chat-ui / src /lib /components /HtmlPreviewModal.svelte
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<script lang="ts">
import Modal from "./Modal.svelte";
import { onMount, onDestroy } from "svelte";
import CarbonClose from "~icons/carbon/close";
import { pendingChatInput } from "$lib/stores/pendingChatInput";
interface Props {
html: string;
onclose?: () => void;
}
let { html, onclose }: Props = $props();
let iframeEl: HTMLIFrameElement | undefined = $state();
let channel = $state(`preview_${Math.random().toString(36).slice(2)}`);
let errors: { message: string; stack?: string }[] = $state([]);
function buildSrcdoc(content: string, channel: string): string {
const trimmed = content.trimStart();
const svgPattern = /^(?:<\?xml[^>]*>\s*)?(?:<!doctype\s+svg[^>]*>\s*)?<svg[\s>]/i;
const baseTag = '<base target="_blank">';
const disabledLinkStyles = `<style>
a[data-chatui-link-disabled] {}
</style>`;
const endScriptTag = "</scr" + "ipt>";
const errorHook = `\n<script>\n(function(){\n function send(detail){\n try{ parent.postMessage({ type: 'chatui.preview.error', channel: '${channel}', detail: detail }, '*'); }catch(e){}\n }\n function markDisabled(anchor){\n if (!anchor || anchor.dataset.chatuiLinkDisabled === 'true') return;\n anchor.dataset.chatuiLinkDisabled = 'true';\n var note = 'Link disabled in preview';\n var title = anchor.getAttribute('title');\n if (!title) {\n anchor.setAttribute('title', note);\n } else if (title.indexOf(note) === -1) {\n anchor.setAttribute('title', title + ' — ' + note);\n }\n }\n function disableAnchors(scope){\n try {\n var root = scope && scope.querySelectorAll ? scope : document;\n var anchors = root.querySelectorAll ? root.querySelectorAll('a') : [];\n for (var i = 0; i < anchors.length; i++) {\n markDisabled(anchors[i]);\n }\n } catch (err) {}\n }\n function nearestAnchor(node){\n while (node && node !== document) {\n if (node.tagName && node.tagName.toLowerCase() === 'a') return node;\n node = node.parentNode;\n }\n return null;\n }\n function intercept(ev){\n var anchor = nearestAnchor(ev.target);\n if (!anchor) return;\n markDisabled(anchor);\n ev.preventDefault();\n ev.stopPropagation();\n }\n disableAnchors();\n if (document.readyState === 'loading') {\n document.addEventListener('DOMContentLoaded', function(){ disableAnchors(); });\n } else {\n setTimeout(function(){ disableAnchors(); }, 0);\n }\n if (window.MutationObserver) {\n var observer = new MutationObserver(function(mutations){\n for (var i = 0; i < mutations.length; i++) {\n var nodes = mutations[i].addedNodes;\n for (var j = 0; j < nodes.length; j++) {\n var node = nodes[j];\n if (!node || node.nodeType !== 1) continue;\n if (node.tagName && node.tagName.toLowerCase() === 'a') {\n markDisabled(node);\n } else {\n disableAnchors(node);\n }\n }\n }\n });\n observer.observe(document.documentElement, { childList: true, subtree: true });\n }\n window.addEventListener('click', intercept, true);\n window.addEventListener('auxclick', intercept, true);\n window.addEventListener('keydown', function(ev){\n if (ev.key === 'Enter' || ev.key === ' ') {\n intercept(ev);\n }\n }, true);\n window.addEventListener('error', function(ev){\n var msg = ev && ev.message ? ev.message : 'Script error';\n var stack = ev && ev.error && ev.error.stack ? ev.error.stack : undefined;\n send({ message: msg, stack: stack });\n });\n window.addEventListener('unhandledrejection', function(ev){\n var r = ev && ev.reason;\n var msg = (typeof r === 'string') ? r : (r && r.message) ? r.message : 'Unhandled promise rejection';\n var stack = r && r.stack ? r.stack : undefined;\n send({ message: msg, stack: stack });\n });\n})();\n${endScriptTag}`;
