feat: add EventStorage

Sources/Confidence/EventStorage.swift

@@ -0,0 +1,87 @@
+import Foundation
+
+internal protocol EventStorage {
+    func startNewBatch() throws
+    func writeEvent(event: Event) throws
+    func batchReadyFiles() throws -> [URL]
+    func eventsFrom(fileURL: URL) throws -> [Event]
+}
+
+internal class EventStorageImpl: EventStorage {
+    let DIRECTORY = "events"
+    let READYTOSENDEXTENSION = ".ready"
+    let encoder = JSONEncoder()
+    let decoder = JSONDecoder()
+    var folderURL: URL = URL(string: "")!
+    var fileURL: URL = URL(string: "")!
+    var currentBatch: [Event] = []
+
+    init() throws {
+        folderURL = try getFolderURL()
+        fileURL = folderURL.appendingPathComponent("events-\(Date().currentTime)")
+    }
+
+    func startNewBatch() throws {
+        let newPath = URL(string: "\(fileURL)"+"\(READYTOSENDEXTENSION)")!
+        try FileManager.default.moveItem(at: fileURL, to: newPath)
+        fileURL = folderURL.appendingPathComponent("events-\(Date().currentTime)")
+        currentBatch = []
+    }
+
+    func writeEvent(event: Event) throws {
+        currentBatch.append(event)
+        let data = try encoder.encode(currentBatch)
+        try data.write(to: fileURL, options: .atomic)
+    }
+
+    func batchReadyFiles() throws -> [URL] {
+        var readyFilesList: [URL] = []
+        let directoryContents = try FileManager.default.contentsOfDirectory(atPath: folderURL.absoluteString)
+        for file in directoryContents {
+            if file.hasSuffix(READYTOSENDEXTENSION) {
+                readyFilesList.append(URL(string: file)!)
+            }
+        }
+        return readyFilesList
+    }
+
+    func eventsFrom(fileURL: URL) throws -> [Event] {
+        let data = try Data(contentsOf: fileURL)
+        let events = try decoder.decode([Event].self, from: data)
+        return events
+    }
+
+    private func getFolderURL() throws -> URL {
+        let rootFolderURL = try FileManager.default.url(
+            for: .cachesDirectory,
+            in: .userDomainMask,
+            appropriateFor: nil,
+            create: true
+        )
+        var nestedFolderURL: URL
+        if #available(iOS 16.0, *) {
+            nestedFolderURL = rootFolderURL.appending(path: DIRECTORY)
+        } else {
+            nestedFolderURL = rootFolderURL.appendingPathComponent(DIRECTORY, isDirectory: true)
+        }
+        return nestedFolderURL
+    }
+}
+
+struct Event: Codable {
+    let eventDefinition: String
+    let eventTime: Date
+    // TODO: fix this to be ConfidenceValue
+    let payload: [String]
+    let context: [String]
+}
+
+
+extension Date {
+    var currentTime: String {
+        let dateFormatter = DateFormatter()
+        dateFormatter.dateStyle = .short
+        return dateFormatter.string(from: self)
+    }
+}
+