// Package aws 提供 Amazon SES 邮件发送通道。
package aws

import (
	"context"
	"fmt"
	"sync"
	"time"

	mailx "code.yun.ink/pkg/mailx"
	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/credentials"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/ses"
	"github.com/aws/aws-sdk-go/service/ses/sesiface"
)

// defaultTimeout 单次 API 调用的默认超时
const defaultTimeout = 30 * time.Second

// Config AWS SES 通道配置
type Config struct {
	AccessKeyID     string // AccessKey ID
	AccessKeySecret string // AccessKey Secret
	Region          string // Region，默认 ap-northeast-1
	Sender          string // 默认发件人（必填，AWS 需要预先验证发件地址）
	Timeout         time.Duration // 单次 API 调用的超时，默认 30s；0 表示交给 ctx 控制
}

// Aws AWS SES 发送通道
type Aws struct {
	cfg Config

	initOnce sync.Once
	svc      sesiface.SESAPI
	initErr  error
}

// New 创建 AWS 通道
func New(cfg Config) *Aws {
	if cfg.Region == "" {
		cfg.Region = "ap-northeast-1"
	}
	return &Aws{cfg: cfg}
}

// Name 返回通道名称
func (a *Aws) Name() string { return "aws" }

// Send 发送一封邮件
func (a *Aws) Send(ctx context.Context, msg *mailx.Message) error {
	logger := mailx.LoggerFromContext(ctx)

	sender := msg.From
	if sender == "" {
		sender = a.cfg.Sender
	}
	if sender == "" {
		return fmt.Errorf("%w: aws sender is required", mailx.ErrInvalidConfig)
	}
	if len(msg.Inline) > 0 {
		return fmt.Errorf("%w: aws SendEmail does not support inline images; use raw message mode", mailx.ErrInvalidConfig)
	}

	svc, err := a.client()
	if err != nil {
		return err
	}

	input := &ses.SendEmailInput{
		Source: aws.String(sender),
		Destination: &ses.Destination{
			ToAddresses:  aws.StringSlice(msg.To),
			CcAddresses:  aws.StringSlice(msg.Cc),
			BccAddresses: aws.StringSlice(msg.Bcc),
		},
		Message: &ses.Message{
			Subject: &ses.Content{Data: aws.String(msg.Subject), Charset: aws.String("UTF-8")},
			Body:    awsBody(msg),
		},
	}
	if msg.ReplyTo != "" {
		input.ReplyToAddresses = aws.StringSlice([]string{msg.ReplyTo})
	}

	ctx, cancel := a.withTimeout(ctx)
	defer cancel()
	if _, err := svc.SendEmailWithContext(ctx, input); err != nil {
		logger.Errorf(ctx, "mailx/aws: send to %v failed: %v", msg.To, err)
		return fmt.Errorf("%w: %v", mailx.ErrSendFailed, err)
	}
	logger.Infof(ctx, "mailx/aws: sent to %v subject=%q", msg.To, msg.Subject)
	return nil
}

// client 惰性初始化并复用 SES 客户端（线程安全）。
// 若已通过测试或其他方式注入 svc，则直接返回注入的客户端。
func (a *Aws) client() (sesiface.SESAPI, error) {
	if a.svc != nil {
		return a.svc, a.initErr
	}
	a.initOnce.Do(func() {
		sess, err := session.NewSession(&aws.Config{
			Region:      aws.String(a.cfg.Region),
			Credentials: credentials.NewStaticCredentials(a.cfg.AccessKeyID, a.cfg.AccessKeySecret, ""),
		})
		if err != nil {
			a.initErr = fmt.Errorf("%w: create aws session: %v", mailx.ErrInvalidConfig, err)
			return
		}
		a.svc = ses.New(sess)
	})
	return a.svc, a.initErr
}

// withTimeout 叠加配置超时到 ctx（已有更早 deadline 时保持不变）
func (a *Aws) withTimeout(ctx context.Context) (context.Context, context.CancelFunc) {
	if a.cfg.Timeout <= 0 {
		return ctx, func() {}
	}
	if dl, ok := ctx.Deadline(); ok && time.Until(dl) <= a.cfg.Timeout {
		return ctx, func() {}
	}
	return context.WithTimeout(ctx, a.cfg.Timeout)
}

// awsBody 构造 SES Body：优先使用 Html，其次 Text；两者都有时同时提供
func awsBody(msg *mailx.Message) *ses.Body {
	body := &ses.Body{}
	if msg.Body != "" {
		body.Html = &ses.Content{Data: aws.String(msg.Body), Charset: aws.String("UTF-8")}
	}
	if msg.TextBody != "" {
		body.Text = &ses.Content{Data: aws.String(msg.TextBody), Charset: aws.String("UTF-8")}
	}
	return body
}