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

package cli

import (
	"errors"
	"fmt"
	"net"
	"regexp"
	"strconv"
	"strings"
	"time"

	"gopkg.in/yaml.v3"

	"github.com/robfig/cron/v3"

	"github.com/spf13/afero"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/copilot-cli/internal/pkg/addon"
	"github.com/aws/copilot-cli/internal/pkg/aws/apprunner"
	"github.com/aws/copilot-cli/internal/pkg/manifest"
	"github.com/aws/copilot-cli/internal/pkg/manifest/manifestinfo"
)

const basicNameRegex = `^[a-z][a-z0-9\-]+$`

var errBasicNameRegexNotMatched = errors.New("value must have a length of at least 2, start with a letter, contain only lower-case letters, numbers, and hyphens, and have no consecutive or trailing hyphen")

var (
	errValueEmpty           = errors.New("value must not be empty")
	errValueTooLong         = errors.New("value must not exceed 255 characters")
	errValueNotAString      = errors.New("value must be a string")
	errValueReserved        = errors.New("value is reserved")
	errValueNotAStringSlice = errors.New("value must be a string slice")
	errValueNotAValidPath   = errors.New("value must be a valid path")
	errValueNotAnIPNet      = errors.New("value must be a valid IP address range (example: 10.0.0.0/16)")
	errValueNotIPNetSlice   = errors.New("value must be a valid slice of IP address range (example: 10.0.0.0/16,10.0.1.0/16)")
	errPortInvalid          = errors.New("value must be in range 1-65535")
	errDomainInvalid        = errors.New("value must contain at least one '.' character")
	errDurationInvalid      = errors.New("value must be a valid Go duration string (example: 1h30m)")
	errDurationBadUnits     = errors.New("duration cannot be in units smaller than a second")
	errScheduleInvalid      = errors.New("value must be a valid cron expression (examples: @weekly; @every 30m; 0 0 * * 0)")
)

// Addons validation errors.
var (
	fmtErrInvalidStorageType = "invalid storage type %s: must be one of %s"

	// S3 errors.
	errS3ValueBadSize      = errors.New("value must be between 3 and 63 characters in length")
	errS3ValueBadFormat    = errors.New("value must not contain consecutive periods or dashes, or be formatted as IP address")
	errS3ValueTrailingDash = errors.New("value must not have trailing -")

	// DDB errors.
	errValueBadFormatWithPeriod           = errors.New("value must contain only lowercase alphanumeric characters and .-")
	errDDBValueBadSize                    = errors.New("value must be between 3 and 255 characters in length")
	errDDBAttributeBadSize                = errors.New("value must be between 1 and 255 characters in length")
	errValueBadFormatWithPeriodUnderscore = errors.New("value must contain only alphanumeric characters and ._-")
	errDDBAttributeBadFormat              = errors.New("value must be of the form <name>:<T> where T is one of S, N, or B")
	errTooManyLSIKeys                     = errors.New("number of specified LSI sort keys must be 5 or less")

	// Aurora-Serverless-specific errors.
	errInvalidRDSNameCharacters    = errors.New("value must start with a letter and followed by alphanumeric letters only")
	errRDWSNotConnectedToVPC       = fmt.Errorf("%s requires a VPC connection", manifestinfo.RequestDrivenWebServiceType)
	fmtErrInvalidEngineType        = "invalid engine type %s: must be one of %s"
	fmtErrInvalidDBNameCharacters  = "invalid database name %s: must contain only alphanumeric characters and underscore; should start with a letter"
	errInvalidSecretNameCharacters = errors.New("value must contain only letters, numbers, periods, hyphens and underscores")

	// Topic subscription errors.
	errMissingPublishTopicField = errors.New("field `publish.topics[].name` cannot be empty")
	errInvalidPubSubTopicName   = errors.New("topic names can only contain letters, numbers, underscores, and hyphens")
	errSubscribeBadFormat       = errors.New("value must be of the form <serviceName>:<topicName>")
)

const fmtErrValueBadSize = "value must be between %d and %d characters in length"

