// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//
// snippet-start:[swift.rds.scenario]
// An example that shows how to use the AWS SDK for Swift to perform a variety
// of operations using Amazon Relational Database Service (RDS).
//

import ArgumentParser
import Foundation
// snippet-start:[swift.rds.import]
import AWSRDS
// snippet-end:[swift.rds.import]

struct ExampleCommand: ParsableCommand {
    @Option(help: "The AWS Region to run AWS API calls in.")
    var awsRegion = "us-east-1"
    @Option(help: "The username to use for the database administrator.")
    var dbUsername = "admin"
    @Option(help: "The password to use for the database administrator.")
    var dbPassword: String

    static var configuration = CommandConfiguration(
        commandName: "rds-scenario",
        abstract: """
        Performs various operations to demonstrate the use of Amazon RDS Instances
        using the AWS SDK for Swift.
        """,
        discussion: """
        """
    )

    /// Called by ``main()`` to run the bulk of the example.
    func runAsync() async throws {
        let example = try await Example(region: awsRegion, username: dbUsername, password: dbPassword)

        await example.run()
    }
}

class Example {
    let rdsClient: RDSClient

    // Storage for AWS RDS properties

    let dbUsername: String
    let dbPassword: String
    var dbInstanceIdentifier: String
    var dbSnapshotIdentifier: String
    var dbParameterGroupName: String
    var dbParameterGroup: RDSClientTypes.DBParameterGroup?
    var selectedEngineVersion: String?

    init(region: String, username: String, password: String) async throws{
        let rdsConfig = try await RDSClient.RDSClientConfiguration(region: region)
        rdsClient = RDSClient(config: rdsConfig)

        dbUsername = username
        dbPassword = password
        dbParameterGroupName = ""
        dbInstanceIdentifier = ""
        dbSnapshotIdentifier = ""
    }

    /// The example's main body.
    func run() async {
        var parameterGroupFamilies: Set<String> = []

        //=====================================================================
        // 1. Get available database engine families for MySQL.
        //=====================================================================

        let engineVersions = await getDBEngineVersions(engineName: "mysql")

        for version in engineVersions {
            if version.dbParameterGroupFamily != nil {
                parameterGroupFamilies.insert(version.dbParameterGroupFamily!)
            }
        }

        if engineVersions.count > 0 {
            selectedEngineVersion = engineVersions.last!.engineVersion
        } else {
            print("*** Unable to find a valid database engine version. Canceling operations.")
            await cleanUp()
            return
        }

        print("Found \(parameterGroupFamilies.count) parameter group families:")
        for family in parameterGroupFamilies {
            print("    \(family)")
        }

        //=====================================================================
        // 2. Select an engine family and create a custom DB parameter group.
        //    We select a family by sorting the set of family names, then
        //    choosing the last one.
        //=====================================================================

        let sortedFamilies = parameterGroupFamilies.sorted()

        guard let selectedFamily = sortedFamilies.last else {
            print("*** Unable to find a database engine family. Canceling operations.")
            await cleanUp()
            return
        }

        print("Selected database engine family \(selectedFamily)")

        dbParameterGroupName = tempName(prefix: "rds-example")
        print("Creating a database parameter group named \(dbParameterGroupName) using \(selectedFamily)")
        dbParameterGroup = await createDBParameterGroup(groupName: dbParameterGroupName,
                                                        familyName: selectedFamily)

        //=====================================================================
        // 3. Get the parameter group's details.
        //=====================================================================

        print("Getting the database parameter group list...")
        let dbParameterGroupList = await describeDBParameterGroups(groupName: dbParameterGroupName)
        guard let dbParameterGroupList else {
            await cleanUp()
            return
        }

        print("Found \(dbParameterGroupList.count) parameter groups...")
        for group in dbParameterGroupList {
            print("    \(group.dbParameterGroupName ?? "<unknown>")")
        }
        print()

