package aws

import (
	"fmt"
	"log"
	"regexp"
	"strings"
	"time"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/awserr"
	"github.com/aws/aws-sdk-go/service/rds"

	"github.com/hashicorp/terraform/helper/resource"
	"github.com/hashicorp/terraform/helper/schema"
)

func resourceAwsDbInstance() *schema.Resource {
	return &schema.Resource{
		Create: resourceAwsDbInstanceCreate,
		Read:   resourceAwsDbInstanceRead,
		Update: resourceAwsDbInstanceUpdate,
		Delete: resourceAwsDbInstanceDelete,
		Importer: &schema.ResourceImporter{
			State: resourceAwsDbInstanceImport,
		},

		Schema: map[string]*schema.Schema{
			"name": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
				ForceNew: true,
			},

			"arn": &schema.Schema{
				Type:     schema.TypeString,
				Computed: true,
			},

			"username": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
				ForceNew: true,
			},

			"password": &schema.Schema{
				Type:      schema.TypeString,
				Optional:  true,
				Sensitive: true,
			},

			"engine": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
				ForceNew: true,
				StateFunc: func(v interface{}) string {
					value := v.(string)
					return strings.ToLower(value)
				},
			},

			"engine_version": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
			},

			"character_set_name": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
				ForceNew: true,
			},

			"storage_encrypted": &schema.Schema{
				Type:     schema.TypeBool,
				Optional: true,
				ForceNew: true,
			},

			"allocated_storage": &schema.Schema{
				Type:     schema.TypeInt,
				Optional: true,
				Computed: true,
			},

			"storage_type": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
			},

			"identifier": &schema.Schema{
				Type:         schema.TypeString,
				Optional:     true,
				Computed:     true,
				ForceNew:     true,
				ValidateFunc: validateRdsId,
			},

			"instance_class": &schema.Schema{
				Type:     schema.TypeString,
				Required: true,
			},

			"availability_zone": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
				ForceNew: true,
			},

			"backup_retention_period": &schema.Schema{
				Type:     schema.TypeInt,
				Optional: true,
				Computed: true,
			},

			"backup_window": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
			},

			"iops": &schema.Schema{
				Type:     schema.TypeInt,
				Optional: true,
			},

			"license_model": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
			},

			"maintenance_window": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
				StateFunc: func(v interface{}) string {
					if v != nil {
						value := v.(string)
						return strings.ToLower(value)
					}
					return ""
				},
			},

			"multi_az": &schema.Schema{
				Type:     schema.TypeBool,
				Optional: true,
				Computed: true,
			},

			"port": &schema.Schema{
				Type:     schema.TypeInt,
				Optional: true,
				Computed: true,
			},

			"publicly_accessible": &schema.Schema{
				Type:     schema.TypeBool,
				Optional: true,
				Default:  false,
			},

			"vpc_security_group_ids": &schema.Schema{
				Type:     schema.TypeSet,
				Optional: true,
				Computed: true,
				Elem:     &schema.Schema{Type: schema.TypeString},
				Set:      schema.HashString,
			},

			"security_group_names": &schema.Schema{
				Type:     schema.TypeSet,
				Optional: true,
				Elem:     &schema.Schema{Type: schema.TypeString},
				Set:      schema.HashString,
			},

			"final_snapshot_identifier": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				ValidateFunc: func(v interface{}, k string) (ws []string, es []error) {
					value := v.(string)
					if !regexp.MustCompile(`^[0-9A-Za-z-]+$`).MatchString(value) {
						es = append(es, fmt.Errorf(
							"only alphanumeric characters and hyphens allowed in %q", k))
					}
					if regexp.MustCompile(`--`).MatchString(value) {
						es = append(es, fmt.Errorf("%q cannot contain two consecutive hyphens", k))
					}
					if regexp.MustCompile(`-$`).MatchString(value) {
						es = append(es, fmt.Errorf("%q cannot end in a hyphen", k))
					}
					return
				},
			},

			"skip_final_snapshot": &schema.Schema{
				Type:     schema.TypeBool,
				Optional: true,
				Default:  true,
			},

			"copy_tags_to_snapshot": &schema.Schema{
				Type:     schema.TypeBool,
				Optional: true,
				Default:  false,
			},

