Fix double posting in poor network conditions

Closes #421

Packages/ComposeUI/Sources/ComposeUI/API/PostService.swift

@@ -77,7 +77,8 @@ class PostService: ObservableObject {
                 pollOptions: draft.poll?.pollOptions.map(\.text),
                 pollExpiresIn: draft.poll == nil ? nil : Int(draft.poll!.duration),
                 pollMultiple: draft.poll?.multiple,
-                localOnly: mastodonController.instanceFeatures.localOnlyPosts ? draft.localOnly : nil
+                localOnly: mastodonController.instanceFeatures.localOnlyPosts ? draft.localOnly : nil,
+                idempotencyKey: draft.id.uuidString
             )
         }
         

Packages/Pachyderm/Sources/Pachyderm/Client.swift

@@ -113,6 +113,9 @@ public class Client {
         var urlRequest = URLRequest(url: url, timeoutInterval: timeoutInterval)
         urlRequest.httpMethod = request.method.name
         urlRequest.httpBody = request.body.data
+        for (name, value) in request.headers {
+            urlRequest.setValue(value, forHTTPHeaderField: name)
+        }
         if let mimeType = request.body.mimeType {
             urlRequest.setValue(mimeType, forHTTPHeaderField: "Content-Type")
         }
@@ -397,19 +400,22 @@ public class Client {
                                     pollOptions: [String]? = nil,
                                     pollExpiresIn: Int? = nil,
                                     pollMultiple: Bool? = nil,
-                                    localOnly: Bool? = nil /* hometown only, not glitch */) -> Request<Status> {
-        return Request<Status>(method: .post, path: "/api/v1/statuses", body: ParametersBody([
-                "status" => text,
-                "content_type" => contentType.mimeType,
-                "in_reply_to_id" => inReplyTo,
-                "sensitive" => sensitive,
-                "spoiler_text" => spoilerText,
-                "visibility" => visibility?.rawValue,
-                "language" => language,
-                "poll[expires_in]" => pollExpiresIn,
-                "poll[multiple]" => pollMultiple,
-                "local_only" => localOnly,
-            ] + "media_ids" => mediaIDs + "poll[options]" => pollOptions))
+                                    localOnly: Bool? = nil, /* hometown only, not glitch */
+                                    idempotencyKey: String) -> Request<Status> {
+        var req = Request<Status>(method: .post, path: "/api/v1/statuses", body: ParametersBody([
+            "status" => text,
+            "content_type" => contentType.mimeType,
+            "in_reply_to_id" => inReplyTo,
+            "sensitive" => sensitive,
+            "spoiler_text" => spoilerText,
+            "visibility" => visibility?.rawValue,
+            "language" => language,
+            "poll[expires_in]" => pollExpiresIn,
+            "poll[multiple]" => pollMultiple,
+            "local_only" => localOnly,
+        ] + "media_ids" => mediaIDs + "poll[options]" => pollOptions))
+        req.headers["Idempotency-Key"] = idempotencyKey
+        return req
     }
     
     public static func editStatus(

Packages/Pachyderm/Sources/Pachyderm/Request/Request.swift

@@ -13,6 +13,7 @@ public struct Request<ResultType: Decodable>: Sendable {
     let endpoint: Endpoint
     let body: Body
     var queryParameters: [Parameter]
+    var headers: [String: String] = [:]
     var additionalAcceptableHTTPCodes: [Int] = []
     
     init(method: Method, path: Endpoint, body: Body = EmptyBody(), queryParameters: [Parameter] = []) {