add ProfileDatabase class to read and write profiles to disk

damus.xcodeproj/project.pbxproj

@@ -261,6 +261,7 @@
 		501F8C822A0224EB001AFC1D /* KeychainStorageTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 501F8C812A0224EB001AFC1D /* KeychainStorageTests.swift */; };
 		501F8C5529FF5EF6001AFC1D /* PersistedProfile.swift in Sources */ = {isa = PBXBuildFile; fileRef = 501F8C5429FF5EF6001AFC1D /* PersistedProfile.swift */; };
 		501F8C5829FF5FC5001AFC1D /* Damus.xcdatamodeld in Sources */ = {isa = PBXBuildFile; fileRef = 501F8C5629FF5FC5001AFC1D /* Damus.xcdatamodeld */; };
+		501F8C5A29FF70F5001AFC1D /* ProfileDatabase.swift in Sources */ = {isa = PBXBuildFile; fileRef = 501F8C5929FF70F5001AFC1D /* ProfileDatabase.swift */; };
 		50A50A8D29A09E1C00C01BE7 /* RequestTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 50A50A8C29A09E1C00C01BE7 /* RequestTests.swift */; };
 		50B5685329F97CB400A23243 /* CredentialHandler.swift in Sources */ = {isa = PBXBuildFile; fileRef = 50B5685229F97CB400A23243 /* CredentialHandler.swift */; };
 		5C42E78C29DB76D90086AAC1 /* EmptyUserSearchView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5C42E78B29DB76D90086AAC1 /* EmptyUserSearchView.swift */; };
@@ -686,6 +687,7 @@
 		501F8C812A0224EB001AFC1D /* KeychainStorageTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = KeychainStorageTests.swift; sourceTree = "<group>"; };
 		501F8C5429FF5EF6001AFC1D /* PersistedProfile.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PersistedProfile.swift; sourceTree = "<group>"; };
 		501F8C5729FF5FC5001AFC1D /* Damus.xcdatamodel */ = {isa = PBXFileReference; lastKnownFileType = wrapper.xcdatamodel; path = Damus.xcdatamodel; sourceTree = "<group>"; };
+		501F8C5929FF70F5001AFC1D /* ProfileDatabase.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ProfileDatabase.swift; sourceTree = "<group>"; };
 		50A50A8C29A09E1C00C01BE7 /* RequestTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RequestTests.swift; sourceTree = "<group>"; };
 		50B5685229F97CB400A23243 /* CredentialHandler.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CredentialHandler.swift; sourceTree = "<group>"; };
 		5C42E78B29DB76D90086AAC1 /* EmptyUserSearchView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = EmptyUserSearchView.swift; sourceTree = "<group>"; };
@@ -1000,6 +1002,7 @@
 				4C75EFBA2804A34C0006080F /* ProofOfWork.swift */,
 				4CEE2AEC2805B22500AB5EEF /* NostrRequest.swift */,
 				4CACA9DB280C38C000D9BBE8 /* Profiles.swift */,
+				501F8C5929FF70F5001AFC1D /* ProfileDatabase.swift */,
 				4C3BEFD32819DE8F00B3DE84 /* NostrKind.swift */,
 				4C363A8F28247A1D006E126D /* NostrLink.swift */,
 				50088DA029E8271A008A1FDF /* WebSocket.swift */,
@@ -1651,6 +1654,7 @@
 				4CD348EF29C3659D00497EB2 /* ImageUploadModel.swift in Sources */,
 				4C7D096E2A0AEA0400943473 /* ScannerCoordinator.swift in Sources */,
 				4C3BEFDC281DCE6100B3DE84 /* Liked.swift in Sources */,
+				501F8C5A29FF70F5001AFC1D /* ProfileDatabase.swift in Sources */,
 				4CF0ABE7298444FD00D66079 /* MutedEventView.swift in Sources */,
 				9C83F89329A937B900136C08 /* TextViewWrapper.swift in Sources */,
 				4CF0ABE12981A83900D66079 /* MutelistView.swift in Sources */,

