Introduce URIEncoder and URIDecoder types

NOTICE.txt

@@ -32,3 +32,12 @@ This product contains derivations of various scripts and templates from SwiftNIO
     * https://www.apache.org/licenses/LICENSE-2.0
   * HOMEPAGE:
     * https://github.com/apple/swift-nio
+
+---
+
+This product contains a coder implementation inspired by swift-http-structured-headers.
+
+  * LICENSE (Apache License 2.0):
+    * https://www.apache.org/licenses/LICENSE-2.0
+  * HOMEPAGE:
+    * https://github.com/apple/swift-http-structured-headers

Sources/OpenAPIRuntime/URICoder/Common/URICodeCodingKey.swift

@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftOpenAPIGenerator open source project
+//
+// Copyright (c) 2023 Apple Inc. and the SwiftOpenAPIGenerator project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftOpenAPIGenerator project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+/// The coding key.
+struct URICoderCodingKey: CodingKey {
+    var stringValue: String
+    var intValue: Int?
+
+    init(stringValue: String) {
+        self.stringValue = stringValue
+        self.intValue = nil
+    }
+
+    init(intValue: Int) {
+        self.stringValue = "\(intValue)"
+        self.intValue = intValue
+    }
+
+    init(_ key: some CodingKey) {
+        self.stringValue = key.stringValue
+        self.intValue = key.intValue
+    }
+}

Sources/OpenAPIRuntime/URICoder/Common/URICoderConfiguration.swift

@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftOpenAPIGenerator open source project
+//
+// Copyright (c) 2023 Apple Inc. and the SwiftOpenAPIGenerator project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftOpenAPIGenerator project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+/// A bag of configuration values used by the URI parser and serializer.
+struct URICoderConfiguration {
+
+    // TODO: Wrap in a struct, as this will grow.
+    // https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.3.md#style-values
+    enum Style {
+        case simple
+        case form
+    }
+
+    var style: Style
+    var explode: Bool
+    var spaceEscapingCharacter: String
+
+    private init(style: Style, explode: Bool, spaceEscapingCharacter: String) {
+        self.style = style
+        self.explode = explode
+        self.spaceEscapingCharacter = spaceEscapingCharacter
+    }
+
+    static let formExplode: Self = .init(
+        style: .form,
+        explode: true,
+        spaceEscapingCharacter: "%20"
+    )
+
+    static let formUnexplode: Self = .init(
+        style: .form,
+        explode: false,
+        spaceEscapingCharacter: "%20"
+    )
+
+    static let simpleExplode: Self = .init(
+        style: .simple,
+        explode: true,
+        spaceEscapingCharacter: "%20"
+    )
+
+    static let simpleUnexplode: Self = .init(
+        style: .simple,
+        explode: false,
+        spaceEscapingCharacter: "%20"
+    )
+
+    static let formDataExplode: Self = .init(
+        style: .form,
+        explode: true,
+        spaceEscapingCharacter: "+"
+    )
+
+    static let formDataUnexplode: Self = .init(
+        style: .form,
+        explode: false,
+        spaceEscapingCharacter: "+"
+    )
+}

