package email

import (
	"crypto/tls"
	"fmt"
	"io"
	"log"
	"regexp"
	"strings"
	"time"

	"reservation-system/backend/internal/db"
	"reservation-system/backend/internal/models"

	"github.com/emersion/go-imap"
	"github.com/emersion/go-imap/client"
)

type EmailProcessor struct {
	db     *db.DB
	running bool
	stop   chan bool
}

func NewEmailProcessor(database *db.DB) *EmailProcessor {
	return &EmailProcessor{
		db:   database,
		stop: make(chan bool),
	}
}

func (ep *EmailProcessor) Start() {
	if ep.running {
		return
	}
	ep.running = true
	go ep.pollLoop()
}

func (ep *EmailProcessor) Stop() {
	ep.running = false
	close(ep.stop)
}

func (ep *EmailProcessor) pollLoop() {
	ticker := time.NewTicker(5 * time.Minute)
	defer ticker.Stop()

	// Run immediately on start
	ep.processEmails()

	for {
		select {
		case <-ticker.C:
			if !ep.running {
				return
			}
			ep.processEmails()
		case <-ep.stop:
			return
		}
	}
}

func (ep *EmailProcessor) processEmails() error {
	cfg, err := ep.db.GetEmailConfig()
	if err != nil {
		log.Printf("Email config error: %v", err)
		return err
	}
	if cfg == nil {
		log.Println("No email config found")
		return nil
	}

	// Connect to IMAP server
	addr := fmt.Sprintf("%s:%d", cfg.Host, cfg.Port)
	var c *client.Client

	if cfg.SSL {
		c, err = client.DialTLS(addr, &tls.Config{InsecureSkipVerify: true})
	} else {
		c, err = client.Dial(addr)
	}
	if err != nil {
		log.Printf("IMAP connect error: %v", err)
		return err
	}
	defer c.Logout()

	// Login
	if err := c.Login(cfg.Username, cfg.Password); err != nil {
		log.Printf("IMAP login error: %v", err)
		return err
	}

	// Select inbox
	mbox, err := c.Select(cfg.Folder, false)
	if err != nil {
		log.Printf("IMAP select error: %v", err)
		return err
	}

	if mbox.Messages == 0 {
		return nil
	}

	// Fetch unread messages
	criteria := imap.NewSearchCriteria()
	criteria.WithoutFlags = []string{imap.SeenFlag}
	uids, err := c.UidSearch(criteria)
	if err != nil {
		log.Printf("IMAP search error: %v", err)
		return err
	}

	if len(uids) == 0 {
		return nil
	}

	for _, uid := range uids {
		ep.processMessage(c, uid)
	}

	return nil
}

func (ep *EmailProcessor) processMessage(c *client.Client, uid uint32) {
	seqSet := new(imap.SeqSet)
	seqSet.AddNum(uid)

	section := &imap.BodySectionName{}
	items := []imap.FetchItem{section.FetchItem()}

	messages := make(chan *imap.Message, 1)
	go func() {
		if err := c.UidFetch(seqSet, items, messages); err != nil {
			log.Printf("Fetch error: %v", err)
		}
	}()

	msg := <-messages
	if msg == nil {
		return
	}

	r := msg.GetBody(section)
	if r == nil {
		return
	}

	body, err := io.ReadAll(r)
	if err != nil {
		log.Printf("Read error: %v", err)
		return
	}

	// Parse reservation from email
	reservation := ep.parseReservation(string(body))
	if reservation != nil {
		// Find available table
		tables, _ := ep.db.GetAllTables()
		for _, table := range tables {
			available, _ := ep.db.CheckAvailability(table.ID, reservation.Date, reservation.TimeFrom, reservation.TimeTo)
			if available && table.MaxGuests >= reservation.Guests {
				reservation.TableID = table.ID
				reservation.Source = "email"
				if err := ep.db.CreateReservation(reservation); err != nil {
					log.Printf("Create reservation error: %v", err)
				}
				break
			}
		}
	}

	// Mark as seen
	seqSet2 := new(imap.SeqSet)
	seqSet2.AddNum(uid)
	c.UidStore(seqSet2, imap.FormatFlagsAdd, []string{imap.SeenFlag})
}

func (ep *EmailProcessor) parseReservation(body string) *models.Reservation {
	res := &models.Reservation{}
	parsed := false

