Add persistence of selected currencies to disk via SQLite

Package.swift

@@ -15,10 +15,23 @@ let package = Package(
     ],
     dependencies: [
         .package(url: "https://source.skip.tools/skip.git", from: "1.0.7"),
-        .package(url: "https://source.skip.tools/skip-ui.git", from: "1.0.0")
+        .package(url: "https://source.skip.tools/skip-ui.git", from: "1.0.0"),
+        .package(url: "https://source.skip.tools/skip-foundation.git", from: "1.0.0"),
+        .package(url: "https://source.skip.tools/skip-model.git", from: "1.0.0"),
+        .package(url: "https://source.skip.tools/skip-sql.git", "0.0.0"..<"2.0.0")
     ],
     targets: [
-        .target(name: "SatsPrice", dependencies: [.product(name: "SkipUI", package: "skip-ui")], resources: [.process("Resources")], plugins: [.plugin(name: "skipstone", package: "skip")]),
+        .target(
+            name: "SatsPrice",
+            dependencies: [
+                .product(name: "SkipUI", package: "skip-ui"),
+                .product(name: "SkipFoundation", package: "skip-foundation"),
+                .product(name: "SkipModel", package: "skip-model"),
+                .product(name: "SkipSQLPlus", package: "skip-sql")
+            ],
+            resources: [.process("Resources")],
+            plugins: [.plugin(name: "skipstone", package: "skip")]
+        ),
         .testTarget(name: "SatsPriceTests", dependencies: ["SatsPrice", .product(name: "SkipTest", package: "skip")], resources: [.process("Resources")], plugins: [.plugin(name: "skipstone", package: "skip")]),
     ]
 )

Sources/SatsPrice/ContentView.swift

@@ -6,11 +6,17 @@ import Combine
 import SwiftUI
 
 public struct ContentView: View {
-    @ObservedObject private var satsViewModel = SatsViewModel()
+    let model: SatsPriceModel
+
+    @StateObject private var satsViewModel: SatsViewModel
 
     private let dateFormatter: DateFormatter
 
-    init() {
+    init(model: SatsPriceModel) {
+        self.model = model
+
+        _satsViewModel = StateObject<SatsViewModel>(wrappedValue: SatsViewModel(model: model))
+
         dateFormatter = DateFormatter()
         dateFormatter.dateStyle = .short
         dateFormatter.timeStyle = .short
@@ -124,6 +130,7 @@ public struct ContentView: View {
                 }
             }
             .task {
+                await satsViewModel.pullSelectedCurrenciesFromDB()
                 await satsViewModel.updatePrice()
             }
             .onChange(of: satsViewModel.priceSource) { newPriceSource in
@@ -140,5 +147,6 @@ public struct ContentView: View {
 }
 
 #Preview {
-    ContentView()
+    let satsPriceModel = try! SatsPriceModel(url: nil)
+    ContentView(model: satsPriceModel)
 }

Sources/SatsPrice/CurrencyPickerView.swift

@@ -31,7 +31,7 @@ struct CurrencyPickerView: View {
                     ForEach(satsViewModel.selectedCurrencies.filter { $0 != currentCurrency }.sorted { $0.identifier < $1.identifier }, id: \.identifier) { currency in
                         Button(
                             action: {
-                                satsViewModel.selectedCurrencies.remove(currency)
+                                satsViewModel.removeSelectedCurrency(currency)
                             },
                             label: {
                                 HStack {
@@ -57,7 +57,7 @@ struct CurrencyPickerView: View {
                 ForEach(satsViewModel.currencies.filter { $0 != currentCurrency && !satsViewModel.selectedCurrencies.contains($0) }, id: \.identifier) { currency in
                     Button(
                         action: {
-                            satsViewModel.selectedCurrencies.insert(currency)
+                            satsViewModel.addSelectedCurrency(currency)
                         },
                         label: {
                             if let localizedCurrency = Locale.current.localizedString(forCurrencyCode: currency.identifier) {
@@ -80,5 +80,6 @@ struct CurrencyPickerView: View {
 }
 
 #Preview {
-    CurrencyPickerView(satsViewModel: SatsViewModel())
+    let satsPriceModel = try! SatsPriceModel(url: nil)
+    CurrencyPickerView(satsViewModel: SatsViewModel(model: satsPriceModel))
 }

