/* 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/. */

package mozilla.components.service.glean

import android.support.annotation.VisibleForTesting
import mozilla.components.service.glean.storages.TimespansStorageEngine
import mozilla.components.support.base.log.logger.Logger

/**
 * This implements the developer facing API for recording timespans.
 *
 * Instances of this class type are automatically generated by the parsers at build time,
 * allowing developers to record values that were previously registered in the metrics.yaml file.
 *
 * The timespans API exposes the [start], [stopAndSum] and [cancel] methods.
 */
data class TimespanMetricType(
    override val disabled: Boolean,
    override val category: String,
    override val lifetime: Lifetime,
    override val name: String,
    override val sendInPings: List<String>,
    val timeUnit: TimeUnit
) : CommonMetricData {

    override val defaultStorageDestinations: List<String> = listOf("metrics")

    private val logger = Logger("glean/TimespanMetricType")

    /**
     * Start tracking time for the provided metric. This records an error if it’s
     * already tracking time (i.e. start was already called with no corresponding
     * [stopAndSum]): in that case the original start time will be preserved.
     */
    fun start() {
        if (!shouldRecord(logger)) {
            return
        }

        TimespansStorageEngine.start(this)
    }

    /**
     * Stop tracking time for the provided metric. Add the elapsed time to the time currently
     * stored in the metric. This will record an error if no [start] was called.
     */
    fun stopAndSum() {
        if (!shouldRecord(logger)) {
            return
        }

        TimespansStorageEngine.stopAndSum(this, timeUnit)
    }

    /**
     * Abort a previous [start] call. No error is recorded if no [start] was called.
     */
    fun cancel() {
        if (!shouldRecord(logger)) {
            return
        }

        TimespansStorageEngine.cancel(this)
    }

    /**
     * Tests whether a value is stored for the metric for testing purposes only
     *
     * @param pingName represents the name of the ping to retrieve the metric for.  Defaults
     *                 to the either the first value in [defaultStorageDestinations] or the first
     *                 value in [sendInPings]
     * @return true if metric value exists, otherwise false
     */
    @VisibleForTesting(otherwise = VisibleForTesting.NONE)
    fun testHasValue(pingName: String = getStorageNames().first()): Boolean {
        return TimespansStorageEngine.getSnapshot(pingName, false)?.get(identifier) != null
    }

    /**
     * Returns the stored value for testing purposes only
     *
     * @param pingName represents the name of the ping to retrieve the metric for.  Defaults
     *                 to the either the first value in [defaultStorageDestinations] or the first
     *                 value in [sendInPings]
     * @return value of the stored metric
     * @throws [NullPointerException] if no value is stored
     */
    @VisibleForTesting(otherwise = VisibleForTesting.NONE)
    fun testGetValue(pingName: String = getStorageNames().first()): Long {
        return TimespansStorageEngine.getSnapshot(pingName, false)!![identifier]!!
    }
}
