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* Base Renderer Class
* Provides common functionality shared across all Coherent.js renderers
* Reduces code duplication and ensures consistent behavior
*/
import {
validateComponent,
isCoherentObject,
hasChildren,
normalizeChildren,
} from '../core/object-utils.js';
import { isTrustedContent } from '../core/html-utils.js';
import { performanceMonitor } from '../performance/monitor.js';
/**
* Unified configuration for all Coherent.js renderers
* Includes options for HTML, Streaming, and DOM renderers
*/
export const DEFAULT_RENDERER_CONFIG = {
// Core rendering options
maxDepth: 100,
enableValidation: true,
enableMonitoring: false,
validateInput: true,
// HTML Renderer specific options
// Off by default: keying a render on its content costs a full walk of
// the tree, which only pays off when identical trees are re-rendered.
enableCache: false,
minify: false,
cacheSize: 1000,
cacheTTL: 300000, // 5 minutes
// Streaming Renderer specific options
chunkSize: 1024, // Size of each chunk in bytes
bufferSize: 4096, // Internal buffer size
enableMetrics: false, // Track streaming metrics
yieldThreshold: 100, // Yield control after N elements
encoding: 'utf8', // Output encoding
// DOM Renderer specific options
enableHydration: true, // Enable hydration support
namespace: null, // SVG namespace support
// Performance options
enablePerformanceTracking: false,
performanceThreshold: 10, // ms threshold for slow renders
// Development options
enableDevWarnings:
typeof process !== 'undefined' &&
process.env &&
process.env.NODE_ENV === 'development',
enableDebugLogging: false,
// Error handling options
errorFallback: '', // Fallback content on errors
throwOnError: true, // Whether to throw or return fallback
};
/**
* Base renderer class with common functionality
*/
export class BaseRenderer {
constructor(options = {}) {
this.config = this.validateAndMergeConfig(options);
this.metrics = {
startTime: null,
endTime: null,
elementsProcessed: 0,
};
}
/**
* Validate and merge configuration options
*/
validateAndMergeConfig(options) {
const config = { ...DEFAULT_RENDERER_CONFIG, ...options };
// Validate critical options
if (typeof config.maxDepth !== 'number') {
throw new Error('maxDepth must be a number');
}
if (config.maxDepth <= 0) {
throw new Error('maxDepth must be a positive number');
}
if (typeof config.chunkSize !== 'number') {
throw new Error('chunkSize must be a number');
}
if (config.chunkSize <= 0) {
throw new Error('chunkSize must be a positive number');
}
if (typeof config.yieldThreshold !== 'number') {
throw new Error('yieldThreshold must be a number');
}
if (config.yieldThreshold <= 0) {
throw new Error('yieldThreshold must be a positive number');
}
// Warn about potentially problematic configurations
Iif (config.enableDevWarnings) {
if (config.maxDepth > 1000) {
console.warn(
'Coherent.js: maxDepth > 1000 may cause performance issues'
);
}
if (config.chunkSize > 16384) {
console.warn('Coherent.js: Large chunkSize may increase memory usage');
}
}
return config;
}
/**
* Get configuration for specific renderer type
*/
getRendererConfig(rendererType) {
const baseConfig = { ...this.config };
switch (rendererType) {
case 'html':
return {
...baseConfig,
// HTML-specific defaults
enableCache: baseConfig.enableCache === true,
enableMonitoring: baseConfig.enableMonitoring !== false,
};
case 'streaming':
return {
...baseConfig,
// Streaming-specific defaults
enableMetrics: baseConfig.enableMetrics ?? false,
maxDepth: baseConfig.maxDepth ?? 1000, // Higher default for streaming
};
case 'dom':
return {
...baseConfig,
// DOM-specific defaults
enableHydration: baseConfig.enableHydration !== false,
};
default:
return baseConfig;
}
}
/**
* Validate component structure
*/
validateComponent(component) {
if (this.config.validateInput !== false) {
return validateComponent(component);
}
return true;
}
/**
* Check if component is valid for rendering
*/
isValidComponent(component, depth = 0) {
if (component === null || component === undefined) return true;
if (typeof component === 'string' || typeof component === 'number')
return true;
if (typeof component === 'function') return true;
if (Array.isArray(component)) {
// Past maxDepth the renderer reports the depth error; recursing
// further overflowed the stack on deeply nested arrays first.
