
+        addHandler(next.resolve)
+        addCatcher { (error) in
+            let newPromise = catcher(error)
+            newPromise.addHandler(next.resolve)
+            newPromise.addCatcher(next.reject)
+        }
+        return next
+    }
+
+    func `catch`(_ catcher: @escaping (Error) -> Result) -> Promise<Result> {
+        let next = Promise<Result>()
+        addHandler(next.resolve)
+        addCatcher { (error) in
+            let newResult = catcher(error)
+            next.resolve(newResult)
+        }
+        return next
+    }
+    
+    func handle(on queue: DispatchQueue) -> Promise<Result> {
+        return self.then { (result) in
+            return Promise { (resolve, reject) in
+                queue.async {
+                    resolve(result)
+                }
+            }
+        }
+    }
+}

PachydermTests/PromiseTests.swift

@@ -0,0 +1,126 @@
+//
+//  PromiseTests.swift
+//  PachydermTests
+//
+//  Created by Shadowfacts on 2/14/20.
+//  Copyright © 2020 Shadowfacts. All rights reserved.
+//
+
+import XCTest
+@testable import Pachyderm
+
+class PromiseTests: XCTestCase {
+
+    override func setUpWithError() throws {
+        // Put setup code here. This method is called before the invocation of each test method in the class.
+    }
+
+    override func tearDownWithError() throws {
+        // Put teardown code here. This method is called after the invocation of each test method in the class.
+    }
+    
+    func assertResultEqual<Result: Equatable>(_ promise: Promise<Result>, _ value: Result, message: String? = nil) {
+        let expectation = self.expectation(description: message ?? "promise result assertion")
+        promise.then {
+            XCTAssertEqual($0, value)
+            expectation.fulfill()
+        }
+        self.waitForExpectations(timeout: 2) { (error) in
+            if let error = error {
+                XCTFail("didn't resolve promise: \(error)")
+            }
+        }
+    }
+
+    func testResolveImmediate() {
+        assertResultEqual(Promise<String>.resolve("blah"), "blah")
+    }
+    
+    func testResolveImmediateMapped() {
+        let promise = Promise<String>.resolve("foo").then {
+            "test \($0)"
+        }.then {
+            Promise<String>.resolve("\($0) bar")
+        }
+        assertResultEqual(promise, "test foo bar")
+    }
+    
+    func testContinueAfterReject() {
+        let promise = Promise<String>.reject(TestError()).then { (res) in
+            XCTFail("then on rejected promise is unreachable")
+        }.catch { (error) -> String in
+            XCTAssertTrue(error is TestError)
+            return "caught"
+        }.then {
+            "\($0) error"
+        }
+        assertResultEqual(promise, "caught error")
+    }
+    
+    func testResolveDelayed() {
+        let promise = Promise<String> { (resolve, reject) in
+            DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
+                resolve("blah")
+            }
+        }
+        assertResultEqual(promise, "blah")
+    }
+    
+    func testResolveMappedDelayed() {
+        let promise = Promise<String> { (resolve, reject) in
+            DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
+                resolve("foo")
+            }
+        }.then {
+            "\($0) bar"
+        }.then { (result) in
+            Promise<String> { (resolve, reject) in
+                DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
+                    resolve("\(result) baz")
+                }
+            }
+        }
+        assertResultEqual(promise, "foo bar baz")
+    }
+    
+    func testResolveAll() {
+        let promise = Promise<[String]>.all([
+            Promise<String>.resolve("a"),
+            Promise<String>.resolve("b"),
+            Promise<String>.resolve("c"),
+        ])
+        assertResultEqual(promise, ["a", "b", "c"])
+    }
+    
+    func testIntermediateReject() {
+        let promise = Promise<String>.resolve("foo").then { (_) -> Promise<String> in
+            Promise<String>.reject(TestError())
+        }.catch { (error) -> String in
+            XCTAssertTrue(error is TestError)
+            return "caught"
+        }.then { (result) -> String in
+            "\(result) error"
+        }
+        assertResultEqual(promise, "caught error")
+    }
+    
+    func testResultHelper() {
+        let success = Promise<String> { (handler) in
+            handler(Result<String, Never>.success("asdf"))
+        }
+        assertResultEqual(success, "asdf")
+        let failure = Promise<String> { (handler) in
+            handler(Result<String, TestError>.failure(TestError()))
+        }.catch { (error) -> String in
+            "blah"
+        }
+        assertResultEqual(failure, "blah")
+    }
+
+}
+
+struct TestError: Error {
+    var localizedDescription: String {
+        "test error"
+    }
+}

