Add endpoint for fetching subscriber history (#795)

Author: Paul Von Schrottky

CHANGELOG.md

@@ -37,6 +37,7 @@ _None._
 - Add `getPost(withID)` to `PostServiceRemoteExtended` [#785]
 - Add support for metadata to `PostServiceRemoteExtended` [#783]
 - Add fetching of `StatsEmailsSummaryData` to `StatsService` [#794]
+- Add fetching of `StatsSubscribersSummaryData` to `StatsService` [#795]
 
 ### Bug Fixes
 

Sources/WordPressKit/Models/Stats/StatsSubscribersSummaryData.swift

@@ -0,0 +1,85 @@
+import Foundation
+import WordPressShared
+
+public struct StatsSubscribersSummaryData: Equatable {
+    public let history: [SubscriberData]
+    public let period: StatsPeriodUnit
+    public let periodEndDate: Date
+
+    public init(history: [SubscriberData], period: StatsPeriodUnit, periodEndDate: Date) {
+        self.history = history
+        self.period = period
+        self.periodEndDate = periodEndDate
+    }
+}
+
+extension StatsSubscribersSummaryData: StatsTimeIntervalData {
+    public static var pathComponent: String {
+        return "stats/subscribers"
+    }
+
+    static var dateFormatter: DateFormatter = {
+        let df = DateFormatter()
+        df.locale = Locale(identifier: "en_US_POS")
+        df.dateFormat = "yyyy-MM-dd"
+        return df
+    }()
+
+    static var weeksDateFormatter: DateFormatter = {
+        let df = DateFormatter()
+        df.locale = Locale(identifier: "en_US_POS")
+        df.dateFormat = "yyyy'W'MM'W'dd"
+        return df
+    }()
+
+    public struct SubscriberData: Equatable {
+        public let date: Date
+        public let count: Int
+
+        public init(date: Date, count: Int) {
+            self.date = date
+            self.count = count
+        }
+    }
+
+    public init?(date: Date, period: StatsPeriodUnit, jsonDictionary: [String: AnyObject]) {
+        guard
+            let fields = jsonDictionary["fields"] as? [String],
+            let data = jsonDictionary["data"] as? [[Any]],
+            let dateIndex = fields.firstIndex(of: "period"),
+            let countIndex = fields.firstIndex(of: "subscribers")
+        else {
+            return nil
+        }
+
+        let history: [SubscriberData?] = data.map { elements in
+            guard elements.indices.contains(dateIndex) && elements.indices.contains(countIndex),
+                  let dateString = elements[dateIndex] as? String,
+                  let date = StatsSubscribersSummaryData.parsedDate(from: dateString, for: period)
+            else {
+                return nil
+            }
+
+            let count = elements[countIndex] as? Int ?? 0
+
+            return SubscriberData(date: date, count: count)
+        }
+
+        let sorted = history.compactMap { $0 }.sorted { $0.date < $1.date }
+
+        self = .init(history: sorted, period: period, periodEndDate: date)
+    }
+
+    private static func parsedDate(from dateString: String, for period: StatsPeriodUnit) -> Date? {
+        switch period {
+        case .week:
+            return self.weeksDateFormatter.date(from: dateString)
+        case .day, .month, .year:
+            return self.dateFormatter.date(from: dateString)
+        }
+    }
+
+    public static func queryProperties(with date: Date, period: StatsPeriodUnit, maxCount: Int) -> [String: String] {
+        return ["quantity": String(maxCount), "unit": period.stringValue]
+    }
+}

Sources/WordPressKit/Services/StatsServiceRemoteV2.swift

@@ -395,7 +395,7 @@ extension StatsTimeIntervalData {
 
 // We'll bring `StatsPeriodUnit` into this file when the "old" `WPStatsServiceRemote` gets removed.
 // For now we can piggy-back off the old type and add this as an extension.
-extension StatsPeriodUnit {
+public extension StatsPeriodUnit {
     var stringValue: String {
         switch self {
         case .day: