[RFC 9651] Add support for Date type to RawStructuredFieldValues (#41)

Motivation:

[RFC 9651](https://www.ietf.org/rfc/rfc9651.html) added the Date Structured Type.

Modifications:

- Implement the parser and serializer for Date in the RawStructuredFieldValues module.

Result:

The RawStructuredFieldValues module will support the Date type.

Author: clintonpi

Sources/RawStructuredFieldValues/ASCII.swift

@@ -28,6 +28,7 @@ let asciiSemicolon = UInt8(ascii: ";")
 let asciiBackslash = UInt8(ascii: "\\")
 let asciiQuestionMark = UInt8(ascii: "?")
 let asciiExclamationMark = UInt8(ascii: "!")
+let asciiAt = UInt8(ascii: "@")
 let asciiOctothorpe = UInt8(ascii: "#")
 let asciiDollar = UInt8(ascii: "$")
 let asciiPercent = UInt8(ascii: "%")

Sources/RawStructuredFieldValues/ComponentTypes.swift

@@ -107,6 +107,9 @@ extension BareItem {
 
         case .token(let t):
             self = .token(t)
+
+        case .date:
+            throw StructuredHeaderError.invalidItem
         }
     }
 }
@@ -135,6 +138,9 @@ public enum RFC9651BareItem: Sendable {
 
     /// A token item.
     case token(String)
+
+    /// A date item.
+    case date(Int)
 }
 
 extension RFC9651BareItem: ExpressibleByBooleanLiteral {

Sources/RawStructuredFieldValues/Errors.swift

@@ -26,6 +26,7 @@ public struct StructuredHeaderError: Error, Sendable {
         case invalidByteSequence
         case invalidBoolean
         case invalidToken
+        case invalidDate
         case invalidList
         case invalidDictionary
         case missingKey
@@ -51,6 +52,7 @@ extension StructuredHeaderError {
     public static let invalidByteSequence = StructuredHeaderError(.invalidByteSequence)
     public static let invalidBoolean = StructuredHeaderError(.invalidBoolean)
     public static let invalidToken = StructuredHeaderError(.invalidToken)
+    public static let invalidDate = StructuredHeaderError(.invalidDate)
     public static let invalidList = StructuredHeaderError(.invalidList)
     public static let invalidDictionary = StructuredHeaderError(.invalidDictionary)
     public static let missingKey = StructuredHeaderError(.missingKey)

Sources/RawStructuredFieldValues/FieldParser.swift

@@ -213,7 +213,7 @@ extension StructuredFieldValueParser {
 
         switch first {
         case asciiDash, asciiDigits:
-            return try self._parseAnIntegerOrDecimal()
+            return try self._parseAnIntegerOrDecimal(isDate: false)
         case asciiDquote:
             return try self._parseAString()
         case asciiColon:
@@ -222,12 +222,14 @@ extension StructuredFieldValueParser {
             return try self._parseABoolean()
         case asciiCapitals, asciiLowercases, asciiAsterisk:
             return try self._parseAToken()
+        case asciiAt:
+            return try self._parseADate()
         default:
             throw StructuredHeaderError.invalidItem
         }
     }
 
-    private mutating func _parseAnIntegerOrDecimal() throws -> RFC9651BareItem {
+    private mutating func _parseAnIntegerOrDecimal(isDate: Bool) throws -> RFC9651BareItem {
         var sign = 1
         var type = IntegerOrDecimal.integer
 
@@ -248,10 +250,19 @@ extension StructuredFieldValueParser {
                 // Do nothing
                 ()
             case asciiPeriod where type == .integer:
+                // If output_date is decimal, fail parsing.
+                if isDate {
+                    throw StructuredHeaderError.invalidDate
+                }
+
                 // If input_number contains more than 12 characters, fail parsing. Otherwise,
                 // set type to decimal and consume.
                 if self.underlyingData.distance(from: self.underlyingData.startIndex, to: index) > 12 {
-                    throw StructuredHeaderError.invalidIntegerOrDecimal
+                    if isDate {
+                        throw StructuredHeaderError.invalidDate
+                    } else {
+                        throw StructuredHeaderError.invalidIntegerOrDecimal
+                    }
                 }
                 type = .decimal
             default:
@@ -268,9 +279,15 @@ extension StructuredFieldValueParser {
             switch type {
             case .integer:
                 if count > 15 {
-                    throw StructuredHeaderError.invalidIntegerOrDecimal
+                    if isDate {
+                        throw StructuredHeaderError.invalidDate
+                    } else {
+                        throw StructuredHeaderError.invalidIntegerOrDecimal
+                    }
                 }
             case .decimal:
+                assert(isDate == false)
+
                 if count > 16 {
                     throw StructuredHeaderError.invalidIntegerOrDecimal
                 }
@@ -286,7 +303,13 @@ extension StructuredFieldValueParser {
             // This intermediate string is sad, we should rewrite this manually to avoid it.
             // This force-unwrap is safe, as we have validated that all characters are ascii digits.
             let baseInt = Int(String(decoding: integerBytes, as: UTF8.self), radix: 10)!
-            return .integer(baseInt * sign)
+            let resultingInt = baseInt * sign
+
+            if isDate {
+                return .date(resultingInt)
+            } else {
+                return .integer(resultingInt)
+            }
         case .decimal:
             // This must be non-nil, otherwise we couldn't have flipped to the decimal type.
             let periodIndex = integerBytes.firstIndex(of: asciiPeriod)!
@@ -459,6 +482,12 @@ extension StructuredFieldValueParser {
         return .token(String(decoding: tokenSlice, as: UTF8.self))
     }
 