Tusker.xcodeproj/project.pbxproj

@@ -156,6 +156,8 @@
 		D67C57AF21E28EAD00C3118B /* Array+Uniques.swift in Sources */ = {isa = PBXBuildFile; fileRef = D67C57AE21E28EAD00C3118B /* Array+Uniques.swift */; };
 		D67C57B221E28FAD00C3118B /* ComposeStatusReplyView.xib in Resources */ = {isa = PBXBuildFile; fileRef = D67C57B121E28FAD00C3118B /* ComposeStatusReplyView.xib */; };
 		D67C57B421E2910700C3118B /* ComposeStatusReplyView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D67C57B321E2910700C3118B /* ComposeStatusReplyView.swift */; };
+		D683418623F79BFC00D06703 /* Promise.swift in Sources */ = {isa = PBXBuildFile; fileRef = D683418523F79BFC00D06703 /* Promise.swift */; };
+		D683418A23F7A3BB00D06703 /* PromiseTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D683418923F7A3BB00D06703 /* PromiseTests.swift */; };
 		D68FEC4F232C5BC300C84F23 /* SegmentedPageViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D68FEC4E232C5BC300C84F23 /* SegmentedPageViewController.swift */; };
 		D6945C2F23AC47C3005C403C /* SavedDataManager.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6945C2E23AC47C3005C403C /* SavedDataManager.swift */; };
 		D6945C3223AC4D36005C403C /* HashtagTimelineViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = D6945C3123AC4D36005C403C /* HashtagTimelineViewController.swift */; };
@@ -431,6 +433,8 @@
 		D67C57AE21E28EAD00C3118B /* Array+Uniques.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Array+Uniques.swift"; sourceTree = "<group>"; };
 		D67C57B121E28FAD00C3118B /* ComposeStatusReplyView.xib */ = {isa = PBXFileReference; lastKnownFileType = file.xib; path = ComposeStatusReplyView.xib; sourceTree = "<group>"; };
 		D67C57B321E2910700C3118B /* ComposeStatusReplyView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ComposeStatusReplyView.swift; sourceTree = "<group>"; };
+		D683418523F79BFC00D06703 /* Promise.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Promise.swift; sourceTree = "<group>"; };
+		D683418923F7A3BB00D06703 /* PromiseTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PromiseTests.swift; sourceTree = "<group>"; };
 		D68FEC4E232C5BC300C84F23 /* SegmentedPageViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SegmentedPageViewController.swift; sourceTree = "<group>"; };
 		D6945C2E23AC47C3005C403C /* SavedDataManager.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SavedDataManager.swift; sourceTree = "<group>"; };
 		D6945C3123AC4D36005C403C /* HashtagTimelineViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = HashtagTimelineViewController.swift; sourceTree = "<group>"; };
@@ -594,6 +598,7 @@
 				D61099AD2144B0CC00432DC2 /* Pachyderm.h */,
 				D61099AE2144B0CC00432DC2 /* Info.plist */,
 				D61099C82144B13C00432DC2 /* Client.swift */,
+				D683418523F79BFC00D06703 /* Promise.swift */,
 				D6109A0A2145953C00432DC2 /* ClientModel.swift */,
 				D6A3BC7223218C6E00FD64D5 /* Utilities */,
 				D61099D72144B74500432DC2 /* Extensions */,
@@ -609,6 +614,7 @@
 			children = (
 				D61099BA2144B0CC00432DC2 /* PachydermTests.swift */,
 				D6E6F26421604242006A8599 /* CharacterCounterTests.swift */,
+				D683418923F7A3BB00D06703 /* PromiseTests.swift */,
 				D61099BC2144B0CC00432DC2 /* Info.plist */,
 			);
 			path = PachydermTests;
@@ -1537,6 +1543,7 @@
 				D61099E92145658300432DC2 /* Card.swift in Sources */,
 				D61099F32145688600432DC2 /* Mention.swift in Sources */,
 				D6109A0F21459B6900432DC2 /* Pagination.swift in Sources */,
+				D683418623F79BFC00D06703 /* Promise.swift in Sources */,
 				D6109A032145722C00432DC2 /* RegisteredApplication.swift in Sources */,
 				D6109A0921458C4A00432DC2 /* Empty.swift in Sources */,
 				D6285B4F21EA695800FE4B39 /* StatusContentType.swift in Sources */,
@@ -1562,6 +1569,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				D683418A23F7A3BB00D06703 /* PromiseTests.swift in Sources */,
 				D6E6F26521604242006A8599 /* CharacterCounterTests.swift in Sources */,
 				D61099BB2144B0CC00432DC2 /* PachydermTests.swift in Sources */,
 			);

