astro/packages/integrations/preact/src/signals.ts

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import type { Context } from './context';
import { incrementId } from './context.js';
import type { AstroPreactAttrs, PropNameToSignalMap, SignalLike } from './types';
function isSignal(x: any): x is SignalLike {
return x != null && typeof x === 'object' && typeof x.peek === 'function' && 'value' in x;
}
export function restoreSignalsOnProps(ctx: Context, props: Record<string, any>) {
// Restore signal props that were mutated for serialization
let propMap: PropNameToSignalMap;
if (ctx.propsToSignals.has(props)) {
propMap = ctx.propsToSignals.get(props)!;
} else {
propMap = new Map();
ctx.propsToSignals.set(props, propMap);
}
for (const [key, signal] of propMap) {
props[key] = signal;
}
return propMap;
}
export function serializeSignals(
ctx: Context,
props: Record<string, any>,
attrs: AstroPreactAttrs,
map: PropNameToSignalMap
) {
// Check for signals
const signals: Record<string, string> = {};
for (const [key, value] of Object.entries(props)) {
if (isSignal(value)) {
// Set the value to the current signal value
// This mutates the props on purpose, so that it will be serialized correct.
props[key] = value.peek();
map.set(key, value);
let id: string;
if (ctx.signals.has(value)) {
id = ctx.signals.get(value)!;
} else {
id = incrementId(ctx);
ctx.signals.set(value, id);
}
signals[key] = id;
}
}
if (Object.keys(signals).length) {
attrs['data-preact-signals'] = JSON.stringify(signals);
}
}