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* High-performance HTML renderer with caching, monitoring, and streaming support
* Converts object-based components to HTML strings with advanced optimizations
*/
import { BaseRenderer, RendererUtils, serializeForCache } from './base-renderer.js';
import { normalizeChildren } from '../core/object-utils.js';
import { validateNesting, FORBIDDEN_CHILDREN } from '../core/html-nesting-rules.js';
import {
escapeHtml,
isTrustedContent,
isVoidElement,
formatAttributes,
minifyHtml,
createStreamMinifier
} from '../core/html-utils.js';
import { performanceMonitor } from '../performance/monitor.js';
import { createCacheManager } from '../performance/cache-manager.js';
import { cssUtils, defaultCSSManager } from './css-manager.js';
import { CoherentError, RenderingError, globalErrorHandler } from '../utils/error-handler.js';
// Element props rendered as content or identity, never as attributes.
const RESERVED_PROPS = new Set(['children', 'text', 'key', 'html']);
// Shared by every render() call that opts in with `enableCache: true`.
const rendererCache = createCacheManager({
maxCacheSize: 1000,
ttlMs: 300000 // 5 minutes
});
/**
* render() is synchronous. A Promise in the tree (an async component, or a
* lazy() factory that returns one) used to render as an empty string
* without any signal.
*/
function assertNotThenable(value, path) {
if (value && (typeof value === 'object' || typeof value === 'function') && typeof value.then === 'function') {
throw new RenderingError(
`Cannot render a Promise at ${path === 'root' ? 'root' : formatRenderPath(path)}: render() is synchronous. Await async components (and their data) before rendering.`,
undefined,
{ path: path === 'root' ? 'root' : formatRenderPath(path), renderer: 'html' }
);
}
}
/**
* Render paths are linked lists ({ parent, segment }, null for the root),
* extended in O(1) per node and formatted only when an error or warning
* needs them. Copying an array per node ([...path, segment]) and formatting
* a string per child made rendering quadratic in tree depth.
*/
function childPath(parent, segment) {
return { parent, segment };
}
function formatRenderPath(path) {
const segments = [];
Iif (Array.isArray(path)) {
segments.push(...path);
} else {
for (let node = path; node; node = node.parent) segments.push(node.segment);
segments.reverse();
}
let rendered = 'root';
for (const segment of segments) {
Iif (typeof segment !== 'string' || segment.length === 0) continue;
if (segment.startsWith('[')) {
rendered += segment;
} else {
rendered += `.${segment}`;
}
}
return rendered;
}
/**
* HTML Renderer Class extending BaseRenderer
*
* @class HTMLRenderer
* @extends BaseRenderer
* @description High-performance HTML renderer with caching, monitoring, and streaming support.
* Converts object-based components to HTML strings with advanced optimizations.
*
* @param {Object} [options={}] - Renderer configuration options
* @param {boolean} [options.enableCache=false] - Cache the HTML of whole renders, keyed on
* the full component tree (trees containing functions are never cached)
* @param {Object} [options.cache] - Cache instance from createCacheManager() to use
* instead of the shared one (e.g. with its own `maxCacheSize` / `ttlMs`)
* @param {boolean} [options.enableMonitoring=true] - Enable performance monitoring
* @param {boolean} [options.minify=false] - Enable HTML minification
* @param {boolean} [options.streaming=false] - Enable streaming mode
* @param {number} [options.maxDepth=100] - Maximum rendering depth
* @param {number} [options.cacheTTL=300000] - Cache TTL in milliseconds for entries this render adds
* @param {Function} [options.onError] - `(error, { path }) => replacement` called when a
* function component throws; its return value is rendered in place of the component
* (return null to omit it). Without it the error propagates out of render().