Tusker/Activities/Account Activities/FollowAccountActivity.swift

@@ -28,14 +28,11 @@ class FollowAccountActivity: AccountActivity {
         UIImpactFeedbackGenerator(style: .medium).impactOccurred()
         
         let request = Account.follow(account.id)
-        mastodonController.run(request) { (response) in
-            if case let .success(relationship, _) = response {
+        mastodonController.run(request).then { (relationship, _) -> Void in
             self.mastodonController.cache.add(relationship: relationship)
-            } else {
-                // todo: display error message
+        }.catch { (error) -> Void in
+            print("could not follow account")
             UINotificationFeedbackGenerator().notificationOccurred(.error)
-                fatalError()
-            }
         }
     }
     

Tusker/Activities/Account Activities/UnfollowAccountActivity.swift

@@ -28,14 +28,11 @@ class UnfollowAccountActivity: AccountActivity {
         UIImpactFeedbackGenerator(style: .medium).impactOccurred()
         
         let request = Account.unfollow(account.id)
-        mastodonController.run(request) { (response) in
-            if case let .success(relationship, _) = response {
+        mastodonController.run(request).then { (relationship, _) -> Void in
             self.mastodonController.cache.add(relationship: relationship)
-            } else {
-                // todo: display error message
+        }.catch { (error) -> Void in
+            print("could not unfollow account: \(error)")
             UINotificationFeedbackGenerator().notificationOccurred(.error)
-                fatalError()
-            }
         }
     }
     

Tusker/Activities/Status Activities/BookmarkStatusActivity.swift

@@ -27,14 +27,11 @@ class BookmarkStatusActivity: StatusActivity {
         guard let status = status else { return }
         
         let request = Status.bookmark(status)
-        mastodonController.run(request) { (response) in
-            if case let .success(status, _) = response {
+        mastodonController.run(request).then { (status, _) -> Void in
             self.mastodonController.cache.add(status: status)
-            } else {
-                // todo: display error message
+        }.catch { (error) -> Void in
+            print("could not bookmark status: \(error)")
             UINotificationFeedbackGenerator().notificationOccurred(.error)
-                fatalError()
-            }
         }
     }
 

Tusker/Activities/Status Activities/PinStatusActivity.swift

@@ -26,14 +26,11 @@ class PinStatusActivity: StatusActivity {
         guard let status = status else { return }
         
         let request = Status.pin(status)
-        mastodonController.run(request) { (response) in
-            if case let .success(status, _) = response {
+        mastodonController.run(request).then { (status, _) -> Void in
             self.mastodonController.cache.add(status: status)
-            } else {
-                // todo: display error message
+        }.catch { (error) -> Void in
+            print("could not pin status: \(error)")
             UINotificationFeedbackGenerator().notificationOccurred(.error)
-                fatalError()
-            }
         }
     }
 }

Tusker/Activities/Status Activities/UnbookmarkStatusActivity.swift

@@ -27,14 +27,11 @@ class UnbookmarkStatusActivity: StatusActivity {
         guard let status = status else { return }
         
         let request = Status.unbookmark(status)
-        mastodonController.run(request) { (response) in
-            if case let .success(status, _) = response {
+        mastodonController.run(request).then { (status, _) -> Void in
             self.mastodonController.cache.add(status: status)
-            } else {
-                // todo: display error message
+        }.catch { (error) -> Void in
+            print("could not unbookmark status: \(error)")
             UINotificationFeedbackGenerator().notificationOccurred(.error)
-                fatalError()
-            }
         }
     }
     