			"db_subnet_group_name": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				ForceNew: true,
				Computed: true,
			},

			"parameter_group_name": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
			},

			"address": &schema.Schema{
				Type:     schema.TypeString,
				Computed: true,
			},

			"endpoint": &schema.Schema{
				Type:     schema.TypeString,
				Computed: true,
			},

			"status": &schema.Schema{
				Type:     schema.TypeString,
				Computed: true,
			},

			// apply_immediately is used to determine when the update modifications
			// take place.
			// See http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Overview.DBInstance.Modifying.html
			"apply_immediately": &schema.Schema{
				Type:     schema.TypeBool,
				Optional: true,
				Computed: true,
			},

			"replicate_source_db": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
			},

			"replicas": &schema.Schema{
				Type:     schema.TypeList,
				Computed: true,
				Elem:     &schema.Schema{Type: schema.TypeString},
			},

			"snapshot_identifier": &schema.Schema{
				Type:     schema.TypeString,
				Computed: false,
				Optional: true,
				ForceNew: true,
				Elem:     &schema.Schema{Type: schema.TypeString},
			},

			"auto_minor_version_upgrade": &schema.Schema{
				Type:     schema.TypeBool,
				Optional: true,
				Default:  true,
			},

			"allow_major_version_upgrade": &schema.Schema{
				Type:     schema.TypeBool,
				Computed: false,
				Optional: true,
			},

			"monitoring_role_arn": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
			},

			"monitoring_interval": &schema.Schema{
				Type:     schema.TypeInt,
				Optional: true,
				Default:  0,
			},

			"option_group_name": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
			},

			"kms_key_id": &schema.Schema{
				Type:     schema.TypeString,
				Optional: true,
				Computed: true,
				ForceNew: true,
			},

			"tags": tagsSchema(),
		},
	}
}

func resourceAwsDbInstanceCreate(d *schema.ResourceData, meta interface{}) error {
	conn := meta.(*AWSClient).rdsconn
	tags := tagsFromMapRDS(d.Get("tags").(map[string]interface{}))

	identifier := d.Get("identifier").(string)
	// Generate a unique ID for the user
	if identifier == "" {
		identifier = resource.PrefixedUniqueId("tf-")
		// SQL Server identifier size is max 15 chars, so truncate
		if engine := d.Get("engine").(string); engine != "" {
			if strings.Contains(strings.ToLower(engine), "sqlserver") {
				identifier = identifier[:15]
			}
		}
		d.Set("identifier", identifier)
	}

	if v, ok := d.GetOk("replicate_source_db"); ok {
		opts := rds.CreateDBInstanceReadReplicaInput{
			SourceDBInstanceIdentifier: aws.String(v.(string)),
			CopyTagsToSnapshot:         aws.Bool(d.Get("copy_tags_to_snapshot").(bool)),
			DBInstanceClass:            aws.String(d.Get("instance_class").(string)),
			DBInstanceIdentifier:       aws.String(identifier),
			PubliclyAccessible:         aws.Bool(d.Get("publicly_accessible").(bool)),
			Tags:                       tags,
		}
		if attr, ok := d.GetOk("iops"); ok {
			opts.Iops = aws.Int64(int64(attr.(int)))
		}

		if attr, ok := d.GetOk("port"); ok {
			opts.Port = aws.Int64(int64(attr.(int)))
		}

		if attr, ok := d.GetOk("availability_zone"); ok {
			opts.AvailabilityZone = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("storage_type"); ok {
			opts.StorageType = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("db_subnet_group_name"); ok {
			opts.DBSubnetGroupName = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("monitoring_role_arn"); ok {
			opts.MonitoringRoleArn = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("monitoring_interval"); ok {
			opts.MonitoringInterval = aws.Int64(int64(attr.(int)))
		}

		if attr, ok := d.GetOk("option_group_name"); ok {
			opts.OptionGroupName = aws.String(attr.(string))
		}

		log.Printf("[DEBUG] DB Instance Replica create configuration: %#v", opts)
		_, err := conn.CreateDBInstanceReadReplica(&opts)
		if err != nil {
			return fmt.Errorf("Error creating DB Instance: %s", err)
		}
	} else if _, ok := d.GetOk("snapshot_identifier"); ok {
		opts := rds.RestoreDBInstanceFromDBSnapshotInput{
			DBInstanceClass:         aws.String(d.Get("instance_class").(string)),
			DBInstanceIdentifier:    aws.String(d.Get("identifier").(string)),
			DBSnapshotIdentifier:    aws.String(d.Get("snapshot_identifier").(string)),
			AutoMinorVersionUpgrade: aws.Bool(d.Get("auto_minor_version_upgrade").(bool)),
			PubliclyAccessible:      aws.Bool(d.Get("publicly_accessible").(bool)),
			Tags:                    tags,
			CopyTagsToSnapshot:      aws.Bool(d.Get("copy_tags_to_snapshot").(bool)),
		}

		if attr, ok := d.GetOk("availability_zone"); ok {
			opts.AvailabilityZone = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("db_subnet_group_name"); ok {
			opts.DBSubnetGroupName = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("engine"); ok {
			opts.Engine = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("iops"); ok {
			opts.Iops = aws.Int64(int64(attr.(int)))
		}

		if attr, ok := d.GetOk("license_model"); ok {
			opts.LicenseModel = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("multi_az"); ok {
			opts.MultiAZ = aws.Bool(attr.(bool))
		}

		if attr, ok := d.GetOk("option_group_name"); ok {
			opts.OptionGroupName = aws.String(attr.(string))

		}

		if attr, ok := d.GetOk("port"); ok {
			opts.Port = aws.Int64(int64(attr.(int)))
		}

		if attr, ok := d.GetOk("tde_credential_arn"); ok {
			opts.TdeCredentialArn = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("storage_type"); ok {
			opts.StorageType = aws.String(attr.(string))
		}

		log.Printf("[DEBUG] DB Instance restore from snapshot configuration: %s", opts)
		_, err := conn.RestoreDBInstanceFromDBSnapshot(&opts)
		if err != nil {
			return fmt.Errorf("Error creating DB Instance: %s", err)
		}

		var sgUpdate bool
		if attr := d.Get("vpc_security_group_ids").(*schema.Set); attr.Len() > 0 {
			sgUpdate = true
		}
		if attr := d.Get("security_group_names").(*schema.Set); attr.Len() > 0 {
			sgUpdate = true
		}
		if sgUpdate {
			log.Printf("[INFO] DB is restoring from snapshot with default security, but custom security should be set, will now update after snapshot is restored!")

			// wait for instance to get up and then modify security
			d.SetId(d.Get("identifier").(string))

			log.Printf("[INFO] DB Instance ID: %s", d.Id())

			log.Println(
				"[INFO] Waiting for DB Instance to be available")

			stateConf := &resource.StateChangeConf{
				Pending: []string{"creating", "backing-up", "modifying", "resetting-master-credentials",
					"maintenance", "renaming", "rebooting", "upgrading"},
				Target:     []string{"available"},
				Refresh:    resourceAwsDbInstanceStateRefreshFunc(d, meta),
				Timeout:    40 * time.Minute,
				MinTimeout: 10 * time.Second,
				Delay:      30 * time.Second, // Wait 30 secs before starting
			}

			// Wait, catching any errors
			_, err := stateConf.WaitForState()
			if err != nil {
				return err
			}

			err = resourceAwsDbInstanceUpdate(d, meta)
			if err != nil {
				return err
			}

		}
	} else {
		if _, ok := d.GetOk("allocated_storage"); !ok {
			return fmt.Errorf(`provider.aws: aws_db_instance: %s: "allocated_storage": required field is not set`, d.Get("name").(string))
		}
		if _, ok := d.GetOk("engine"); !ok {
			return fmt.Errorf(`provider.aws: aws_db_instance: %s: "engine": required field is not set`, d.Get("name").(string))
		}
		if _, ok := d.GetOk("password"); !ok {
			return fmt.Errorf(`provider.aws: aws_db_instance: %s: "password": required field is not set`, d.Get("name").(string))
		}
		if _, ok := d.GetOk("username"); !ok {
			return fmt.Errorf(`provider.aws: aws_db_instance: %s: "username": required field is not set`, d.Get("name").(string))
		}
		opts := rds.CreateDBInstanceInput{
			AllocatedStorage:        aws.Int64(int64(d.Get("allocated_storage").(int))),
			DBName:                  aws.String(d.Get("name").(string)),
			DBInstanceClass:         aws.String(d.Get("instance_class").(string)),
			DBInstanceIdentifier:    aws.String(d.Get("identifier").(string)),
			MasterUsername:          aws.String(d.Get("username").(string)),
			MasterUserPassword:      aws.String(d.Get("password").(string)),
			Engine:                  aws.String(d.Get("engine").(string)),
			EngineVersion:           aws.String(d.Get("engine_version").(string)),
			StorageEncrypted:        aws.Bool(d.Get("storage_encrypted").(bool)),
			AutoMinorVersionUpgrade: aws.Bool(d.Get("auto_minor_version_upgrade").(bool)),
			PubliclyAccessible:      aws.Bool(d.Get("publicly_accessible").(bool)),
			Tags:                    tags,
			CopyTagsToSnapshot:      aws.Bool(d.Get("copy_tags_to_snapshot").(bool)),
		}

