WIP improve variable interface

Sources/ScreamURITemplate/Internal/Components.swift

@@ -17,7 +17,7 @@ import Foundation
 typealias ComponentBase = Sendable
 
 protocol Component: ComponentBase {
-    func expand(variables: [String: VariableValue]) throws -> String
+    func expand(variables: VariableProvider) throws -> String
     var variableNames: [String] { get }
 }
 
@@ -33,7 +33,7 @@ struct LiteralComponent: Component {
         literal = string
     }
 
-    func expand(variables _: [String: VariableValue]) throws -> String {
+    func expand(variables _: VariableProvider) throws -> String {
         let expansion = String(literal)
         guard let encodedExpansion = expansion.addingPercentEncoding(withAllowedCharacters: reservedAndUnreservedCharacterSet) else {
             throw URITemplate.Error.expansionFailure(position: literal.startIndex, reason: "Percent Encoding Failed")
@@ -48,7 +48,7 @@ struct LiteralPercentEncodedTripletComponent: Component {
         literal = string
     }
 
-    func expand(variables _: [String: VariableValue]) throws -> String {
+    func expand(variables _: VariableProvider) throws -> String {
         return String(literal)
     }
 }
@@ -65,16 +65,17 @@ struct ExpressionComponent: Component {
     }
 
     // swiftlint:disable:next cyclomatic_complexity
-    func expand(variables: [String: VariableValue]) throws -> String {
+    func expand(variables: VariableProvider) throws -> String {
         let configuration = expressionOperator.expansionConfiguration()
         let expansions = try variableList.compactMap { variableSpec -> String? in
-            guard let value = variables[String(variableSpec.name)] else {
+            guard let value = variables[String(variableSpec.name)]?.asTypedVariableValue() else {
                 return nil
             }
             do {
-                if let stringValue = value as? String {
-                    return try stringValue.formatForTemplateExpansion(variableSpec: variableSpec, expansionConfiguration: configuration)
-                } else if let arrayValue = value as? [String] {
+                switch value {
+                case let .string(plainValue):
+                    return try plainValue.formatForTemplateExpansion(variableSpec: variableSpec, expansionConfiguration: configuration)
+                case let .list(arrayValue):
                     switch variableSpec.modifier {
                     case .prefix:
                         throw FormatError.failure(reason: "Prefix operator can only be applied to string")
@@ -83,17 +84,15 @@ struct ExpressionComponent: Component {
                     case .none:
                         return try arrayValue.formatForTemplateExpansion(variableSpec: variableSpec, expansionConfiguration: configuration)
                     }
-                } else if let dictionaryValue = value as? [String: String] {
+                case let .associativeArray(associativeArrayValue):
                     switch variableSpec.modifier {
                     case .prefix:
                         throw FormatError.failure(reason: "Prefix operator can only be applied to string")
                     case .explode:
-                        return try dictionaryValue.explodeForTemplateExpansion(variableSpec: variableSpec, expansionConfiguration: configuration)
+                        return try associativeArrayValue.explodeForTemplateExpansion(variableSpec: variableSpec, expansionConfiguration: configuration)
                     case .none:
-                        return try dictionaryValue.formatForTemplateExpansion(variableSpec: variableSpec, expansionConfiguration: configuration)
+                        return try associativeArrayValue.formatForTemplateExpansion(variableSpec: variableSpec, expansionConfiguration: configuration)
                     }
-                } else {
-                    throw FormatError.failure(reason: "Invalid Value Type")
                 }
             } catch let FormatError.failure(reason) {
                 throw URITemplate.Error.expansionFailure(position: templatePosition, reason: "Failed expanding variable \"\(variableSpec.name)\": \(reason)")

Sources/ScreamURITemplate/Internal/ValueFormatting.swift

@@ -101,7 +101,7 @@ extension Array where Element: StringProtocol {
     }
 }
 
-extension Dictionary where Key: StringProtocol, Value: StringProtocol {
+extension [TypedVariableValue.AssociativeArrayElement] {
     func formatForTemplateExpansion(variableSpec: VariableSpec, expansionConfiguration: ExpansionConfiguration) throws -> String? {
         let encodedExpansions = try map { key, value -> String in
             let encodedKey = try percentEncode(string: String(key), withAllowedCharacters: expansionConfiguration.percentEncodingAllowedCharacterSet, allowPercentEncodedTriplets: expansionConfiguration.allowPercentEncodedTriplets)