// App Runner validation errors.
var (
	errAppRunnerSvcNameTooLong    = errors.New("value must not exceed 40 characters")
	errAppRunnerImageNotSupported = errors.New("value must be an ECR or ECR Public image URI")
)

// Pipelines
const (
	maxPipelineStackNameLen   = 128
	fmtErrPipelineNameTooLong = "value must not exceed %d characters"
)

var (
	emptyIPNet = net.IPNet{}
	emptyIP    = net.IP{}
)

// matches alphanumeric, ._-, from 3 to 255 characters long
// https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.NamingRulesDataTypes.html
var ddbRegExp = regexp.MustCompile(`^[a-zA-Z0-9\-\.\_]+$`)

// s3 validation expressions.
// s3RegExp matches alphanumeric, .- from 3 to 63 characters long.
// punctuationRegExp matches consecutive dashes or periods.
// trailingPunctRegExp matches a trailing dash.
// ipAddressRegExp checks for a bucket in the format of an IP address.
// https://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-s3-bucket-naming-requirements.html
// The punctuation and trailing punctuation guidelines also apply to ECR repositories, though
// the requirements are not documented.
var (
	s3RegExp = regexp.MustCompile("" +
		`^` + // start of line.
		`[a-z0-9\.\-]{3,63}` + // Main match: lowercase alphanumerics, ., - from 3-63 characters.
		`$`, // end of line.
	)
	punctuationRegExp = regexp.MustCompile(
		`[\.\-]{2,}`, // Check for consecutive periods or dashes.
	)
	trailingPunctRegExp = regexp.MustCompile(
		`[\-\.]$`, // Check for trailing dash or dot.
	)
	ipAddressRegexp = regexp.MustCompile(
		`^(?:\d{1,3}\.){3}\d{1,3}$`, // Match any 1-3 digits in xxx.xxx.xxx.xxx format.
	)

	domainNameRegexp = regexp.MustCompile(`\.`) // Check for at least one dot in domain name.

	awsScheduleRegexp = regexp.MustCompile(`(?:rate|cron)\(.*\)`) // Check for strings of the form rate(*) or cron(*).
)

// RDS Aurora Serverless validation expressions.
var (
	// Referred to name constraints here: https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/Aurora.CreateInstance.html#Aurora.CreateInstance.Settings
	// However, the doc on name constraints is somewhat misleading.
	// PostgreSQL db name cannot start with an underscore (doc says it must begin with a letter or an underscore).
	// MySQL db name can contain underscores (not limited to alphanumeric as described in the doc).
	dbNameCharacterRegExp = regexp.MustCompile("" +
		"^" + // Start of string.
		"[A-Za-z]" + // Starts with a letter.
		"[0-9A-Za-z_]*" + // Subsequent characters can be letters, underscores or digits
		"$", // End of string.
	)

	// The storage name for RDS storage type is used as the logical ID of the Aurora Serverless DB cluster in the CFN template.
	// When creating the DB cluster, CFN will use the logical ID to generate a DB cluster identifier.
	// Since the logical ID has stricter character restrictions than cluster identifier, we only need to check if the
	// starting character is a letter.
	// https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/Aurora.CreateInstance.html#Aurora.CreateInstance.Settings
	// https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/resources-section-structure.html
	rdsStorageNameRegExp = regexp.MustCompile("" +
		"^" + // Start of string.
		"[A-Za-z]" + // Starts with a letter. The DB cluster identifier must start with a letter.
		`[a-zA-Z0-9\-\.\_]*` + // Followed by alphanumeric, ._-. Refers to POSIX portable file name character set.
		"$", // End of string.
	)
)