		attr := d.Get("backup_retention_period")
		opts.BackupRetentionPeriod = aws.Int64(int64(attr.(int)))
		if attr, ok := d.GetOk("multi_az"); ok {
			opts.MultiAZ = aws.Bool(attr.(bool))

		}

		if attr, ok := d.GetOk("character_set_name"); ok {
			opts.CharacterSetName = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("maintenance_window"); ok {
			opts.PreferredMaintenanceWindow = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("backup_window"); ok {
			opts.PreferredBackupWindow = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("license_model"); ok {
			opts.LicenseModel = aws.String(attr.(string))
		}
		if attr, ok := d.GetOk("parameter_group_name"); ok {
			opts.DBParameterGroupName = aws.String(attr.(string))
		}

		if attr := d.Get("vpc_security_group_ids").(*schema.Set); attr.Len() > 0 {
			var s []*string
			for _, v := range attr.List() {
				s = append(s, aws.String(v.(string)))
			}
			opts.VpcSecurityGroupIds = s
		}

		if attr := d.Get("security_group_names").(*schema.Set); attr.Len() > 0 {
			var s []*string
			for _, v := range attr.List() {
				s = append(s, aws.String(v.(string)))
			}
			opts.DBSecurityGroups = s
		}
		if attr, ok := d.GetOk("storage_type"); ok {
			opts.StorageType = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("db_subnet_group_name"); ok {
			opts.DBSubnetGroupName = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("iops"); ok {
			opts.Iops = aws.Int64(int64(attr.(int)))
		}

		if attr, ok := d.GetOk("port"); ok {
			opts.Port = aws.Int64(int64(attr.(int)))
		}

		if attr, ok := d.GetOk("availability_zone"); ok {
			opts.AvailabilityZone = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("monitoring_role_arn"); ok {
			opts.MonitoringRoleArn = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("monitoring_interval"); ok {
			opts.MonitoringInterval = aws.Int64(int64(attr.(int)))
		}

		if attr, ok := d.GetOk("option_group_name"); ok {
			opts.OptionGroupName = aws.String(attr.(string))
		}

		if attr, ok := d.GetOk("kms_key_id"); ok {
			opts.KmsKeyId = aws.String(attr.(string))
		}

		log.Printf("[DEBUG] DB Instance create configuration: %#v", opts)
		var err error
		err = resource.Retry(5*time.Minute, func() *resource.RetryError {
			_, err = conn.CreateDBInstance(&opts)
			if err != nil {
				if awsErr, ok := err.(awserr.Error); ok {
					if awsErr.Code() == "InvalidParameterValue" && strings.Contains(awsErr.Message(), "ENHANCED_MONITORING") {
						return resource.RetryableError(awsErr)
					}
				}
				return resource.NonRetryableError(err)
			}
			return nil
		})
		if err != nil {
			return fmt.Errorf("Error creating DB Instance: %s", err)
		}
	}

	d.SetId(d.Get("identifier").(string))

	log.Printf("[INFO] DB Instance ID: %s", d.Id())

	log.Println(
		"[INFO] Waiting for DB Instance to be available")

	stateConf := &resource.StateChangeConf{
		Pending: []string{"creating", "backing-up", "modifying", "resetting-master-credentials",
			"maintenance", "renaming", "rebooting", "upgrading", "configuring-enhanced-monitoring"},
		Target:     []string{"available"},
		Refresh:    resourceAwsDbInstanceStateRefreshFunc(d, meta),
		Timeout:    40 * time.Minute,
		MinTimeout: 10 * time.Second,
		Delay:      30 * time.Second, // Wait 30 secs before starting
	}