Sources/OpenAPIRuntime/URICoder/Common/URIEncodedNode.swift

@@ -0,0 +1,99 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftOpenAPIGenerator open source project
+//
+// Copyright (c) 2023 Apple Inc. and the SwiftOpenAPIGenerator project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftOpenAPIGenerator project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+enum URIEncodedNode: Equatable {
+
+    case unset
+    case primitive(Primitive)
+    case array([Self])
+    case dictionary([String: Self])
+
+    enum Primitive: Equatable {
+        case bool(Bool)
+        case string(String)
+        case integer(Int)
+        case double(Double)
+    }
+}
+
+extension URIEncodedNode {
+
+    enum InsertionError: Swift.Error {
+        case settingPrimitiveValueAgain
+        case settingValueOnAContainer
+        case appendingToNonArrayContainer
+        case insertingChildValueIntoNonContainer
+        case insertingChildValueIntoArrayUsingNonIntValueKey
+    }
+
+    mutating func set(_ value: Primitive) throws {
+        switch self {
+        case .unset:
+            self = .primitive(value)
+        case .primitive:
+            throw InsertionError.settingPrimitiveValueAgain
+        case .array, .dictionary:
+            throw InsertionError.settingValueOnAContainer
+        }
+    }
+
+    mutating func insert<Key: CodingKey>(
+        _ childValue: Self,
+        atKey key: Key
+    ) throws {
+        switch self {
+        case .dictionary(var dictionary):
+            self = .unset
+            dictionary[key.stringValue] = childValue
+            self = .dictionary(dictionary)
+        case .array(var array):
+            // Check that this is a valid key for an unkeyed container,
+            // but don't actually extract the index, we only support appending
+            // here.
+            guard let intValue = key.intValue else {
+                throw InsertionError.insertingChildValueIntoArrayUsingNonIntValueKey
+            }
+            precondition(
+                intValue == array.count,
+                "Unkeyed container inserting at an incorrect index"
+            )
+            self = .unset
+            array.append(childValue)
+            self = .array(array)
+        case .unset:
+            if let _ = key.intValue {
+                self = .array([childValue])
+            } else {
+                self = .dictionary([key.stringValue: childValue])
+            }
+        default:
+            throw InsertionError.insertingChildValueIntoNonContainer
+        }
+    }
+
+    mutating func append(_ childValue: Self) throws {
+        switch self {
+        case .array(var items):
+            self = .unset
+            items.append(childValue)
+            self = .array(items)
+        case .unset:
+            self = .array([childValue])
+        default:
+            throw InsertionError.appendingToNonArrayContainer
+        }
+    }
+}

Sources/OpenAPIRuntime/URICoder/Common/URIParsedNode.swift

@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftOpenAPIGenerator open source project
+//
+// Copyright (c) 2023 Apple Inc. and the SwiftOpenAPIGenerator project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftOpenAPIGenerator project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+typealias URIParsedKey = String.SubSequence
+typealias URIParsedValue = String.SubSequence
+typealias URIParsedValueArray = [URIParsedValue]
+typealias URIParsedNode = [URIParsedKey: URIParsedValueArray]

Sources/OpenAPIRuntime/URICoder/Decoding/URIDecoder.swift

@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftOpenAPIGenerator open source project
+//
+// Copyright (c) 2023 Apple Inc. and the SwiftOpenAPIGenerator project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftOpenAPIGenerator project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+/// A type that decodes a `Decodable` objects from an URI-encoded string
+/// using the rules from RFC 6570, RFC 1866, and OpenAPI 3.0.3, depending on
+/// the configuration.
+struct URIDecoder: Sendable {
+
+    private let configuration: URICoderConfiguration
+
+    init(configuration: URICoderConfiguration) {
+        self.configuration = configuration
+    }
+}
+
+extension URIDecoder {
+
+    /// Attempt to decode an object from an URI string.
+    ///
+    /// Under the hood, URIDecoder first parses the string into a URIParsedNode
+    /// using URIParser, and then uses URIValueFromNodeDecoder to decode
+    /// the Decodable value.
+    ///
+    /// - Parameters:
+    ///     - type: The type to decode.
+    ///     - data: The URI-encoded string.
+    /// - Returns: The decoded value.
+    func decode<T: Decodable>(
+        _ type: T.Type = T.self,
+        from data: String
+    ) throws -> T {
+        var parser = URIParser(configuration: configuration, data: data)
+        let parsedNode = try parser.parseRoot()
+        let decoder = URIValueFromNodeDecoder(
+            node: parsedNode,
+            explode: configuration.explode
+        )
+        return try decoder.decodeRoot()
+    }
+}