Add Codable support for Context and unsafe add functionality (#3)

.github/workflows/build.yml

@@ -17,7 +17,6 @@ on:
 jobs:
   build_and_test:
     name: Build and Test
-    uses: Apodini/.github/.github/workflows/build-and-test.yml@main
+    uses: Apodini/.github/.github/workflows/build-and-test.yml@v1
     with:
       packagename: MetadataSystem
-      xcodebuildpostfix: -Package

.github/workflows/pull_request.yml

@@ -15,13 +15,12 @@ on:
 jobs:
   build_and_test:
     name: Build and Test
-    uses: Apodini/.github/.github/workflows/build-and-test.yml@main
+    uses: Apodini/.github/.github/workflows/build-and-test.yml@v1
     with:
       packagename: MetadataSystem
-      xcodebuildpostfix: -Package
   reuse_action:
     name: REUSE Compliance Check
-    uses: Apodini/.github/.github/workflows/reuse.yml@main
+    uses: Apodini/.github/.github/workflows/reuse.yml@v1
   swiftlint:
     name: SwiftLint
-    uses: Apodini/.github/.github/workflows/swiftlint.yml@main
+    uses: Apodini/.github/.github/workflows/swiftlint.yml@v1

.github/workflows/release.yml

@@ -16,6 +16,6 @@ on:
 jobs:
   docs:
     name: Generate Docs
-    uses: Apodini/.github/.github/workflows/docs.yml@main
+    uses: Apodini/.github/.github/workflows/docs.yml@v1
     with:
       packagename: MetadataSystem

.github/workflows/update.yml

@@ -16,6 +16,6 @@ on:
 jobs:
   spm_update:
     name: Swift Package Update
-    uses: Apodini/.github/.github/workflows/spm-update.yml@main
+    uses: Apodini/.github/.github/workflows/spm-update.yml@v1
     secrets:
       token: ${{ secrets.ACCESS_TOKEN }}

Sources/ApodiniContext/CodableContextKey.swift

@@ -0,0 +1,43 @@
+//
+// This source file is part of the Apodini open source project
+//
+// SPDX-FileCopyrightText: 2019-2022 Paul Schmiedmayer and the Apodini project authors (see CONTRIBUTORS.md) <paul.schmiedmayer@tum.de>
+//
+// SPDX-License-Identifier: MIT
+//
+
+import Foundation
+
+/// Type erased ``CodableContextKey``.
+public protocol AnyCodableContextKey: AnyContextKey {
+    static var identifier: String { get }
+
+    static func anyEncode(value: Any) throws -> Data
+}
+
+/// An ``OptionalContextKey`` which value is able to be encoded and decoded.
+public protocol CodableContextKey: AnyCodableContextKey, OptionalContextKey where Value: Codable {
+    static func decode(from data: Data) throws -> Value
+}
+
+// Data, by default, is encoded as base64
+private let encoder = JSONEncoder()
+private let decoder = JSONDecoder()
+
+extension CodableContextKey {
+    public static var identifier: String {
+        "\(Self.self)"
+    }
+
+    public static func anyEncode(value: Any) throws -> Data {
+        guard let value = value as? Self.Value else {
+            fatalError("CodableContextKey.anyEncode(value:) received illegal value type \(type(of: value)) instead of \(Value.self)")
+        }
+
+        return try encoder.encode(value)
+    }
+
+    public static func decode(from data: Data) throws -> Value {
+        try decoder.decode(Value.self, from: data)
+    }
+}

Sources/ApodiniContext/Context.swift

@@ -6,13 +6,33 @@
 // SPDX-License-Identifier: MIT
 //
 
+import Foundation
+
+private class ContextBox {
+    var entries: [ObjectIdentifier: StoredContextValue]
+
+    init(_ entries: [ObjectIdentifier: StoredContextValue]) {
+        self.entries = entries
+    }
+}
+
+struct StoredContextValue {
+    let key: AnyContextKey.Type
+    let value: Any
+}
+
 /// Defines some sort of `Context` for a given representation (like `Endpoint`).
 /// A `Context` holds a collection of values for predefined `ContextKey`s or `OptionalContextKey`s.
 public struct Context: ContextKeyRetrievable {
-    private let entries: [ObjectIdentifier: Any]
+    private var boxedEntries: ContextBox
+    private var entries: [ObjectIdentifier: StoredContextValue] {
+        boxedEntries.entries
+    }
+    private let decodedEntries: [String: Data]
 
