package tools

import (
	"encoding/base64"
	"fmt"
	"log"
	"net/smtp"
	"os"
	"strconv"
	"strings"
)

// SMTPConfig holds email server configuration.
type SMTPConfig struct {
	Host     string
	Port     int
	User     string
	Password string
	From     string
}

// Attachment represents an email file attachment.
type Attachment struct {
	Filename    string
	ContentType string
	Data        []byte
}

// LoadSMTPConfig loads SMTP settings from environment variables.
// It first checks ODOO_SMTP_* prefixed vars, then falls back to SMTP_*.
func LoadSMTPConfig() *SMTPConfig {
	cfg := &SMTPConfig{
		Port: 587,
	}

	// Prefer ODOO_SMTP_* env vars, fall back to SMTP_*
	cfg.Host = envOr("ODOO_SMTP_HOST", os.Getenv("SMTP_HOST"))
	cfg.User = envOr("ODOO_SMTP_USER", os.Getenv("SMTP_USER"))
	cfg.Password = envOr("ODOO_SMTP_PASSWORD", os.Getenv("SMTP_PASSWORD"))
	cfg.From = envOr("ODOO_SMTP_FROM", os.Getenv("SMTP_FROM"))

	if v := envOr("ODOO_SMTP_PORT", os.Getenv("SMTP_PORT")); v != "" {
		if p, err := strconv.Atoi(v); err == nil {
			cfg.Port = p
		}
	}

	return cfg
}

// envOr returns the value of the named environment variable if set, otherwise fallback.
func envOr(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}

// SendEmail sends a simple HTML email without attachments.
// Returns nil (with a log message) if SMTP is not configured.
func SendEmail(cfg *SMTPConfig, to, subject, body string) error {
	if cfg.Host == "" {
		log.Printf("email: SMTP not configured, would send to=%s subject=%s", to, subject)
		return nil
	}

	msg := fmt.Sprintf("From: %s\r\nTo: %s\r\nSubject: %s\r\nMIME-Version: 1.0\r\nContent-Type: text/html; charset=utf-8\r\n\r\n%s",
		cfg.From, to, subject, body)

	auth := smtp.PlainAuth("", cfg.User, cfg.Password, cfg.Host)
	addr := fmt.Sprintf("%s:%d", cfg.Host, cfg.Port)

	return smtp.SendMail(addr, auth, cfg.From, []string{to}, []byte(msg))
}

// SendEmailWithAttachments sends an HTML email with optional file attachments.
// If SMTP is not configured, it logs the intent and returns nil.
func SendEmailWithAttachments(cfg *SMTPConfig, to []string, subject, bodyHTML string, attachments []Attachment) error {
	if cfg.Host == "" {
		log.Printf("email: SMTP not configured, would send to=%s subject=%s attachments=%d",
			strings.Join(to, ","), subject, len(attachments))
		return nil
	}

	addr := fmt.Sprintf("%s:%d", cfg.Host, cfg.Port)
	boundary := "==odoo-go-boundary-42=="

	var msg strings.Builder
	msg.WriteString(fmt.Sprintf("From: %s\r\n", cfg.From))
	msg.WriteString(fmt.Sprintf("To: %s\r\n", strings.Join(to, ", ")))
	msg.WriteString(fmt.Sprintf("Subject: %s\r\n", subject))
	msg.WriteString("MIME-Version: 1.0\r\n")

	if len(attachments) > 0 {
		msg.WriteString(fmt.Sprintf("Content-Type: multipart/mixed; boundary=\"%s\"\r\n\r\n", boundary))

		// HTML body part
		msg.WriteString(fmt.Sprintf("--%s\r\n", boundary))
		msg.WriteString("Content-Type: text/html; charset=utf-8\r\n")
		msg.WriteString("Content-Transfer-Encoding: 7bit\r\n\r\n")
		msg.WriteString(bodyHTML)
		msg.WriteString("\r\n")

		// Attachment parts
		for _, att := range attachments {
			msg.WriteString(fmt.Sprintf("\r\n--%s\r\n", boundary))
			ct := att.ContentType
			if ct == "" {
				ct = "application/octet-stream"
			}
			msg.WriteString(fmt.Sprintf("Content-Type: %s; name=\"%s\"\r\n", ct, att.Filename))
			msg.WriteString(fmt.Sprintf("Content-Disposition: attachment; filename=\"%s\"\r\n", att.Filename))
			msg.WriteString("Content-Transfer-Encoding: base64\r\n\r\n")
			msg.WriteString(base64.StdEncoding.EncodeToString(att.Data))
		}
		msg.WriteString(fmt.Sprintf("\r\n--%s--\r\n", boundary))
	} else {
		msg.WriteString("Content-Type: text/html; charset=utf-8\r\n\r\n")
		msg.WriteString(bodyHTML)
	}

	// Auth (nil if no user/password for relay servers)
	var auth smtp.Auth
	if cfg.User != "" {
		auth = smtp.PlainAuth("", cfg.User, cfg.Password, cfg.Host)
	}

	return smtp.SendMail(addr, auth, cfg.From, to, []byte(msg.String()))
}