	// Try to extract date
	datePatterns := []*regexp.Regexp{
		regexp.MustCompile(`(?i)(?:am|den)\s+(\d{1,2})[./](\d{1,2})[./](\d{2,4})`),
		regexp.MustCompile(`(?i)(\d{1,2})[./](\d{1,2})[./](\d{2,4})`),
		regexp.MustCompile(`(?i)(\d{4})-(\d{2})-(\d{2})`),
	}

	for _, pattern := range datePatterns {
		if matches := pattern.FindStringSubmatch(body); matches != nil {
			if len(matches) >= 4 {
				if len(matches[3]) == 2 {
					res.Date = fmt.Sprintf("20%s-%s-%s", matches[3], matches[2], matches[1])
				} else {
					res.Date = fmt.Sprintf("%s-%s-%s", matches[3], matches[2], matches[1])
				}
				parsed = true
				break
			}
		}
	}

	// Try to extract time
	timePatterns := []*regexp.Regexp{
		regexp.MustCompile(`(?i)(\d{1,2})[:.](\d{2})\s*[Uu]hr`),
		regexp.MustCompile(`(?i)(\d{1,2})[:.](\d{2})`),
		regexp.MustCompile(`(?i)(\d{1,2})\s*[Uu]hr`),
	}

	for _, pattern := range timePatterns {
		if matches := pattern.FindStringSubmatch(body); matches != nil {
			if len(matches) >= 2 {
				res.TimeFrom = fmt.Sprintf("%02s:00", matches[1])
				res.TimeTo = fmt.Sprintf("%02d:00", parseInt(matches[1])+2)
				parsed = true
				break
			}
		}
	}

	// Try to extract guest count
	guestPatterns := []*regexp.Regexp{
		regexp.MustCompile(`(?i)(\d+)\s*(?:Personen|Gäste|Leute)`),
		regexp.MustCompile(`(?i)für\s+(\d+)\s*Personen`),
		regexp.MustCompile(`(?i)(\d+)\s*Personen`),
	}

	for _, pattern := range guestPatterns {
		if matches := pattern.FindStringSubmatch(body); matches != nil {
			res.Guests = parseInt(matches[1])
			parsed = true
			break
		}
	}

	// Try to extract name
	namePatterns := []*regexp.Regexp{
		regexp.MustCompile(`(?i)Name\s*[:\-]?\s*([^\n\r]+)`),
		regexp.MustCompile(`(?i)(?:von|Name)\s+([A-Z][a-z]+\s+[A-Z][a-z]+)`),
	}

	for _, pattern := range namePatterns {
		if matches := pattern.FindStringSubmatch(body); matches != nil {
			res.Name = strings.TrimSpace(matches[1])
			parsed = true
			break
		}
	}

	// Try to extract phone
	phonePattern := regexp.MustCompile(`(?i)Tel(?:efon)?[:\s]*([\d\s\-\+\(\)]{7,})`)
	if matches := phonePattern.FindStringSubmatch(body); matches != nil {
		res.Phone = strings.TrimSpace(matches[1])
	}

	// Try to extract email
	emailPattern := regexp.MustCompile(`[\w\.-]+@[\w\.-]+\.\w+`)
	if matches := emailPattern.FindStringSubmatch(body); matches != nil {
		res.Email = matches[0]
	}

	// Try to extract notes
	notePatterns := []*regexp.Regexp{
		regexp.MustCompile(`(?i)Notiz(?:en)?\s*[:\-]?\s*([^\n\r]+)`),
		regexp.MustCompile(`(?i)Bemerkung(?:en)?\s*[:\-]?\s*([^\n\r]+)`),
	}

	for _, pattern := range notePatterns {
		if matches := pattern.FindStringSubmatch(body); matches != nil {
			res.Notes = strings.TrimSpace(matches[1])
			break
		}
	}

	if parsed && res.Name != "" {
		return res
	}

	return nil
}

func parseInt(s string) int {
	var n int
	fmt.Sscanf(s, "%d", &n)
	return n
}