*
* @example
* const renderer = new HTMLRenderer({
* enableCache: true,
* enableMonitoring: true,
* minify: true
* });
*
* const html = renderer.render({ div: { text: 'Hello World' } });
*/
class HTMLRenderer extends BaseRenderer {
constructor(options = {}) {
super({
enableMonitoring: options.enableMonitoring !== false,
minify: options.minify || false,
streaming: options.streaming || false,
maxDepth: options.maxDepth || 100,
...options,
enableCache: options.enableCache === true
});
if (this.config.enableCache) {
this.cache = options.cache || rendererCache;
}
}
/**
* Main render method - converts components to HTML string
*
* @param {Object|Array|string|Function} component - Component to render
* @param {Object} [options={}] - Rendering options
* @param {Object} [options.context] - Rendering context
* @param {boolean} [options.enableCache] - Override cache setting
* @param {number} [options.depth=0] - Current rendering depth
* @returns {string} Rendered HTML string
*
* @example
* const html = renderer.render({
* div: {
* className: 'container',
* children: [
* { h1: { text: 'Title' } },
* { p: { text: 'Content' } }
* ]
* }
* });
*/
render(component, options = {}) {
const config = { ...this.config, ...options };
this.startTiming();
try {
assertNotThenable(component, 'root');
// Input validation
if (config.validateInput && !this.isValidComponent(component)) {
throw new Error('Invalid component structure');
}
// One cache entry per whole render. Caching every element
// separately meant serializing each subtree again at every level
// (quadratic in depth) and made rendering slower than not caching.
const cacheKey = this.cache && config.enableCache
? serializeForCache(component)
: null;
const fullKey = cacheKey === null ? null : `render:${config.minify ? 'min' : 'raw'}:${cacheKey}`;
if (fullKey !== null) {
const cached = this.cache.get(fullKey);
if (cached !== null) {
this.endTiming();
return cached;
}
}
// Initialize seenObjects for circular reference detection
const renderOptions = {
...config,
seenObjects: new WeakSet()
};
// Main rendering logic
const html = this.renderComponent(component, renderOptions, 0, null);
const finalHtml = config.minify ? minifyHtml(html, config) : html;
if (fullKey !== null) {
this.cache.set(fullKey, finalHtml, 'component', {
ttlMs: typeof config.cacheTTL === 'number' ? config.cacheTTL : undefined
});
}
// Performance monitoring
this.endTiming();
this.recordPerformance('render', this.metrics.startTime, false, {
cacheEnabled: config.enableCache
});
return finalHtml;
} catch (_error) {
this.recordError('render', _error);
const enhancedError = globalErrorHandler.handle(_error, {
renderContext: { path: 'root', renderer: 'html' }
});
Iif (config.throwOnError === false) {
return config.errorFallback;
}
throw enhancedError;
}
}
/**
* Render a single component with full optimization pipeline
*/
renderComponent(component, options, depth = 0, path = null) {
// Handle nullish and empty inputs immediately
if (component === null || component === undefined) {
return '';
}
if (Array.isArray(component) && component.length === 0) {
return '';
}
// Before cycle tracking: a marker is an inert leaf, so the same one
// may appear twice without that being a cycle.
if (isTrustedContent(component)) {
return component.__html;
}
// Its keys (__isLazy, evaluate...) aren't tag names, so a lazy() value
// used to render as nothing unless evaluateLazy() ran first.
if (typeof component === 'object' && component.__isLazy === true && typeof component.evaluate === 'function') {
return this.renderComponent(component.evaluate(), options, depth + 1, childPath(path, '()'));
}
assertNotThenable(component, path);
// Detect circular references. Only the current ancestor path is
// tracked (added here, removed in `finally`): the same object may
// legitimately appear twice in a tree — a shared node, or a memo()
// result rendered twice — and that used to be reported as a cycle.
