package awsses

import (
	"fmt"
	"strings"

	"github.com/TwiN/gatus/v5/alerting/alert"
	"github.com/TwiN/gatus/v5/core"
	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/awserr"
	"github.com/aws/aws-sdk-go/aws/credentials"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/ses"
)

const (
	CharSet = "UTF-8"
)

// AlertProvider is the configuration necessary for sending an alert using AWS Simple Email Service
type AlertProvider struct {
	AccessKeyID     string `yaml:"access-key-id"`
	SecretAccessKey string `yaml:"secret-access-key"`
	Region          string `yaml:"region"`

	From string `yaml:"from"`
	To   string `yaml:"to"`

	// DefaultAlert is the default alert configuration to use for endpoints with an alert of the appropriate type
	DefaultAlert *alert.Alert `yaml:"default-alert,omitempty"`

	// Overrides is a list of Override that may be prioritized over the default configuration
	Overrides []Override `yaml:"overrides,omitempty"`
}

// Override is a case under which the default integration is overridden
type Override struct {
	Group string `yaml:"group"`
	To    string `yaml:"to"`
}

// IsValid returns whether the provider's configuration is valid
func (provider *AlertProvider) IsValid() bool {
	registeredGroups := make(map[string]bool)
	if provider.Overrides != nil {
		for _, override := range provider.Overrides {
			if isAlreadyRegistered := registeredGroups[override.Group]; isAlreadyRegistered || override.Group == "" || len(override.To) == 0 {
				return false
			}
			registeredGroups[override.Group] = true
		}
	}
	// if both AccessKeyID and SecretAccessKey are specified, we'll use these to authenticate,
	// otherwise if neither are specified, then we'll fall back on IAM authentication.
	return len(provider.From) > 0 && len(provider.To) > 0 &&
		((len(provider.AccessKeyID) == 0 && len(provider.SecretAccessKey) == 0) || (len(provider.AccessKeyID) > 0 && len(provider.SecretAccessKey) > 0))
}

// Send an alert using the provider
func (provider *AlertProvider) Send(endpoint *core.Endpoint, alert *alert.Alert, result *core.Result, resolved bool) error {
	sess, err := provider.createSession()
	if err != nil {
		return err
	}
	svc := ses.New(sess)
	subject, body := provider.buildMessageSubjectAndBody(endpoint, alert, result, resolved)
	emails := strings.Split(provider.getToForGroup(endpoint.Group), ",")

	input := &ses.SendEmailInput{
		Destination: &ses.Destination{
			ToAddresses: aws.StringSlice(emails),
		},
		Message: &ses.Message{
			Body: &ses.Body{
				Text: &ses.Content{
					Charset: aws.String(CharSet),
					Data:    aws.String(body),
				},
			},
			Subject: &ses.Content{
				Charset: aws.String(CharSet),
				Data:    aws.String(subject),
			},
		},
		Source: aws.String(provider.From),
	}
	_, err = svc.SendEmail(input)

	if err != nil {
		if aerr, ok := err.(awserr.Error); ok {
			switch aerr.Code() {
			case ses.ErrCodeMessageRejected:
				fmt.Println(ses.ErrCodeMessageRejected, aerr.Error())
			case ses.ErrCodeMailFromDomainNotVerifiedException:
				fmt.Println(ses.ErrCodeMailFromDomainNotVerifiedException, aerr.Error())
			case ses.ErrCodeConfigurationSetDoesNotExistException:
				fmt.Println(ses.ErrCodeConfigurationSetDoesNotExistException, aerr.Error())
			default:
				fmt.Println(aerr.Error())
			}
		} else {
			// Print the error, cast err to awserr.Error to get the Code and
			// Message from an error.
			fmt.Println(err.Error())
		}

		return err
	}
	return nil
}

// buildMessageSubjectAndBody builds the message subject and body
func (provider *AlertProvider) buildMessageSubjectAndBody(endpoint *core.Endpoint, alert *alert.Alert, result *core.Result, resolved bool) (string, string) {
	var subject, message string
	if resolved {
		subject = fmt.Sprintf("[%s] Alert resolved", endpoint.DisplayName())
		message = fmt.Sprintf("An alert for %s has been resolved after passing successfully %d time(s) in a row", endpoint.DisplayName(), alert.SuccessThreshold)
	} else {
		subject = fmt.Sprintf("[%s] Alert triggered", endpoint.DisplayName())
		message = fmt.Sprintf("An alert for %s has been triggered due to having failed %d time(s) in a row", endpoint.DisplayName(), alert.FailureThreshold)
	}
	var formattedConditionResults string
	if len(result.ConditionResults) > 0 {
		formattedConditionResults = "\n\nCondition results:\n"
		for _, conditionResult := range result.ConditionResults {
			var prefix string
			if conditionResult.Success {
				prefix = "✅"
			} else {
				prefix = "❌"
			}
			formattedConditionResults += fmt.Sprintf("%s %s\n", prefix, conditionResult.Condition)
		}
	}
	var description string
	if alertDescription := alert.GetDescription(); len(alertDescription) > 0 {
		description = "\n\nAlert description: " + alertDescription
	}
	return subject, message + description + formattedConditionResults
}

// getToForGroup returns the appropriate email integration to for a given group
func (provider *AlertProvider) getToForGroup(group string) string {
	if provider.Overrides != nil {
		for _, override := range provider.Overrides {
			if group == override.Group {
				return override.To
			}
		}
	}
	return provider.To
}

// GetDefaultAlert returns the provider's default alert configuration
func (provider *AlertProvider) GetDefaultAlert() *alert.Alert {
	return provider.DefaultAlert
}

func (provider *AlertProvider) createSession() (*session.Session, error) {
	config := &aws.Config{
		Region: aws.String(provider.Region),
	}
	if len(provider.AccessKeyID) > 0 && len(provider.SecretAccessKey) > 0 {
		config.Credentials = credentials.NewStaticCredentials(provider.AccessKeyID, provider.SecretAccessKey, "")
	}
	return session.NewSession(config)
}