if (svgPattern.test(trimmed)) {
const svgContent = trimmed
.replace(/^(<\?xml[^>]*>\s*)/i, "")
.replace(/^(<!doctype[^>]*>\s*)/i, "");
return `<!doctype html><html><head>${baseTag}${disabledLinkStyles}${errorHook}</head><body>${svgContent}</body></html>`;
}
const headMatch = content.match(/<head[^>]*>/i);
if (headMatch) {
return content.replace(headMatch[0], headMatch[0] + baseTag + disabledLinkStyles + errorHook);
}
const htmlTagMatch = content.match(/<html[^>]*>/i);
if (htmlTagMatch) {
return content.replace(
htmlTagMatch[0],
htmlTagMatch[0] + "\n<head>" + baseTag + disabledLinkStyles + errorHook + "</head>"
);
}
const doctypeMatch = content.match(/<!doctype[^>]*>/i);
if (doctypeMatch) {
const idx = content.indexOf(doctypeMatch[0]) + doctypeMatch[0].length;
return (
content.slice(0, idx) +
"\n<head>" +
baseTag +
disabledLinkStyles +
errorHook +
"</head>" +
content.slice(idx)
);
}
return "<head>" + baseTag + disabledLinkStyles + errorHook + "</head>\n" + content;
}
let srcdoc = $derived(buildSrcdoc(html, channel));
type PreviewMessage = {
type: string;
channel: string;
detail?: { message?: unknown; stack?: string };
};
function onMessage(ev: MessageEvent) {
if (!iframeEl || ev.source !== iframeEl.contentWindow) return;
const raw = ev.data as unknown;
if (!raw || typeof raw !== "object") return;
const data = raw as Partial<PreviewMessage>;
if (data.type !== "chatui.preview.error" || data.channel !== channel) return;
const detail = (data.detail ?? {}) as { message?: unknown; stack?: string };
errors = [...errors, { message: String(detail.message ?? "Error"), stack: detail.stack }];
}
onMount(() => {
window.addEventListener("message", onMessage);
});
onDestroy(() => {
window.removeEventListener("message", onMessage);
});
function composeText(): string {
const lines = errors.map((e, i) => `${i + 1}. ${e.message}${e.stack ? `\n${e.stack}` : ""}`);
const summary = lines[0] ?? "Unknown error";
return errors.length > 1
? `it's not working: ${summary} (+${errors.length - 1} more) - can you fix it?`
: `it's not working: ${summary} - can you fix it?`;
}
function handleKeydown(event: KeyboardEvent) {
// Close preview on ESC key
if (event.key === "Escape") {
event.preventDefault();
onclose?.();
}
}
</script>
<svelte:window on:keydown={handleKeydown} />
<Modal
width="max-w-none max-h-none w-[100dvw] h-[100dvh] !rounded-none"
onclose={() => onclose?.()}
>
<div class="relative h-[100dvh] w-[100dvw]">
<iframe
bind:this={iframeEl}
title="HTML Preview"
class="h-full w-full"
sandbox="allow-scripts allow-popups"
referrerpolicy="no-referrer"
{srcdoc}
></iframe>
<!-- Close button with visible container -->
<button
class="btn fixed right-6 top-4 z-50 flex h-7 items-center gap-1 rounded-lg border border-gray-500/60 bg-gray-800 px-2 text-xs text-white shadow-sm backdrop-blur transition-none hover:border-gray-500 hover:bg-gray-700 active:shadow-inner"
title="Close preview (Esc)"
onclick={() => onclose?.()}
>
<CarbonClose class="size-3.5" />
Close preview
</button>
{#if errors.length > 0}
<button
class="btn fixed bottom-4 right-4 z-50 flex items-center gap-2 rounded-full border-2 border-red-500/60 bg-red-800/90 px-4 py-1.5 text-sm text-white shadow-lg"
title="Send error to chat"
onclick={() => {
pendingChatInput.set(composeText());
onclose?.();
}}
>
<span>Error caught ({errors.length})</span>
</button>
{/if}
</div>
</Modal>