/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the Source EULA. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

'use strict';

// --- trie'ish datastructure

class Node<E> {
	element?: E;
	readonly children = new Map<string, Node<E>>();
}

/**
 * A trie map that allows for fast look up when keys are substrings
 * to the actual search keys (dir/subdir-problem).
 */
export class TrieMap<E> {

	static PathSplitter = (s: string) => s.split(/[\\/]/).filter(s => !!s);

	private readonly _splitter: (s: string) => string[];
	private _root = new Node<E>();

	constructor(splitter: (s: string) => string[] = TrieMap.PathSplitter) {
		this._splitter = s => splitter(s).filter(s => Boolean(s));
	}

	insert(path: string, element: E): void {
		const parts = this._splitter(path);
		let i = 0;

		// find insertion node
		let node = this._root;
		for (; i < parts.length; i++) {
			let child = node.children.get(parts[i]);
			if (child) {
				node = child;
				continue;
			}
			break;
		}

		// create new nodes
		let newNode: Node<E>;
		for (; i < parts.length; i++) {
			newNode = new Node<E>();
			node.children.set(parts[i], newNode);
			node = newNode;
		}

		node.element = element;
	}

	lookUp(path: string): E {
		const parts = this._splitter(path);

		let { children } = this._root;
		let node: Node<E>;
		for (const part of parts) {
			node = children.get(part);
			if (!node) {
				return undefined;
			}
			children = node.children;
		}

		return node.element;
	}

	findSubstr(path: string): E {
		const parts = this._splitter(path);

		let lastNode: Node<E>;
		let { children } = this._root;
		for (const part of parts) {
			const node = children.get(part);
			if (!node) {
				break;
			}
			if (node.element) {
				lastNode = node;
			}
			children = node.children;
		}

		// return the last matching node
		// that had an element
		if (lastNode) {
			return lastNode.element;
		}
		return undefined;
	}

	findSuperstr(path: string): TrieMap<E> {
		const parts = this._splitter(path);

		let { children } = this._root;
		let node: Node<E>;
		for (const part of parts) {
			node = children.get(part);
			if (!node) {
				return undefined;
			}
			children = node.children;
		}

		const result = new TrieMap<E>(this._splitter);
		result._root = node;
		return result;
	}
}