	// Wait, catching any errors
	_, err := stateConf.WaitForState()
	if err != nil {
		return err
	}

	return resourceAwsDbInstanceRead(d, meta)
}

func resourceAwsDbInstanceRead(d *schema.ResourceData, meta interface{}) error {
	v, err := resourceAwsDbInstanceRetrieve(d, meta)

	if err != nil {
		return err
	}
	if v == nil {
		d.SetId("")
		return nil
	}

	d.Set("name", v.DBName)
	d.Set("identifier", v.DBInstanceIdentifier)
	d.Set("username", v.MasterUsername)
	d.Set("engine", v.Engine)
	d.Set("engine_version", v.EngineVersion)
	d.Set("allocated_storage", v.AllocatedStorage)
	d.Set("iops", v.Iops)
	d.Set("copy_tags_to_snapshot", v.CopyTagsToSnapshot)
	d.Set("auto_minor_version_upgrade", v.AutoMinorVersionUpgrade)
	d.Set("storage_type", v.StorageType)
	d.Set("instance_class", v.DBInstanceClass)
	d.Set("availability_zone", v.AvailabilityZone)
	d.Set("backup_retention_period", v.BackupRetentionPeriod)
	d.Set("backup_window", v.PreferredBackupWindow)
	d.Set("license_model", v.LicenseModel)
	d.Set("maintenance_window", v.PreferredMaintenanceWindow)
	d.Set("publicly_accessible", v.PubliclyAccessible)
	d.Set("multi_az", v.MultiAZ)
	d.Set("kms_key_id", v.KmsKeyId)
	d.Set("port", v.DbInstancePort)
	if v.DBSubnetGroup != nil {
		d.Set("db_subnet_group_name", v.DBSubnetGroup.DBSubnetGroupName)
	}

	if v.CharacterSetName != nil {
		d.Set("character_set_name", v.CharacterSetName)
	}

	if len(v.DBParameterGroups) > 0 {
		d.Set("parameter_group_name", v.DBParameterGroups[0].DBParameterGroupName)
	}

	if v.Endpoint != nil {
		d.Set("port", v.Endpoint.Port)
		d.Set("address", v.Endpoint.Address)

		if v.Endpoint.Address != nil && v.Endpoint.Port != nil {
			d.Set("endpoint",
				fmt.Sprintf("%s:%d", *v.Endpoint.Address, *v.Endpoint.Port))
		}
	}

	d.Set("status", v.DBInstanceStatus)
	d.Set("storage_encrypted", v.StorageEncrypted)
	if v.OptionGroupMemberships != nil {
		d.Set("option_group_name", v.OptionGroupMemberships[0].OptionGroupName)
	}

	if v.MonitoringInterval != nil {
		d.Set("monitoring_interval", v.MonitoringInterval)
	}

	if v.MonitoringRoleArn != nil {
		d.Set("monitoring_role_arn", v.MonitoringRoleArn)
	}

	// list tags for resource
	// set tags
	conn := meta.(*AWSClient).rdsconn
	arn, err := buildRDSARN(d.Id(), meta.(*AWSClient).accountid, meta.(*AWSClient).region)
	if err != nil {
		name := "<empty>"
		if v.DBName != nil && *v.DBName != "" {
			name = *v.DBName
		}
		log.Printf("[DEBUG] Error building ARN for DB Instance, not setting Tags for DB %s", name)
	} else {
		d.Set("arn", arn)
		resp, err := conn.ListTagsForResource(&rds.ListTagsForResourceInput{
			ResourceName: aws.String(arn),
		})

		if err != nil {
			log.Printf("[DEBUG] Error retrieving tags for ARN: %s", arn)
		}

		var dt []*rds.Tag
		if len(resp.TagList) > 0 {
			dt = resp.TagList
		}
		d.Set("tags", tagsToMapRDS(dt))
	}