const tracked = options.seenObjects && typeof component === 'object' && component !== null
? component
: null;
if (tracked) {
if (options.seenObjects.has(tracked)) {
throw new RenderingError(
'Circular reference detected in component tree',
component,
{ path: formatRenderPath(path) },
['Remove the circular reference', 'Use lazy loading to break the cycle']
);
}
options.seenObjects.add(tracked);
}
// Use base class depth validation
this.validateDepth(depth);
try {
// Use base class component type processing
const { type, value } = this.processComponentType(component);
switch (type) {
case 'empty':
return '';
case 'text':
return escapeHtml(value);
case 'function':
{
const result = this.runFunctionComponent(value, options, depth, path);
return this.renderComponent(result, options, depth + 1, childPath(path, '()'));
}
case 'array':
// Development mode warning for missing keys
if (typeof process !== 'undefined' &&
process.env &&
process.env.NODE_ENV !== 'production' &&
value.length > 1) {
const missingKeyCount = value.filter((child) => {
if (child && typeof child === 'object' && !Array.isArray(child)) {
const tagName = Object.keys(child)[0];
const props = child[tagName];
return props && typeof props === 'object' && props.key === undefined;
}
return false; // primitives don't need keys
}).length;
if (missingKeyCount > 0) {
console.warn(
`[Coherent.js] Array of ${value.length} elements at ${formatRenderPath(path)} ` +
`has ${missingKeyCount} items missing "key" props. ` +
`Keys help identify which items changed for efficient updates. ` +
`Add unique key props like: { div: { key: 'unique-id', ... } }`
);
}
}
{
let html = '';
for (let index = 0; index < value.length; index++) {
html += this.renderComponent(value[index], options, depth + 1, childPath(path, `[${index}]`));
}
return html;
}
case 'element':
{
// Every key is an element; siblings render in order.
// Keys after the first used to be dropped silently.
const tagNames = Object.keys(value);
if (tagNames.length === 1) {
return this.renderElement(tagNames[0], value[tagNames[0]], options, depth, childPath(path, tagNames[0]));
}
let html = '';
for (const tagName of tagNames) {
html += this.renderElement(tagName, value[tagName], options, depth, childPath(path, tagName));
}
return html;
}
default:
this.recordError('renderComponent', new Error(`Unknown component type: ${type}`));
return '';
}
} catch (_error) {
const renderPath = formatRenderPath(path);
if (_error instanceof CoherentError) {
Iif (!_error.context || typeof _error.context !== 'object') {
_error.context = { path: renderPath };
I} else if (!_error.context.path) {
_error.context = { ..._error.context, path: renderPath };
}
throw _error;
}
const wrapped = new RenderingError(_error.message, undefined, { path: renderPath, renderer: 'html' });
wrapped.cause = _error;
throw wrapped;
} finally {
if (tracked) options.seenObjects.delete(tracked);
}
}
/**
* Run a function component, giving `options.onError` the chance to
* replace a component that throws.
*/
runFunctionComponent(func, options, depth, path) {
try {
return this.executeFunctionComponent(func, depth);
} catch (error) {
if (typeof options.onError === 'function') {
return options.onError(error, { path: formatRenderPath(path) });
}
throw error;
}
}
/**
* Render an HTML element with advanced caching and optimization
*/
renderElement(tagName, element, options, depth = 0, path = null) {
// Check for circular references in element props (ancestor path only,
// see renderComponent).
const tracked = options.seenObjects && element && typeof element === 'object' && !Array.isArray(element)
? element
: null;
if (tracked) {
if (options.seenObjects.has(tracked)) {
throw new RenderingError(
'Circular reference detected in component tree',
element,
{ path: formatRenderPath(path) },
['Remove the circular reference', 'Use lazy loading to break the cycle']
);
}
options.seenObjects.add(tracked);
}
try {
return this.renderElementContent(tagName, element, options, depth, path);
} finally {
if (tracked) options.seenObjects.delete(tracked);
}
}
renderElementContent(tagName, element, options, depth = 0, path = null) {
const startTime = options.enableMonitoring ? performance.now() : 0;
// Handle text-only elements including booleans
if (typeof element === 'string' || typeof element === 'number' || typeof element === 'boolean') {
const html = isVoidElement(tagName)
? `<${tagName}>`
: `<${tagName}>${escapeHtml(String(element))}</${tagName}>`;
this.recordPerformance(tagName, startTime, false);
return html;
}
// Handle function elements
if (typeof element === 'function') {
let result;
try {
result = this.executeFunctionComponent(element, depth);
} catch (error) {
Iif (typeof options.onError !== 'function') throw error;
// The replacement stands in for the whole element: rendered
// as the element's content it became attributes
// (`<div p="[object Object]">`).