-    init(_ entries: [ObjectIdentifier: Any] = [:]) {
-        self.entries = entries
+    init(_ entries: [ObjectIdentifier: StoredContextValue] = [:], _ decodedEntries: [String: Data] = [:]) {
+        self.boxedEntries = ContextBox(entries)
+        self.decodedEntries = decodedEntries
     }
 
     /// Create a new empty ``Context``.
@@ -22,22 +42,73 @@ public struct Context: ContextKeyRetrievable {
 
     /// Creates a new ``Context`` by copying the contents of the provided ``Context``.
     public init(copying context: Context) {
-        self.entries = context.entries
+        self.init(context.entries, context.decodedEntries)
     }
 
     /// Retrieves the value for a given `ContextKey`.
     /// - Parameter contextKey: The `ContextKey` to retrieve the value for.
     /// - Returns: Returns the stored value or the `ContextKey.defaultValue` if it does not exist on the given `Context`.
     public func get<C: ContextKey>(valueFor contextKey: C.Type = C.self) -> C.Value {
-        entries[ObjectIdentifier(contextKey)] as? C.Value
+        entries[ObjectIdentifier(contextKey)]?.value as? C.Value
             ?? C.defaultValue
     }
 
     /// Retrieves the value for a given `OptionalContextKey`.
     /// - Parameter contextKey: The `OptionalContextKey` to retrieve the value for.
     /// - Returns: Returns the stored value or `nil` if it does not exist on the given `Context`.
     public func get<C: OptionalContextKey>(valueFor contextKey: C.Type = C.self) -> C.Value? {
-        entries[ObjectIdentifier(contextKey)] as? C.Value
+        entries[ObjectIdentifier(contextKey)]?.value as? C.Value
+    }
+
+    /// Retrieves the value for a given `CodableContextKey`.
+    /// - Parameter contextKey: The `OptionalContextKey` to retrieve the value for.
+    /// - Returns: Returns the stored value or `nil` if it does not exist on the given `Context`.
+    public func get<C: CodableContextKey>(valueFor contextKey: C.Type = C.self) -> C.Value? {
+        entries[ObjectIdentifier(contextKey)]?.value as? C.Value
+            ?? checkForDecodedEntries(for: contextKey)
+    }
+
+    /// Retrieves the value for a given `ContextKey & CodableContextKey`.
+    /// - Parameter contextKey: The `ContextKey` to retrieve the value for.
+    /// - Returns: Returns the stored value or the `ContextKey.defaultValue` if it does not exist on the given `Context`.
+    public func get<C: ContextKey & CodableContextKey>(valueFor contextKey: C.Type = C.self) -> C.Value {
+        entries[ObjectIdentifier(contextKey)]?.value as? C.Value
+            ?? checkForDecodedEntries(for: contextKey)
+            ?? C.defaultValue
+    }
+
+    /// This method can be used to unsafely add new entries to a constructed ``Context``.
+    /// This method is considered unsafe as it changes the ``Context`` which is normally considered non-mutable.
+    /// Try to not used this method!
+    ///
+    /// Note: This method does NOT reduce multiple values for the same key. You cannot add a value
+    /// if there is already a value for the given context key!
+    ///
+    /// - Parameters:
+    ///   - contextKey: The context to add value for.
+    ///   - value: The value to add.
+    public func unsafeAdd<C: OptionalContextKey>(_ contextKey: C.Type = C.self, value: C.Value) {
+        let key = ObjectIdentifier(contextKey)
+
+        precondition(entries[key] == nil, "Cannot overwrite existing ContextKey entry with `unsafeAdd`: \(C.self): \(value)")
+        if let codableContextKey = contextKey as? AnyCodableContextKey.Type {
+            // we need to prevent this. as Otherwise we would need to handle merging this stuff which get really complex
+            precondition(decodedEntries[codableContextKey.identifier] == nil, "Cannot overwrite existing CodableContextKey entry with `unsafeAdd`: \(C.self): \(value)")
+        }
+
+        boxedEntries.entries[key] = StoredContextValue(key: contextKey, value: value)
+    }
+
+    private func checkForDecodedEntries<Key: CodableContextKey>(for key: Key.Type = Key.self) -> Key.Value? {
+        guard let dataValue = decodedEntries[Key.identifier] else {
+            return nil
+        }
+
+        do {
+            return try Key.decode(from: dataValue)
+        } catch {
+            fatalError("Error occurred when trying to decode `CodableContextKey` `\(Key.self)` with stored value '\(dataValue)': \(error)")
+        }
     }
 }
 
