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import { CONTROLLER_REGISTRY } from './registry.js';
import { isFunction } from '@beerush/utils';
import { assign } from './helper.js';
import { captureStack } from './exception.js';
import { anchor } from './anchor.js';
/**
* Derives a new subscription from an existing anchored state.
* This is a convenience function to subscribe to changes of an already anchored state.
*
* @template T The type of the state.
* @param state - The anchored state object to derive from.
* @param handler - The subscriber function to call on state changes.
* @param recursive - Whether to recursively subscribe to child states (Default: follow).
* @returns A function to unsubscribe from the derived state.
*/
function deriveFn<T extends Linkable>(
state: State<T>,
handler: StateSubscriber<T>,
recursive?: boolean
): StateUnsubscribe {
const ctrl = CONTROLLER_REGISTRY.get(state);
if (typeof ctrl?.subscribe !== 'function') {
captureStack.warning.external(
'Invalid subscription target:',
'Attempted to subscribe to non-reactive state.',
'Object is not reactive',
deriveFn,
deriveFn.pipe
);
try {
handler(state, { type: 'init', keys: [] });
} catch (error) {
captureStack.error.external(
'Unable to execute the subscription handler function.',
error as Error,
deriveFn,
deriveFn.pipe
);
}
return () => {
// No-op, as there is no subscription to unsubscribe from.
};
}
return ctrl?.subscribe(handler as StateSubscriber<unknown>, undefined, recursive);
}
deriveFn.log = ((state) => {
return deriveFn(state, console.log);
}) satisfies DeriveFn['log'];
deriveFn.resolve = ((state) => {
return CONTROLLER_REGISTRY.get(state) as never;
}) satisfies DeriveFn['resolve'];
deriveFn.pipe = ((source, target, transform) => {
if (!anchor.has(source)) {
const error = new Error('State is not reactive.');
captureStack.violation.derivation('Attempted to pipe state from a non-reactive state.', error);
return () => {};
}
if (typeof target !== 'object' || target === null) {
const error = new Error('Target is not an assignable object.');
captureStack.violation.derivation('Attempted to pipe state to a non-assignable target.', error);
return () => {};
}
if (!isFunction(transform)) {
return deriveFn(source, (current) => {
assign(target as ObjLike, current as ObjLike);
});
}
return deriveFn(source, (current) => {
assign(target as ObjLike, transform(current));
});
}) satisfies DeriveFn['pipe'];
deriveFn.bind = ((left, right, transformLeft, transformRight) => {
if (!anchor.has(left)) {
const error = new Error('State is not reactive.');
captureStack.violation.derivation('Attempted to bind state from a non-reactive state.', error);
return () => {};
}
if (!anchor.has(right)) {
const error = new Error('State is not reactive.');
captureStack.violation.derivation('Attempted to bind state to a non-reactive state.', error);
return () => {};
}
let updatingLeft = false;
let updatingRight = false;
const unsubscribeLeft = deriveFn(left, (current) => {
if (updatingLeft) return;
updatingRight = true;
if (isFunction(transformLeft)) {
const result = transformLeft(current);
if (result) {
anchor.assign(right, result);
} else {
captureStack.warning.external(
'Invalid binding transformation:',
'The transformation function returned an invalid value. Please check your transformation function.',
'Undefined is not assignable value.'
);
}
} else {
anchor.assign(right as ObjLike, current as ObjLike);
}
updatingRight = false;
});
const unsubscribeRight = deriveFn(right, (current) => {
if (updatingRight) return;
updatingLeft = true;
if (isFunction(transformRight)) {
const result = transformRight(current);
if (result) {
anchor.assign(left, result);
} else {
captureStack.warning.external(
'Invalid binding transformation:',
'The transformation function returned an invalid value. Please check your transformation function.',
'Undefined is not assignable value.'
);
}
} else {
assign(left as ObjLike, current as ObjLike);
}
updatingLeft = false;
});
return () => {
unsubscribeLeft();
unsubscribeRight();
};
}) satisfies DeriveFn['bind'];
export const derive = deriveFn as DeriveFn;
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