// SSM secret parameter name validation expression.
// https://docs.aws.amazon.com/systems-manager/latest/APIReference/API_PutParameter.html#systemsmanager-PutParameter-request-Name
var secretParameterNameRegExp = regexp.MustCompile("^[a-zA-Z0-9_.-]+$")

var (
	awsSNSTopicRegexp       = regexp.MustCompile(`^[a-zA-Z0-9_-]*$`) // Validates that an expression contains only letters, numbers, underscores, and hyphens.
	regexpMatchSubscription = regexp.MustCompile(`^(\S+):(\S+)`)     // Validates that an expression contains the format serviceName:topicName
)

const regexpFindAllMatches = -1

// reservedWorkloadNames is a constant map of reserved workload names that users are not allowed to name their workloads
func reservedWorkloadNames() map[string]bool {
	return map[string]bool{
		"pipelines":    true, // reserved to avoid directory conflict with copilot pipelines
		"environments": true, // reserved to avoid directory conflict with copilot environments
	}
}

func validateAppNameString(val interface{}) error {
	if err := basicNameValidation(val); err != nil {
		return fmt.Errorf("application name %v is invalid: %w", val, err)
	}
	return nil
}

func validateSvcName(val interface{}, svcType string) error {
	var err error
	switch svcType {
	case manifestinfo.RequestDrivenWebServiceType:
		err = validateAppRunnerSvcName(val)
	default:
		err = basicNameValidation(val)
	}
	if err != nil {
		return fmt.Errorf("service name %v is invalid: %w", val, err)
	}
	if err := validateNotReservedWorkloadName(val); err != nil {
		return fmt.Errorf("service name %v is invalid: %w", val, err)
	}
	return nil
}

func validateNotReservedWorkloadName(val interface{}) error {
	name, ok := val.(string)
	switch {
	case !ok:
		return errValueNotAString
	case reservedWorkloadNames()[name]:
		return errValueReserved
	}

	return nil
}

func validateSvcPort(val interface{}) error {
	if err := basicPortValidation(val); err != nil {
		return fmt.Errorf("port %v is invalid: %w", val, err)
	}
	return nil
}

func validateSvcType(val interface{}) error {
	svcType, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	return validateWorkloadType(svcType, manifestinfo.ServiceTypes(), service)
}

func validateWorkloadType(wkldType string, validTypes []string, errFlavor string) error {
	for _, validType := range validTypes {
		if wkldType == validType {
			return nil
		}
	}

	return fmt.Errorf("invalid %s type %s: must be one of %s", errFlavor, wkldType, prettify(validTypes))
}

func validateJobType(val interface{}) error {
	jobType, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	return validateWorkloadType(jobType, manifestinfo.JobTypes(), job)
}

func validateJobName(val interface{}) error {
	if err := basicNameValidation(val); err != nil {
		return fmt.Errorf("job name %v is invalid: %w", val, err)
	}
	if err := validateNotReservedWorkloadName(val); err != nil {
		return fmt.Errorf("service name %v is invalid: %w", val, err)
	}
	return nil
}

func validatePipelineName(val interface{}, appName string) error {
	// compute the longest name a user can name their pipeline for this app
	// since we prefix their name with 'pipeline-[app]-'. the limit is required
	// because it's the name we give the cfn stack for the pipeline.
	maxNameLen := maxPipelineStackNameLen - len(fmt.Sprintf(fmtPipelineStackName, appName, ""))
	errFmt := "pipeline name %v is invalid: %w"

	if err := basicNameValidation(val); err != nil {
		return fmt.Errorf(errFmt, val, err)
	}

	name, ok := val.(string)
	switch {
	case !ok:
		return fmt.Errorf(errFmt, val, errValueNotAString)
	case len(name) > maxNameLen:
		err := fmt.Errorf(fmtErrPipelineNameTooLong, maxNameLen)
		return fmt.Errorf(errFmt, val, err)
	}
	return nil
}

func validateSchedule(sched interface{}) error {
	s, ok := sched.(string)
	if !ok {
		return errValueNotAString
	}
	return validateCron(s)
}

func validateAppRunnerImage(img interface{}) error {
	if err := apprunnerImageValidation(img); err != nil {
		return fmt.Errorf("image %s is not supported by App Runner: %w", img, err)
	}
	return nil
}

