package service

import (
	"context"
	"fmt"
	"net/mail"
	"net/smtp"
	"os"
	"strconv"
	"strings"

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

const contactExportCompleteSubject = "Your contact's export file is available to download."

// ContactExportMailer delivers the administrator notification emitted by
// Chatwoot's Account::ContactsExportJob after the CSV artifact is attached.
type ContactExportMailer interface {
	SendContactExportComplete(ctx context.Context, account *model.Account, user *model.User, export *model.ContactExport) error
}

type SMTPContactExportMailer struct {
	Address     string
	Port        int
	Username    string
	Password    string
	From        string
	FrontendURL string
}

func NewEnvContactExportMailer() *SMTPContactExportMailer {
	return &SMTPContactExportMailer{
		Address:     strings.TrimSpace(os.Getenv("SMTP_ADDRESS")),
		Port:        envInt("SMTP_PORT", 587),
		Username:    firstEnv("SMTP_USERNAME", "SMTP_LOGIN"),
		Password:    os.Getenv("SMTP_PASSWORD"),
		From:        firstEnv("MAILER_SENDER_EMAIL", "SMTP_FROM"),
		FrontendURL: strings.TrimRight(os.Getenv("FRONTEND_URL"), "/"),
	}
}

func (m *SMTPContactExportMailer) SendContactExportComplete(ctx context.Context, account *model.Account, user *model.User, export *model.ContactExport) error {
	_ = ctx
	if m == nil || strings.TrimSpace(m.Address) == "" || user == nil || strings.TrimSpace(user.Email) == "" || export == nil {
		return nil
	}
	fromHeader := strings.TrimSpace(m.From)
	if fromHeader == "" {
		fromHeader = "Chatwoot <accounts@chatwoot.com>"
	}
	fromAddress := fromHeader
	if parsed, err := mail.ParseAddress(fromHeader); err == nil {
		fromAddress = parsed.Address
	}

	to := strings.TrimSpace(user.Email)
	body := contactExportEmailBody(account, export, m.FrontendURL)
	message := smtpMessage(fromHeader, to, contactExportCompleteSubject, body)
	addr := fmt.Sprintf("%s:%d", strings.TrimSpace(m.Address), m.Port)

	var auth smtp.Auth
	if strings.TrimSpace(m.Username) != "" {
		auth = smtp.PlainAuth("", strings.TrimSpace(m.Username), m.Password, strings.TrimSpace(m.Address))
	}
	return smtp.SendMail(addr, auth, fromAddress, []string{to}, []byte(message))
}

func contactExportEmailBody(account *model.Account, export *model.ContactExport, frontendURL string) string {
	accountName := "your account"
	if account != nil && strings.TrimSpace(account.Name) != "" {
		accountName = account.Name
	}
	fileURL := export.FileURL
	if frontendURL != "" && strings.HasPrefix(fileURL, "/") {
		fileURL = frontendURL + fileURL
	}
	return fmt.Sprintf("The contact export for %s is ready.\n\nDownload: %s\n", accountName, fileURL)
}

func smtpMessage(from, to, subject, body string) string {
	return strings.Join([]string{
		"From: " + from,
		"To: " + to,
		"Subject: " + subject,
		"MIME-Version: 1.0",
		"Content-Type: text/plain; charset=UTF-8",
		"",
		body,
	}, "\r\n")
}

func firstEnv(keys ...string) string {
	for _, key := range keys {
		if value := strings.TrimSpace(os.Getenv(key)); value != "" {
			return value
		}
	}
	return ""
}

func envInt(key string, fallback int) int {
	value := strings.TrimSpace(os.Getenv(key))
	if value == "" {
		return fallback
	}
	parsed, err := strconv.Atoi(value)
	if err != nil || parsed <= 0 {
		return fallback
	}
	return parsed
}