since3-portal/modules/templates/ui/components/editor/preview-frame.tsx

"use client"

import { useEffect, useEffectEvent, useRef, useState } from "react"
import { MonitorIcon, SmartphoneIcon, TabletIcon } from "lucide-react"
import { cn } from "@/lib/utils"
import { DEVICES, PREVIEW_CONTENT, PREVIEW_READY, type Device } from "../../../lib/preview"
import type { TemplateContent } from "../../../lib/types"

const icons = { desktop: MonitorIcon, tablet: TabletIcon, mobile: SmartphoneIcon }

// Die Vorlage läuft in echter Gerätebreite im iframe (damit Media Queries greifen) und wird
// passend herunterskaliert. Änderungen gehen per postMessage hinein, ohne Neuladen.
export function PreviewFrame({ templateKey, variantId, content }: { templateKey: string; variantId: string; content: TemplateContent }) {
    const frameRef = useRef<HTMLIFrameElement>(null)
    const containerRef = useRef<HTMLDivElement>(null)
    const [size, setSize] = useState({ width: 0, height: 0 })
    const [device, setDevice] = useState<Device>("desktop")

    const post = useEffectEvent(() => {
        frameRef.current?.contentWindow?.postMessage({ type: PREVIEW_CONTENT, content }, window.location.origin)
    })

    useEffect(() => {
        post()
    }, [content])

    useEffect(() => {
        function onMessage(event: MessageEvent) {
            if (event.origin === window.location.origin && event.source === frameRef.current?.contentWindow && event.data?.type === PREVIEW_READY) {
                post()
            }
        }
        window.addEventListener("message", onMessage)
        return () => window.removeEventListener("message", onMessage)
    }, [])

    useEffect(() => {
        const container = containerRef.current
        if (!container) return
        const observer = new ResizeObserver(([entry]) => setSize({ width: entry.contentRect.width, height: entry.contentRect.height }))
        observer.observe(container)
        return () => observer.disconnect()
    }, [])

    const deviceWidth = DEVICES[device].width
    const inset = device === "desktop" ? 0 : 16
    const scale = size.width ? Math.min(1, (size.width - inset * 2) / deviceWidth) : 1

    return (
        <section className="flex min-h-[75vh] flex-col overflow-hidden rounded-xl border bg-surface lg:min-h-0">
            <div className="flex items-center justify-between gap-2 border-b bg-card px-2 py-1.5">
                <div className="flex gap-1">
                    {(Object.keys(DEVICES) as Device[]).map((key) => {
                        const Icon = icons[key]
                        return (
                            <button
                                key={key}
                                type="button"
                                aria-pressed={device === key}
                                onClick={() => setDevice(key)}
                                className={cn(
                                    "flex cursor-pointer items-center gap-1.5 rounded-md px-2.5 py-1.5 text-xs transition-colors",
                                    device === key ? "bg-surface font-medium" : "text-muted-foreground hover:text-foreground"
                                )}
                            >
                                <Icon className="size-3.5" />
                                {DEVICES[key].label}
                            </button>
                        )
                    })}
                </div>
                <span className="font-mono text-[11px] text-muted-foreground">
                    {deviceWidth}px · {Math.round(scale * 100)}%
                </span>
            </div>
            <div ref={containerRef} className="relative min-h-0 flex-1 overflow-hidden">
                {size.width > 0 && (
                    <iframe
                        ref={frameRef}
                        src={`/preview/${templateKey}?live=1&variant=${variantId}`}
                        title="Vorschau der Variante"
                        className={cn("absolute origin-top-left border-0 bg-white", inset > 0 && "rounded-2xl shadow-xl ring-1 ring-black/10")}
                        style={{
                            width: deviceWidth,
                            height: (size.height - inset * 2) / scale,
                            top: inset,
                            left: Math.max(0, (size.width - deviceWidth * scale) / 2),
                            transform: `scale(${scale})`,
                        }}
                    />
                )}
            </div>
        </section>
    )
}