since3-portal/modules/shared/mail/send-mail.ts

import "server-only"
import { readFileSync } from "node:fs"
import path from "node:path"
import { COMPANY } from "@/modules/shared/data/company"
import { LOGO_CIDS } from "./layout"

const RESEND_ENDPOINT = "https://api.resend.com/emails"
const DEFAULT_FROM = "Since3 <portal@contact.since3.de>"

const ASSET_DIR = path.join(process.cwd(), "modules/shared/mail/assets")

let logoAttachments: { filename: string; content: string; content_type: string; content_id: string }[] | null = null

function logos() {
    logoAttachments ??= (["light", "dark"] as const).map((variant) => ({
        filename: `since3-logo-${variant}.png`,
        content: readFileSync(path.join(ASSET_DIR, `since3-logo-${variant}.png`)).toString("base64"),
        content_type: "image/png",
        content_id: LOGO_CIDS[variant],
    }))
    return logoAttachments
}

export type MailAttachment = { filename: string; content: Uint8Array; contentType: string }

export type SendMailResult = { ok: true; id: string } | { ok: false; error: string }

// Wirft nie: Mailversand ist Nebeneffekt, der eigentliche Vorgang (Client, Rechnung, ...) soll davon nicht scheitern.
export async function sendMail({
    to,
    subject,
    html,
    type,
    attachments = [],
    idempotencyKey,
}: {
    to: string
    subject: string
    html: string
    type: "welcome" | "credential" | "invoice"
    attachments?: MailAttachment[]
    idempotencyKey?: string
}): Promise<SendMailResult> {
    const apiKey = process.env.RESEND_SECRET_API_KEY
    if (!apiKey) {
        console.error("[mail] RESEND_SECRET_API_KEY ist nicht gesetzt.")
        return { ok: false, error: "Mailversand ist nicht eingerichtet." }
    }

    try {
        const response = await fetch(RESEND_ENDPOINT, {
            method: "POST",
            headers: {
                Authorization: `Bearer ${apiKey}`,
                "Content-Type": "application/json",
                ...(idempotencyKey ? { "Idempotency-Key": idempotencyKey } : {}),
            },
            body: JSON.stringify({
                from: process.env.MAIL_FROM ?? DEFAULT_FROM,
                to: [to],
                reply_to: COMPANY.email,
                subject,
                html,
                tags: [{ name: "type", value: type }],
                attachments: [
                    ...logos(),
                    ...attachments.map((attachment) => ({
                        filename: attachment.filename,
                        content: Buffer.from(attachment.content).toString("base64"),
                        content_type: attachment.contentType,
                    })),
                ],
            }),
            signal: AbortSignal.timeout(15_000),
        })

        const body = await response.json().catch(() => null)
        if (!response.ok || typeof body?.id !== "string") {
            console.error(`[mail] Resend hat ${type}-Mail abgelehnt (${response.status}):`, body?.message ?? body)
            return { ok: false, error: "E-Mail konnte nicht gesendet werden." }
        }

        return { ok: true, id: body.id }
    } catch (error) {
        console.error(`[mail] ${type}-Mail fehlgeschlagen:`, error)
        return { ok: false, error: "E-Mail konnte nicht gesendet werden." }
    }
}