From e52f44f168909eb694d1f0c1b4ab17543729620a Mon Sep 17 00:00:00 2001
From: Christoph Hagen <github@christophhagen.de>
Date: Thu, 7 Sep 2023 15:23:44 +0200
Subject: [PATCH] Attempt metric log migration

---
 Package.swift               |  2 +
 Sources/App/configure.swift | 98 +++++++++++++++++++++++++++++++++++++
 2 files changed, 100 insertions(+)

diff --git a/Package.swift b/Package.swift
index 8f28cbd..030677c 100644
--- a/Package.swift
+++ b/Package.swift
@@ -11,6 +11,7 @@ let package = Package(
         .package(url: "https://github.com/christophhagen/Clairvoyant", from: "0.9.0"),
         .package(url: "https://github.com/christophhagen/ClairvoyantVapor", from: "0.2.0"),
         .package(url: "https://github.com/christophhagen/ClairvoyantBinaryCodable", from: "0.3.1"),
+        .package(url:"https://github.com/christophhagen/CBORCoding", from: "1.0.0"),
     ],
     targets: [
         .target(
@@ -20,6 +21,7 @@ let package = Package(
                 .product(name: "Clairvoyant", package: "Clairvoyant"),
                 .product(name: "ClairvoyantVapor", package: "ClairvoyantVapor"),
                 .product(name: "ClairvoyantBinaryCodable", package: "ClairvoyantBinaryCodable"),
+                .product(name: "CBORCoding", package: "CBORCoding")
             ],
             swiftSettings: [
                 // Enable better optimizations when building in Release configuration. Despite the use of
diff --git a/Sources/App/configure.swift b/Sources/App/configure.swift
index 8d7b00a..353a048 100755
--- a/Sources/App/configure.swift
+++ b/Sources/App/configure.swift
@@ -23,6 +23,8 @@ private let dateFormatter: DateFormatter = {
 public func configure(_ app: Application) async throws {
     let storageFolder = URL(fileURLWithPath: app.directory.resourcesDirectory)
     let logFolder = storageFolder.appendingPathComponent("logs")
+    try await migrate(folder: logFolder)
+    fatalError("Done")
 
     let monitor = MetricObserver(logFileFolder: logFolder, logMetricId: "sesame.log")
     MetricObserver.standard = monitor
@@ -86,3 +88,99 @@ func log(_ message: String) {
     }
     observer.log(message)
 }
+
+import CBORCoding
+
+private func migrate(folder: URL) async throws {
+    try await migrateMetric("sesame.log", containing: String.self, in: folder)
+    try await migrateMetric("sesame.status", containing: ServerStatus.self, in: folder)
+    try await migrateMetric("sesame.connected", containing: Bool.self, in: folder)
+    try await migrateMetric("sesame.messages", containing: Int.self, in: folder)
+}
+
+private func migrateMetric<T>(_ id: String, containing type: T.Type, in folder: URL) async throws where T: MetricValue {
+    print("Processing metric \(id)")
+    let file = id.hashed()
+    let url = folder.appendingPathComponent(file)
+
+    let files = try FileManager.default.contentsOfDirectory(at: url, includingPropertiesForKeys: nil)
+        .filter { Int($0.lastPathComponent) != nil }
+    print("Found \(files.count) files for \(id)")
+
+    let all: [Timestamped<T>] = try files.map(readElements(from:))
+        .reduce([], +)
+        .sorted { $0.timestamp < $1.timestamp }
+
+    print("Found \(all.count) items for \(id)")
+
+    try FileManager.default.removeItem(at: url)
+
+    print("Removed log folder")
+
+    // TODO: Write values back to disk
+    let observer = MetricObserver(logFileFolder: folder, logMetricId: "sesame.migration")
+    let metric: Metric<T> = observer.addMetric(id: id)
+    try await metric.update(all)
+
+    print("Finished metric \(id)")
+}
+
+private func readElements<T>(from url: URL) throws -> [Timestamped<T>] where T: MetricValue {
+    let data = try Data(contentsOf: url)
+    let file = url.lastPathComponent
+    print("File \(file): Loaded \(data.count) bytes")
+
+    let decoder = CBORDecoder()
+    let timestampLength = 9
+    let byteCountLength = 2
+
+    var result: [Timestamped<T>] = []
+    var currentIndex = data.startIndex
+    while currentIndex < data.endIndex {
+        let startIndexOfTimestamp = currentIndex + byteCountLength
+        guard startIndexOfTimestamp <= data.endIndex else {
+            print("File \(file): Only \(data.endIndex - currentIndex) bytes, needed \(byteCountLength) for byte count")
+            throw MetricError.logFileCorrupted
+        }
+        guard let byteCount = UInt16(fromData: data[currentIndex..<startIndexOfTimestamp]) else {
+            print("File \(file): Invalid byte count")
+            throw MetricError.logFileCorrupted
+        }
+        let nextIndex = startIndexOfTimestamp + Int(byteCount)
+        guard nextIndex <= data.endIndex else {
+            print("File \(file): Needed \(byteCountLength + Int(byteCount)) for timestamped value, has \(data.endIndex - startIndexOfTimestamp)")
+            throw MetricError.logFileCorrupted
+        }
+        guard byteCount >= timestampLength else {
+            print("File \(file): Only \(byteCount) bytes, needed \(timestampLength) for timestamp")
+            throw MetricError.logFileCorrupted
+        }
+        let timestampData = data[startIndexOfTimestamp..<startIndexOfTimestamp+timestampLength]
+        let timestamp = try decoder.decode(Double.self, from: timestampData)
+        let date = Date(timeIntervalSince1970: timestamp)
+        let elementData = data[currentIndex..<nextIndex]
+        let element: T = try decoder.decode(from: elementData)
+        result.append(.init(value: element, timestamp: date))
+        currentIndex = nextIndex
+        if result.count % 100 == 0 {
+            print("File \(file): \(result.count) entries loaded (\(currentIndex)/\(data.endIndex) bytes)")
+        }
+    }
+    print("Loaded \(result.count) data points")
+    return result
+}
+
+extension UInt16 {
+
+    func toData() -> Data {
+        Data([UInt8(self >> 8 & 0xFF), UInt8(self & 0xFF)])
+    }
+
+    init?<T: DataProtocol>(fromData data: T) {
+        guard data.count == 2 else {
+            return nil
+        }
+        let bytes = Array(data)
+        self = UInt16(UInt32(bytes[0]) << 8 | UInt32(bytes[1]))
+    }
+}