const replacement = options.onError(error, { path: formatRenderPath(path) });
return this.renderComponent(replacement, options, depth + 1, childPath(path, '()'));
}
return this.renderElement(tagName, result, options, depth, childPath(path, '()'));
}
// Handle object elements (complex elements with props and children)
if (element && typeof element === 'object') {
return this.renderObjectElement(tagName, element, options, depth, path);
}
// Handle null and undefined by returning empty tags
Eif (element === null || element === undefined) {
const html = isVoidElement(tagName)
? `<${tagName}>`
: `<${tagName}></${tagName}>`;
this.recordPerformance(tagName, startTime, false);
return html;
}
// Fallback for any other types
const html = `<${tagName}>${escapeHtml(String(element))}</${tagName}>`;
this.recordPerformance(tagName, startTime, false);
return html;
}
/**
* Render complex object elements with attributes and children
*/
renderObjectElement(tagName, element, options, depth = 0, path = null) {
const startTime = options.enableMonitoring ? performance.now() : 0;
const parts = elementParts(tagName, element);
let html = parts.open + parts.content;
if (parts.children) {
const forbidden = FORBIDDEN_CHILDREN[tagName.toLowerCase()];
for (let index = 0; index < parts.children.length; index++) {
const child = parts.children[index];
const segment = childPath(path, `children[${index}]`);
checkNesting(tagName, forbidden, child, segment);
html += this.renderComponent(child, options, depth + 1, segment);
}
}
html += parts.close;
this.recordPerformance(tagName, startTime, false);
return html;
}
/**
* Streaming counterpart of renderComponent: yields HTML pieces. Elements
* with many children are streamed child by child; everything else goes
* through the synchronous renderer, which is exact and faster, so the
* streamed output is the same as render()'s by construction.
*/
async *streamComponent(component, options, depth = 0, path = null) {
Iif (component === null || component === undefined) return;
// Every branch, like renderComponent: deeply nested arrays or
// functions returning functions overflowed the stack instead of
// reporting maxDepth.
this.validateDepth(depth);
if (typeof component === 'function') {
const result = this.runFunctionComponent(component, options, depth, path);
yield* this.streamComponent(result, options, depth + 1, childPath(path, '()'));
return;
}
if (Array.isArray(component)) {
yield* this.streamTracked(component, options, path, async function* (renderer) {
for (let index = 0; index < component.length; index++) {
yield* renderer.streamComponent(component[index], options, depth + 1, childPath(path, `[${index}]`));
}
});
return;
}
Eif (typeof component === 'object' && !isTrustedContent(component) && component.__isLazy !== true) {
const { type, value } = this.processComponentType(component);
Eif (type === 'element') {
yield* this.streamTracked(component, options, path, async function* (renderer) {
for (const tagName of Object.keys(value)) {
yield* renderer.streamElement(tagName, value[tagName], options, depth, childPath(path, tagName));
}
});
return;
}
}
yield this.renderComponent(component, options, depth, path);
}
async *streamElement(tagName, element, options, depth, path) {
if (!element || typeof element !== 'object' || Array.isArray(element) || !shouldStream(element.children)) {
yield this.renderElement(tagName, element, options, depth, path);
return;
}
yield* this.streamTracked(element, options, path, async function* (renderer) {
const parts = elementParts(tagName, element);
yield parts.open + parts.content;
Eif (parts.children) {
const forbidden = FORBIDDEN_CHILDREN[tagName.toLowerCase()];
for (let index = 0; index < parts.children.length; index++) {
const child = parts.children[index];
const segment = childPath(path, `children[${index}]`);
checkNesting(tagName, forbidden, child, segment);
yield* renderer.streamComponent(child, options, depth + 1, segment);
}
}
yield parts.close;
});
}
/**
* Run `body` with `value` on the ancestor path used for cycle detection.
*/
async *streamTracked(value, options, path, body) {
if (options.seenObjects.has(value)) {
throw new RenderingError(
'Circular reference detected in component tree',
value,
{ path: formatRenderPath(path) },
['Remove the circular reference', 'Use lazy loading to break the cycle']
);
}
options.seenObjects.add(value);
try {
yield* body(this);
} finally {
options.seenObjects.delete(value);
}
}
}
// Elements with at least this many children are streamed child by child.
const STREAM_MIN_CHILDREN = 8;
/**
* Whether to stream an element's children one by one rather than render the
* element in one synchronous step: when it has many children, or when a
* child has children of its own (wrappers like body > main > list must be
* descended into to reach the long list) or is a function whose output size
* is unknown. Leaf-level rows (a <tr> of text <td>s) render synchronously.
