import { clamp } from "./clamp";

export interface GetPushedThumbValuesParams {
	values: readonly number[];
	index: number;
	nextValue: number;
	min: number;
	max: number;
	step: number;
	minStepsBetweenValues: number;
	initialValues?: readonly number[] | undefined;
}

/**
 * Returns a new array of slider values where attempting to move the thumb at
 * `index` beyond its neighbours "pushes" them while respecting
 * `minStepsBetweenValues`. When `initialValues` is provided, pushed
 * neighbours restore toward their initial value as space opens back up.
 */
export function getPushedThumbValues({
	values,
	index,
	nextValue,
	min,
	max,
	step,
	minStepsBetweenValues,
	initialValues,
}: GetPushedThumbValuesParams): number[] {
	if (values.length === 0) {
		return [];
	}

	const nextValues = values.slice();
	const minValueDifference = step * minStepsBetweenValues;
	const lastIndex = nextValues.length - 1;
	const baseInitialValues = initialValues ?? values;

	const indexMin = min + index * minValueDifference;
	const indexMax = max - (lastIndex - index) * minValueDifference;
	nextValues[index] = clamp(nextValue, indexMin, indexMax);

	for (let i = index + 1; i <= lastIndex; i += 1) {
		// biome-ignore lint/style/noNonNullAssertion: loop invariant keeps i-1 in range
		const minAllowed = nextValues[i - 1]! + minValueDifference;
		const maxAllowed = max - (lastIndex - i) * minValueDifference;
		// biome-ignore lint/style/noNonNullAssertion: i is within bounds
		const initialValue = baseInitialValues[i] ?? nextValues[i]!;
		// biome-ignore lint/style/noNonNullAssertion: i is within bounds
		let candidate = Math.max(nextValues[i]!, minAllowed);

		if (initialValue < candidate) {
			candidate = Math.max(initialValue, minAllowed);
		}

		nextValues[i] = clamp(candidate, minAllowed, maxAllowed);
	}

	for (let i = index - 1; i >= 0; i -= 1) {
		// biome-ignore lint/style/noNonNullAssertion: loop invariant keeps i+1 in range
		const maxAllowed = nextValues[i + 1]! - minValueDifference;
		const minAllowed = min + i * minValueDifference;
		// biome-ignore lint/style/noNonNullAssertion: i is within bounds
		const initialValue = baseInitialValues[i] ?? nextValues[i]!;
		// biome-ignore lint/style/noNonNullAssertion: i is within bounds
		let candidate = Math.min(nextValues[i]!, maxAllowed);

		if (initialValue > candidate) {
			candidate = Math.min(initialValue, maxAllowed);
		}

		nextValues[i] = clamp(candidate, minAllowed, maxAllowed);
	}

	for (let i = 0; i <= lastIndex; i += 1) {
		// biome-ignore lint/style/noNonNullAssertion: i is within bounds
		nextValues[i] = Number(nextValues[i]!.toFixed(12));
	}

	return nextValues;
}