        //=====================================================================
        // 4. Get a list of the parameter group's parameters. This list is
        //    likely to be long, so use pagination. Find the
        //    auto_increment_offset and auto_increment_increment parameters.
        //=====================================================================

        let parameters = await describeDBParameters(groupName: dbParameterGroupName)
        
        //=====================================================================
        // 5. Parse and display each parameter's name, description, and
        //    allowed values.
        //=====================================================================

        for parameter in parameters {
            let name = parameter.parameterName
            guard let name else {
                print("*** Unable to get parameter name!")
                continue
            }

            if name == "auto_increment_offset" || name == "auto_increment_increment" {
                print("Parameter \(name):")
                print("          Value: \(parameter.parameterValue ?? "<undefined>")")
                print("      Data type: \(parameter.dataType ?? "<unknown>")")
                print("    Description: \(parameter.description ?? "")")
                print(" Allowed values: \(parameter.allowedValues ?? "<unspecified")")
                print(String(repeating: "=", count: 78))
            }
        }

        //=====================================================================
        // 6. Modify both the auto_increment_offset and
        //    auto_increment_increment parameters in one call in the custom
        //    parameter group. Set their parameterValue fields to a new
        //    permitted value.
        //=====================================================================

        print("Setting auto_increment_offset and auto_increment_increment both to 5...")
        await modifyDBParameters(groupName: dbParameterGroupName)

        //=====================================================================
        // 7. Get and display the updated parameters, specifying a source of
        //    "user" to get only the modified parameters.
        //=====================================================================

        let updatedParameters = await describeDBParameters(groupName: dbParameterGroupName, source: "user")

        for parameter in updatedParameters {
            let name = parameter.parameterName
            guard let name else {
                print("*** Unable to get parameter name!")
                continue
            }

            print("Parameter \(name):")
            print("          Value: \(parameter.parameterValue ?? "<undefined>")")
            print("      Data type: \(parameter.dataType ?? "<unknown>")")
            print("    Description: \(parameter.description ?? "")")
            print(" Allowed values: \(parameter.allowedValues ?? "<unspecified")")
            print(String(repeating: "=", count: 78))
        }

        //=====================================================================
        // 8. Get a list of allowed engine versions using
        //    DescribeRDSEngineVersions.
        //=====================================================================

        await listAllowedEngines(family: selectedFamily)

        //=====================================================================
        // 9. Get a list of micro instance classes available for the selected
        //    engine and engine version.
        //=====================================================================

        let dbInstanceClass = await chooseMicroInstance(engine: "mysql", engineVersion: selectedEngineVersion)
        guard let dbInstanceClass else {
            print("Did not get a valid instance class. Canceling operations.")
            await cleanUp()
            return
        }

        //=====================================================================
        // 10. Create an RDS database that contains a MySQL database and uses
        //     the parameter group we created.
        //=====================================================================
        
        print("Creating the database instance...")

        guard let instanceClass = dbInstanceClass.dbInstanceClass else {
            print("Instance class name is unknown. Canceling operations.")
            await cleanUp()
            return
        }

        dbInstanceIdentifier = tempName(prefix: "sample-identifier")
        let dbInstanceArn = await createDBInstance(
            name: "SampleDatabase\(Int.random(in: 1000000..<1000000000))",
            instanceIdentifier: dbInstanceIdentifier,
            parameterGroupName: dbParameterGroupName,
            engine: "mysql",
            engineVersion: selectedEngineVersion!,
            instanceClass: instanceClass,
            username: dbUsername,
            password: dbPassword
        )

        if dbInstanceArn == nil {
            await cleanUp()
            return
        }