if (depth >= this.config.maxDepth) return true;
return component.every((child) =>
this.isValidComponent(child, depth + 1)
);
}
if (isCoherentObject(component)) return true;
return false;
}
/**
* Validate rendering depth to prevent stack overflow
*/
validateDepth(depth) {
if (depth > this.config.maxDepth) {
throw new Error(
`Maximum render depth (${this.config.maxDepth}) exceeded`
);
}
}
/**
* Handle different component types with consistent logic
*/
processComponentType(component) {
// Null/undefined
if (component === null || component === undefined) {
return { type: 'empty', value: '' };
}
// String
if (typeof component === 'string') {
return { type: 'text', value: component };
}
// Booleans render nothing, so `cond && { li: ... }` can sit in a
// children array (it used to print "false").
if (typeof component === 'boolean') {
return { type: 'empty', value: '' };
}
// Number
if (typeof component === 'number') {
return { type: 'text', value: String(component) };
}
// Function
if (typeof component === 'function') {
return { type: 'function', value: component };
}
// Array
if (Array.isArray(component)) {
return { type: 'array', value: component };
}
// Object (Coherent element)
if (isCoherentObject(component)) {
return { type: 'element', value: component };
}
// Unknown type
return { type: 'unknown', value: component };
}
/**
* Execute function components. Errors propagate: they used to be
* swallowed here (the component rendered as nothing, logged only when
* NODE_ENV=development), so a broken component produced a partial page
* with a 200 and error boundaries never saw nested failures.
*/
executeFunctionComponent(func, depth = 0) {
try {
// Always called without arguments. Functions declaring a parameter
// used to receive a render callback returning an HTML string,
// which then got escaped (double-escaped context providers), and a
// `({ name }) => ...` child destructured its props from it.
const result = func();
// Handle case where function returns another function
Iif (typeof result === 'function') {
return this.executeFunctionComponent(result, depth);
}
return result;
} catch (error) {
Iif (this.config.enableMonitoring) {
performanceMonitor.recordError('functionComponent', error);
}
throw error;
}
}
/**
* Process element children consistently
*/
processChildren(children, options, depth) {
if (!hasChildren({ children })) {
return [];
}
const normalizedChildren = normalizeChildren(children);
return normalizedChildren.map((child) =>
this.renderComponent(child, options, depth + 1)
);
}
/**
* Extract and process element attributes
*/
extractElementAttributes(props) {
if (!props || typeof props !== 'object') return {};
const attributes = { ...props };
delete attributes.children;
delete attributes.text;
return attributes;
}
/**
* Record performance metrics
*/
recordPerformance(operation, startTime, fromCache = false, metadata = {}) {
if (this.config.enableMonitoring) {
performanceMonitor.recordRender(
operation,
this.getCurrentTime() - startTime,
fromCache,
metadata
);
}
}
/**
* Record _error for monitoring
*/
recordError(operation, _error, metadata = {}) {
Iif (this.config.enableMonitoring) {
performanceMonitor.recordError(operation, _error, metadata);
}
}
/**
* Get current timestamp with fallback
*/
getCurrentTime() {
Eif (typeof performance !== 'undefined' && performance.now) {
return performance.now();
}
return Date.now();
}
/**
* Start performance timing
*/
startTiming() {
this.metrics.startTime = this.getCurrentTime();
}
/**
* End performance timing
*/
endTiming() {
this.metrics.endTime = this.getCurrentTime();
}
/**
* Get performance metrics
*/
getMetrics() {
const duration = this.metrics.endTime
? this.metrics.endTime - this.metrics.startTime
: this.getCurrentTime() - this.metrics.startTime;
return {
...this.metrics,
duration,
elementsPerSecond: this.metrics.elementsProcessed / (duration / 1000),
};
}
/**
* Reset metrics for new render
*/
resetMetrics() {
this.metrics = {
startTime: null,
endTime: null,
elementsProcessed: 0,
};
}
/**
* Abstract method - must be implemented by subclasses
*/
renderComponent() {
throw new Error('renderComponent must be implemented by subclass');
}
/**
* Abstract method - must be implemented by subclasses
*/
render() {
throw new Error('render must be implemented by subclass');
}
}
const UNCACHEABLE = Symbol('uncacheable');
/**
* Serialize a component tree into a string that identifies its rendered
* output: two trees with the same key always render the same HTML.
