Add support for Display String type to StructuredFieldValues (#51)

clintonpi · Lukasa · web-flow · commit be84570e9f05 · 2024-12-10T07:56:51.000Z
Motivation:

The parser and serializer for the Display String type have been
implemented. The high-level encoder and decoder should follow.

Modifications:

Implement the encoder and decoder for Display String.

Result:

The StructuredFieldValues module will support the Display String type.

---------

Co-authored-by: Cory Benfield &lt;lukasa@apple.com&gt;
diff --git a/Sources/StructuredFieldValues/Decoder/BareInnerListDecoder.swift b/Sources/StructuredFieldValues/Decoder/BareInnerListDecoder.swift
@@ -66,16 +66,20 @@ extension BareInnerListDecoder: UnkeyedDecodingContainer {
             self.decoder.pop()
         }
 
-        if type is Data.Type {
+        switch type {
+        case is Data.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Data.self) as! T
-        } else if type is Decimal.Type {
+        case is Decimal.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Decimal.self) as! T
-        } else if type is Date.Type {
+        case is Date.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Date.self) as! T
-        } else {
+        case is DisplayString.Type:
+            let container = try self.decoder.singleValueContainer()
+            return try container.decode(DisplayString.self) as! T
+        default:
             return try type.init(from: self.decoder)
         }
     }
diff --git a/Sources/StructuredFieldValues/Decoder/BareItemDecoder.swift b/Sources/StructuredFieldValues/Decoder/BareItemDecoder.swift
@@ -141,6 +141,14 @@ extension BareItemDecoder: SingleValueDecodingContainer {
         return Date(timeIntervalSince1970: Double(date))
     }
 
+    func decode(_: DisplayString.Type) throws -> DisplayString {
+        guard case .displayString(let string) = self.item else {
+            throw StructuredHeaderError.invalidTypeForItem
+        }
+
+        return DisplayString(rawValue: string)
+    }
+
     func decodeNil() -> Bool {
         // Items are never nil.
         false
@@ -182,6 +190,8 @@ extension BareItemDecoder: SingleValueDecodingContainer {
             return try self.decode(Decimal.self) as! T
         case is Date.Type:
             return try self.decode(Date.self) as! T
+        case is DisplayString.Type:
+            return try self.decode(DisplayString.self) as! T
         default:
             throw StructuredHeaderError.invalidTypeForItem
         }
diff --git a/Sources/StructuredFieldValues/Decoder/DictionaryKeyedContainer.swift b/Sources/StructuredFieldValues/Decoder/DictionaryKeyedContainer.swift
@@ -49,16 +49,20 @@ extension DictionaryKeyedContainer: KeyedDecodingContainerProtocol {
             self.decoder.pop()
         }
 
-        if type is Data.Type {
+        switch type {
+        case is Data.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Data.self) as! T
-        } else if type is Decimal.Type {
+        case is Decimal.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Decimal.self) as! T
-        } else if type is Date.Type {
+        case is Date.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Date.self) as! T
-        } else {
+        case is DisplayString.Type:
+            let container = try self.decoder.singleValueContainer()
+            return try container.decode(DisplayString.self) as! T
+        default:
             return try type.init(from: self.decoder)
         }
     }
diff --git a/Sources/StructuredFieldValues/Decoder/KeyedInnerListDecoder.swift b/Sources/StructuredFieldValues/Decoder/KeyedInnerListDecoder.swift
@@ -54,16 +54,20 @@ extension KeyedInnerListDecoder: KeyedDecodingContainerProtocol {
             self.decoder.pop()
         }
 
-        if type is Data.Type {
+        switch type {
+        case is Data.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Data.self) as! T
-        } else if type is Decimal.Type {
+        case is Decimal.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Decimal.self) as! T
-        } else if type is Date.Type {
+        case is Date.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Date.self) as! T
-        } else {
+        case is DisplayString.Type:
+            let container = try self.decoder.singleValueContainer()
+            return try container.decode(DisplayString.self) as! T
+        default:
             return try type.init(from: self.decoder)
         }
     }
diff --git a/Sources/StructuredFieldValues/Decoder/KeyedItemDecoder.swift b/Sources/StructuredFieldValues/Decoder/KeyedItemDecoder.swift
@@ -54,16 +54,20 @@ extension KeyedItemDecoder: KeyedDecodingContainerProtocol {
             self.decoder.pop()
         }
 