        //=====================================================================
        // 11. Wait for the database instance to be ready by calling
        //     DescribeDBInstances repeatedly until it reports
        //     dbInstanceStatus as "available". This can take upwards of 10
        //     minutes, let the user know that.
        //=====================================================================

        guard let endpoint = await waitUntilDBInstanceReady(instanceIdentifier: dbInstanceIdentifier) else {
            print("\nDid not get a valid endpoint from AWS RDS.")
            await cleanUp()
            return
        }
        
        guard let endpointAddress = endpoint.address else {
            print("\nNo endpoint address returned.")
            await cleanUp()
            return
        }
        guard let endpointPort = endpoint.port else {
            print("\nNo endpoint port returned.")
            await cleanUp()
            return
        }

        //=====================================================================
        // 12. Display connection information for the database instance.
        //=====================================================================

        print("\nTo connect to the new database instance using 'mysql' from the shell:")
        print("    mysql -h \(endpointAddress) -P \(endpointPort) -u \(self.dbUsername)")

        //=====================================================================
        // 13. Create a snapshot of the database instance.
        //=====================================================================

        dbSnapshotIdentifier = tempName(prefix: "sample-snapshot")
        await createDBSnapshot(instanceIdentifier: dbInstanceIdentifier, snapshotIdentifier: dbSnapshotIdentifier)

        //=====================================================================
        // 14. Wait for the snapshot to be ready.
        //=====================================================================

        await waitUntilDBSnapshotReady(instanceIdentifier: dbInstanceIdentifier, snapshotIdentifier: dbSnapshotIdentifier)

        // That's it! Clean up and exit!

        print("Example complete! Cleaning up...")
        await cleanUp()
    }

    /// Clean up by discarding and closing down all allocated EC2 items. 
    func cleanUp() async {
        print("Deleting the database instance \(dbInstanceIdentifier)...")
        await deleteDBInstance(instanceIdentifier: dbInstanceIdentifier)
        await waitUntilDBInstanceDeleted(instanceIdentifier: dbInstanceIdentifier)

        print("Deleting the database parameter group \(dbParameterGroupName)...")
        await deleteDBParameterGroup(groupName: dbParameterGroupName)
    }

    // snippet-start:[swift.rds.DescribeDBEngineVersions]
    /// Get all the database engine versions available for the specified
    /// database engine.
    /// 
    /// - Parameter engineName: The name of the database engine to query.
    /// 
    /// - Returns: An array of `RDSClientTypes.DBEngineVersion` structures,
    ///   each describing one supported version of the specified database.
    func getDBEngineVersions(engineName: String) async -> [RDSClientTypes.DBEngineVersion] {
        do {
            let output = try await rdsClient.describeDBEngineVersions(
                input: DescribeDBEngineVersionsInput(
                    engine: engineName
                )
            )

            return output.dbEngineVersions ?? []
        } catch {
            return []
        }
    }
    // snippet-end:[swift.rds.DescribeDBEngineVersions]

    // snippet-start:[swift.rds.CreateDBParameterGroup]
    /// Create a new database parameter group with the specified name.
    /// 
    /// - Parameters:
    ///   - groupName: The name of the new parameter group.
    ///   - familyName: The name of the parameter group family.
    /// - Returns: 
    func createDBParameterGroup(groupName: String, familyName: String) async -> RDSClientTypes.DBParameterGroup? {
        do {
            let output = try await rdsClient.createDBParameterGroup(
                input: CreateDBParameterGroupInput(
                    dbParameterGroupFamily: familyName,
                    dbParameterGroupName: groupName,
                    description: "Created using the AWS SDK for Swift"
                )
            )
            return output.dbParameterGroup
        } catch {
            print("*** Error creating the parameter group: \(error.localizedDescription)")
            return nil
        }
    }
    // snippet-end:[swift.rds.CreateDBParameterGroup]

