glean-core/ios/Glean/Metrics/ObjectMetric.swift

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/// An object that can be serialized into JSON.
///
/// Objects are defined by their structure in the metrics definition.
public protocol ObjectSerialize: Codable, Decodable {
    func intoSerializedObject() -> String
}

extension Array: ObjectSerialize where Element: Codable {
    public func intoSerializedObject() -> String {
        let jsonEncoder = JSONEncoder()
        let jsonData = try! jsonEncoder.encode(self)
        let json = String(data: jsonData, encoding: String.Encoding.utf8)!
        return json
    }
}

/// This implements the developer facing API for the object metric type.
///
/// Instances of this class type are automatically generated by the parsers at built time,
/// allowing developers to record events that were previously registered in the metrics.yaml file.
///
/// The Events API only exposes the `ObjectMetricType.set(obj:)` method, which takes care of validating the input
/// data and making sure that limits are enforced.
public class ObjectMetricType<K: ObjectSerialize> {
    let inner: ObjectMetric

    /// The public constructor used by automatically generated metrics.
    public init(_ meta: CommonMetricData) {
        self.inner = ObjectMetric(meta)
    }

    /// Sets to the associated structure.
    ///
    /// - parameters:
    ///     * object: the object to set.
    public func set(_ object: K) {
        self.inner.setString(object.intoSerializedObject())
    }

    /// Returns the stored value for testing purposes only. This function will attempt to await the
    /// last task (if any) writing to the the metric's storage engine before returning a value.
    ///
    /// - parameters:
    ///     * pingName: represents the name of the ping to retrieve the metric for.
    ///                 Defaults to the first value in `sendInPings`.
    ///
    /// - returns: value of the stored metric decoded into the associated object
    ///            or `nil` if nothing was recorded.
    public func testGetValue(_ pingName: String? = nil) -> K? {
        guard let data = self.inner.testGetValue(pingName) else { return nil }
        let jsonDecoder = JSONDecoder()
        return try! jsonDecoder.decode(K.self, from: Data(data.utf8))
    }

    /// Returns the number of errors recorded for the given metric.
    ///
    /// - parameters:
    ///     * errorType: The type of error recorded.
    ///
    /// - returns: The number of errors recorded for the metric for the given error type.
    public func testGetNumRecordedErrors(_ errorType: ErrorType) -> Int32 {
        return self.inner.testGetNumRecordedErrors(errorType)
    }
}