+    private mutating func _parseADate() throws -> RFC9651BareItem {
+        assert(self.underlyingData.first == asciiAt)
+        self.underlyingData.consumeFirst()
+        return try self._parseAnIntegerOrDecimal(isDate: true)
+    }
+
     private mutating func _parseParameters() throws -> OrderedMap<Key, RFC9651BareItem> {
         var parameters = OrderedMap<Key, RFC9651BareItem>()
 

Sources/RawStructuredFieldValues/FieldSerializer.swift

@@ -204,6 +204,15 @@ extension StructuredFieldValueSerializer {
             self.data.append(asciiQuestionMark)
             let character = bool ? asciiOne : asciiZero
             self.data.append(character)
+        case .date(let date):
+            self.data.append(asciiAt)
+
+            // Then, serialize as integer.
+            guard let wideInt = Int64(exactly: date), validIntegerRange.contains(wideInt) else {
+                throw StructuredHeaderError.invalidDate
+            }
+
+            self.data.append(contentsOf: String(date, radix: 10).utf8)
         }
     }
 }

Sources/sh-parser/main.swift

@@ -166,6 +166,8 @@ extension RFC9651BareItem {
             let d = Decimal(sign: decimal.mantissa > 0 ? .plus : .minus,
                             exponent: Int(decimal.exponent), significand: Decimal(decimal.mantissa))
             return "decimal \(d)"
+        case .date(let date):
+            return "date \(date)"
         }
     }
 }

Tests/StructuredFieldValuesTests/StructuredFieldParserTests.swift

@@ -60,6 +60,14 @@ final class StructuredFieldParserTests: XCTestCase {
             XCTAssertEqual(decodedValue, decodedExpected, "\(fixtureName): Got \(Array(decodedValue)), expected \(Array(decodedExpected))")
         case (.bool(let baseBool), .bool(let expectedBool)):
             XCTAssertEqual(baseBool, expectedBool, "\(fixtureName): Got \(baseBool), expected \(expectedBool)")
+        case(.date(let baseDate), .dictionary(let typeDictionary)):
+            guard typeDictionary.count == 2, case .string(let typeName) = typeDictionary["__type"], case .integer(let typeValue) = typeDictionary["value"] else {
+                XCTFail("\(fixtureName): Unexpected type dict \(typeDictionary)")
+                return
+            }
+
+            XCTAssertEqual(typeName, "date", "\(fixtureName): Expected type date, got type \(typeName)")
+            XCTAssertEqual(typeValue, baseDate, "\(fixtureName): Got \(baseDate), expected \(typeValue)")
         default:
             XCTFail("\(fixtureName): Got \(bareItem), expected \(schema)")
         }

Tests/StructuredFieldValuesTests/StructuredFieldSerializerTests.swift

@@ -198,6 +198,9 @@ extension RFC9651BareItem {
                 let expectedBase64Bytes = Data(base32Encoded: Data(value.utf8)).base64EncodedString()
                 self = .undecodedByteSequence(expectedBase64Bytes)
 
+            case (.some(.string("date")), .some(.integer(let value))):
+                self = .date(value)
+
             default:
                 preconditionFailure("Unexpected type object \(typeObject)")
             }

Tests/TestFixtures/date.json

@@ -0,0 +1,38 @@
+[
+    {
+        "name": "date - 1970-01-01 00:00:00",
+        "raw": ["@0"],
+        "header_type": "item",
+        "expected": [{"__type": "date", "value": 0}, {}]
+    },
+    {
+        "name": "date - 2022-08-04 01:57:13",
+        "raw": ["@1659578233"],
+        "header_type": "item",
+        "expected": [{"__type": "date", "value": 1659578233}, {}]
+    },
+    {
+        "name": "date - 1917-05-30 22:02:47",
+        "raw": ["@-1659578233"],
+        "header_type": "item",
+        "expected": [{"__type": "date", "value": -1659578233}, {}]
+    },
+    {
+        "name": "date - 2^31",
+        "raw": ["@2147483648"],
+        "header_type": "item",
+        "expected": [{"__type": "date", "value": 2147483648}, {}]
+    },
+    {
+        "name": "date - 2^32",
+        "raw": ["@4294967296"],
+        "header_type": "item",
+        "expected": [{"__type": "date", "value": 4294967296}, {}]
+    },
+    {
+        "name": "date - decimal",
+        "raw": ["@1659578233.12"],
+        "header_type": "item",
+        "must_fail": true
+    }
+]