// @ts-check
import { WalkerBase } from './walker.js';

/** @typedef { import('estree').BaseNode} BaseNode */
/** @typedef { import('./walker').WalkerContext} WalkerContext */

/** @typedef {(
 *    this: WalkerContext,
 *    node: BaseNode,
 *    parent: BaseNode,
 *    key: string,
 *    index: number
 * ) => Promise<void>} AsyncHandler */

export class AsyncWalker extends WalkerBase {
	/**
	 *
	 * @param {AsyncHandler} enter
	 * @param {AsyncHandler} leave
	 */
	constructor(enter, leave) {
		super();

		/** @type {AsyncHandler} */
		this.enter = enter;

		/** @type {AsyncHandler} */
		this.leave = leave;
	}

	/**
	 *
	 * @param {BaseNode} node
	 * @param {BaseNode} parent
	 * @param {string} [prop]
	 * @param {number} [index]
	 * @returns {Promise<BaseNode>}
	 */
	async visit(node, parent, prop, index) {
		if (node) {
			if (this.enter) {
				const _should_skip = this.should_skip;
				const _should_remove = this.should_remove;
				const _replacement = this.replacement;
				this.should_skip = false;
				this.should_remove = false;
				this.replacement = null;

				await this.enter.call(this.context, node, parent, prop, index);

				if (this.replacement) {
					node = this.replacement;
					this.replace(parent, prop, index, node);
				}

				if (this.should_remove) {
					this.remove(parent, prop, index);
				}

				const skipped = this.should_skip;
				const removed = this.should_remove;

				this.should_skip = _should_skip;
				this.should_remove = _should_remove;
				this.replacement = _replacement;

				if (skipped) return node;
				if (removed) return null;
			}

			for (const key in node) {
				const value = node[key];

				if (typeof value !== "object") {
					continue;
				} else if (Array.isArray(value)) {
					for (let i = 0; i < value.length; i += 1) {
						if (value[i] !== null && typeof value[i].type === 'string') {
							if (!(await this.visit(value[i], node, key, i))) {
								// removed
								i--;
							}
						}
					}
				} else if (value !== null && typeof value.type === "string") {
					await this.visit(value, node, key, null);
				}
			}

			if (this.leave) {
				const _replacement = this.replacement;
				const _should_remove = this.should_remove;
				this.replacement = null;
				this.should_remove = false;

				await this.leave.call(this.context, node, parent, prop, index);

				if (this.replacement) {
					node = this.replacement;
					this.replace(parent, prop, index, node);
				}

				if (this.should_remove) {
					this.remove(parent, prop, index);
				}

				const removed = this.should_remove;

				this.replacement = _replacement;
				this.should_remove = _should_remove;

				if (removed) return null;
			}
		}

		return node;
	}
}