Sources/SatsPrice/Model/SatsPriceModel.swift

@@ -0,0 +1,156 @@
+// This is free software: you can redistribute and/or modify it
+// under the terms of the GNU General Public License 3.0
+// as published by the Free Software Foundation https://fsf.org
+//
+//  SatsPriceModel.swift
+//  sats-price
+//
+//  Created by Terry Yiu on 11/15/24.
+//
+
+import Foundation
+import OSLog
+import Observation
+import SkipSQL
+
+public struct SelectedCurrency: Identifiable {
+    public var id: String {
+        currencyCode
+    }
+
+    public var currencyCode: String
+}
+
+/// Notification posted by the model when selected currencies change.
+extension Notification.Name {
+    public static var selectedCurrenciesDidChange: Notification.Name {
+        return Notification.Name("selectedCurrenciesChange")
+    }
+}
+
+/// Payload of `selectedCurrenciesDidChange` notifications.
+public struct SelectedCurrenciesChange {
+    public let inserts: [SelectedCurrency]
+    /// Nil set means all records were deleted.
+    public let deletes: Set<String>?
+
+    public init(inserts: [SelectedCurrency] = [], deletes: [String]? = []) {
+        self.inserts = inserts
+        self.deletes = deletes == nil ? nil : Set(deletes!)
+    }
+}
+
+public actor SatsPriceModel {
+    private let ctx: SQLContext
+    private var schemaInitializationResult: Result<Void, Error>?
+
+    public init(url: URL?) throws {
+        ctx = try SQLContext(path: url?.path ?? ":memory:", flags: [.readWrite, .create], logLevel: .info, configuration: .platform)
+    }
+
+    public func selectedCurrencies() throws -> [SelectedCurrency] {
+        do {
+            try initializeSchema()
+            let statement = try ctx.prepare(sql: "SELECT currencyCode FROM SelectedCurrency")
+            defer {
+                do {
+                    try statement.close()
+                } catch {
+                    logger.warning("Failed to close statement: \(error)")
+                }
+            }
+
+            var selectedCurrencies: [SelectedCurrency] = []
+
+            while try statement.next() {
+                let currencyCode = statement.string(at: 0) ?? ""
+                selectedCurrencies.append(SelectedCurrency(currencyCode: currencyCode))
+            }
+
+            return selectedCurrencies
+        } catch {
+            logger.error("Failed to get selected currencies from DB. Error: \(error)")
+            throw error
+        }
+    }
+
+    @discardableResult
+    public func insert(_ selectedCurrency: SelectedCurrency) throws -> [SelectedCurrency] {
+        try initializeSchema()
+        let statement = try ctx.prepare(sql: "INSERT INTO SelectedCurrency (currencyCode) VALUES (?)")
+        defer {
+            do {
+                try statement.close()
+            } catch {
+                logger.warning("Failed to close statement: \(error)")
+            }
+        }
+
+        var insertedItems: [SelectedCurrency] = []
+        try ctx.transaction {
+            statement.reset()
+            let values = Self.bindingValues(for: selectedCurrency)
+            try statement.update(parameters: values)
+
+            insertedItems.append(selectedCurrency)
+        }
+        NotificationCenter.default.post(name: .selectedCurrenciesDidChange, object: SelectedCurrenciesChange(inserts: insertedItems))
+        return insertedItems
+    }
+
+    private static func bindingValues(for selectedCurrency: SelectedCurrency) -> [SQLValue] {
+        return [
+            .text(selectedCurrency.currencyCode)
+        ]
+    }
+
+    @discardableResult
+    public func deleteSelectedCurrency(currencyCode: String) throws -> Int {
+        try initializeSchema()
+        try ctx.exec(sql: "DELETE FROM SelectedCurrency WHERE currencyCode = ?", parameters: [.text(currencyCode)])
+        NotificationCenter.default.post(name: .selectedCurrenciesDidChange, object: SelectedCurrenciesChange(deletes: [currencyCode]))
+        return Int(ctx.changes)
+    }
+
+    private func initializeSchema() throws {
+        switch schemaInitializationResult {
+        case .success:
+            return
+        case .failure(let failure):
+            throw failure
+        case nil:
+            break
+        }
+
+        do {
+            var currentVersion = try currentSchemaVersion()
+            currentVersion = try migrateSchema(v: Int64(1), current: currentVersion, ddl: """
+            CREATE TABLE SelectedCurrency (currencyCode TEXT PRIMARY KEY NOT NULL)
+            """)
+            // Future column additions, etc here...
+            schemaInitializationResult = .success(())
+        } catch {
+            schemaInitializationResult = .failure(error)
+            throw error
+        }
+    }
+
+    private func currentSchemaVersion() throws -> Int64 {
+        try ctx.exec(sql: "CREATE TABLE IF NOT EXISTS SchemaVersion (id INTEGER PRIMARY KEY, version INTEGER)")
+        try ctx.exec(sql: "INSERT OR IGNORE INTO SchemaVersion (id, version) VALUES (0, 0)")
+        return try ctx.query(sql: "SELECT version FROM SchemaVersion").first?.first?.integerValue ?? Int64(0)
+    }
+
+    private func migrateSchema(v version: Int64, current: Int64, ddl: String) throws -> Int64 {
+        guard current < version else {
+            return current
+        }
+        let startTime = Date.now
+        try ctx.transaction {
+            try ctx.exec(sql: ddl)
+            try ctx.exec(sql: "UPDATE SchemaVersion SET version = ?", parameters: [.integer(version)])
+        }
+        logger.log("Updated database schema to \(version) in \(Date.now.timeIntervalSince1970 - startTime.timeIntervalSince1970)")
+        return version
+    }
+}