	// Create an empty schema.Set to hold all vpc security group ids
	ids := &schema.Set{
		F: schema.HashString,
	}
	for _, v := range v.VpcSecurityGroups {
		ids.Add(*v.VpcSecurityGroupId)
	}
	d.Set("vpc_security_group_ids", ids)

	// Create an empty schema.Set to hold all security group names
	sgn := &schema.Set{
		F: schema.HashString,
	}
	for _, v := range v.DBSecurityGroups {
		sgn.Add(*v.DBSecurityGroupName)
	}
	d.Set("security_group_names", sgn)

	// replica things

	var replicas []string
	for _, v := range v.ReadReplicaDBInstanceIdentifiers {
		replicas = append(replicas, *v)
	}
	if err := d.Set("replicas", replicas); err != nil {
		return fmt.Errorf("[DEBUG] Error setting replicas attribute: %#v, error: %#v", replicas, err)
	}

	d.Set("replicate_source_db", v.ReadReplicaSourceDBInstanceIdentifier)

	return nil
}

func resourceAwsDbInstanceDelete(d *schema.ResourceData, meta interface{}) error {
	conn := meta.(*AWSClient).rdsconn

	log.Printf("[DEBUG] DB Instance destroy: %v", d.Id())

	opts := rds.DeleteDBInstanceInput{DBInstanceIdentifier: aws.String(d.Id())}

	skipFinalSnapshot := d.Get("skip_final_snapshot").(bool)
	opts.SkipFinalSnapshot = aws.Bool(skipFinalSnapshot)

	if skipFinalSnapshot == false {
		if name, present := d.GetOk("final_snapshot_identifier"); present {
			opts.FinalDBSnapshotIdentifier = aws.String(name.(string))
		} else {
			return fmt.Errorf("DB Instance FinalSnapshotIdentifier is required when a final snapshot is required")
		}
	}

	log.Printf("[DEBUG] DB Instance destroy configuration: %v", opts)
	if _, err := conn.DeleteDBInstance(&opts); err != nil {
		return err
	}

	log.Println(
		"[INFO] Waiting for DB Instance to be destroyed")
	stateConf := &resource.StateChangeConf{
		Pending: []string{"creating", "backing-up",
			"modifying", "deleting", "available"},
		Target:     []string{},
		Refresh:    resourceAwsDbInstanceStateRefreshFunc(d, meta),
		Timeout:    40 * time.Minute,
		MinTimeout: 10 * time.Second,
		Delay:      30 * time.Second, // Wait 30 secs before starting
	}
	if _, err := stateConf.WaitForState(); err != nil {
		return err
	}

	return nil
}

func resourceAwsDbInstanceUpdate(d *schema.ResourceData, meta interface{}) error {
	conn := meta.(*AWSClient).rdsconn

	d.Partial(true)

	req := &rds.ModifyDBInstanceInput{
		ApplyImmediately:     aws.Bool(d.Get("apply_immediately").(bool)),
		DBInstanceIdentifier: aws.String(d.Id()),
	}
	d.SetPartial("apply_immediately")