    // snippet-start:[swift.rds.DescribeDBParameterGroups]
    /// Get descriptions of the database parameter groups matching the given
    /// name.
    ///
    /// - Parameter groupName: The name of the parameter group to describe.
    /// 
    /// - Returns: An array of [RDSClientTypes.DBParameterGroup] objects
    ///   describing the parameter group.
    func describeDBParameterGroups(groupName: String) async -> [RDSClientTypes.DBParameterGroup]? {
        do {
            let output = try await rdsClient.describeDBParameterGroups(
                input: DescribeDBParameterGroupsInput(
                    dbParameterGroupName: groupName
                )
            )
            return output.dbParameterGroups
        } catch {
            print("*** Error getting the database parameter group's details: \(error.localizedDescription)")
            return nil
        }
    }
    // snippet-end:[swift.rds.DescribeDBParameterGroups]

    // snippet-start:[swift.rds.DescribeDBParametersPaginated]
    // snippet-start:[swift.rds.DescribeDBParameters]
    /// Returns the detailed parameter list for the specified database
    /// parameter group.
    /// 
    /// - Parameters:
    ///   - groupName: The name of the parameter group to return parameters for.
    ///   - source: The types of parameters to return (`user`, `system`, or
    ///     `engine-default`).
    /// 
    /// - Returns: An array of `RdSClientTypes.Parameter` objects, each
    ///   describing one of the group's parameters.
    func describeDBParameters(groupName: String, source: String? = nil) async -> [RDSClientTypes.Parameter] {
        var parameterList: [RDSClientTypes.Parameter] = []

        do {
            let pages = rdsClient.describeDBParametersPaginated(
                input: DescribeDBParametersInput(
                    dbParameterGroupName: groupName,
                    source: source
                )
            )

            for try await page in pages {
                guard let parameters = page.parameters else {
                    return []
                }

                parameterList += parameters
            }
        } catch {
            print("*** Error getting database parameters: \(error.localizedDescription)")
            return []
        }

        return parameterList
    }
    // snippet-end:[swift.rds.DescribeDBParameters]
    // snippet-end:[swift.rds.DescribeDBParametersPaginated]

    // snippet-start:[swift.rds.ModifyDBParameterGroup]
    /// Demonstrates modifying two of the specified database parameter group's
    /// parameters.
    /// 
    /// - Parameter groupName: The name of the parameter group to change
    ///   parameters for.
    func modifyDBParameters(groupName: String) async {
        let parameter1 = RDSClientTypes.Parameter(
            applyMethod: RDSClientTypes.ApplyMethod.immediate,
            parameterName: "auto_increment_offset",
            parameterValue: "5"
        )
        let parameter2 = RDSClientTypes.Parameter(
            applyMethod: RDSClientTypes.ApplyMethod.immediate,
            parameterName: "auto_increment_increment",
            parameterValue: "5"
        )

        let parameterList = [parameter1, parameter2]

        do {
            _ = try await rdsClient.modifyDBParameterGroup(
                input: ModifyDBParameterGroupInput(
                    dbParameterGroupName: groupName,
                    parameters: parameterList
                )
            )

            print("Successfully modified the parameter group \(groupName).")
        } catch {
            print("*** Error modifying the parameter group \(groupName): \(error.localizedDescription)")
        }
    }
    // snippet-end:[swift.rds.ModifyDBParameterGroup]

    /// Output a list of the database engine versions supported by the
    /// specified family.
    /// 
    /// - Parameter family: The family for which to list allowed database
    ///   engines.
    func listAllowedEngines(family: String?) async {
        do {
            let output = try await rdsClient.describeDBEngineVersions(
                input: DescribeDBEngineVersionsInput(
                    dbParameterGroupFamily: family,
                    engine: "mysql"
                )
            )

            guard let engineVersions = output.dbEngineVersions else {
                print("No engine versions returned.")
                return
            }

            print("Found \(engineVersions.count) database engine versions:")
            for version in engineVersions {
                print("    \(version.engineVersion ?? "<unknown>"): \(version.dbEngineDescription ?? "")")
            }
        } catch {
            print("*** Error getting database engine version list: \(error.localizedDescription)")
            return
        }
    }