Sources/SatsPrice/SatsPriceApp.swift

@@ -11,6 +11,9 @@ let logger: Logger = Logger(subsystem: "xyz.tyiu.SatsPrice", category: "SatsPric
 /// The Android SDK number we are running against, or `nil` if not running on Android
 let androidSDK = ProcessInfo.processInfo.environment["android.os.Build.VERSION.SDK_INT"].flatMap({ Int($0) })
 
+/// The shared data model.
+private let model = try! SatsPriceModel(url: URL.documentsDirectory.appendingPathComponent("satsprice.sqlite"))
+
 /// The shared top-level view for the app, loaded from the platform-specific App delegates below.
 ///
 /// The default implementation merely loads the `ContentView` for the app and logs a message.
@@ -19,7 +22,7 @@ public struct RootView : View {
     }
 
     public var body: some View {
-        ContentView()
+        ContentView(model: model)
             .task {
                 logger.log("Welcome to Skip on \(androidSDK != nil ? "Android" : "Darwin")!")
                 logger.warning("Skip app logs are viewable in the Xcode console for iOS; Android logs can be viewed in Studio or using adb logcat")

Sources/SatsPrice/SatsViewModel.swift

@@ -13,6 +13,8 @@ import Foundation
 import SwiftUI
 
 class SatsViewModel: ObservableObject {
+    let model: SatsPriceModel
+
     @Published var lastUpdated: Date?
 
     @Published var priceSourceInternal: PriceSource = .coinbase
@@ -20,7 +22,6 @@ class SatsViewModel: ObservableObject {
 
     @Published var satsStringInternal: String = ""
     @Published var btcStringInternal: String = ""
-    @Published var selectedCurrency: Locale.Currency = Locale.current.currency ?? Locale.Currency("USD")
     @Published var selectedCurrencies = Set<Locale.Currency>()
     @Published var currencyValueStrings: [Locale.Currency: String] = [:]
 
@@ -28,6 +29,10 @@ class SatsViewModel: ObservableObject {
 
     let currentCurrency: Locale.Currency = Locale.current.currency ?? Locale.Currency("USD")
 
+    init(model: SatsPriceModel) {
+        self.model = model
+    }
+
     var currencies: [Locale.Currency] {
         let commonISOCurrencyCodes = Set(Locale.commonISOCurrencyCodes)
         if commonISOCurrencyCodes.contains(currentCurrency.identifier) {
@@ -40,6 +45,34 @@ class SatsViewModel: ObservableObject {
         }
     }
 
+    @MainActor
+    func pullSelectedCurrenciesFromDB() async {
+        do {
+            let selectedCurrencies = Set(try await model.selectedCurrencies().compactMap { Locale.Currency($0.currencyCode) })
+            let currenciesToAdd = selectedCurrencies.subtracting(self.selectedCurrencies)
+            let currenciesToRemove = self.selectedCurrencies.subtracting(selectedCurrencies)
+
+            self.selectedCurrencies.subtract(currenciesToRemove)
+            self.selectedCurrencies.formUnion(currenciesToAdd)
+        } catch {
+            logger.error("Unable to pull selected currencies from DB. Error: \(error)")
+        }
+    }
+
+    func addSelectedCurrency(_ currency: Locale.Currency) {
+        selectedCurrencies.insert(currency)
+        Task {
+            try await model.insert(SelectedCurrency(currencyCode: currency.identifier))
+        }
+    }
+
+    func removeSelectedCurrency(_ currency: Locale.Currency) {
+        selectedCurrencies.remove(currency)
+        Task {
+            try await model.deleteSelectedCurrency(currencyCode: currency.identifier)
+        }
+    }
+
     var priceSource: PriceSource {
         get {
             priceSourceInternal