package email

// EmailService provides high-level operations for the Email channel.
// Reference: Chatwoot app/services/channel/email/process_mail_service.rb
// + app/services/channel/email/fetch_imap_email_service.rb
//
// This service coordinates:
//   - IMAPListener (IMAP polling and message fetching)
//   - SMTPSender (outbound email delivery)
//   - Content processing (HTML/text conversion, sanitization)
//   - Address mapping (email → contact identification)
//   - Thread context (In-Reply-To, References for conversation threading)
//
// The service implements EmailServiceInterface defined in provider/email.go,
// which is the contract between EmailProvider and the email sub-package.

import (
	"context"
	"net/mail"
	"strings"

	channelpkg "github.com/gochat/gochat/internal/channel"
	"github.com/gochat/gochat/internal/model"
)

// Service coordinates Email channel operations.
// This is the concrete implementation of EmailServiceInterface.
type Service struct {
	imapListener *IMAPListener
	smtpSender   *SMTPSender
}

// NewService creates a new Email service with IMAP and SMTP components.
func NewService() *Service {
	return &Service{
		imapListener: NewIMAPListener(),
		smtpSender:   NewSMTPSender(),
	}
}

// === EmailServiceInterface implementation ===

// ValidateIMAPConnection checks IMAP server connectivity and auth.
func (s *Service) ValidateIMAPConnection(config channelpkg.ChannelConfig) error {
	return s.imapListener.ValidateConnection(config)
}

// ValidateSMTPConnection checks SMTP server connectivity and auth.
func (s *Service) ValidateSMTPConnection(config channelpkg.ChannelConfig) error {
	return s.smtpSender.ValidateConnection(config)
}

// FetchIMAPMessages polls IMAP for new messages and converts them to IncomingMessage.
func (s *Service) FetchIMAPMessages(ctx context.Context, inbox *model.Inbox, config channelpkg.ChannelConfig) ([]*channelpkg.IncomingMessage, error) {
	return s.imapListener.Fetch(ctx, inbox, config)
}

// SendViaSMTP sends an outgoing email and returns the message ID.
func (s *Service) SendViaSMTP(config channelpkg.ChannelConfig, from, to, subject, body string) (string, error) {
	return s.smtpSender.Send(config, from, to, subject, body)
}

// === Address processing helpers (unique to service.go) ===

// extractEmailAddress extracts just the email address from a full address string.
// Handles formats like "John Doe <john@example.com>" or "john@example.com".
func extractEmailAddress(addr string) string {
	if addr == "" {
		return ""
	}
	// Try RFC 5322 parsing first
	addresses, err := mail.ParseAddressList(addr)
	if err == nil && len(addresses) > 0 {
		return addresses[0].Address
	}
	// Fallback: extract content between < and >
	start := strings.Index(addr, "<")
	end := strings.Index(addr, ">")
	if start >= 0 && end > start {
		return strings.TrimSpace(addr[start+1:end])
	}
	// Plain email address
	return strings.TrimSpace(addr)
}

// extractDisplayName extracts the display name from a full address string.
// Handles formats like "John Doe <john@example.com>" → "John Doe".
func extractDisplayName(addr string) string {
	if addr == "" {
		return ""
	}
	// Try RFC 5322 parsing first
	addresses, err := mail.ParseAddressList(addr)
	if err == nil && len(addresses) > 0 {
		if addresses[0].Name != "" {
			return addresses[0].Name
		}
		return "" // No display name, just email address
	}
	// Fallback: extract content before < if present
	start := strings.Index(addr, "<")
	if start >= 0 {
		name := strings.TrimSpace(addr[:start])
		// Remove surrounding quotes
		name = strings.Trim(name, "\"")
		return name
	}
	return "" // Just an email address, no display name
}