Sources/ScreamURITemplate/URITemplate.swift

@@ -14,11 +14,6 @@
 
 import Foundation
 
-public protocol VariableValue {}
-extension String: VariableValue {}
-extension Array: VariableValue where Element: StringProtocol {}
-extension Dictionary: VariableValue where Key: StringProtocol, Value: StringProtocol {}
-
 public struct URITemplate {
     public enum Error: Swift.Error {
         case malformedTemplate(position: String.Index, reason: String)
@@ -38,14 +33,18 @@ public struct URITemplate {
         self.components = components
     }
 
-    public func process(variables: [String: VariableValue]) throws -> String {
+    public func process(variables: VariableProvider) throws -> String {
         var result = ""
         for component in components {
             result += try component.expand(variables: variables)
         }
         return result
     }
 
+    public func process(variables: [String: String]) throws -> String {
+        return try process(variables: variables as VariableDictionary)
+    }
+
     public var variableNames: [String] {
         return components.flatMap { component in
             return component.variableNames

Sources/ScreamURITemplate/VariableProvider.swift

@@ -0,0 +1,22 @@
+//
+//   Licensed under the Apache License, Version 2.0 (the "License");
+//   you may not use this file except in compliance with the License.
+//   You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+//   Unless required by applicable law or agreed to in writing, software
+//   distributed under the License is distributed on an "AS IS" BASIS,
+//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//   See the License for the specific language governing permissions and
+//   limitations under the License.
+
+import Foundation
+
+public protocol VariableProvider {
+    subscript(_: String) -> VariableValue? { get }
+}
+
+public typealias VariableDictionary = [String: VariableValue]
+
+extension VariableDictionary: VariableProvider {}

Sources/ScreamURITemplate/VariableValue.swift

@@ -0,0 +1,85 @@
+//   Copyright 2018-2023 Alex Deem
+//
+//   Licensed under the Apache License, Version 2.0 (the "License");
+//   you may not use this file except in compliance with the License.
+//   You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+//   Unless required by applicable law or agreed to in writing, software
+//   distributed under the License is distributed on an "AS IS" BASIS,
+//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//   See the License for the specific language governing permissions and
+//   limitations under the License.
+
+import Foundation
+
+public enum TypedVariableValue {
+    public typealias AssociativeArrayElement = (key: String, value: String)
+
+    case string(String)
+    case list([String])
+    case associativeArray([AssociativeArrayElement])
+}
+
+public protocol VariableValue {
+    func asTypedVariableValue() -> TypedVariableValue?
+}
+
+public protocol StringVariableValue: VariableValue {
+    func asStringVariableValue() -> String
+}
+
+public extension StringVariableValue {
+    func asTypedVariableValue() -> TypedVariableValue? {
+        .string(asStringVariableValue())
+    }
+}
+
+extension [StringVariableValue]: VariableValue {
+    public func asTypedVariableValue() -> TypedVariableValue? {
+        .list(map { $0.asStringVariableValue() })
+    }
+}
+
+extension KeyValuePairs<String, StringVariableValue>: VariableValue {
+    public func asTypedVariableValue() -> TypedVariableValue? {
+        .associativeArray(map { ($0, $1.asStringVariableValue()) })
+    }
+}
+
+extension [String: StringVariableValue]: VariableValue {
+    public func asTypedVariableValue() -> TypedVariableValue? {
+        .associativeArray(map { ($0, $1.asStringVariableValue()) }.sorted { $0.0 < $1.0 })
+    }
+}
+
+public extension LosslessStringConvertible {
+    func asStringVariableValue() -> String {
+        description
+    }
+}
+
+extension String: StringVariableValue {}
+extension Bool: StringVariableValue {}
+extension Character: StringVariableValue {}
+extension Double: StringVariableValue {}
+extension Float: StringVariableValue {}
+extension Int: StringVariableValue {}
+extension Int16: StringVariableValue {}
+extension Int32: StringVariableValue {}
+extension Int64: StringVariableValue {}
+extension Int8: StringVariableValue {}
+extension Substring: StringVariableValue {}
+extension UInt: StringVariableValue {}
+extension UInt16: StringVariableValue {}
+extension UInt32: StringVariableValue {}
+extension UInt64: StringVariableValue {}
+extension UInt8: StringVariableValue {}
+extension Unicode.Scalar: StringVariableValue {}
+
+extension UUID: StringVariableValue {
+    public func asStringVariableValue() -> String {
+        uuidString
+    }
+}