    // snippet-start:[swift.rds.DescribeOrderableDBInstanceOptionsPaginated]
    // snippet-start:[swift.rds.DescribeOrderableDBInstanceOptions]
    /// Print a list of available database instances with "micro" in the class
    /// name, then return one of them to be used by other code.
    /// 
    /// - Parameters:
    ///   - engine: The database engine for which to list database instance
    ///     classes.
    ///   - engineVersion: The database version for which to list instances.
    /// 
    /// - Returns: An `RDSClientTypes.OrderableDBInstanceOption` describing
    ///   the selected instance type.
    func chooseMicroInstance(engine: String = "mysql", engineVersion: String? = nil) async -> RDSClientTypes.OrderableDBInstanceOption? {
        do {
            let pages = rdsClient.describeOrderableDBInstanceOptionsPaginated(
                input: DescribeOrderableDBInstanceOptionsInput(
                    engine: engine,
                    engineVersion: engineVersion
                )
            )

            var optionsList: [RDSClientTypes.OrderableDBInstanceOption] = []

            for try await page in pages {
                guard let orderableDBInstanceOptions = page.orderableDBInstanceOptions else {
                    continue
                }

                for dbInstanceOption in orderableDBInstanceOptions {
                    guard let className = dbInstanceOption.dbInstanceClass else {
                        continue
                    }
                    if className.contains("micro") {
                        optionsList.append(dbInstanceOption)
                    }
                }
            }

            print("Found \(optionsList.count) database instances of 'micro' class types:")
            for dbInstanceOption in optionsList {
                print("    \(dbInstanceOption.engine ?? "<unknown>") \(dbInstanceOption.engineVersion ?? "<unknown>") (\(dbInstanceOption.dbInstanceClass ?? "<unknown class>"))")
            }

            return optionsList[0]
        } catch {
            print("*** Error getting a list of orderable instance options: \(error.localizedDescription)")
            return nil
        }
    }
    // snippet-end:[swift.rds.DescribeOrderableDBInstanceOptions]
    // snippet-end:[swift.rds.DescribeOrderableDBInstanceOptionsPaginated]

    // snippet-start:[swift.rds.CreateDBInstance]
    /// Create a new database instance.
    /// 
    /// - Parameters:
    ///   - name: The name of the database to create.
    ///   - instanceIdentifier: The identifier to give the new database
    ///     instance.
    ///   - parameterGroupName: The name of the parameter group to associate
    ///     with the new database instance.
    ///   - engine: The database engine to use.
    ///   - engineVersion: The version of the database given by `engine` to
    ///     use.
    ///   - instanceClass: The memory and compute capacity of the database
    ///     instance, such as `db.m5.large``.
    ///   - username: The admin user's username to establish for the new
    ///     instance.
    ///   - password: The password to use for the specified user's access.
    /// 
    /// - Returns: A string indicating the ARN of the newly created database
    ///   instance, or nil if the instance couldn't be created.
    func createDBInstance(name: String, instanceIdentifier: String, parameterGroupName: String,
                          engine: String, engineVersion: String, instanceClass: String,
                          username: String, password: String) async -> String? {
        do {
            let output = try await rdsClient.createDBInstance(
                input: CreateDBInstanceInput(
                    allocatedStorage: 100,
                    dbInstanceClass: instanceClass,
                    dbInstanceIdentifier: instanceIdentifier,
                    dbName: name,
                    dbParameterGroupName: parameterGroupName,
                    engine: engine,
                    engineVersion: engineVersion,
                    masterUserPassword: password,
                    masterUsername: username,
                    storageType: "gp2"
                )
            )

            guard let dbInstance = output.dbInstance else {
                print("*** Unable to get the database instance.")
                return nil
            }

            return dbInstance.dbInstanceArn
        } catch {
            print("*** An error occurred while creating the database instance: \(error.localizedDescription)")
            return nil
        }
    }
    // snippet-end:[swift.rds.CreateDBInstance]

