/* 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.telemetry.glean.private

import androidx.annotation.VisibleForTesting
import com.sun.jna.StringArray
import mozilla.telemetry.glean.Dispatchers
import mozilla.telemetry.glean.rust.getAndConsumeRustString
import mozilla.telemetry.glean.rust.LibGleanFFI
import mozilla.telemetry.glean.rust.toBoolean
import mozilla.telemetry.glean.rust.toByte
import java.util.UUID

/**
 * This implements the developer facing API for recording UUID metrics.
 *
 * 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 UUID API exposes the [generateAndSet] and [set] methods.
 *
 * The internal constructor is only used by [LabeledMetricType] directly.
 */
class UuidMetricType(
    private var handle: Long,
    private val disabled: Boolean,
    private val sendInPings: List<String>
) {
    /**
     * The public constructor used by automatically generated metrics.
     */
    constructor(
        disabled: Boolean,
        category: String,
        lifetime: Lifetime,
        name: String,
        sendInPings: List<String>
    ) : this(handle = 0, disabled = disabled, sendInPings = sendInPings) {
        val ffiPingsList = StringArray(sendInPings.toTypedArray(), "utf-8")
        this.handle = LibGleanFFI.INSTANCE.glean_new_uuid_metric(
            category = category,
            name = name,
            send_in_pings = ffiPingsList,
            send_in_pings_len = sendInPings.size,
            lifetime = lifetime.ordinal,
            disabled = disabled.toByte())
    }

    /**
     * Generate a new UUID value and set it in the metric store.
     */
    fun generateAndSet(): UUID? {
        // Even if `set` is already checking if we're allowed to record,
        // we need to check here as well otherwise we'd return a `UUID`
        // that won't be stored anywhere.
        if (disabled) {
            return null
        }

        val uuid = UUID.randomUUID()
        set(uuid)
        return uuid
    }

    /**
     * Explicitly set an existing UUID value
     *
     * @param value a valid [UUID] to set the metric to
     */
    fun set(value: UUID) {
        if (disabled) {
            return
        }

        @Suppress("EXPERIMENTAL_API_USAGE")
        Dispatchers.API.launch {
            LibGleanFFI.INSTANCE.glean_uuid_set(
                this@UuidMetricType.handle,
                value.toString())
        }
    }

    /**
     * Explicitly set a value synchronously.
     *
     * This is only to be used for the glean-ac to glean-core data migration.
     */
    internal fun setSync(value: UUID) {
        if (disabled) {
            return
        }

        LibGleanFFI.INSTANCE.glean_uuid_set(
            this@UuidMetricType.handle,
            value.toString())
    }

    /**
     * Tests whether a value is stored for the metric 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.
     *
     * @param pingName represents the name of the ping to retrieve the metric for.
     *                 Defaults to the first value in `sendInPings`.
     * @return true if metric value exists, otherwise false
     */
    @VisibleForTesting(otherwise = VisibleForTesting.NONE)
    @JvmOverloads
    fun testHasValue(pingName: String = sendInPings.first()): Boolean {
        @Suppress("EXPERIMENTAL_API_USAGE")
        Dispatchers.API.assertInTestingMode()

        val res = LibGleanFFI.INSTANCE.glean_uuid_test_has_value(this.handle, pingName)
        return res.toBoolean()
    }

    /**
     * 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.
     *
     * @param pingName represents the name of the ping to retrieve the metric for.
     *                 Defaults to the first value in `sendInPings`.
     * @return value of the stored metric
     * @throws [NullPointerException] if no value is stored
     */
    @VisibleForTesting(otherwise = VisibleForTesting.NONE)
    @JvmOverloads
    fun testGetValue(pingName: String = sendInPings.first()): UUID {
        @Suppress("EXPERIMENTAL_API_USAGE")
        Dispatchers.API.assertInTestingMode()

        if (!testHasValue(pingName)) {
            throw NullPointerException("Metric has no value")
        }
        val ptr = LibGleanFFI.INSTANCE.glean_uuid_test_get_value(this.handle, pingName)!!
        return UUID.fromString(ptr.getAndConsumeRustString())
    }
}