func validateTimeout(timeout interface{}) error {
	t, ok := timeout.(string)
	if !ok {
		return errValueNotAString
	}
	if err := validateDuration(t, 1*time.Second); err != nil {
		return fmt.Errorf("timeout value %s is invalid: %w", t, err)
	}
	return nil
}

func validateRate(rate interface{}) error {
	r, ok := rate.(string)
	if !ok {
		return errValueNotAString
	}
	return validateDuration(r, 60*time.Second)
}

func validateDomainName(val interface{}) error {
	domainName, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	dots := domainNameRegexp.FindAllString(domainName, regexpFindAllMatches)
	if dots == nil {
		return errDomainInvalid
	}
	return nil
}

func validatePath(fs afero.Fs, val interface{}) error {
	path, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	if path == "" {
		return errValueEmpty
	}
	_, err := fs.Stat(path)
	if err != nil {
		return errValueNotAValidPath
	}
	return nil
}

func validateNonEmptyString(val interface{}) error {
	path, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	if path == "" {
		return errValueEmpty
	}
	return nil
}

type validateStorageTypeOpts struct {
	ws           manifestReader
	workloadName string
}

func validateStorageType(val interface{}, opts validateStorageTypeOpts) error {
	storageType, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	if !contains(storageType, storageTypes) {
		return fmt.Errorf(fmtErrInvalidStorageType, storageType, prettify(storageTypes))
	}

	if storageType == rdsStorageType {
		return validateAuroraStorageType(opts.ws, opts.workloadName)
	}
	return nil
}

func validateAuroraStorageType(ws manifestReader, workloadName string) error {
	if workloadName == "" {
		return nil // Workload not yet selected while validating storage type flag.
	}
	mft, err := ws.ReadWorkloadManifest(workloadName)
	if err != nil {
		return fmt.Errorf("invalid storage type %s: read manifest file for %s: %w", rdsStorageType, workloadName, err)
	}
	mftType, err := mft.WorkloadType()
	if err != nil {
		return fmt.Errorf("invalid storage type %s: read type of workload from manifest file for %s: %w", rdsStorageType, workloadName, err)
	}
	if mftType != manifestinfo.RequestDrivenWebServiceType {
		return nil
	}
	data := struct {
		Network manifest.RequestDrivenWebServiceNetworkConfig `yaml:"network"`
	}{}
	if err := yaml.Unmarshal(mft, &data); err != nil {
		return fmt.Errorf("invalid storage type %s: unmarshal manifest for %s to read network config: %w", rdsStorageType, workloadName, err)
	}
	if data.Network.IsEmpty() {
		return fmt.Errorf("invalid storage type %s: %w", rdsStorageType, errRDWSNotConnectedToVPC)
	}
	return nil
}

func validateMySQLDBName(val interface{}) error {
	const (
		minMySQLDBNameLength = 1
		maxMySQLDBNameLength = 64
	)

	dbName, ok := val.(string)
	if !ok {
		return errValueNotAString
	}

	// Check for db name length.
	if len(dbName) < minMySQLDBNameLength || len(dbName) > maxMySQLDBNameLength {
		return fmt.Errorf(fmtErrValueBadSize, minMySQLDBNameLength, maxMySQLDBNameLength)
	}

	return validateDBNameCharacters(dbName)
}

func validateAppRunnerSvcName(val interface{}) error {
	const maxNameLen = 40
	name, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	if len(name) > maxNameLen {
		return errAppRunnerSvcNameTooLong
	}
	return basicNameValidation(val)
}

func validatePostgreSQLDBName(val interface{}) error {
	const (
		minPostgreSQLDBNameLength = 1
		maxPostgreSQLDBNameLength = 63
	)

	dbName, ok := val.(string)
	if !ok {
		return errValueNotAString
	}

	// Check for db name length.
	if len(dbName) < minPostgreSQLDBNameLength || len(dbName) > maxPostgreSQLDBNameLength {
		return fmt.Errorf(fmtErrValueBadSize, minPostgreSQLDBNameLength, maxPostgreSQLDBNameLength)
	}

