es-vm/src/statement.js

A visual machine run in ES env like Node/Browser

'use strict';
const statementClassMap = {};


const error = {
	NO_EXECUTE: (symbol) => {
		return `The Statement:${symbol} miss prototype.execute.`;
	}
};

function linkNode(syntaxNode) {
	try {
		return new statementClassMap[syntaxNode.SYMBOL](syntaxNode);
	} catch (err) {
		console.error(syntaxNode);
		throw err;
	}
}

/**
 * Bind statement with a symbol.
 * @param {String} $Symbol Statement symbol.
 */
function register(statementClass, symbol, execution = true) {
	if (!statementClass.prototype.execute && execution) {
		throw new Error(`[ESVM-DEV]: ${error.NO_EXECUTE(symbol)}`);
	}
	statementClassMap[symbol] = statementClass;
	return statementClass;
}

/**
 * The most simple statement looks like:
 * 	{
 * 		SYMBOL: <string | used to query how to execute>,
 * 		[POSITION]: {
 * 			[IDENTIFIER]: <string | the line name user assigned>,
 * 			LINE: <unsigned number | the line of statement in the code>,
 * 			[COL]: <unsigned number | the line of statement in the code>
 * 		}, <object | statement position info from syntax tree>
 * 		BODY: {
 * 			[PROPERTIES]
 * 		} <object | >
 * 	}
 * 
 * @class Statement
 */
class Statement {
	/**
	 * @constructor
	 * @param {Object} [POSITION={}] Position info of the statement.
	 */
	constructor ({POSITION} = {type: 'native'}) {
		this.position = POSITION;
	}

	/**
	 * Link each statement node from a syntax tree by statement symbol.
	 * @param {Object} syntaxNode Statement content.
	 * @returns {Statement} Statement instance.
	 */
	linkNode (syntaxNode) {
		return linkNode(syntaxNode);
	}

	/**
	 * Define execution rule for the statement.
	 * Operation will be record in a stack.
	 * @param {Kernel} vm
	 * @param {Scope} scope
	 */
	*doExecution($) {
		$.vm.pushOperation(this);
		const ret = yield* this.execute($);
		$.vm.emit('writeback', ret, $.vm);
		$.vm.popOperation();

		return ret;
	}
}

module.exports = {Statement, linkNode, register};