Tests/ScreamURITemplateTests/TestFileTests.swift

@@ -17,7 +17,7 @@ import XCTest
 
 class TestFileTests: XCTestCase {
     private var templateString: String!
-    private var variables: [String: VariableValue]!
+    private var variables: VariableDictionary!
     private var acceptableExpansions: [String]!
     private var failPosition: Int?
     private var failReason: String?

Tests/ScreamURITemplateTests/TestModels.swift

@@ -26,7 +26,7 @@ private struct TestGroupDecodable: Decodable {
 public struct TestGroup {
     public let name: String
     public let level: Int?
-    public let variables: [String: VariableValue]
+    public let variables: VariableDictionary
     public let testcases: [TestCase]
 }
 
@@ -38,35 +38,33 @@ public struct TestCase {
     public let failReason: String?
 }
 
-extension JSONValue {
-    func toVariableValue() -> VariableValue? {
+extension JSONValue: VariableValue {
+    public func asTypedVariableValue() -> ScreamURITemplate.TypedVariableValue? {
+        switch self {
+        case let .int(int):
+            return int.asTypedVariableValue()
+        case let .double(double):
+            return double.asTypedVariableValue()
+        case let .string(string):
+            return string.asTypedVariableValue()
+        case let .object(object):
+            return object.compactMapValues { $0.asString() }.asTypedVariableValue()
+        case let .array(array):
+            return array.compactMap { $0.asString() }.asTypedVariableValue()
+        case .null, .bool:
+            return nil
+        }
+    }
+
+    private func asString() -> String? {
         switch self {
         case let .int(int):
             return String(int)
         case let .double(double):
             return String(double)
         case let .string(string):
             return string
-        case let .object(object):
-            return object.mapValues { element -> String? in
-                switch element {
-                case let .string(string):
-                    return string
-                default:
-                    return nil
-                }
-            }.filter { $0.value != nil }
-                .mapValues { $0! }
-        case let .array(array):
-            return array.compactMap { element -> String? in
-                switch element {
-                case let .string(string):
-                    return string
-                default:
-                    return nil
-                }
-            }
-        default:
+        case .null, .bool, .object, .array:
             return nil
         }
     }
@@ -86,18 +84,7 @@ extension TestCase {
         let expansionsData = data[1]
         switch expansionsData {
         case let .string(string):
-            // HACK: ensure the tests support alternate ordering for dictionary explode tests
-            // A PR has been raised to add support for the alternate ordering https://github.com/uri-templates/uritemplate-test/pull/58
-            switch string {
-            case "key1,val1%2F,key2,val2%2F":
-                acceptableExpansions = [string, "key2,val2%2F,key1,val1%2F"]
-            case "#key1,val1%2F,key2,val2%2F":
-                acceptableExpansions = [string, "#key2,val2%2F,key1,val1%2F"]
-            case "key1,val1%252F,key2,val2%252F":
-                acceptableExpansions = [string, "key2,val2%252F,key1,val1%252F"]
-            default:
-                acceptableExpansions = [string]
-            }
+            acceptableExpansions = [string]
             shouldFail = false
         case let .array(array):
             acceptableExpansions = array.compactMap { value in
@@ -143,15 +130,10 @@ public func parseTestFile(URL: URL) -> [TestGroup]? {
     }
 
     return testCollection.map { testGroupName, testGroupData in
-        let variables = testGroupData.variables.mapValues { element in
-            return element.toVariableValue()
-        }.filter { return $0.value != nil }
-            .mapValues { return $0! }
-
         let testcases = testGroupData.testcases.compactMap { element in
             return TestCase(element)
         }
 
-        return TestGroup(name: testGroupName, level: testGroupData.level, variables: variables, testcases: testcases)
+        return TestGroup(name: testGroupName, level: testGroupData.level, variables: testGroupData.variables, testcases: testcases)
     }
 }