	return validateDBNameCharacters(dbName)
}

func validateDBNameCharacters(name string) error {
	// Check for character constraints.
	match := dbNameCharacterRegExp.FindStringSubmatch(name)
	if match != nil {
		return nil
	}

	return fmt.Errorf(fmtErrInvalidDBNameCharacters, name)
}

func validateEngine(val interface{}) error {
	engine, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	for _, valid := range engineTypes {
		if engine == valid {
			return nil
		}
	}
	return fmt.Errorf(fmtErrInvalidEngineType, engine, prettify(engineTypes))
}

func validateEnvironmentName(val interface{}) error {
	if err := basicNameValidation(val); err != nil {
		return fmt.Errorf("environment name %v is invalid: %w", val, err)
	}
	return nil
}

func basicNameValidation(val interface{}) error {
	s, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	if s == "" {
		return errValueEmpty
	}
	if len(s) > 255 {
		return errValueTooLong
	}
	if !isCorrectFormat(s) {
		return errBasicNameRegexNotMatched
	}

	return nil
}

func validateCron(sched string) error {
	// If the schedule is wrapped in aws terms `rate()` or `cron()`, don't validate it--
	// instead, pass it in as-is for serverside validation. AWS cron is weird (year field, nonstandard wildcards)
	// so for edge cases we need to support it
	awsSchedMatch := awsScheduleRegexp.FindStringSubmatch(sched)
	if awsSchedMatch != nil {
		return nil
	}
	every := "@every "
	if strings.HasPrefix(sched, every) {
		if err := validateDuration(sched[len(every):], 60*time.Second); err != nil {
			if err == errDurationInvalid {
				return fmt.Errorf("interval %s must include a valid Go duration string (example: @every 1h30m)", sched)
			}
			return fmt.Errorf("interval %s is invalid: %s", sched, err)
		}
	}
	_, err := cron.ParseStandard(sched)
	if err != nil {
		return fmt.Errorf("schedule %s is invalid: %s", sched, errScheduleInvalid)
	}
	return nil
}

func validateDuration(duration string, min time.Duration) error {
	parsedDuration, err := time.ParseDuration(duration)
	if err != nil {
		return errDurationInvalid
	}
	// This checks if the duration has parts smaller than a whole second.
	if parsedDuration > parsedDuration.Truncate(time.Second) {
		return errDurationBadUnits
	}
	if parsedDuration < min {
		return fmt.Errorf("duration must be %v or greater", min)
	}
	return nil
}

func isCorrectFormat(s string) bool {
	valid, err := regexp.MatchString(basicNameRegex, s)
	if err != nil {
		return false // bubble up error?
	}

	// Check for bad punctuation (no consecutive dashes or dots)
	formatMatch := punctuationRegExp.FindStringSubmatch(s)
	if len(formatMatch) != 0 {
		return false
	}

	trailingMatch := trailingPunctRegExp.FindStringSubmatch(s)
	if len(trailingMatch) != 0 {
		return false
	}

	return valid
}

func apprunnerImageValidation(val interface{}) error {
	strVal, ok := val.(string)
	if ok && apprunner.ImageIsSupported(strVal) {
		return nil
	}
	return errAppRunnerImageNotSupported
}

func basicPortValidation(val interface{}) error {

	var err error

	switch val := val.(type) {
	case []byte:
		err = bytePortValidation(val)
	case string:
		err = stringPortValidation(val)
	case uint16:
		if val == 0 {
			err = errPortInvalid
		}
	default:
		err = errPortInvalid
	}
	return err
}

func bytePortValidation(val []byte) error {
	s := string(val)
	err := stringPortValidation(s)
	if err != nil {
		return err
	}
	return nil
}

func stringPortValidation(val string) error {
	portList := strings.Split(val, ",")
	for _, port := range portList {
		port64, err := strconv.ParseUint(port, 10, 64)
		if err != nil {
			return errPortInvalid
		}
		if port64 < 1 || port64 > 65535 {
			return errPortInvalid
		}
	}
	return nil
}