-        if type is Data.Type {
+        switch type {
+        case is Data.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Data.self) as! T
-        } else if type is Decimal.Type {
+        case is Decimal.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Decimal.self) as! T
-        } else if type is Date.Type {
+        case is Date.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Date.self) as! T
-        } else {
+        case is DisplayString.Type:
+            let container = try self.decoder.singleValueContainer()
+            return try container.decode(DisplayString.self) as! T
+        default:
             return try type.init(from: self.decoder)
         }
     }
diff --git a/Sources/StructuredFieldValues/Decoder/KeyedTopLevelListDecoder.swift b/Sources/StructuredFieldValues/Decoder/KeyedTopLevelListDecoder.swift
@@ -54,16 +54,20 @@ extension KeyedTopLevelListDecoder: KeyedDecodingContainerProtocol {
             self.decoder.pop()
         }
 
-        if type is Data.Type {
+        switch type {
+        case is Data.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Data.self) as! T
-        } else if type is Decimal.Type {
+        case is Decimal.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Decimal.self) as! T
-        } else if type is Date.Type {
+        case is Date.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Date.self) as! T
-        } else {
+        case is DisplayString.Type:
+            let container = try self.decoder.singleValueContainer()
+            return try container.decode(DisplayString.self) as! T
+        default:
             return try type.init(from: self.decoder)
         }
     }
diff --git a/Sources/StructuredFieldValues/Decoder/ParametersDecoder.swift b/Sources/StructuredFieldValues/Decoder/ParametersDecoder.swift
@@ -49,16 +49,20 @@ extension ParametersDecoder: KeyedDecodingContainerProtocol {
             self.decoder.pop()
         }
 
-        if type is Data.Type {
+        switch type {
+        case is Data.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Data.self) as! T
-        } else if type is Decimal.Type {
+        case is Decimal.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Decimal.self) as! T
-        } else if type is Date.Type {
+        case is Date.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Date.self) as! T
-        } else {
+        case is DisplayString.Type:
+            let container = try self.decoder.singleValueContainer()
+            return try container.decode(DisplayString.self) as! T
+        default:
             return try type.init(from: self.decoder)
         }
     }
diff --git a/Sources/StructuredFieldValues/Decoder/StructuredFieldValueDecoder.swift b/Sources/StructuredFieldValues/Decoder/StructuredFieldValueDecoder.swift
@@ -111,16 +111,20 @@ extension StructuredFieldValueDecoder {
 
         // An escape hatch here for top-level data: if we don't do this, it'll ask for
         // an unkeyed container and get very confused.
-        if type is Data.Type {
+        switch type {
+        case is Data.Type:
             let container = try decoder.singleValueContainer()
             return try container.decode(Data.self) as! StructuredField
-        } else if type is Decimal.Type {
+        case is Decimal.Type:
             let container = try decoder.singleValueContainer()
             return try container.decode(Decimal.self) as! StructuredField
-        } else if type is Date.Type {
+        case is Date.Type:
             let container = try decoder.singleValueContainer()
             return try container.decode(Date.self) as! StructuredField
-        } else {
+        case is DisplayString.Type:
+            let container = try decoder.singleValueContainer()
+            return try container.decode(DisplayString.self) as! StructuredField
+        default:
             return try type.init(from: decoder)
         }
     }
diff --git a/Sources/StructuredFieldValues/Decoder/TopLevelListDecoder.swift b/Sources/StructuredFieldValues/Decoder/TopLevelListDecoder.swift
@@ -66,16 +66,20 @@ extension TopLevelListDecoder: UnkeyedDecodingContainer {
             self.decoder.pop()
         }
 
-        if type is Data.Type {
+        switch type {
+        case is Data.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Data.self) as! T
-        } else if type is Decimal.Type {
+        case is Decimal.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Decimal.self) as! T
-        } else if type is Date.Type {
+        case is Date.Type:
             let container = try self.decoder.singleValueContainer()
             return try container.decode(Date.self) as! T
-        } else {
+        case is DisplayString.Type:
+            let container = try self.decoder.singleValueContainer()
+            return try container.decode(DisplayString.self) as! T
+        default:
             return try type.init(from: self.decoder)
         }
     }
diff --git a/Sources/StructuredFieldValues/DisplayString.swift b/Sources/StructuredFieldValues/DisplayString.swift
@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2020-2024 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+/// A type that represents the Display String Structured Type.
+public struct DisplayString: RawRepresentable, Codable, Equatable, Hashable {
+    public typealias RawValue = String
+    public var rawValue: String
+
+    public init(rawValue: String) {
+        self.rawValue = rawValue
+    }
+}
diff --git a/Sources/StructuredFieldValues/Encoder/StructuredFieldValueEncoder.swift b/Sources/StructuredFieldValues/Encoder/StructuredFieldValueEncoder.swift
@@ -150,19 +150,20 @@ class _StructuredFieldEncoder {
     fileprivate func encodeItemField<StructuredField: Encodable>(_ data: StructuredField) throws -> [UInt8] {
         self.push(key: .init(stringValue: ""), newStorage: .itemHeader)
 
