package main

import (
	"fmt"
	"strings"
	"time"

	imap "github.com/BrianLeishman/go-imap"
)

type ReceivedEmail struct {
	UID       uint32
	From      string
	FromName  string
	Subject   string
	Date      time.Time
	Preview   string
	Account   string
	AccountID string
}

func getEmailProviderName(email string) string {
	if len(email) == 0 {
		return "Email"
	}
	atIdx := -1
	for i := len(email) - 1; i >= 0; i-- {
		if email[i] == '@' {
			atIdx = i
			break
		}
	}
	if atIdx == -1 {
		return "Email"
	}
	domain := email[atIdx+1:]
	for i := len(domain) - 1; i >= 0; i-- {
		if domain[i] == '.' {
			return domain[:i]
		}
	}
	return domain
}

func FetchUnreadEmails(account Account, days int) ([]ReceivedEmail, error) {
	if account.IMAP.Host == "" {
		return nil, fmt.Errorf("IMAP host not configured for account: %s", account.Email)
	}

	port := account.IMAP.Port
	if port == 0 {
		port = 993
	}

	username := account.IMAP.Username
	if username == "" {
		username = account.Email
	}

	m, err := imap.New(username, account.IMAP.Password, account.IMAP.Host, port)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to IMAP server: %w", err)
	}
	defer m.Close()

	if account.CheckID != nil && *account.CheckID {
		info := ProjectConfig.Info
		idCmd := fmt.Sprintf("ID (\"name\" \"%s\" \"version\" \"%s\" \"vendor\" \"%s\")",
			info.Name, info.Version, info.Vendor)
		_, err := m.Exec(idCmd, false, 0, func(line []byte) error {
			return nil
		})
		if err != nil {
			fmt.Printf("WARNING: failed to send IMAP ID: %v\n", err)
		}

		m.Exec("NOOP", false, 0, nil)
	}

	err = m.SelectFolder("INBOX")
	if err != nil {
		return nil, fmt.Errorf("failed to select inbox: %w", err)
	}

	sinceDate := time.Now().AddDate(0, 0, -days)

	uids, err := m.GetUIDs(imap.Search().Since(sinceDate).Unseen().Build())
	if err != nil {
		return nil, fmt.Errorf("failed to search emails: %w", err)
	}

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

	overviews, err := m.GetOverviews(uids...)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch emails: %w", err)
	}

	var emails []ReceivedEmail
	accountName := getEmailProviderName(account.Email)
	accountID := account.Email
	if account.Name != "" {
		accountName = account.Name
		accountID = account.Name
	}

	for uid, email := range overviews {
		from := ""
		if len(email.From) > 0 {
			for _, addr := range email.From {
				from = addr
				break
			}
		}

		emails = append(emails, ReceivedEmail{
			UID:       uint32(uid),
			From:      from,
			FromName:  "",
			Subject:   email.Subject,
			Date:      email.Sent,
			Preview:   fmt.Sprintf("(%.1f KB)", float64(email.Size)/1024),
			Account:   accountName,
			AccountID: accountID,
		})
	}

	return emails, nil
}

func GetAccountByEmail(email string) (Account, error) {
	accounts, err := getAccounts()
	if err != nil {
		return Account{}, err
	}

	for _, acc := range accounts {
		if acc.Email == email || acc.Name == email {
			return acc, nil
		}
	}

	return Account{}, fmt.Errorf("account not found: %s", email)
}

func GetAccountByID(id string) (Account, error) {
	accounts, err := getAccounts()
	if err != nil {
		return Account{}, err
	}

	for _, acc := range accounts {
		if acc.Email == id || acc.Name == id {
			return acc, nil
		}
	}

	return Account{}, fmt.Errorf("account not found: %s", id)
}

func FetchAllUnreadEmails(days int) ([]ReceivedEmail, error) {
	accounts, err := getAccounts()
	if err != nil {
		return nil, err
	}