// s3 bucket names: 'a-z0-9.-'
func s3BucketNameValidation(val interface{}) error {
	const minS3Length = 3
	const maxS3Length = 63
	s, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	if len(s) < minS3Length || len(s) > maxS3Length {
		return errS3ValueBadSize
	}

	// check for correct character set
	nameMatch := s3RegExp.FindStringSubmatch(s)
	if len(nameMatch) == 0 {
		return errValueBadFormatWithPeriod
	}

	// Check for bad punctuation (no consecutive dashes or dots)
	formatMatch := punctuationRegExp.FindStringSubmatch(s)
	if len(formatMatch) != 0 {
		return errS3ValueBadFormat
	}

	dashMatch := trailingPunctRegExp.FindStringSubmatch(s)
	if len(dashMatch) != 0 {
		return errS3ValueTrailingDash
	}

	ipMatch := ipAddressRegexp.FindStringSubmatch(s)
	if len(ipMatch) != 0 {
		return errS3ValueBadFormat
	}

	return nil
}

// Dynamo table names: 'a-zA-Z0-9.-_'
func dynamoTableNameValidation(val interface{}) error {
	// https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.NamingRulesDataTypes.html
	const minDDBTableNameLength = 3
	const maxDDBTableNameLength = 255

	s, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	if len(s) < minDDBTableNameLength || len(s) > maxDDBTableNameLength {
		return errDDBValueBadSize
	}
	m := ddbRegExp.FindStringSubmatch(s)
	if len(m) == 0 {
		return errValueBadFormatWithPeriodUnderscore
	}
	return nil
}

// Dynamo attribute names: 1 to 255 characters
func dynamoAttributeNameValidation(val interface{}) error {
	// https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.NamingRulesDataTypes.html
	const minDDBAttributeNameLength = 1
	const maxDDBAttributeNameLength = 255

	s, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	if len(s) < minDDBAttributeNameLength || len(s) > maxDDBAttributeNameLength {
		return errDDBAttributeBadSize
	}
	return nil
}

// RDS storage name: '[a-zA-Z][a-zA-Z0-9]*'
func rdsNameValidation(val interface{}) error {
	// This length constrains needs to satisfy: 1. logical ID length; 2. DB Cluster identifier length.
	// For 1. logical ID, there is no documented length limit.
	// For 2. DB Cluster identifier, the maximal length is 63.
	// DB Cluster identifier is auto-generated by CFN using the cluster's logical ID, which is the storage name appended
	// by "DBCluster". Hence the maximal length of the storage name is 63 - len("DBCluster")
	const minRDSNameLength = 1
	const maxRDSNameLength = 63 - len("DBCluster")

	s, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	if len(s) < minRDSNameLength || len(s) > maxRDSNameLength {
		return fmt.Errorf(fmtErrValueBadSize, minRDSNameLength, maxRDSNameLength)
	}
	m := rdsStorageNameRegExp.FindStringSubmatch(s)
	if m == nil {
		return errInvalidRDSNameCharacters
	}
	return nil
}

func validateKey(val interface{}) error {
	s, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	attr, err := addon.DDBAttributeFromKey(s)
	if err != nil {
		return errDDBAttributeBadFormat
	}
	err = dynamoAttributeNameValidation(*attr.Name)
	if err != nil {
		return err
	}
	err = validateDynamoDataType(*attr.DataType)
	if err != nil {
		return err
	}
	return nil
}

func validateDynamoDataType(val interface{}) error {
	s, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	if !strings.Contains("SNB", strings.ToUpper(s)) {
		return errDDBAttributeBadFormat
	}
	return nil
}

func validateLSIs(val interface{}) error {
	s, ok := val.([]string)
	if !ok {
		return errValueNotAStringSlice
	}
	if len(s) > 5 {
		return errTooManyLSIKeys
	}
	for _, att := range s {
		err := validateKey(att)
		if err != nil {
			return err
		}
	}
	return nil
}