*
* JSON.stringify can't be used for this. It drops functions and undefined,
* turns NaN into null and Dates into ISO strings, and ignores the brand on
* trusted content, so different trees (rendering different HTML) collided.
* Values whose output isn't a pure function of their content — functions,
* class instances, Dates — make the tree uncacheable instead.
*
* @param {*} value - Component tree
* @returns {string|null} Cache key, or null when the tree can't be cached
*/
export function serializeForCache(value) {
try {
return serialize(value, new Set());
} catch (error) {
Eif (error === UNCACHEABLE) return null;
throw error;
}
}
function serialize(value, ancestors) {
switch (typeof value) {
case 'string':
return JSON.stringify(value);
case 'number':
return `n${value}`;
case 'boolean':
return value ? 't' : 'f';
case 'undefined':
return 'u';
case 'object': {
if (value === null) return 'z';
if (isTrustedContent(value)) return `T${JSON.stringify(value.__html)}`;
Iif (ancestors.has(value)) throw UNCACHEABLE;
const isArray = Array.isArray(value);
if (!isArray) {
const proto = Object.getPrototypeOf(value);
if (proto !== Object.prototype && proto !== null) throw UNCACHEABLE;
}
ancestors.add(value);
const body = isArray
? value.map((item) => serialize(item, ancestors)).join(',')
: Object.keys(value)
.map(
(key) =>
`${JSON.stringify(key)}:${serialize(value[key], ancestors)}`
)
.join(',');
ancestors.delete(value);
return isArray ? `[${body}]` : `{${body}}`;
}
default:
// functions, symbols, bigints
throw UNCACHEABLE;
}
}
/**
* Utility functions for renderer implementations
*/
export const RendererUtils = {
/**
* Check if element is static (no functions or circular references)
*/
isStaticElement(element, visited = new WeakSet()) {
if (!element || typeof element !== 'object') {
return typeof element === 'string' || typeof element === 'number';
}
// Handle circular references - treat as non-static (will be caught during render)
if (visited.has(element)) {
return false;
}
visited.add(element);
// Check if element has any dynamic content
for (const [_key, value] of Object.entries(element)) {
if (typeof value === 'function') return false;
// Recursively check arrays (including children)
if (Array.isArray(value)) {
const allStatic = value.every((child) =>
RendererUtils.isStaticElement(child, visited)
);
if (!allStatic) return false;
}
// Recursively check nested objects
else if (typeof value === 'object' && value !== null) {
if (!RendererUtils.isStaticElement(value, visited)) return false;
}
}
return true;
},
/**
* Check if object has functions (for caching decisions)
*/
hasFunctions(obj, visited = new WeakSet()) {
if (visited.has(obj)) return false;
visited.add(obj);
for (const value of Object.values(obj)) {
if (typeof value === 'function') return true;
if (
typeof value === 'object' &&
value !== null &&
RendererUtils.hasFunctions(value, visited)
) {
return true;
}
}
return false;
},
/**
* Get element complexity score
*/
getElementComplexity(element) {
if (!element || typeof element !== 'object') return 1;
let complexity = Object.keys(element).length;
if (element.children && Array.isArray(element.children)) {
complexity += element.children.reduce(
(sum, child) => sum + RendererUtils.getElementComplexity(child),
0
);
}
return complexity;
},
/**
* Generate cache key for element
*/
generateCacheKey(tagName, element) {
// The whole element, not a summary of it: a key that leaves out any
// part of the content lets two different elements share an entry.
const serialized = serializeForCache(element);
return serialized === null
? null
: `element:${JSON.stringify(tagName)}:${serialized}`;
},
/**
* Check if element is cacheable
*/
isCacheable(element, options) {
// Don't cache if caching is disabled
if (!options.enableCache) return false;
// Don't cache elements with functions (dynamic content)
if (RendererUtils.hasFunctions(element)) return false;
// Don't cache very large elements (memory consideration)
if (RendererUtils.getElementComplexity(element) > 1000) return false;
// Don't cache if we can't generate a stable cache key
const cacheKey = RendererUtils.generateCacheKey(
element.tagName || 'unknown',
element
);
if (!cacheKey) return false;
return true;
},
};
export default BaseRenderer;
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