Tusker/Activities/Status Activities/UnpinStatusActivity.swift

@@ -26,14 +26,11 @@ class UnpinStatusActivity: StatusActivity {
         guard let status = status else { return }
         
         let request = Status.unpin(status)
-        mastodonController.run(request) { (response) in
-            if case let .success(status, _) = response {
+        mastodonController.run(request).then { (status, _) -> Void in
             self.mastodonController.cache.add(status: status)
-            } else {
-                // todo: display error message
+        }.catch { (error) -> Void in
+            print("could not unpin status: \(error)")
             UINotificationFeedbackGenerator().notificationOccurred(.error)
-                fatalError()
-            }
         }
     }
 }

Tusker/Caching/ImageCache.swift

@@ -8,6 +8,7 @@
 
 import UIKit
 import Cache
+import Pachyderm
 
 class ImageCache {
     
@@ -56,6 +57,18 @@ class ImageCache {
         }
     }
     
+    func get(_ url: URL) -> Promise<Data> {
+        return Promise<Data> { (resolve, reject) in
+            _ = self.get(url) { (data) in
+                if let data = data {
+                    resolve(data)
+                } else {
+                    reject(Error.unknown)
+                }
+            }
+        }
+    }
+    
     func get(_ url: URL) -> Data? {
         return try? cache.object(forKey: url.absoluteString)
     }
@@ -142,4 +155,8 @@ class ImageCache {
         }
     }
     
+    enum Error: Swift.Error {
+        case unknown
+    }
+    
 }

Tusker/Controllers/MastodonController.swift

@@ -8,6 +8,7 @@
 
 import Foundation
 import Pachyderm
+import Combine
 
 class MastodonController {
 
@@ -50,6 +51,14 @@ class MastodonController {
         client.run(request, completion: completion)
     }
     
+    func run<Result: Decodable>(_ request: Request<Result>) -> Promise<(Result, Pagination?)> {
+        return client.run(request)
+    }
+    
+    func run<Result: Decodable>(_ request: Request<Result>) -> AnyPublisher<(Result, Pagination?), Error> {
+        return client.run(request)
+    }
+    
     func registerApp(completion: @escaping (_ clientID: String, _ clientSecret: String) -> Void) {
         guard client.clientID == nil,
             client.clientSecret == nil else {
@@ -79,20 +88,22 @@ class MastodonController {
             completion?(account)
         } else {
             let request = Client.getSelfAccount()
-            run(request) { response in
-                guard case let .success(account, _) = response else { fatalError() }
+            run(request).then { (account, _) -> Void in
                 self.account = account
                 self.cache.add(account: account)
                 completion?(account)
+            }.catch { (error) -> Void in
+                fatalError("couldn't get own account: \(error)")
             }
         }
     }
     
     func getOwnInstance() {
         let request = Client.getInstance()
-        run(request) { (response) in
-            guard case let .success(instance, _) = response else { fatalError() }
+        run(request).then { (instance, _) -> Void in
             self.instance = instance
+        }.catch { (error) -> Void in
+            fatalError("couldn't get own instance: \(error)")
         }
     }
     

Tusker/MastodonCache.swift

@@ -57,6 +57,16 @@ class MastodonCache {
         }
     }
     
+    func status(for id: String) -> Promise<Status> {
+        guard let mastodonController = mastodonController else {
+            fatalError("The MastodonController for this cache has been deinitialized, so this cache should no longer exist. Are you storing a strong reference to it?")
+        }
+        let request = Client.getStatus(id: id)
+        return mastodonController.run(request).then { (status, _) in
+            status
+        }.then(self.add(status:))
+    }
+    
     func add(status: Status) {
         set(status: status, for: status.id)
     }
@@ -90,6 +100,16 @@ class MastodonCache {
         }
     }
     
+    func account(for id: String) -> Promise<Account> {
+        guard let mastodonController = mastodonController else {
+            fatalError("The MastodonController for this cache has been deinitialized, so this cache should no longer exist. Are you storing a strong reference to it?")
+        }
+        let request = Client.getAccount(id: id)
+        return mastodonController.run(request).then { (account, _) in
+            account
+        }.then(self.add(account:))
+    }
+    
     func add(account: Account) {
         set(account: account, for: account.id)
     }
@@ -123,6 +143,16 @@ class MastodonCache {
         }
     }
     