*/
function shouldStream(children) {
if (children === undefined || children === null) return false;
const list = Array.isArray(children) ? children : [children];
if (list.length >= STREAM_MIN_CHILDREN) return true;
for (const child of list) {
if (typeof child === 'function' || Array.isArray(child)) return true;
if (child && typeof child === 'object') {
for (const key in child) {
const content = child[key];
if (typeof content === 'function') return true;
if (content && typeof content === 'object' && content.children !== undefined && content.children !== null) return true;
}
}
}
return false;
}
/**
* Split an element into the markup around its children. Shared by render()
* and renderToStream() so the two can't drift apart (the old streaming
* renderer escaped <script> bodies, dropped children next to text, emitted
* key="..." and skipped tag-name validation).
*
* @returns {{open: string, content: string, children: Array|null, close: string}}
*/
function elementParts(tagName, element) {
// children/text/html are content, and key is reconciliation identity:
// none of them is rendered as an attribute. formatAttributes skips
// them instead of this copying the props with rest destructuring.
const { children, text: rawText, html: rawHtml } = element || {};
const attributeString = formatAttributes(element, RESERVED_PROPS);
const open = attributeString ? `<${tagName} ${attributeString}>` : `<${tagName}>`;
// Void elements: no closing tag; any text/children are dropped.
if (isVoidElement(tagName)) {
return { open, content: '', children: null, close: '' };
}
const close = `</${tagName}>`;
// Raw HTML injection (unescaped) — for SSR use cases like syntax
// highlighting. null (or a function returning it) means no raw HTML, as
// for `text`, instead of the string "null".
const html = typeof rawHtml === 'function' ? rawHtml() : rawHtml;
if (html !== undefined && html !== null) {
return { open, content: isTrustedContent(html) ? html.__html : String(html), children: null, close };
}
const text = typeof rawText === 'function' && !isTrustedContent(rawText) ? rawText() : rawText;
// Content marked by dangerouslySetInnerContent() is emitted verbatim.
if (isTrustedContent(text)) {
return { open, content: text.__html, children: null, close };
}
// Text content (null means "no text", not the string "null")
let content = '';
if (text !== undefined && text !== null) {
const raw = String(text);
if (tagName === 'script' || tagName === 'style') {
// Prevent </script> or </style> early-terminating the tag
content = raw
.replace(/<\/(script)/gi, '<\\/$1')
.replace(/<\/(style)/gi, '<\\/$1')
// Escape problematic Unicode line separators in JS
.replace(/\u2028/g, '\\u2028')
.replace(/\u2029/g, '\\u2029');
} else {
content = escapeHtml(raw);
}
}
// Children are checked directly: hasChildren() validates every prop name
// against the tag-name pattern, so an element with a prop like `@click`
// or `data_id` silently lost all of its children.
const normalized = children !== undefined && children !== null ? normalizeChildren(children) : null;
return { open, content, children: normalized && normalized.length > 0 ? normalized : null, close };
}
/**
* Validate HTML nesting, formatting the path only on a violation.