-        // There's an awkward special hook here: if the outer type is `Data` or `Decimal`,
-        // we skip the regular encoding path. This is because otherwise `Data` will
-        // ask for an unkeyed container and `Decimal` for a keyed one,
-        // and it all falls apart.
+        // There's an awkward special hook here: if the outer type is `Data`, `Decimal`, `Date` or
+        // `DisplayString`, we skip the regular encoding path.
         //
         // Everything else goes through the normal flow.
-        if let value = data as? Data {
-            try self.encode(value)
-        } else if let value = data as? Decimal {
-            try self.encode(value)
-        } else if let value = data as? Date {
-            try self.encode(value)
-        } else {
+        switch data {
+        case is Data:
+            try self.encode(data)
+        case is Decimal:
+            try self.encode(data)
+        case is Date:
+            try self.encode(data)
+        case is DisplayString:
+            try self.encode(data)
+        default:
             try data.encode(to: self)
         }
 
@@ -316,6 +317,10 @@ extension _StructuredFieldEncoder: SingleValueEncodingContainer {
         try self.currentStackEntry.storage.insertBareItem(.date(date))
     }
 
+    func encode(_ data: DisplayString) throws {
+        try self.currentStackEntry.storage.insertBareItem(.displayString(data.rawValue))
+    }
+
     func encode<T>(_ value: T) throws where T: Encodable {
         switch value {
         case let value as UInt8:
@@ -352,6 +357,8 @@ extension _StructuredFieldEncoder: SingleValueEncodingContainer {
             try self.encode(value)
         case let value as Date:
             try self.encode(value)
+        case let value as DisplayString:
+            try self.encode(value)
         default:
             throw StructuredHeaderError.invalidTypeForItem
         }
@@ -480,6 +487,10 @@ extension _StructuredFieldEncoder {
         try self.currentStackEntry.storage.appendBareItem(.date(date))
     }
 
+    func append(_ value: DisplayString) throws {
+        try self.currentStackEntry.storage.appendBareItem(.displayString(value.rawValue))
+    }
+
     func append<T>(_ value: T) throws where T: Encodable {
         switch value {
         case let value as UInt8:
@@ -516,6 +527,8 @@ extension _StructuredFieldEncoder {
             try self.append(value)
         case let value as Date:
             try self.append(value)
+        case let value as DisplayString:
+            try self.append(value)
         default:
             // Some other codable type.
             switch self.currentStackEntry.storage {
@@ -658,6 +671,12 @@ extension _StructuredFieldEncoder {
         try self.currentStackEntry.storage.insertBareItem(.date(date), atKey: key)
     }
 
+    func encode(_ value: DisplayString, forKey key: String) throws {
+        let key = self.sanitizeKey(key)
+        let displayString = value.rawValue
+        try self.currentStackEntry.storage.insertBareItem(.displayString(displayString), atKey: key)
+    }
+
     func encode<T>(_ value: T, forKey key: String) throws where T: Encodable {
         let key = self.sanitizeKey(key)
 
@@ -696,6 +715,8 @@ extension _StructuredFieldEncoder {
             try self.encode(value, forKey: key)
         case let value as Date:
             try self.encode(value, forKey: key)
+        case let value as DisplayString:
+            try self.encode(value, forKey: key)
         default:
             // Ok, we don't know what this is. This can only happen for a dictionary, or
             // for anything with parameters, or for lists, or for inner lists.
diff --git a/Tests/StructuredFieldValuesTests/StructuredFieldDecoderTests.swift b/Tests/StructuredFieldValuesTests/StructuredFieldDecoderTests.swift
diff --git a/Tests/StructuredFieldValuesTests/StructuredFieldEncoderTests.swift b/Tests/StructuredFieldValuesTests/StructuredFieldEncoderTests.swift
