const nodemailer = require('nodemailer')
const debug = require('debug')('48hr-email:smtp-service')

/**
 * SMTP Service for forwarding emails
 * Uses nodemailer to send forwarded emails via configured SMTP server
 */
class SmtpService {
    constructor(config) {
        this.config = config
        this.transporter = null

        // Only initialize transporter if SMTP is configured
        if (this._isConfigured()) {
            this._initializeTransporter()
        } else {
            debug('SMTP not configured - forwarding functionality will be unavailable')
        }
    }

    /**
     * Check if SMTP is properly configured
     * @returns {boolean}
     */
    _isConfigured() {
        return !!(
            this.config.smtp.enabled &&
            this.config.smtp.host &&
            this.config.smtp.user &&
            this.config.smtp.password
        )
    }

    /**
     * Initialize the nodemailer transporter
     * @private
     */
    _initializeTransporter() {
        try {
            this.transporter = nodemailer.createTransport({
                host: this.config.smtp.host,
                port: this.config.smtp.port,
                secure: this.config.smtp.secure,
                auth: {
                    user: this.config.smtp.user,
                    pass: this.config.smtp.password
                },
                tls: {
                    // Allow self-signed certificates and skip verification
                    // This is useful for development or internal SMTP servers
                    rejectUnauthorized: false
                }
            })

            debug(`SMTP transporter initialized: ${this.config.smtp.host}:${this.config.smtp.port}`)
        } catch (error) {
            debug('Failed to initialize SMTP transporter:', error.message)
            throw new Error(`SMTP initialization failed: ${error.message}`)
        }
    }

    /**
     * Forward an email to a destination address
     * @param {Object} mail - Parsed email object from mailparser
     * @param {string} destinationEmail - Email address to forward to
     * @returns {Promise<{success: boolean, error?: string, messageId?: string}>}
     */
    async forwardMail(mail, destinationEmail) {
        if (!this.transporter) {
            return {
                success: false,
                error: 'SMTP is not configured. Please configure SMTP settings to enable forwarding.'
            }
        }

        if (!mail) {
            return {
                success: false,
                error: 'Email not found'
            }
        }

        try {
            debug(`Forwarding email (Subject: "${mail.subject}") to ${destinationEmail}`)

            const forwardMessage = this._buildForwardMessage(mail, destinationEmail)

            const info = await this.transporter.sendMail(forwardMessage)

            debug(`Email forwarded successfully. MessageId: ${info.messageId}`)

            return {
                success: true,
                messageId: info.messageId
            }
        } catch (error) {
            debug('Failed to forward email:', error.message)
            return {
                success: false,
                error: `Failed to send email: ${error.message}`
            }
        }
    }

    /**
     * Build the forward message structure
     * @param {Object} mail - Parsed email object
     * @param {string} destinationEmail - Destination address
     * @returns {Object} - Nodemailer message object
     * @private
     */
    _buildForwardMessage(mail, destinationEmail) {
        // Extract original sender info
        const originalFrom = (mail.from && mail.from.text) || 'Unknown Sender'
        const originalTo = (mail.to && mail.to.text) || 'Unknown Recipient'
        const originalDate = mail.date ? new Date(mail.date).toLocaleString() : 'Unknown Date'
        const originalSubject = mail.subject || '(no subject)'

        // Build forwarded message body
        let forwardedBody = `
---------- Forwarded message ----------
From: ${originalFrom}
Date: ${originalDate}
Subject: ${originalSubject}
To: ${originalTo}


`

        // Add original text body if available
        if (mail.text) {
            forwardedBody += mail.text
        } else if (mail.html) {
            // If only HTML is available, mention it
            forwardedBody += '[This email contains HTML content. See attachment or HTML version below.]\n\n'
        }

        // Build the message object
        const message = {
            from: {
                name: this.config.smtp.fromName,
                address: this.config.smtp.user
            },
            to: destinationEmail,
            subject: `Fwd: ${originalSubject}`,
            text: forwardedBody,
            replyTo: originalFrom
        }

        // Add HTML body if available
        if (mail.html) {
            const htmlForwardedBody = `
<div style="border-left: 2px solid #ccc; padding-left: 10px; margin: 10px 0;">
    <p><strong>---------- Forwarded message ----------</strong><br>
    <strong>From:</strong> ${this._escapeHtml(originalFrom)}<br>
    <strong>Date:</strong> ${this._escapeHtml(originalDate)}<br>
    <strong>Subject:</strong> ${this._escapeHtml(originalSubject)}<br>
    <strong>To:</strong> ${this._escapeHtml(originalTo)}</p>
</div>
${mail.html}
`
            message.html = htmlForwardedBody
        }

        // Add attachments if present
        if (mail.attachments && mail.attachments.length > 0) {
            message.attachments = mail.attachments.map(att => ({
                filename: att.filename || 'attachment',
                content: att.content,
                contentType: att.contentType,
                contentDisposition: att.contentDisposition || 'attachment'
            }))

            debug(`Including ${mail.attachments.length} attachment(s) in forwarded email`)
        }

        return message
    }

    /**
     * Simple HTML escape for email headers
     * @param {string} text
     * @returns {string}
     * @private
     */
    _escapeHtml(text) {
        if (!text) return ''
        return String(text)
            .replace(/&/g, '&amp;')
            .replace(/</g, '&lt;')
            .replace(/>/g, '&gt;')
            .replace(/"/g, '&quot;')
            .replace(/'/g, '&#039;')
    }

    /**
     * Verify SMTP connection
     * @returns {Promise<{success: boolean, error?: string}>}
     */
    async verifyConnection() {
        if (!this.transporter) {
            return {
                success: false,
                error: 'SMTP is not configured'
            }
        }

        try {
            await this.transporter.verify()
            debug('SMTP connection verified successfully')
            return { success: true }
        } catch (error) {
            debug('SMTP connection verification failed:', error.message)
            return {
                success: false,
                error: error.message
            }
        }
    }
}

module.exports = SmtpService