+    func relationship(for id: String) -> Promise<Relationship> {
+        guard let mastodonController = mastodonController else {
+            fatalError("The MastodonController for this cache has been deinitialized, so this cache should no longer exist. Are you storing a strong reference to it?")
+        }
+        let request = Client.getRelationships(accounts: [id])
+        return mastodonController.run(request).then { (relationships, _) in
+            relationships.first!
+        }.then(self.add(relationship:))
+    }
+    
     func add(relationship: Relationship) {
         set(relationship: relationship, id: relationship.id)
     }

Tusker/Screens/Compose/ComposeViewController.swift

@@ -491,40 +491,23 @@ class ComposeViewController: UIViewController {
         let sensitive = contentWarning != nil
         let visibility = self.visibility!
 
-        let group = DispatchGroup()
-        
-        var attachments: [Attachment?] = []
-        for compAttachment in selectedAttachments {
-            let index = attachments.count
-            attachments.append(nil)
-            
-            let mediaView = attachmentsStackView.arrangedSubviews[index] as! ComposeMediaView
-            let description = mediaView.descriptionTextView.text
-            
-            group.enter()
-            
-            compAttachment.getData { (data, mimeType) in
-                self.postProgressView.step()
-                
-                let request = Client.upload(attachment: FormAttachment(mimeType: mimeType, data: data, fileName: "file"), description: description)
-                self.mastodonController.run(request) { (response) in
-                    guard case let .success(attachment, _) = response else { fatalError() }
-
-                    attachments[index] = attachment
-
-                    self.postProgressView.step()
-
-                    group.leave()
-                }
-            }
-        }
-        
-        postProgressView.steps = 2 + (attachments.count * 2) // 2 steps (request data, then upload) for each attachment
+        postProgressView.steps = 2 + (selectedAttachments.count * 2) // 2 steps (request data, then upload) for each attachment
         postProgressView.currentStep = 1
         
-        group.notify(queue: .main) {
-            let attachments = attachments.compactMap { $0 }
+        let attachmentPromises = selectedAttachments.map { (attachment) -> Promise<Attachment> in
+            let view = attachmentsStackView.arrangedSubviews.first { ($0 as! ComposeMediaView).attachment == attachment } as! ComposeMediaView
+            let description = view.description
 
+            return attachment.getData().then { (data, mimeType) -> Promise<(Attachment, Pagination?)> in
+                let request = Client.upload(attachment: FormAttachment(mimeType: mimeType, data: data, fileName: "file"), description: description)
+                return self.mastodonController.run(request)
+            }.then { (attachment, _) -> Attachment in
+                self.postProgressView.step()
+                return attachment
+            }
+        }
+        
+        Promise<[Attachment]>.all(attachmentPromises).then { (attachments) -> Promise<(Status, Pagination?)> in
             let request = Client.createStatus(text: text,
                                               contentType: Preferences.shared.statusContentType,
                                               inReplyTo: self.inReplyToID,
@@ -533,8 +516,8 @@ class ComposeViewController: UIViewController {
                                               spoilerText: contentWarning,
                                               visibility: visibility,
                                               language: nil)
-            self.mastodonController.run(request) { (response) in
-                guard case let .success(status, _) = response else { fatalError() }
+            return self.mastodonController.run(request)
+        }.then { (status, _) -> Status in
             self.postedStatus = status
             self.mastodonController.cache.add(status: status)
 
@@ -542,19 +525,17 @@ class ComposeViewController: UIViewController {
                 DraftsManager.shared.remove(draft)
             }
 
-                DispatchQueue.main.async {
+            return status
+        }.handle(on: DispatchQueue.main).then { (status) in
             self.postProgressView.step()
             self.dismiss(animated: true)
 
-                    let conversationVC = ConversationTableViewController(for: status.id, mastodonController: self.mastodonController)
-                    self.show(conversationVC, sender: self)
-                    
             self.xcbSession?.complete(with: .success, additionalData: [
                 "statusURL": status.url?.absoluteString,
                 "statusURI": status.uri
             ])
-                }
-            }
+        }.catch { (error) -> Void in
+            fatalError("couldn't create post: \(error)")
         }
     }
     

