commonMain.aws.sdk.kotlin.runtime.region.RegionProviderChain.kt Maven / Gradle / Ivy

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/*
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */

package aws.sdk.kotlin.runtime.region

import aws.smithy.kotlin.runtime.telemetry.logging.logger
import aws.smithy.kotlin.runtime.util.asyncLazy
import kotlin.coroutines.coroutineContext

/**
 * Composite [RegionProvider] that delegates to a chain of providers.
 * [providers] are consulted in the order given and the first region found is returned
 *
 * @param providers the list of providers to delegate to
 */
public open class RegionProviderChain(
    protected vararg val providers: RegionProvider,
) : RegionProvider {

    public constructor(providers: List) : this(*providers.toTypedArray())

    private val resolvedRegion = asyncLazy(::resolveRegion)

    init {
        require(providers.isNotEmpty()) { "at least one provider must be in the chain" }
    }

    override fun toString(): String =
        (listOf(this) + providers).map { it::class.simpleName }.joinToString(" -> ")

    override suspend fun getRegion(): String? = resolvedRegion.get()

    private suspend fun resolveRegion(): String? {
        val logger = coroutineContext.logger()
        for (provider in providers) {
            try {
                val region = provider.getRegion()
                if (region != null) {
                    logger.debug { "resolved region ($region) from $provider " }
                    return region
                }
                logger.debug { "failed to resolve region from $provider" }
            } catch (ex: Exception) {
                logger.debug { "unable to load region from $provider: ${ex.message}" }
            }
        }

        return null
    }
}