package mailer

import (
	"crypto/tls"
	"fmt"
	"net/smtp"
	"os"
	"strconv"
	"strings"
)

func envBool(key string) bool {
	v, err := strconv.ParseBool(strings.TrimSpace(os.Getenv(key)))
	if err != nil {
		return false
	}
	return v
}

func Send(to, subject, body string) error {
	host := strings.TrimSpace(os.Getenv("EMAIL_HOST"))
	port := strings.TrimSpace(os.Getenv("EMAIL_PORT"))
	from := strings.TrimSpace(os.Getenv("EMAIL_FROM"))
	username := strings.TrimSpace(os.Getenv("EMAIL_HOST_USER"))
	password := strings.TrimSpace(os.Getenv("EMAIL_HOST_PASSWORD"))

	if host == "" || port == "" || from == "" {
		return fmt.Errorf("email configuration is incomplete")
	}

	addr := host + ":" + port
	msg := strings.Join([]string{
		"From: " + from,
		"To: " + to,
		"Subject: " + subject,
		"MIME-Version: 1.0",
		"Content-Type: text/plain; charset=UTF-8",
		"",
		body,
	}, "\r\n")

	var auth smtp.Auth
	if username != "" {
		auth = smtp.PlainAuth("", username, password, host)
	}

	useSSL := envBool("EMAIL_USE_SSL")
	useTLS := envBool("EMAIL_USE_TLS")

	if useSSL {
		conn, err := tls.Dial("tcp", addr, &tls.Config{ServerName: host})
		if err != nil {
			return err
		}
		defer conn.Close()

		client, err := smtp.NewClient(conn, host)
		if err != nil {
			return err
		}
		defer client.Quit()

		if auth != nil {
			if err := client.Auth(auth); err != nil {
				return err
			}
		}

		if err := client.Mail(from); err != nil {
			return err
		}
		if err := client.Rcpt(to); err != nil {
			return err
		}

		w, err := client.Data()
		if err != nil {
			return err
		}
		if _, err := w.Write([]byte(msg)); err != nil {
			_ = w.Close()
			return err
		}
		return w.Close()
	}

	if !useTLS {
		return smtp.SendMail(addr, auth, from, []string{to}, []byte(msg))
	}

	client, err := smtp.Dial(addr)
	if err != nil {
		return err
	}
	defer client.Quit()

	if err := client.StartTLS(&tls.Config{ServerName: host}); err != nil {
		return err
	}

	if auth != nil {
		if err := client.Auth(auth); err != nil {
			return err
		}
	}

	if err := client.Mail(from); err != nil {
		return err
	}
	if err := client.Rcpt(to); err != nil {
		return err
	}

	w, err := client.Data()
	if err != nil {
		return err
	}
	if _, err := w.Write([]byte(msg)); err != nil {
		_ = w.Close()
		return err
	}
	return w.Close()
}