*/
function checkNesting(tagName, forbidden, child, path) {
if (forbidden && child && typeof child === 'object' && !Array.isArray(child)) {
const childTagName = Object.keys(child)[0];
if (childTagName && forbidden.has(childTagName.toLowerCase())) {
validateNesting(tagName, childTagName, formatRenderPath(path));
}
}
}
// Note: globalCache is now imported from cache-manager.js
/**
* Main render function - converts object components to HTML
*/
export function render(component, options = {}) {
// Merge default options with provided options
const mergedOptions = {
enableMonitoring: false,
...options
};
const renderer = new HTMLRenderer(mergedOptions);
return renderer.render(component, mergedOptions);
}
/**
* Renders component to complete HTML document with DOCTYPE
* Better alternative to manual DOCTYPE concatenation
* Supports CSS file inclusion and inline styles
*/
export async function renderHTML(component, options = {}) {
const htmlContent = render(component, options);
// Process CSS options
const cssOptions = cssUtils.processCSSOptions(options);
// Generate CSS HTML if any CSS is specified
let cssHtml = '';
if (cssOptions.files.length > 0 || cssOptions.links.length > 0 || cssOptions.inline) {
cssHtml = await cssUtils.generateCSSHtml(cssOptions, defaultCSSManager);
}
// If the component includes a head tag, inject CSS into it
if (cssHtml && htmlContent.includes('<head>')) {
const htmlWithCSS = htmlContent.replace(
'</head>',
`${cssHtml}\n</head>`
);
return `<!DOCTYPE html>\n${htmlWithCSS}`;
}
// If there's CSS but no head tag, wrap the component with a basic HTML structure
if (cssHtml) {
return `<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
${cssHtml}
</head>
<body>
${htmlContent}
</body>
</html>`;
}
return `<!DOCTYPE html>\n${htmlContent}`;
}
/**
* Synchronous version of render for cases without CSS files
* Falls back to async if CSS files are detected
*/
export function renderHTMLSync(component, options = {}) {
const cssOptions = cssUtils.processCSSOptions(options);
// If CSS files are specified, return a promise
if (cssOptions.files.length > 0) {
console.warn('CSS files detected, use render() (async) instead of renderSync()');
return render(component, options);
}
const htmlContent = render(component, options);
// Handle inline CSS and external links only
let cssHtml = '';
if (cssOptions.links.length > 0) {
cssHtml += defaultCSSManager.generateCSSLinks(cssOptions.links);
}
if (cssOptions.inline) {
cssHtml += `\n${ defaultCSSManager.generateInlineStyles(cssOptions.inline)}`;
}
if (cssHtml && htmlContent.includes('<head>')) {
const htmlWithCSS = htmlContent.replace(
'</head>',
`${cssHtml}\n</head>`
);
return `<!DOCTYPE html>\n${htmlWithCSS}`;
}
if (cssHtml) {
return `<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
${cssHtml}
</head>
<body>
${htmlContent}
</body>
</html>`;
}
return `<!DOCTYPE html>\n${htmlContent}`;
}
// Old functions removed - now part of HTMLRenderer class
// Old helper functions removed - now available in RendererUtils from BaseRenderer
/**
* Batch rendering for multiple components
*/
export function renderBatch(components, options = {}) {
if (!Array.isArray(components)) {
throw new Error('renderBatch expects an array of components');
}
// Merge default options with provided options
const mergedOptions = {
enableMonitoring: false,
...options
};
const renderer = new HTMLRenderer(mergedOptions);
return components.map(component => renderer.render(component, mergedOptions));
}
/**
* Stream a component as HTML chunks: an async generator yielding strings of
* about `chunkSize` characters. The output is exactly render()'s; the event
* loop gets a turn after every chunk, so a large page doesn't block other
* requests and the first bytes can leave before the whole tree is rendered.
*
* Errors propagate out of the generator (after the chunks already yielded):
* abort the response rather than end it, so a truncated page isn't taken as
* complete. `onError` works as in render().
*
* @example
* import { Readable } from 'node:stream';
* Readable.from(renderToStream(Page())).pipe(res);
*
* @param {*} component - Component to render
* @param {Object} [options] - render() options, plus `chunkSize` (default 8192)
* @returns {AsyncGenerator<string>}
*/
export async function* renderToStream(component, options = {}) {
const { chunkSize = 8192, ...renderOptions } = options;
const renderer = new HTMLRenderer({ enableMonitoring: false, ...renderOptions, enableCache: false });
const config = { ...renderer.config, seenObjects: new WeakSet() };
assertNotThenable(component, 'root');
if (config.validateInput && !renderer.isValidComponent(component)) {
throw new Error('Invalid component structure');
}
// `minify` used to be ignored here, so the stream differed from render().
const minifier = config.minify ? createStreamMinifier() : null;
let buffer = '';
for await (const piece of renderer.streamComponent(component, config, 0, null)) {
buffer += minifier ? minifier.push(piece) : piece;
if (buffer.length >= chunkSize) {
yield buffer;
buffer = '';
await yieldToEventLoop();
}
}
if (minifier) buffer += minifier.end();
if (buffer) yield buffer;
}
const yieldToEventLoop = typeof setImmediate === 'function'
? () => new Promise((resolve) => setImmediate(resolve))
: () => new Promise((resolve) => setTimeout(resolve, 0));
/**
* Wait until `response` can take more data. Resolves `true` on 'drain' and
* `false` when the response closes (or errors) first.
