From 03a4d1299d5dc34b2ec938e41378307e6cf7f3c0 Mon Sep 17 00:00:00 2001
From: Justin Mazzocchi <2831158+jzzocc@users.noreply.github.com>
Date: Wed, 2 Dec 2020 11:39:42 -0800
Subject: [PATCH] Ephemeral timelines

---
 DB/Sources/DB/Content/ContentDatabase.swift   | 21 ++++++++++
 DB/Sources/DB/Entities/Timeline.swift         | 39 +++++++++++++++++++
 .../DB/Extensions/Timeline+Extensions.swift   | 35 -----------------
 3 files changed, 60 insertions(+), 35 deletions(-)
 delete mode 100644 DB/Sources/DB/Extensions/Timeline+Extensions.swift

diff --git a/DB/Sources/DB/Content/ContentDatabase.swift b/DB/Sources/DB/Content/ContentDatabase.swift
index 3b22e10..ef45334 100644
--- a/DB/Sources/DB/Content/ContentDatabase.swift
+++ b/DB/Sources/DB/Content/ContentDatabase.swift
@@ -11,6 +11,7 @@ import Secrets
 public struct ContentDatabase {
     public let activeFiltersPublisher: AnyPublisher<[Filter], Error>
 
+    private let id: Identity.Id
     private let databaseWriter: DatabaseWriter
 
     public init(id: Identity.Id,
@@ -19,6 +20,8 @@ public struct ContentDatabase {
                 inMemory: Bool,
                 appGroup: String,
                 keychain: Keychain.Type) throws {
+        self.id = id
+
         if inMemory {
             databaseWriter = DatabaseQueue()
             try Self.migrator.migrate(databaseWriter)
@@ -378,6 +381,21 @@ public extension ContentDatabase {
             TimelineItemsInfo.request(TimelineRecord.filter(TimelineRecord.Columns.id == timeline.id)).fetchOne)
             .removeDuplicates()
             .publisher(in: databaseWriter)
+            .handleEvents(
+                receiveSubscription: { _ in
+                    if let ephemeralityId = timeline.ephemeralityId(id: id) {
+                        Self.ephemeralTimelines.add(ephemeralityId)
+                    }
+                },
+                receiveCancel: {
+                    guard let ephemeralityId = timeline.ephemeralityId(id: id) else { return }
+
+                    Self.ephemeralTimelines.remove(ephemeralityId)
+
+                    if Self.ephemeralTimelines.count(for: ephemeralityId) == 0 {
+                        databaseWriter.asyncWrite(TimelineRecord(timeline: timeline).delete) { _, _ in }
+                    }
+                })
             .combineLatest(activeFiltersPublisher)
             .compactMap { $0?.items(filters: $1) }
             .eraseToAnyPublisher()
@@ -480,6 +498,9 @@ public extension ContentDatabase {
 
 private extension ContentDatabase {
     static let cleanAfterLastReadIdCount = 40
+
+    static let ephemeralTimelines = NSCountedSet()
+
     static func fileURL(id: Identity.Id, appGroup: String) throws -> URL {
         try FileManager.default.databaseDirectoryURL(name: id.uuidString, appGroup: appGroup)
     }
diff --git a/DB/Sources/DB/Entities/Timeline.swift b/DB/Sources/DB/Entities/Timeline.swift
index de73ec7..60e54cd 100644
--- a/DB/Sources/DB/Entities/Timeline.swift
+++ b/DB/Sources/DB/Entities/Timeline.swift
@@ -56,3 +56,42 @@ extension Timeline: Identifiable {
         }
     }
 }
+
+extension Timeline {
+    init?(record: TimelineRecord) {
+        switch (record.id,
+                record.listId,
+                record.listTitle,
+                record.tag,
+                record.accountId,
+                record.profileCollection) {
+        case (Timeline.home.id, _, _, _, _, _):
+            self = .home
+        case (Timeline.local.id, _, _, _, _, _):
+            self = .local
+        case (Timeline.federated.id, _, _, _, _, _):
+            self = .federated
+        case (_, .some(let listId), .some(let listTitle), _, _, _):
+            self = .list(List(id: listId, title: listTitle))
+        case (_, _, _, .some(let tag), _, _):
+            self = .tag(tag)
+        case (_, _, _, _, .some(let accountId), .some(let profileCollection)):
+            self = .profile(accountId: accountId, profileCollection: profileCollection)
+        case (Timeline.favorites.id, _, _, _, _, _):
+            self = .favorites
+        case (Timeline.bookmarks.id, _, _, _, _, _):
+            self = .bookmarks
+        default:
+            return nil
+        }
+    }
+
+    func ephemeralityId(id: Identity.Id) -> String? {
+        switch self {
+        case .tag, .favorites, .bookmarks:
+            return "\(id)-\(self.id)"
+        default:
+            return nil
+        }
+    }
+}
diff --git a/DB/Sources/DB/Extensions/Timeline+Extensions.swift b/DB/Sources/DB/Extensions/Timeline+Extensions.swift
deleted file mode 100644
index 84a1b7c..0000000
--- a/DB/Sources/DB/Extensions/Timeline+Extensions.swift
+++ /dev/null
@@ -1,35 +0,0 @@
-// Copyright © 2020 Metabolist. All rights reserved.
-
-import Foundation
-import GRDB
-import Mastodon
-
-extension Timeline {
-    init?(record: TimelineRecord) {
-        switch (record.id,
-                record.listId,
-                record.listTitle,
-                record.tag,
-                record.accountId,
-                record.profileCollection) {
-        case (Timeline.home.id, _, _, _, _, _):
-            self = .home
-        case (Timeline.local.id, _, _, _, _, _):
-            self = .local
-        case (Timeline.federated.id, _, _, _, _, _):
-            self = .federated
-        case (_, .some(let listId), .some(let listTitle), _, _, _):
-            self = .list(List(id: listId, title: listTitle))
-        case (_, _, _, .some(let tag), _, _):
-            self = .tag(tag)
-        case (_, _, _, _, .some(let accountId), .some(let profileCollection)):
-            self = .profile(accountId: accountId, profileCollection: profileCollection)
-        case (Timeline.favorites.id, _, _, _, _, _):
-            self = .favorites
-        case (Timeline.bookmarks.id, _, _, _, _, _):
-            self = .bookmarks
-        default:
-            return nil
-        }
-    }
-}