    // snippet-start:[swift.rds.DescribeDBInstances]
    /// Wait until the specified database is available to use.
    ///
    /// - Parameter instanceIdentifier: The database instance identifier of the
    ///   database to wait for.
    func waitUntilDBInstanceReady(instanceIdentifier: String) async -> RDSClientTypes.Endpoint? {
        do {
            putString("Waiting for the database instance to be ready to use. This may take 10 minutes or more...")
            while true {
                let output = try await rdsClient.describeDBInstances(
                    input: DescribeDBInstancesInput(
                        dbInstanceIdentifier: instanceIdentifier
                    )
                )

                guard let instanceList = output.dbInstances else {
                    continue
                }

                for instance in instanceList {
                    let status = instance.dbInstanceStatus

                    guard let status else {
                        print("\nUnable to determine the status.")
                        continue
                    }

                    if status.contains("available") {
                        return instance.endpoint
                    } else {
                        putString(".")
                        do {
                            try await Task.sleep(for: .seconds(15))
                        } catch {
                            print("*** Error pausing the task!")
                        }
                    }
                }
            }
        } catch {
            print("*** Unable to wait until the database is ready: \(error.localizedDescription)")
            return nil
        }
    }
    // snippet-end:[swift.rds.DescribeDBInstances]

    // snippet-start:[swift.rds.CreateDBSnapshot]
    /// Create a snapshot of the specified name.
    /// 
    /// - Parameters:
    ///   - instanceIdentifier: The identifier of the database instance to
    ///     snapshot.
    ///   - snapshotIdentifier: A unique identifier to give the newly-created
    ///     snapshot.
    func createDBSnapshot(instanceIdentifier: String, snapshotIdentifier: String) async {
        do {
            let output = try await rdsClient.createDBSnapshot(
                input: CreateDBSnapshotInput(
                    dbInstanceIdentifier: instanceIdentifier,
                    dbSnapshotIdentifier: snapshotIdentifier
                )
            )

            guard let snapshot = output.dbSnapshot else {
                print("No snapshot returned.")
                return
            }

            print("The snapshot has been created with ID \(snapshot.dbiResourceId ?? "<unknown>")")
        } catch {
            print("*** Unable to create the database snapshot named \(snapshotIdentifier): \(error.localizedDescription)")
        }
    }
    // snippet-end:[swift.rds.CreateDBSnapshot]

    // snippet-start:[swift.rds.DescribeDBSnapshots]
    /// Wait until the specified database snapshot is available to use.
    /// 
    /// - Parameters:
    ///   - instanceIdentifier: The identifier of the database for which the
    ///     snapshot was taken.
    ///   - snapshotIdentifier: The identifier of the snapshot to wait for.
    func waitUntilDBSnapshotReady(instanceIdentifier: String, snapshotIdentifier: String) async {
        var snapshotReady = false

        putString("Waiting for the snapshot to be ready...")

        do {
            while !snapshotReady {
                let output = try await rdsClient.describeDBSnapshots(
                    input: DescribeDBSnapshotsInput(
                        dbInstanceIdentifier: instanceIdentifier,
                        dbSnapshotIdentifier: snapshotIdentifier
                    )
                )

                guard let snapshotList = output.dbSnapshots else {
                    return
                }

                for snapshot in snapshotList {
                    guard let snapshotReadyStr = snapshot.status else {
                        return
                    }

                    if snapshotReadyStr.contains("available") {
                        snapshotReady = true
                        print()
                    } else {
                        putString(".")
                        do {
                            try await Task.sleep(for: .seconds(15))
                        } catch {
                            print("\n*** Error pausing the task!")
                        }
                    }
                }
            }
        } catch {
            print("\n*** Unable to wait for the database snapshot to be ready: \(error.localizedDescription)")
        }
    }
    // snippet-end:[swift.rds.DescribeDBSnapshots]