func validateSubscribe(noSubscription bool, subscribeTags []string) error {
	// --no-subscriptions and --subscribe are mutually exclusive.
	if noSubscription && len(subscribeTags) != 0 {
		return fmt.Errorf("validate subscribe configuration: cannot specify both --%s and --%s", noSubscriptionFlag, subscribeTopicsFlag)
	}
	if len(subscribeTags) != 0 {
		if err := validateSubscriptions(subscribeTags); err != nil {
			return err
		}
	}

	return nil
}

func validateSubscriptions(val interface{}) error {
	s, ok := val.([]string)
	if !ok {
		return errValueNotAStringSlice
	}
	for _, sub := range s {
		err := validateSubscriptionKey(sub)
		if err != nil {
			return err
		}
	}
	return nil
}

func validateSubscriptionKey(val interface{}) error {
	s, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	sub, err := parseSerializedSubscription(s)
	if err != nil {
		return errSubscribeBadFormat
	}
	if err := validatePubSubName(aws.StringValue(sub.Name)); err != nil {
		return fmt.Errorf("invalid topic subscription topic name `%s`: %w", aws.StringValue(sub.Name), err)
	}
	if err = basicNameValidation(aws.StringValue(sub.Service)); err != nil {
		return fmt.Errorf("invalid topic subscription service name `%s`: %w", aws.StringValue(sub.Service), err)
	}
	return nil
}

// ValidatePubSubName validates naming is correct for topics in publishing/subscribing cases, such as naming for a
// SNS Topic intended for a publisher.
func validatePubSubName(name string) error {
	if len(name) == 0 {
		return errMissingPublishTopicField
	}

	// Name must contain letters, numbers, and can't use special characters besides underscores and hyphens.
	if !awsSNSTopicRegexp.MatchString(name) {
		return errInvalidPubSubTopicName
	}

	return nil
}

func prettify(inputStrings []string) string {
	prettyTypes := applyAll(inputStrings, strconv.Quote)
	return strings.Join(prettyTypes, ", ")
}

func validateCIDR(val interface{}) error {
	s, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	ip, _, err := net.ParseCIDR(s)
	if err != nil || ip.String() == emptyIP.String() {
		return errValueNotAnIPNet
	}
	return nil
}

func validatePublicSubnetsCIDR(numAZs int) func(v interface{}) error {
	return func(v interface{}) error {
		s, ok := v.(string)
		if !ok {
			return errValueNotAString
		}
		if numCIDRs := len(strings.Split(s, ",")); numCIDRs != numAZs {
			return fmt.Errorf("number of public subnet CIDRs (%d) does not match number of AZs (%d)", numCIDRs, numAZs)
		}
		return validateCIDRSlice(v)
	}
}

func validatePrivateSubnetsCIDR(numAZs int) func(v interface{}) error {
	return func(v interface{}) error {
		s, ok := v.(string)
		if !ok {
			return errValueNotAString
		}
		if numCIDRs := len(strings.Split(s, ",")); numCIDRs != numAZs {
			return fmt.Errorf("number of private subnet CIDRs (%d) does not match number of AZs (%d)", numCIDRs, numAZs)
		}
		return validateCIDRSlice(v)
	}
}

func validateCIDRSlice(val interface{}) error {
	s, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	slice := strings.Split(s, ",")
	if len(slice) == 0 {
		return errValueNotIPNetSlice
	}
	for _, str := range slice {
		if err := validateCIDR(str); err != nil {
			return errValueNotIPNetSlice
		}
	}
	return nil
}

func validateSecretName(val interface{}) error {
	const minSecretNameLength = 1
	const maxSecretNameLength = 2048 - (len("/copilot/") + len("/") + len("/secrets/"))

	s, ok := val.(string)
	if !ok {
		return errValueNotAString
	}
	if len(s) < minSecretNameLength || len(s) > maxSecretNameLength {
		return fmt.Errorf(fmtErrValueBadSize, minSecretNameLength, maxSecretNameLength)
	}
	m := secretParameterNameRegExp.FindStringSubmatch(s)
	if m == nil {
		return errInvalidSecretNameCharacters
	}
	return nil
}