	if len(accounts) == 0 {
		return nil, fmt.Errorf("no accounts configured")
	}

	var allEmails []ReceivedEmail

	for _, account := range accounts {
		emails, err := FetchUnreadEmails(account, days)
		if err != nil {
			continue
		}
		allEmails = append(allEmails, emails...)
	}

	sortEmailsByDate(allEmails)

	return allEmails, nil
}

func sortEmailsByDate(emails []ReceivedEmail) {
	for i := 0; i < len(emails)-1; i++ {
		for j := i + 1; j < len(emails); j++ {
			if emails[j].Date.After(emails[i].Date) {
				emails[i], emails[j] = emails[j], emails[i]
			}
		}
	}
}

type EmailDetail struct {
	UID       uint32
	From      string
	FromName  string
	To        string
	Cc        string
	Subject   string
	Date      time.Time
	TextBody  string
	HTMLBody  string
	Account   string
	AccountID string
}

func FetchEmailDetailByUID(accountID string, uid uint32) (*EmailDetail, error) {
	account, err := GetAccountByID(accountID)
	if err != nil {
		return nil, err
	}

	if account.IMAP.Host == "" {
		return nil, fmt.Errorf("IMAP host not configured for account: %s", account.Email)
	}

	port := account.IMAP.Port
	if port == 0 {
		port = 993
	}

	username := account.IMAP.Username
	if username == "" {
		username = account.Email
	}

	m, err := imap.New(username, account.IMAP.Password, account.IMAP.Host, port)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to IMAP server: %w", err)
	}
	defer m.Close()

	if account.CheckID != nil && *account.CheckID {
		info := ProjectConfig.Info
		idCmd := fmt.Sprintf("ID (\"name\" \"%s\" \"version\" \"%s\" \"vendor\" \"%s\")",
			info.Name, info.Version, info.Vendor)
		_, err := m.Exec(idCmd, false, 0, func(line []byte) error {
			return nil
		})
		if err != nil {
			fmt.Printf("WARNING: failed to send IMAP ID: %v\n", err)
		}

		m.Exec("NOOP", false, 0, nil)
	}

	err = m.SelectFolder("INBOX")
	if err != nil {
		return nil, fmt.Errorf("failed to select inbox: %w", err)
	}

	emails, err := m.GetEmails(int(uid))
	if err != nil {
		return nil, fmt.Errorf("failed to fetch email: %w", err)
	}

	if len(emails) == 0 {
		return nil, fmt.Errorf("email not found")
	}

	var email imap.Email
	found := false
	for i := range emails {
		if emails[i] != nil {
			email = *emails[i]
			found = true
			break
		}
	}

	if !found {
		return nil, fmt.Errorf("email not found or has been removed")
	}

	accountName := getEmailProviderName(account.Email)
	accountIDName := account.Email
	if account.Name != "" {
		accountName = account.Name
		accountIDName = account.Name
	}

	var fromName string
	var fromAddr string
	if email.From != nil {
		for name, addr := range email.From {
			fromName = name
			fromAddr = addr
			break
		}
	}

	var toList []string
	if email.To != nil {
		for name, addr := range email.To {
			if name != "" {
				toList = append(toList, fmt.Sprintf("%s <%s>", name, addr))
			} else {
				toList = append(toList, addr)
			}
		}
	}

	var ccList []string
	if email.CC != nil {
		for name, addr := range email.CC {
			if name != "" {
				ccList = append(ccList, fmt.Sprintf("%s <%s>", name, addr))
			} else {
				ccList = append(ccList, addr)
			}
		}
	}

	fromStr := fromAddr
	if fromName != "" {
		fromStr = fmt.Sprintf("%s <%s>", fromName, fromAddr)
	}

	return &EmailDetail{
		UID:       uint32(email.UID),
		From:      fromStr,
		FromName:  fromName,
		To:        strings.Join(toList, ", "),
		Cc:        strings.Join(ccList, ", "),
		Subject:   email.Subject,
		Date:      email.Sent,
		TextBody:  email.Text,
		HTMLBody:  email.HTML,
		Account:   accountName,
		AccountID: accountIDName,
	}, nil
}