package mail

import (
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"log"
	"net/smtp"
	"strings"
	"time"

	"wedding-server/internal/config"
	"wedding-server/internal/store"
)

type Mailer struct {
	cfg config.EmailConfig
}

func New(cfg config.EmailConfig) *Mailer {
	return &Mailer{cfg: cfg}
}

// newMessageID builds an RFC 5322 Message-ID, scoped to the sender's own
// domain so it satisfies mail servers that reject messages lacking one.
func newMessageID(from string) string {
	domain := "localhost"
	if i := strings.LastIndex(from, "@"); i != -1 {
		domain = strings.TrimSuffix(from[i+1:], ">")
	}

	var buf [16]byte
	_, _ = rand.Read(buf[:])
	return fmt.Sprintf("<%d.%s@%s>", time.Now().UnixNano(), hex.EncodeToString(buf[:]), domain)
}

func (m *Mailer) send(subject, body string) error {
	if m.cfg.SMTPHost == "" {
		log.Printf("mail: SMTP not configured, skipping email %q", subject)
		return nil
	}

	addr := fmt.Sprintf("%s:%d", m.cfg.SMTPHost, m.cfg.SMTPPort)
	auth := smtp.PlainAuth("", m.cfg.SMTPUser, m.cfg.SMTPPass, m.cfg.SMTPHost)

	msg := fmt.Sprintf(
		"From: %s\r\nTo: %s\r\nSubject: %s\r\nMessage-ID: %s\r\nDate: %s\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\n%s",
		m.cfg.From, m.cfg.To, subject, newMessageID(m.cfg.From), time.Now().Format(time.RFC1123Z), body,
	)

	recipients := []string{m.cfg.To}
	for bcc := range strings.SplitSeq(m.cfg.Bcc, ",") {
		if bcc = strings.TrimSpace(bcc); bcc != "" {
			recipients = append(recipients, bcc)
		}
	}

	return smtp.SendMail(addr, auth, m.cfg.From, recipients, []byte(msg))
}

func (m *Mailer) SendRSVP(r store.RSVP, allGuests []store.Guest) error {
	names := make([]string, len(r.Guests))
	adults, children := 0, 0
	for i, g := range r.Guests {
		if g.IsChild {
			names[i] = g.Name + " (child)"
			children++
		} else {
			names[i] = g.Name
			adults++
		}
	}
	joined := strings.Join(names, ", ")

	var b strings.Builder
	fmt.Fprintf(&b, "New RSVP for %d guest(s) — %d adult(s), %d child(ren): %s\n", len(r.Guests), adults, children, joined)
	if r.Message != "" {
		fmt.Fprintf(&b, "\nMessage:\n%s\n", r.Message)
	}

	if len(allGuests) > 0 {
		totalAdults, totalChildren := 0, 0
		fmt.Fprintf(&b, "\nRSVPs so far (%d guest(s)):\n", len(allGuests))
		for _, g := range allGuests {
			if g.IsChild {
				totalChildren++
				fmt.Fprintf(&b, "- %s (child)\n", g.Name)
			} else {
				totalAdults++
				fmt.Fprintf(&b, "- %s\n", g.Name)
			}
		}
		fmt.Fprintf(&b, "\n%d adult(s), %d child(ren) total\n", totalAdults, totalChildren)
	}

	return m.send(fmt.Sprintf("RSVP from %s", joined), b.String())
}

func (m *Mailer) SendPhotoUpload(u store.PhotoUpload, files []store.PhotoFile) error {
	var b strings.Builder
	fmt.Fprintf(&b, "%s uploaded %d photo(s)\n\n", u.Name, len(files))
	if u.Email != "" {
		fmt.Fprintf(&b, "Email: %s\n", u.Email)
	}
	if u.Phone != "" {
		fmt.Fprintf(&b, "Phone: %s\n", u.Phone)
	}
	if u.Message != "" {
		fmt.Fprintf(&b, "\nMessage:\n%s\n", u.Message)
	}
	b.WriteString("\nPhotos:\n")
	for _, f := range files {
		fmt.Fprintf(&b, "- %s\n", f.URL)
	}
	return m.send(fmt.Sprintf("%s uploaded photos", u.Name), b.String())
}