*/
function waitForDrain(response) {
Iif (response.destroyed) return Promise.resolve(false);
return new Promise((resolve) => {
const settle = (drained) => () => {
response.off('drain', onDrain);
response.off('close', onClose);
response.off('error', onClose);
resolve(drained);
};
const onDrain = settle(true);
const onClose = settle(false);
response.on('drain', onDrain);
response.on('close', onClose);
response.on('error', onClose);
});
}
/**
* Streaming utilities for common use cases
*/
export const streamingUtils = {
/**
* Collect all chunks into a single string
*/
async collectChunks(chunkGenerator) {
let html = '';
for await (const chunk of chunkGenerator) {
html += chunk;
}
return html;
},
/**
* Stream directly to a Node.js response, with backpressure.
*
* Resolves with the number of bytes written once the response has ended.
* If the client disconnects first, rendering stops (the generator is
* closed) and it resolves with the bytes written so far without ending
* the response. If rendering fails, the response is destroyed and it
* rejects with the rendering error.
*/
async streamToResponse(chunkGenerator, response) {
let totalBytes = 0;
Eif (!response.headersSent && !response.getHeader?.('Content-Type')) {
response.setHeader('Content-Type', 'text/html; charset=utf-8');
}
try {
// Leaving the loop early closes the generator, so a client that
// went away stops the render instead of leaving it suspended.
for await (const chunk of chunkGenerator) {
Iif (response.destroyed) return totalBytes;
totalBytes += Buffer.byteLength(chunk);
// Respect backpressure instead of buffering the whole page
// in the socket when the client reads slowly. 'drain' never
// comes once the client disconnects: waiting for it alone
// left the promise (and the render) pending forever.
if (!response.write(chunk) && !(await waitForDrain(response))) {
return totalBytes;
}
}
} catch (error) {
// Headers are gone: abort the connection so the client sees a
// failed response, not a complete-looking truncated page.
response.destroy(error);
throw error;
}
response.end();
return totalBytes;
},
/**
* Stream with progress callback
*/
async* streamWithProgress(chunkGenerator, onProgress) {
let totalBytes = 0;
let chunkCount = 0;
for await (const chunk of chunkGenerator) {
totalBytes += Buffer.byteLength(chunk);
chunkCount++;
if (onProgress) {
onProgress({ chunkCount, totalBytes, chunk });
}
yield chunk;
}
}
};
/**
* Render to chunks (legacy - kept for backward compatibility)
* For true streaming, use renderToStream() instead
*/
export function* renderToChunks(component, options = {}) {
const mergedOptions = {
enableMonitoring: false,
...options,
chunkSize: options.chunkSize || 1024 // Default 1KB chunks
};
const html = render(component, mergedOptions);
for (let i = 0; i < html.length; i += mergedOptions.chunkSize) {
yield html.slice(i, i + mergedOptions.chunkSize);
}
}
/**
* Get global cache instance for external access
*/
export function getCache() {
return rendererCache;
}
/**
* Reset cache (useful for testing)
*/
export function resetCache() {
Eif (rendererCache) {
rendererCache.clear();
}
}
/**
* Get rendering statistics
*/
export function getRenderingStats() {
return {
cache: rendererCache ? rendererCache.getStats() : null,
performance: performanceMonitor.getStats()
};
}
/**
* Precompile static components for maximum performance
*/
export function precompileComponent(component, options = {}) {
if (!RendererUtils.isStaticElement(component)) {
throw new Error('Can only precompile static components');
}
const html = render(component, { ...options, enableCache: false });
return {
html,
isPrecompiled: true,
render: () => html
};
}
/**
* Development helper - render with detailed timing
*/
export function renderWithTiming(component, options = {}) {
const start = performance.now();
const html = render(component, { ...options, enableMonitoring: true });
const end = performance.now();
return {
html,
timing: {
total: end - start,
breakdown: performanceMonitor.getStats()
}
};
}
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