feature: DateTime timezone support

Author: NeedleInAJayStack

Sources/Haystack/DateTime.swift

@@ -2,25 +2,106 @@ import Foundation
 
 public struct DateTime: Val {
     public static var valType: ValType { .DateTime }
-    public static let gmtName = "GMT"
+    public static let utcName = "UTC"
 
     public let date: Foundation.Date
-    public let timezone: String // TODO: Align with Foundation.TimeZone
+    public let timezone: String
 
-    public init(date: Foundation.Date, timezone: String) {
+    public init(date: Foundation.Date, gmtOffset: Int = 0, timezone: String = Self.utcName) {
         self.date = date
         self.timezone = timezone
     }
 
+    public init(
+        year: Int,
+        month: Int,
+        day: Int,
+        hour: Int = 0,
+        minute: Int = 0,
+        second: Int = 0,
+        millisecond: Int = 0,
+        gmtOffset: Int = 0,
+        timezone: String = Self.utcName
+    ) throws {
+        let components = DateComponents(
+            calendar: calendar,
+            timeZone: .init(secondsFromGMT: gmtOffset),
+            year: year,
+            month: month,
+            day: day,
+            hour: hour,
+            minute: minute,
+            second: second,
+            nanosecond: millisecond * 1_000_000
+        )
+        guard let date = components.date else {
+            throw ValError.invalidDateTimeDefinition
+        }
+        self.date = date
+        self.timezone = timezone
+    }
+    
+    public init(
+        date: Date,
+        time: Time,
+        gmtOffset: Int = 0,
+        timezone: String = Self.utcName
+    ) throws {
+        let components = DateComponents(
+            calendar: calendar,
+            timeZone: .init(secondsFromGMT: gmtOffset),
+            year: date.year,
+            month: date.month,
+            day: date.day,
+            hour: time.hour,
+            minute: time.minute,
+            second: time.second,
+            nanosecond: time.millisecond * 1_000_000
+        )
+        guard let date = components.date else {
+            throw ValError.invalidDateTimeDefinition
+        }
+        self.date = date
+        self.timezone = timezone
+    }
+    
+    public init(_ string: String) throws {
+        let splits = string.split(separator: " ")
+        let dateTimeStr = String(splits[0])
+        self.date = try Self.dateFromString(dateTimeStr)
+        if splits.count > 1 {
+            self.timezone = String(splits[1])
+        } else {
+            self.timezone = Self.utcName
+        }
+    }
+    
     public func toZinc() -> String {
-        let formatter = ISO8601DateFormatter()
-        formatter.formatOptions = [.withInternetDateTime]
-        var zinc = formatter.string(from: date)
-        if timezone != Self.gmtName {
+        var zinc: String
+        if hasMilliseconds {
+            zinc = dateTimeWithMillisFormatter.string(from: date)
+        } else {
+            zinc = dateTimeFormatter.string(from: date)
+        }
+        if timezone != Self.utcName {
             zinc += " \(timezone)"
         }
         return zinc
     }
+    
+    static func dateFromString(_ isoString: String) throws -> Foundation.Date {
+        if let date = dateTimeFormatter.date(from: isoString) {
+            return date
+        } else if let date = dateTimeWithMillisFormatter.date(from: isoString) {
+            return date
+        } else {
+            throw ValError.invalidDateTimeFormat(isoString)
+        }
+    }
+    
+    private var hasMilliseconds: Bool {
+        return calendar.component(.nanosecond, from: date) != 0
+    }
 }
 
 /// Singleton Haystack DateTime formatter
@@ -30,13 +111,15 @@ var dateTimeFormatter: ISO8601DateFormatter {
     return formatter
 }
 
-/// Singleton Haystack DateTime formatter
+/// Singleton Haystack DateTime formatter with fractional second support
 var dateTimeWithMillisFormatter: ISO8601DateFormatter {
     let formatter = ISO8601DateFormatter()
     formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
     return formatter
 }
 
+var calendar = Calendar(identifier: .gregorian)
+
 /// See https://project-haystack.org/doc/docHaystack/Json#dateTime
 extension DateTime {
     static let kindValue = "dateTime"
@@ -69,11 +152,9 @@ extension DateTime {
         }
 
         let isoString = try container.decode(String.self, forKey: .val)
-        if let date = dateTimeFormatter.date(from: isoString) {
-            self.date = date
-        } else if let date = dateTimeWithMillisFormatter.date(from: isoString) {
-            self.date = date
-        } else {
+        do {
+            self.date = try Self.dateFromString(isoString)
+        } catch {
             throw DecodingError.typeMismatch(
                 Self.self,
                 .init(
@@ -83,7 +164,7 @@ extension DateTime {
             )
         }
 
-        let timezone = (try? container.decode(String.self, forKey: .tz)) ?? Self.gmtName
+        let timezone = (try? container.decode(String.self, forKey: .tz)) ?? Self.utcName
         self.timezone = timezone
     }
 
@@ -97,12 +178,8 @@ extension DateTime {
             isoString = dateTimeFormatter.string(from: self.date)
         }
         try container.encode(isoString, forKey: .val)
-        if timezone != DateTime.gmtName {
+        if timezone != DateTime.utcName {
             try container.encode(timezone, forKey: .tz)
         }
     }
-    
-    private var hasMilliseconds: Bool {
-        return date.timeIntervalSinceReferenceDate.remainder(dividingBy: 1.0) != 0.0
-    }
 }

Sources/Haystack/ValError.swift

@@ -2,5 +2,7 @@
 public enum ValError: Error {
     case invalidDateDefinition
     case invalidDateFormat(String)
+    case invalidDateTimeDefinition
+    case invalidDateTimeFormat(String)
     case invalidTimeFormat(String)
 }

Tests/HaystackTests/DateTimeTests.swift

@@ -5,7 +5,7 @@ final class DateTimeTests: XCTestCase {
     func testJsonCoding() throws {
         let value = DateTime(
             date: Date(timeIntervalSince1970: 0.458),
-            timezone: DateTime.gmtName
+            timezone: DateTime.utcName
         )
         let jsonString = #"{"_kind":"dateTime","val":"1970-01-01T00:00:00.458Z"}"#
 
@@ -46,7 +46,7 @@ final class DateTimeTests: XCTestCase {
         XCTAssertEqual(
             DateTime(
                 date: Date(timeIntervalSince1970: 0),
-                timezone: DateTime.gmtName
+                timezone: DateTime.utcName
             ).toZinc(),
             "1970-01-01T00:00:00Z"
         )