damus/Nostr/ProfileDatabase.swift

@@ -0,0 +1,110 @@
+//
+//  ProfileDatabase.swift
+//  damus
+//
+//  Created by Bryan Montz on 4/30/23.
+//
+
+import Foundation
+import CoreData
+
+enum ProfileDatabaseError: Error {
+    case missing_context
+    case outdated_input
+}
+
+final class ProfileDatabase {
+    
+    private let entity_name = "PersistedProfile"
+    private var persistent_container: NSPersistentContainer?
+    private var background_context: NSManagedObjectContext?
+    
+    init() {
+        set_up()
+    }
+    
+    private var profile_cache_url: URL {
+        (FileManager.default.urls(for: .cachesDirectory, in: .userDomainMask).first?.appendingPathComponent("profiles"))!
+    }
+    
+    private var persistent_store_description: NSPersistentStoreDescription {
+        let description = NSPersistentStoreDescription(url: profile_cache_url)
+        description.type = NSSQLiteStoreType
+        description.setOption(true as NSNumber, forKey: NSMigratePersistentStoresAutomaticallyOption)
+        description.setOption(true as NSNumber, forKey: NSInferMappingModelAutomaticallyOption)
+        description.setOption(true as NSNumber, forKey: NSSQLiteManualVacuumOption)
+        return description
+    }
+    
+    private var object_model: NSManagedObjectModel? {
+        guard let url = Bundle.main.url(forResource: "Damus", withExtension: "momd") else {
+            return nil
+        }
+        return NSManagedObjectModel(contentsOf: url)
+    }
+    
+    private func set_up() {
+        guard let object_model else {
+            print("⚠️ Warning: ProfileDatabase failed to load its object model")
+            return
+        }
+        
+        persistent_container = NSPersistentContainer(name: "Damus", managedObjectModel: object_model)
+        persistent_container?.persistentStoreDescriptions = [persistent_store_description]
+        persistent_container?.loadPersistentStores { _, error in
+            if let error {
+                print("WARNING: ProfileDatabase failed to load: \(error)")
+            }
+        }
+        
+        persistent_container?.viewContext.automaticallyMergesChangesFromParent = true
+        persistent_container?.viewContext.mergePolicy = NSMergePolicy(merge: .mergeByPropertyObjectTrumpMergePolicyType)
+        
+        background_context = persistent_container?.newBackgroundContext()
+        background_context?.mergePolicy = NSMergePolicy(merge: .mergeByPropertyObjectTrumpMergePolicyType)
+    }
+    
+    private func get_persisted(id: String) -> PersistedProfile? {
+        let request = NSFetchRequest<PersistedProfile>(entityName: entity_name)
+        request.predicate = NSPredicate(format: "id == %@", id)
+        request.fetchLimit = 1
+        return try? persistent_container?.viewContext.fetch(request).first
+    }
+    
+    // MARK: - Public
+    
+    /// Updates or inserts a new Profile into the local database. Rejects profiles whose update date
+    /// is older than one we already have. Database writes occur on a background context for best performance.
+    /// - Parameters:
+    ///   - id: Profile id (pubkey)
+    ///   - profile: Profile object to be stored
+    ///   - last_update: Date that the Profile was updated
+    func upsert(id: String, profile: Profile, last_update: Date) throws {
+        guard let context = background_context else {
+            throw ProfileDatabaseError.missing_context
+        }
+        
+        var persisted_profile: PersistedProfile?
+        if let profile = get_persisted(id: id) {
+            if let existing_last_update = profile.last_update, last_update < existing_last_update {
+                throw ProfileDatabaseError.outdated_input
+            } else {
+                persisted_profile = profile
+            }
+        } else {
+            persisted_profile = NSEntityDescription.insertNewObject(forEntityName: entity_name, into: context) as? PersistedProfile
+            persisted_profile?.id = id
+        }
+        persisted_profile?.copyValues(from: profile)
+        persisted_profile?.last_update = last_update
+        
+        try context.save()
+    }
+    
+    func get(id: String) -> Profile? {
+        guard let profile = get_persisted(id: id) else {
+            return nil
+        }
+        return Profile(persisted_profile: profile)
+    }
+}