Refactoring I.

- Revamp whole DB to Display flow
- Filter Pipeline, arbitrary filtering and sorting
- Binary tree arrays for faster lookup & manipulation
- DB: introducing custom functions
- DB scheme: split req into heap & cache
- cache written by GlassVPN only
- heap written by Main App only
- Introducing DB separation: DBCore, DBCommon, DBAppOnly
- Introducing DB data sources: TestDataSource, GroupedDomainDataSource, RecordingsDB, DomainFilter
- Background sync: Move entries from cache to heap and notify all observers
- GlassVPN: Binary tree filter lookup
- GlassVPN: Reusing prepared statement

main/Data Source/SyncUpdate.swift

@@ -0,0 +1,44 @@
+import Foundation
+
+class SyncUpdate {
+	private var timer: Timer!
+	private var paused: Int = 1 // first start() will decrement
+	private(set) var tsEarliest: Timestamp
+	
+	init(periodic interval: TimeInterval) {
+		tsEarliest = Pref.DateFilter.lastXMinTimestamp() ?? 0
+		NotifyDateFilterChanged.observe(call: #selector(didChangeDateFilter), on: self)
+		timer = Timer.repeating(interval, call: #selector(periodicUpdate), on: self)
+	}
+	
+	@objc private func didChangeDateFilter() {
+		let lastXFilter = Pref.DateFilter.lastXMinTimestamp() ?? 0
+		if tsEarliest < lastXFilter {
+			if let excess = AppDB?.dnsLogsRowRange(between: tsEarliest, and: lastXFilter) {
+				NotifySyncRemove.post(excess)
+			}
+		} else if tsEarliest > lastXFilter {
+			if let missing = AppDB?.dnsLogsRowRange(between: lastXFilter, and: tsEarliest) {
+				NotifySyncInsert.post(missing)
+			}
+		}
+		tsEarliest = lastXFilter
+	}
+	
+	func pause() { paused += 1 }
+	func start() { if paused > 0 { paused -= 1 } }
+	
+	@objc private func periodicUpdate() {
+		guard paused == 0, let db = AppDB else { return }
+		if let inserted = db.dnsLogsPersist() { // move cache -> heap
+			NotifySyncInsert.post(inserted)
+		}
+		if let lastXFilter = Pref.DateFilter.lastXMinTimestamp(), tsEarliest < lastXFilter {
+			if let removed = db.dnsLogsRowRange(between: tsEarliest, and: lastXFilter) {
+				NotifySyncRemove.post(removed)
+			}
+			tsEarliest = lastXFilter
+		}
+		// TODO: periodic hard delete old logs (will reset rowids!)
+	}
+}