Merge Conflicts (#41)

Co-authored-by: Sayan Datta <sayan@Sayans-MacBook-Air.local>
Reviewed-on: #41

iOS/velocity-ipad/velocity/Core/Math/SunMath.swift

@@ -0,0 +1,134 @@
+import CoreLocation
+import Foundation
+
+struct SunPosition {
+    let azimuth: Double   // 0...360, degrees clockwise from true north
+    let elevation: Double // -90...90 degrees above horizon
+}
+
+enum SunMath {
+
+    // MARK: - Single Position
+
+    static func calculateSunPosition(date: Date, coordinate: CLLocationCoordinate2D) -> SunPosition {
+        let timezone = TimeZone.current
+        let localOffsetHours = Double(timezone.secondsFromGMT(for: date)) / 3600.0
+        let julianDay = date.julianDay
+
+        let n = julianDay - 2_451_545.0
+        let meanLongitude = normalizeDegrees(280.46 + 0.985_647_4 * n)
+        let meanAnomaly   = normalizeDegrees(357.528 + 0.985_600_3 * n)
+
+        let lambda = meanLongitude
+            + 1.915 * sin(meanAnomaly.radians)
+            + 0.020 * sin((2.0 * meanAnomaly).radians)
+        let obliquity = 23.439 - 0.000_000_4 * n
+
+        let rightAscension = atan2(
+            cos(obliquity.radians) * sin(lambda.radians),
+            cos(lambda.radians)
+        ).degrees
+        let declination = asin(sin(obliquity.radians) * sin(lambda.radians)).degrees
+
+        let utcHours = date.utcHours
+        let lst = normalizeDegrees(100.46 + 0.985_647 * n + coordinate.longitude + 15.0 * utcHours + localOffsetHours)
+        let hourAngle = normalizeDegrees(lst - rightAscension)
+        let signedHourAngle = hourAngle > 180.0 ? hourAngle - 360.0 : hourAngle
+
+        let latitude       = coordinate.latitude.radians
+        let declinationRad = declination.radians
+        let hourAngleRad   = signedHourAngle.radians
+
+        let elevation = asin(
+            sin(latitude) * sin(declinationRad)
+            + cos(latitude) * cos(declinationRad) * cos(hourAngleRad)
+        ).degrees
+
+        let azimuth = normalizeDegrees(
+            atan2(
+                -sin(hourAngleRad),
+                tan(declinationRad) * cos(latitude) - sin(latitude) * cos(hourAngleRad)
+            ).degrees
+        )
+
+        return SunPosition(azimuth: azimuth, elevation: elevation)
+    }
+
+    // MARK: - Hourly Arc (used by legacy code & DashedSunLine)
+
+    /// 5-sample dictionary kept for backward compat with the Dollhouse slider.
+    static func sunPathSamples(for date: Date, coordinate: CLLocationCoordinate2D) -> [Date: SunPosition] {
+        let calendar = Calendar.current
+        let sampleHours = [8, 10, 12, 14, 16]
+        var output: [Date: SunPosition] = [:]
+        for hour in sampleHours {
+            if let sampleDate = calendar.date(bySettingHour: hour, minute: 0, second: 0, of: date) {
+                output[sampleDate] = calculateSunPosition(date: sampleDate, coordinate: coordinate)
+            }
+        }
+        return output
+    }
+
+    /// Dense arc for the AR overlay — one sample per hour from 4 AM to 8 PM.
+    /// Filters out below-horizon positions (elevation < -5°).
+    static func sunPathArc(for date: Date, coordinate: CLLocationCoordinate2D) -> [(date: Date, position: SunPosition)] {
+        let calendar = Calendar.current
+        var result: [(Date, SunPosition)] = []
+        for hour in 4...20 {
+            guard let sampleDate = calendar.date(bySettingHour: hour, minute: 0, second: 0, of: date) else { continue }
+            let pos = calculateSunPosition(date: sampleDate, coordinate: coordinate)
+            // include a small below-horizon buffer so arc starts/ends smoothly
+            if pos.elevation > -5 {
+                result.append((sampleDate, pos))
+            }
+        }
+        return result
+    }
+
+    /// Approximate sunrise and sunset by scanning for elevation sign changes.
+    static func sunRiseSet(for date: Date, coordinate: CLLocationCoordinate2D) -> (rise: Date?, set: Date?) {
+        let calendar = Calendar.current
+        var rise: Date? = nil
+        var set: Date? = nil
+        var prevElevation: Double? = nil
+        var prevDate: Date? = nil
+
+        for minuteOffset in stride(from: 0, through: 24 * 60, by: 10) {
+            guard let sampleDate = calendar.date(byAdding: .minute, value: minuteOffset, to: calendar.startOfDay(for: date)) else { continue }
+            let pos = calculateSunPosition(date: sampleDate, coordinate: coordinate)
+            if let prev = prevElevation, let prevD = prevDate {
+                if prev < 0 && pos.elevation >= 0 { rise = prevD }
+                if prev >= 0 && pos.elevation < 0 { set = prevD }
+            }
+            prevElevation = pos.elevation
+            prevDate = sampleDate
+        }
+        return (rise, set)
+    }
+
+    // MARK: - Helpers
+
+    static func normalizeDegrees(_ value: Double) -> Double {
+        let reduced = value.truncatingRemainder(dividingBy: 360.0)
+        return reduced >= 0 ? reduced : reduced + 360.0
+    }
+}
+
+// MARK: - Date helpers
+
+private extension Date {
+    var utcHours: Double {
+        let calendar = Calendar(identifier: .gregorian)
+        let comps = calendar.dateComponents(in: TimeZone(secondsFromGMT: 0)!, from: self)
+        return Double(comps.hour ?? 0) + Double(comps.minute ?? 0) / 60.0 + Double(comps.second ?? 0) / 3600.0
+    }
+
+    var julianDay: Double {
+        timeIntervalSince1970 / 86_400.0 + 2_440_587.5
+    }
+}
+
+private extension Double {
+    var radians: Double { self * .pi / 180.0 }
+    var degrees: Double { self * 180.0 / .pi }
+}