    // snippet-start:[swift.rds.DeleteDBInstance]
    /// Delete the specified database instance.
    /// 
    /// - Parameter instanceIdentifier: The identifier of the database
    ///   instance to delete.
    func deleteDBInstance(instanceIdentifier: String) async {
        do {
            _ = try await rdsClient.deleteDBInstance(
                input: DeleteDBInstanceInput(
                    dbInstanceIdentifier: instanceIdentifier,
                    deleteAutomatedBackups: true,
                    skipFinalSnapshot: true
                )
            )
        } catch {
            print("*** Error deleting the database instance \(instanceIdentifier): \(error.localizedDescription)")
        }
    }
    // snippet-end:[swift.rds.DeleteDBInstance]

    /// Wait until the specified database instance has been deleted.
    /// 
    /// - Parameter instanceIdentifier: The identifier of the database
    ///   instance to wait for.
    func waitUntilDBInstanceDeleted(instanceIdentifier: String) async {
        putString("Waiting for the database instance to be deleted. This may take a few minutes...")
        do {
            var isDatabaseDeleted = false
            var foundInstance = false

            while !isDatabaseDeleted {
                let output = try await rdsClient.describeDBInstances(input: DescribeDBInstancesInput())
                guard let instanceList = output.dbInstances else {
                    return
                }

                foundInstance = false

                for instance in instanceList {
                    guard let foundInstanceIdentifier = instance.dbInstanceIdentifier else {
                        continue
                    }

                    if instanceIdentifier == foundInstanceIdentifier {
                        foundInstance = true
                        break
                    } else {
                        putString(".")
                        do {
                            try await Task.sleep(for: .seconds(15))
                        } catch {
                            print("\n*** Error pausing the task!")
                        }
                    }
                }
                if !foundInstance {
                    isDatabaseDeleted = true
                    print()
                }
            }
        } catch {
            print("\n*** Error waiting for the database instance to be deleted: \(error.localizedDescription)")
        }
    }

    // snippet-start:[swift.rds.DeleteDBParameterGroup]
    /// Delete the specified database parameter group.
    /// 
    /// - Parameter groupName: The name of the parameter group to delete.
    func deleteDBParameterGroup(groupName: String) async {
        do {
            _ = try await rdsClient.deleteDBParameterGroup(
                input: DeleteDBParameterGroupInput(
                    dbParameterGroupName: groupName
                )
            )
        } catch {
            print("*** Error deleting the database parameter group \(groupName): \(error.localizedDescription)")
        }
    }
    // snippet-end:[swift.rds.DeleteDBParameterGroup]

    /// Generate and return a unique file name that begins with the specified
    /// string.
    ///
    /// - Parameters:
    ///   - prefix: Text to use at the beginning of the returned name.
    ///
    /// - Returns: A string containing a unique filename that begins with the
    ///   specified `prefix`.
    ///
    /// The returned name uses a random number between 1 million and 1 billion to
    /// provide reasonable certainty of uniqueness for the purposes of this
    /// example.
    func tempName(prefix: String) -> String {
        return "\(prefix)-\(Int.random(in: 1000000..<1000000000))"
    }

    /// Print a string to standard output without a trailing newline, and
    /// without buffering.
    /// 
    /// - Parameter str: The string to output.
    func putString(_ str: String = "") {
        if str.length >= 1 {
            let data = str.data(using: .utf8)
            guard let data else {
                return
            }
            FileHandle.standardOutput.write(data)
        }
    }
}

/// The program's asynchronous entry point.
@main
struct Main {
    static func main() async {
        let args = Array(CommandLine.arguments.dropFirst())

        do {
            let command = try ExampleCommand.parse(args)
            try await command.runAsync()
        } catch {
            ExampleCommand.exit(withError: error)
        }
    }    
}
// snippet-end:[swift.rds.scenario]