@@ -46,3 +117,55 @@ extension Context: CustomStringConvertible {
         "Context(entries: \(entries))"
     }
 }
+
+// MARK: LazyCodable
+extension Context: Codable {
+    private struct StringContextKey: CodingKey {
+        let stringValue: String
+        let intValue: Int? = nil
+
+        init(stringValue: String) {
+            self.stringValue = stringValue
+        }
+
+        init?(intValue: Int) {
+            nil
+        }
+    }
+
+    public init(from decoder: Decoder) throws {
+        let container = try decoder.container(keyedBy: StringContextKey.self)
+
+        self.boxedEntries = ContextBox([:])
+
+        var decodedEntries: [String: Data] = [:]
+
+        for key in container.allKeys {
+            decodedEntries[key.stringValue] = try container.decode(Data.self, forKey: key)
+        }
+
+        self.decodedEntries = decodedEntries
+    }
+
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: StringContextKey.self)
+
+        var entries: [String: Data] = [:]
+
+        for storedValue in self.entries.values {
+            guard let contextKey = storedValue.key as? AnyCodableContextKey.Type else {
+                continue
+            }
+
+            entries[contextKey.identifier] = try contextKey.anyEncode(value: storedValue.value)
+        }
+
+        entries.merge(self.decodedEntries) { current, new in
+            fatalError("Encountered context value conflicts of \(current) and \(new)!")
+        }
+
+        for (key, data) in entries {
+            try container.encode(data, forKey: StringContextKey(stringValue: key))
+        }
+    }
+}

Sources/ApodiniContext/ContextEntry.swift

@@ -37,7 +37,7 @@ protocol AnyContextEntry {
 
     /// Reduces all collected context keys according to the respective `OptionalContextKey.reduce(...)`.
     /// - Returns: Returns the reduced value of the respective `OptionalContextKey.Value` type.
-    func reduce() -> Any
+    func reduce() -> StoredContextValue
 
     /// Creates a new `ContextEntryCollection` with expected generic typing.
     /// - Parameters:
@@ -86,7 +86,7 @@ class ContextEntry<Key: OptionalContextKey>: AnyContextEntry {
         return ContextEntry(lhsValues + selfRHS.values)
     }
 
-    func reduce() -> Any {
+    func reduce() -> StoredContextValue {
         guard var value = values.first?.value else {
             // we guarantee in the initializer that values won't ever be empty
             fatalError("Found inconsistency. \(type(of: self)) was found with empty values array.")
@@ -104,7 +104,7 @@ class ContextEntry<Key: OptionalContextKey>: AnyContextEntry {
 
         Key.mapFinal(value: &value)
 
-        return value
+        return StoredContextValue(key: Key.self, value: value)
     }
 
     func deriveCollection(entry: AnyContextEntry, derivedFromModifier: Bool) -> AnyContextEntryCollection {

Sources/ApodiniContext/ContextKey.swift

@@ -1,17 +1,20 @@
-//                   
+//
 // This source file is part of the Apodini open source project
 //
-// SPDX-FileCopyrightText: 2019-2021 Paul Schmiedmayer and the Apodini project authors (see CONTRIBUTORS.md) <paul.schmiedmayer@tum.de>
+// SPDX-FileCopyrightText: 2019-2022 Paul Schmiedmayer and the Apodini project authors (see CONTRIBUTORS.md) <paul.schmiedmayer@tum.de>
 //
 // SPDX-License-Identifier: MIT
-//              
+//
+
+/// Type erased ContextKey.
+public protocol AnyContextKey {}
 
