// email/client.go – IMAP-Client für Email-Abfragen
package email

import (
	"crypto/tls"
	"fmt"

	imap "github.com/emersion/go-imap/v2"
	"github.com/emersion/go-imap/v2/imapclient"

	"my-brain-importer/internal/config"
)

// Message repräsentiert eine Email (ohne Body für schnelle Übersichten).
type Message struct {
	Subject string
	From    string
	Date    string
}

// Client wraps die IMAP-Verbindung.
type Client struct {
	c *imapclient.Client
}

// Connect öffnet eine IMAP-Verbindung.
func Connect() (*Client, error) {
	cfg := config.Cfg.Email
	addr := fmt.Sprintf("%s:%d", cfg.Host, cfg.Port)

	var (
		c   *imapclient.Client
		err error
	)

	switch {
	case cfg.TLS:
		tlsCfg := &tls.Config{ServerName: cfg.Host}
		c, err = imapclient.DialTLS(addr, &imapclient.Options{TLSConfig: tlsCfg})
	case cfg.StartTLS:
		tlsCfg := &tls.Config{ServerName: cfg.Host}
		c, err = imapclient.DialStartTLS(addr, &imapclient.Options{TLSConfig: tlsCfg})
	default:
		c, err = imapclient.DialInsecure(addr, nil)
	}
	if err != nil {
		return nil, fmt.Errorf("IMAP verbinden: %w", err)
	}

	if err := c.Login(cfg.User, cfg.Password).Wait(); err != nil {
		c.Close()
		return nil, fmt.Errorf("IMAP login: %w", err)
	}

	return &Client{c: c}, nil
}

// Close schließt die Verbindung.
func (cl *Client) Close() {
	cl.c.Logout().Wait()
	cl.c.Close()
}

// FetchRecent holt die letzten n Emails (Envelope-Daten, kein Body).
func (cl *Client) FetchRecent(n uint32) ([]Message, error) {
	folder := config.Cfg.Email.Folder
	if folder == "" {
		folder = "INBOX"
	}

	selectData, err := cl.c.Select(folder, &imap.SelectOptions{ReadOnly: true}).Wait()
	if err != nil {
		return nil, fmt.Errorf("IMAP select: %w", err)
	}
	if selectData.NumMessages == 0 {
		return nil, nil
	}

	start := uint32(1)
	if selectData.NumMessages > n {
		start = selectData.NumMessages - n + 1
	}

	var seqSet imap.SeqSet
	seqSet.AddRange(start, selectData.NumMessages)

	msgs, err := cl.c.Fetch(seqSet, &imap.FetchOptions{Envelope: true}).Collect()
	if err != nil {
		return nil, fmt.Errorf("IMAP fetch: %w", err)
	}

	return parseMessages(msgs), nil
}

// FetchUnread holt ungelesene Emails (Envelope-Daten, kein Body).
func (cl *Client) FetchUnread() ([]Message, error) {
	folder := config.Cfg.Email.Folder
	if folder == "" {
		folder = "INBOX"
	}

	if _, err := cl.c.Select(folder, &imap.SelectOptions{ReadOnly: true}).Wait(); err != nil {
		return nil, fmt.Errorf("IMAP select: %w", err)
	}

	searchData, err := cl.c.Search(&imap.SearchCriteria{
		NotFlag: []imap.Flag{imap.FlagSeen},
	}, nil).Wait()
	if err != nil {
		return nil, fmt.Errorf("IMAP search: %w", err)
	}

	seqNums := searchData.AllSeqNums()
	if len(seqNums) == 0 {
		return nil, nil
	}

	var seqSet imap.SeqSet
	seqSet.AddNum(seqNums...)

	msgs, err := cl.c.Fetch(seqSet, &imap.FetchOptions{Envelope: true}).Collect()
	if err != nil {
		return nil, fmt.Errorf("IMAP fetch: %w", err)
	}

	return parseMessages(msgs), nil
}

func parseMessages(msgs []*imapclient.FetchMessageBuffer) []Message {
	result := make([]Message, 0, len(msgs))
	for _, msg := range msgs {
		if msg.Envelope == nil {
			continue
		}
		m := Message{
			Subject: msg.Envelope.Subject,
			Date:    msg.Envelope.Date.Format("2006-01-02 15:04"),
		}
		if len(msg.Envelope.From) > 0 {
			addr := msg.Envelope.From[0]
			if addr.Name != "" {
				m.From = fmt.Sprintf("%s <%s@%s>", addr.Name, addr.Mailbox, addr.Host)
			} else {
				m.From = fmt.Sprintf("%s@%s", addr.Mailbox, addr.Host)
			}
		}
		result = append(result, m)
	}
	return result
}