	requestUpdate := false
	if d.HasChange("allocated_storage") || d.HasChange("iops") {
		d.SetPartial("allocated_storage")
		d.SetPartial("iops")
		req.Iops = aws.Int64(int64(d.Get("iops").(int)))
		req.AllocatedStorage = aws.Int64(int64(d.Get("allocated_storage").(int)))
		requestUpdate = true
	}
	if d.HasChange("allow_major_version_upgrade") {
		d.SetPartial("allow_major_version_upgrade")
		req.AllowMajorVersionUpgrade = aws.Bool(d.Get("allow_major_version_upgrade").(bool))
		requestUpdate = true
	}
	if d.HasChange("backup_retention_period") {
		d.SetPartial("backup_retention_period")
		req.BackupRetentionPeriod = aws.Int64(int64(d.Get("backup_retention_period").(int)))
		requestUpdate = true
	}
	if d.HasChange("copy_tags_to_snapshot") {
		d.SetPartial("copy_tags_to_snapshot")
		req.CopyTagsToSnapshot = aws.Bool(d.Get("copy_tags_to_snapshot").(bool))
		requestUpdate = true
	}
	if d.HasChange("instance_class") {
		d.SetPartial("instance_class")
		req.DBInstanceClass = aws.String(d.Get("instance_class").(string))
		requestUpdate = true
	}
	if d.HasChange("parameter_group_name") {
		d.SetPartial("parameter_group_name")
		req.DBParameterGroupName = aws.String(d.Get("parameter_group_name").(string))
		requestUpdate = true
	}
	if d.HasChange("engine_version") {
		d.SetPartial("engine_version")
		req.EngineVersion = aws.String(d.Get("engine_version").(string))
		req.AllowMajorVersionUpgrade = aws.Bool(d.Get("allow_major_version_upgrade").(bool))
		requestUpdate = true
	}
	if d.HasChange("backup_window") {
		d.SetPartial("backup_window")
		req.PreferredBackupWindow = aws.String(d.Get("backup_window").(string))
		requestUpdate = true
	}
	if d.HasChange("maintenance_window") {
		d.SetPartial("maintenance_window")
		req.PreferredMaintenanceWindow = aws.String(d.Get("maintenance_window").(string))
		requestUpdate = true
	}
	if d.HasChange("password") {
		d.SetPartial("password")
		req.MasterUserPassword = aws.String(d.Get("password").(string))
		requestUpdate = true
	}
	if d.HasChange("multi_az") {
		d.SetPartial("multi_az")
		req.MultiAZ = aws.Bool(d.Get("multi_az").(bool))
		requestUpdate = true
	}
	if d.HasChange("publicly_accessible") {
		d.SetPartial("publicly_accessible")
		req.PubliclyAccessible = aws.Bool(d.Get("publicly_accessible").(bool))
		requestUpdate = true
	}
	if d.HasChange("storage_type") {
		d.SetPartial("storage_type")
		req.StorageType = aws.String(d.Get("storage_type").(string))
		requestUpdate = true

		if *req.StorageType == "io1" {
			req.Iops = aws.Int64(int64(d.Get("iops").(int)))
		}
	}
	if d.HasChange("auto_minor_version_upgrade") {
		d.SetPartial("auto_minor_version_upgrade")
		req.AutoMinorVersionUpgrade = aws.Bool(d.Get("auto_minor_version_upgrade").(bool))
		requestUpdate = true
	}

	if d.HasChange("monitoring_role_arn") {
		d.SetPartial("monitoring_role_arn")
		req.MonitoringRoleArn = aws.String(d.Get("monitoring_role_arn").(string))
		requestUpdate = true
	}

	if d.HasChange("monitoring_interval") {
		d.SetPartial("monitoring_interval")
		req.MonitoringInterval = aws.Int64(int64(d.Get("monitoring_interval").(int)))
		requestUpdate = true
	}

	if d.HasChange("vpc_security_group_ids") {
		if attr := d.Get("vpc_security_group_ids").(*schema.Set); attr.Len() > 0 {
			var s []*string
			for _, v := range attr.List() {
				s = append(s, aws.String(v.(string)))
			}
			req.VpcSecurityGroupIds = s
		}
		requestUpdate = true
	}

	if d.HasChange("security_group_names") {
		if attr := d.Get("security_group_names").(*schema.Set); attr.Len() > 0 {
			var s []*string
			for _, v := range attr.List() {
				s = append(s, aws.String(v.(string)))
			}
			req.DBSecurityGroups = s
		}
		requestUpdate = true
	}

	if d.HasChange("option_group_name") {
		d.SetPartial("option_group_name")
		req.OptionGroupName = aws.String(d.Get("option_group_name").(string))
		requestUpdate = true
	}

	if d.HasChange("port") {
		d.SetPartial("port")
		req.DBPortNumber = aws.Int64(int64(d.Get("port").(int)))
		requestUpdate = true
	}

	log.Printf("[DEBUG] Send DB Instance Modification request: %t", requestUpdate)
	if requestUpdate {
		log.Printf("[DEBUG] DB Instance Modification request: %s", req)
		_, err := conn.ModifyDBInstance(req)
		if err != nil {
			return fmt.Errorf("Error modifying DB Instance %s: %s", d.Id(), err)
		}

		log.Println("[INFO] Waiting for DB Instance to be available")

		stateConf := &resource.StateChangeConf{
			Pending: []string{"creating", "backing-up", "modifying", "resetting-master-credentials",
				"maintenance", "renaming", "rebooting", "upgrading", "configuring-enhanced-monitoring"},
			Target:     []string{"available"},
			Refresh:    resourceAwsDbInstanceStateRefreshFunc(d, meta),
			Timeout:    80 * time.Minute,
			MinTimeout: 10 * time.Second,
			Delay:      30 * time.Second, // Wait 30 secs before starting
		}