 /// A `OptionalContextKey` serves as a key definition for a `ContextNode`.
 /// Optionally it can serve a reduction logic when inserting a new value into the `ContextNode`,
 /// see `OptionalContextKey.reduce(...)`.
 /// The `OptionalContextKey` is optional in the sense that it doesn't provide a default value, meaning
 /// it may not exist on the `Context` for a given `Handler`.
-public protocol OptionalContextKey {
+public protocol OptionalContextKey: AnyContextKey {
     /// The type of the value the `OptionalContextKey` identifies. The value MUST NOT be of type `Optional`.
     associatedtype Value
 

Sources/ApodiniContext/ContextNode.swift

@@ -92,7 +92,6 @@ public class ContextNode {
         precondition(exportedEntries == nil, "Tried adding additional context values on a ContextNode which was already exported!")
 
         guard !(C.Value.self is SomeOptional.Type) else {
-        // guard !isOptional(C.Value.self) else {
             fatalError(
                 """
                 The `Value` type of a `ContextKey` or `OptionalContextKey` must not be a `Optional` type.
@@ -197,7 +196,7 @@ public class ContextNode {
     /// retrieved when everything was fully parsed.
     /// `peekValue` doesn't guarantee that. The value might change after the call as parsing continues.
     public func peekValue<C: ContextKey>(for contextKey: C.Type = C.self) -> C.Value {
-        peekExportEntry(for: contextKey)?.reduce() as? C.Value
+        peekExportEntry(for: contextKey)?.reduce().value as? C.Value
             ?? C.defaultValue
     }
 
@@ -206,7 +205,7 @@ public class ContextNode {
     /// retrieved when everything was fully parsed.
     /// `peekValue` doesn't guarantee that. The value might change after the call as parsing continues.
     public func peekValue<C: OptionalContextKey>(for contextKey: C.Type = C.self) -> C.Value? {
-        peekExportEntry(for: contextKey)?.reduce() as? C.Value
+        peekExportEntry(for: contextKey)?.reduce().value as? C.Value
     }
 }
 

Tests/ApodiniContextTests/ContextKeyTests.swift

@@ -72,9 +72,36 @@ class ContextKeyTests: XCTestCase {
     }
 
     func testContextKeyCopying() {
-        let context = Context([ObjectIdentifier(String.self): "asdf"])
+        let context = Context([ObjectIdentifier(String.self): .init(key: StringContextKey.self, value: "asdf")])
         let copied = Context(copying: context)
 
         XCTAssertEqual(context.description, copied.description)
     }
+
+    func testCodableSupportAndUnsafeAdd() throws {
+        struct CodableStringContextKey: CodableContextKey {
+            typealias Value = String
+        }
+
+        struct RequiredCodableStringContextKey: CodableContextKey, ContextKey {
+            static var defaultValue: String = "Default Value!"
+            typealias Value = String
+        }
+
+        let context = Context()
+        context.unsafeAdd(CodableStringContextKey.self, value: "Hello World")
+        XCTAssertRuntimeFailure(context.unsafeAdd(CodableStringContextKey.self, value: "Hello Mars"))
+
+        XCTAssertEqual(context.get(valueFor: CodableStringContextKey.self), "Hello World")
+        XCTAssertEqual(context.get(valueFor: RequiredCodableStringContextKey.self), "Default Value!")
+
+        let encoder = JSONEncoder()
+        let decoder = JSONDecoder()
+
+        let encodedContext = try encoder.encode(context)
+        let decodedContext = try decoder.decode(Context.self, from: encodedContext)
+
+        XCTAssertEqual(decodedContext.get(valueFor: CodableStringContextKey.self), "Hello World")
+        XCTAssertEqual(decodedContext.get(valueFor: RequiredCodableStringContextKey.self), "Default Value!")
+    }
 }