package mail

import (
	"fmt"
	"log"
	"net"
	"net/smtp"
	"strings"
)

var smtpSendMail = smtp.SendMail

// Message is an outbound email. Callers must not log Address or Body (PII).
type Message struct {
	To      string
	Subject string
	Text    string
	HTML    string
}

type Mailer interface {
	Send(msg Message) error
	Enabled() bool
}

type Config struct {
	Enabled  bool
	Host     string
	Port     string
	User     string
	Password string
	From     string
}

// New returns an SMTP mailer when enabled and configured; otherwise a no-op that logs event type only.
func New(cfg Config) Mailer {
	if !cfg.Enabled || strings.TrimSpace(cfg.Host) == "" {
		return &noopMailer{}
	}
	return &smtpMailer{cfg: cfg}
}

type noopMailer struct{}

func (n *noopMailer) Enabled() bool { return false }

func (n *noopMailer) Send(msg Message) error {
	log.Printf("mail: skipped (SMTP disabled) subject=%q", msg.Subject)
	return nil
}

type smtpMailer struct {
	cfg Config
}

func (s *smtpMailer) Enabled() bool { return true }

func (s *smtpMailer) Send(msg Message) error {
	to := strings.TrimSpace(msg.To)
	if to == "" {
		return fmt.Errorf("mail: recipient required")
	}
	if hasHeaderBreak(to) {
		return fmt.Errorf("mail: invalid recipient")
	}
	from := strings.TrimSpace(s.cfg.From)
	if from == "" {
		return fmt.Errorf("mail: from address required")
	}
	if hasHeaderBreak(from) {
		return fmt.Errorf("mail: invalid from address")
	}
	if hasHeaderBreak(msg.Subject) {
		return fmt.Errorf("mail: invalid subject")
	}
	addr := net.JoinHostPort(s.cfg.Host, s.cfg.Port)
	boundary := "descrybe_boundary_7f3a"
	var body strings.Builder
	body.WriteString(fmt.Sprintf("From: %s\r\n", from))
	body.WriteString(fmt.Sprintf("To: %s\r\n", to))
	body.WriteString(fmt.Sprintf("Subject: %s\r\n", msg.Subject))
	body.WriteString("MIME-Version: 1.0\r\n")
	if strings.TrimSpace(msg.HTML) != "" {
		body.WriteString(fmt.Sprintf("Content-Type: multipart/alternative; boundary=%s\r\n\r\n", boundary))
		body.WriteString(fmt.Sprintf("--%s\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\n%s\r\n", boundary, msg.Text))
		body.WriteString(fmt.Sprintf("--%s\r\nContent-Type: text/html; charset=UTF-8\r\n\r\n%s\r\n", boundary, msg.HTML))
		body.WriteString(fmt.Sprintf("--%s--\r\n", boundary))
	} else {
		body.WriteString("Content-Type: text/plain; charset=UTF-8\r\n\r\n")
		body.WriteString(msg.Text)
	}

	var auth smtp.Auth
	if s.cfg.User != "" {
		auth = smtp.PlainAuth("", s.cfg.User, s.cfg.Password, s.cfg.Host)
	}
	if err := smtpSendMail(addr, auth, from, []string{to}, []byte(body.String())); err != nil {
		log.Printf("mail: send failed subject=%q", msg.Subject)
		return fmt.Errorf("mail send failed")
	}
	log.Printf("mail: sent subject=%q", msg.Subject)
	return nil
}

func hasHeaderBreak(v string) bool {
	return strings.ContainsAny(v, "\r\n")
}

func InviteMessage(webOrigin, email, token, companyName string) Message {
	link := AcceptInviteURL(webOrigin, token)
	text := fmt.Sprintf("You have been invited to %s on Descrybe.\n\nAccept: %s\n", companyName, link)
	html := fmt.Sprintf(
		`<p>You have been invited to <strong>%s</strong> on Descrybe.</p><p><a href="%s">Accept invite</a></p>`,
		companyName, link,
	)
	return Message{To: email, Subject: "You are invited to Descrybe", Text: text, HTML: html}
}

// AcceptInviteURL builds the durable invite / set-password accept link (hashed invite tokens).
func AcceptInviteURL(webOrigin, token string) string {
	return strings.TrimRight(webOrigin, "/") + "/accept-invite?token=" + token
}

// SetPasswordURL builds the HMAC set-password accept-invite link.
func SetPasswordURL(webOrigin, token string) string {
	return strings.TrimRight(webOrigin, "/") + "/accept-invite?token=" + token + "&mode=set-password"
}

func SetPasswordMessage(webOrigin, email, token string) Message {
	link := SetPasswordURL(webOrigin, token)
	text := fmt.Sprintf("Set your Descrybe password:\n\n%s\n\nThis link expires in 72 hours.\n", link)
	html := fmt.Sprintf(
		`<p>Set your Descrybe password:</p><p><a href="%s">Set password</a></p><p>This link expires in 72 hours.</p>`,
		link,
	)
	return Message{To: email, Subject: "Set your Descrybe password", Text: text, HTML: html}
}

// MigratedSetPasswordMessage uses migrator invite tokens (accept-invite flow).
func MigratedSetPasswordMessage(webOrigin, email, token string) Message {
	link := AcceptInviteURL(webOrigin, token)
	text := fmt.Sprintf(
		"Your Descrybe account was migrated. Set your password here:\n\n%s\n\nIf you did not expect this email, ignore it.\n",
		link,
	)
	html := fmt.Sprintf(
		`<p>Your Descrybe account was migrated.</p><p><a href="%s">Set your password</a></p><p>If you did not expect this email, ignore it.</p>`,
		link,
	)
	return Message{To: email, Subject: "Set your Descrybe password", Text: text, HTML: html}
}

// ResetPasswordURL builds the self-serve forgot-password reset link.
// Token is placed in the URL fragment so it is not sent on the page GET (Referer/access logs).
func ResetPasswordURL(webOrigin, token string) string {
	return strings.TrimRight(webOrigin, "/") + "/reset-password#token=" + token
}

// ForgotPasswordMessage is the self-serve reset email (not first-set / accept-invite).
func ForgotPasswordMessage(webOrigin, email, token string) Message {
	link := ResetPasswordURL(webOrigin, token)
	text := fmt.Sprintf(
		"Reset your Descrybe password:\n\n%s\n\nThis link expires in 1 hour. If you did not request a reset, ignore this email.\n",
		link,
	)
	html := fmt.Sprintf(
		`<p>Reset your Descrybe password:</p><p><a href="%s">Reset password</a></p><p>This link expires in 1 hour. If you did not request a reset, ignore this email.</p>`,
		link,
	)
	return Message{To: email, Subject: "Reset your Descrybe password", Text: text, HTML: html}
}