		// Wait, catching any errors
		_, dbStateErr := stateConf.WaitForState()
		if dbStateErr != nil {
			return dbStateErr
		}
	}

	// separate request to promote a database
	if d.HasChange("replicate_source_db") {
		if d.Get("replicate_source_db").(string) == "" {
			// promote
			opts := rds.PromoteReadReplicaInput{
				DBInstanceIdentifier: aws.String(d.Id()),
			}
			attr := d.Get("backup_retention_period")
			opts.BackupRetentionPeriod = aws.Int64(int64(attr.(int)))
			if attr, ok := d.GetOk("backup_window"); ok {
				opts.PreferredBackupWindow = aws.String(attr.(string))
			}
			_, err := conn.PromoteReadReplica(&opts)
			if err != nil {
				return fmt.Errorf("Error promoting database: %#v", err)
			}
			d.Set("replicate_source_db", "")
		} else {
			return fmt.Errorf("cannot elect new source database for replication")
		}
	}

	if arn, err := buildRDSARN(d.Id(), meta.(*AWSClient).accountid, meta.(*AWSClient).region); err == nil {
		if err := setTagsRDS(conn, d, arn); err != nil {
			return err
		} else {
			d.SetPartial("tags")
		}
	}
	d.Partial(false)

	return resourceAwsDbInstanceRead(d, meta)
}

// resourceAwsDbInstanceRetrieve fetches DBInstance information from the AWS
// API. It returns an error if there is a communication problem or unexpected
// error with AWS. When the DBInstance is not found, it returns no error and a
// nil pointer.
func resourceAwsDbInstanceRetrieve(
	d *schema.ResourceData, meta interface{}) (*rds.DBInstance, error) {
	conn := meta.(*AWSClient).rdsconn

	opts := rds.DescribeDBInstancesInput{
		DBInstanceIdentifier: aws.String(d.Id()),
	}

	log.Printf("[DEBUG] DB Instance describe configuration: %#v", opts)

	resp, err := conn.DescribeDBInstances(&opts)
	if err != nil {
		dbinstanceerr, ok := err.(awserr.Error)
		if ok && dbinstanceerr.Code() == "DBInstanceNotFound" {
			return nil, nil
		}
		return nil, fmt.Errorf("Error retrieving DB Instances: %s", err)
	}

	if len(resp.DBInstances) != 1 ||
		*resp.DBInstances[0].DBInstanceIdentifier != d.Id() {
		if err != nil {
			return nil, nil
		}
	}

	return resp.DBInstances[0], nil
}

func resourceAwsDbInstanceImport(
	d *schema.ResourceData, meta interface{}) ([]*schema.ResourceData, error) {
	// Neither skip_final_snapshot nor final_snapshot_identifier can be fetched
	// from any API call, so we need to default skip_final_snapshot to true so
	// that final_snapshot_identifier is not required
	d.Set("skip_final_snapshot", true)
	return []*schema.ResourceData{d}, nil
}

func resourceAwsDbInstanceStateRefreshFunc(
	d *schema.ResourceData, meta interface{}) resource.StateRefreshFunc {
	return func() (interface{}, string, error) {
		v, err := resourceAwsDbInstanceRetrieve(d, meta)

		if err != nil {
			log.Printf("Error on retrieving DB Instance when waiting: %s", err)
			return nil, "", err
		}

		if v == nil {
			return nil, "", nil
		}

		if v.DBInstanceStatus != nil {
			log.Printf("[DEBUG] DB Instance status for instance %s: %s", d.Id(), *v.DBInstanceStatus)
		}

		return v, *v.DBInstanceStatus, nil
	}
}

func buildRDSARN(identifier, accountid, region string) (string, error) {
	if accountid == "" {
		return "", fmt.Errorf("Unable to construct RDS ARN because of missing AWS Account ID")
	}
	arn := fmt.Sprintf("arn:aws:rds:%s:%s:db:%s", region, accountid, identifier)
	return arn, nil

}