Tusker/Screens/Compose/CompositionAttachment.swift

@@ -9,6 +9,7 @@
 import UIKit
 import Photos
 import MobileCoreServices
+import Pachyderm
 
 enum CompositionAttachment {
     case asset(PHAsset)
@@ -93,6 +94,14 @@ enum CompositionAttachment {
         }
     }
     
+    func getData() -> Promise<(Data, String)> {
+        return Promise { (resolve, reject) in
+            self.getData { (data, mimeType) in
+                resolve((data, mimeType))
+            }
+        }
+    }
+    
     private static func exportVideoData(session: AVAssetExportSession, completion: @escaping (Data, String) -> Void) {
         session.outputFileType = .mp4
         session.outputURL = FileManager.default.temporaryDirectory.appendingPathComponent("exported_video_\(UUID())").appendingPathExtension("mp4")

Tusker/Screens/Notifications/NotificationsTableViewController.swift

@@ -187,16 +187,11 @@ class NotificationsTableViewController: EnhancedTableViewController {
     }
     
     func dismissNotificationsInGroup(at indexPath: IndexPath, completion: (() -> Void)? = nil) {
-        let group = DispatchGroup()
-        groups[indexPath.row].notificationIDs
-            .map(Pachyderm.Notification.dismiss(id:))
-            .forEach { (request) in
-                group.enter()
-                mastodonController.run(request) { (response) in
-                    group.leave()
+        let dismissPromises = groups[indexPath.row].notificationIDs.map { (id) -> Promise<(Empty, Pagination?)> in
+            let req = Pachyderm.Notification.dismiss(id: id)
+            return self.mastodonController.run(req)
         }
-        }
-        group.notify(queue: .main) {
+        Promise<[(Empty, Pagination?)]>.all(dismissPromises).handle(on: .main).then { (_) in
             self.groups.remove(at: indexPath.row)
             self.tableView.deleteRows(at: [indexPath], with: .automatic)
             completion?()

Tusker/Views/ContentTextView.swift

@@ -43,33 +43,27 @@ class ContentTextView: LinkTextView {
     func setEmojis(_ emojis: [Emoji]) {
         guard !emojis.isEmpty else { return }
         
-        let emojiImages = CachedDictionary<UIImage>(name: "ContentTextView Emoji Images")
-        
-        let group = DispatchGroup()
-        
-        for emoji in emojis {
-            group.enter()
-            _ = ImageCache.emojis.get(emoji.url) { (data) in
-                defer { group.leave() }
-                guard let data = data, let image = UIImage(data: data) else {
-                    return
-                }
-                emojiImages[emoji.shortcode] = image
+        let emojiPromises = emojis.map { (emoji) -> Promise<(String, UIImage)> in
+            ImageCache.emojis.get(emoji.url).then { (data) -> Promise<(String, UIImage)> in
+                if let image = UIImage(data: data) {
+                    return Promise<(String, UIImage)>.resolve((emoji.shortcode, image))
+                } else {
+                    return Promise<(String, UIImage)>.reject(ImageCache.Error.unknown)
                 }
             }
-        
-        group.notify(queue: .main) {
+        }
+        Promise<[(String, UIImage)]>.all(emojiPromises).then { (emojis) in
             let mutAttrString = NSMutableAttributedString(attributedString: self.attributedText!)
             let string = mutAttrString.string
             let matches = emojiRegex.matches(in: string, options: [], range: mutAttrString.fullRange)
-            // replaces the emojis started from the end of the string as to not alter the indexes of the other emojis
+            // replaces emojis starting from the end of the string as to not alter the indices of earlier emojis
             for match in matches.reversed() {
                 let shortcode = (string as NSString).substring(with: match.range(at: 1))
-                guard let emojiImage = emojiImages[shortcode] else {
+                guard let emojiImage = emojis.first(where: { $0.0 == shortcode }) else {
                     continue
                 }
                 
-                let attachment = self.createEmojiTextAttachment(image: emojiImage, index: match.range.location)
+                let attachment = self.createEmojiTextAttachment(image: emojiImage.1, index: match.range.location)
                 let attachmentStr = NSAttributedString(attachment: attachment)
                 mutAttrString.replaceCharacters(in: match.range, with: attachmentStr)
             }