/* *************************************************************************************
* copyright: Copyright (c) 2021 Lowell D. Thomas, all rights reserved
* license: BSD-2-Clause (https://opensource.org/licenses/BSD-2-Clause)
* ********************************************************************************* */This is the main or driver function for the parser generator. It handles:
Note on teminology.
APG is a parser generator. However, it really only generates a “grammar object” (see below) from the defining SABNF grammar. The generated parser is incomplete at this stage. Remaining, it is the job of the user to develop the generated parser from the grammar object and the APG Library (apg-lib).
The following terminology my help clear up the confusion between the idea of a “generated parser” versus a “generated grammar object”.
module.exports = function apg(args) {
const fs = require('fs');
const ApiCtor = require('../apg-api/api');
const getConfig = require('./command-line');
const thisFileName = 'apg.js: ';
const util = require('util');
function logErrors(api, header) {
console.log('\nORIGINAL GRAMMAR:');
console.log(api.linesToAscii());
console.log(`\n${header}:`);
console.log(api.errorsToAscii());
}
try {
/* Get command line parameters and set up the configuration accordingly. */
const config = getConfig(args);
if (config.error) {
console.log(config.error);
console.log(config.help);
return;
}
if (config.help) {
console.log(config.help);
return;
}
if (config.version) {
console.log(config.version);
return;
}
/* Get and validate the input SABNF grammar. */
const api = new ApiCtor(config.src);
api.scan(config.strict);
if (api.errors.length) {
logErrors(api, 'GRAMMAR CHARACTER ERRORS');
throw new Error(`${thisFileName}invalid input grammar`);
}
/* parse the grammar - the syntax phase */
api.parse(config.strict, config.lite);
if (api.errors.length) {
logErrors(api, 'GRAMMAR SYNTAX ERRORS');
throw new Error(`${thisFileName}grammar has syntax errors`);
}
/* translate the AST - the semantic phase */
api.translate();
if (api.errors.length) {
logErrors(api, 'GRAMMAR SEMANTIC ERRORS');
throw new Error(`${thisFileName}grammar has semantic errors`);
}
if (config.displayRules) {
console.log(api.displayRules('alpha'));
console.log();
}
/* attribute generation */
const errorCount = api.attributes();
if (errorCount > 0) {
console.log('GRAMMAR ATTRIBUTE ERRORS');
console.log(api.displayAttributeErrors());
console.log();
if (config.displayAttributes) {
console.log(api.displayAttributes('type'));
console.log();
}
throw new Error(`${thisFileName}grammar has attribute errors`);
}
if (config.displayRuleDependencies) {
console.log(api.displayRuleDependencies('type'));
console.log();
}
if (config.displayAttributes) {
console.log(api.displayAttributes('type'));
console.log();
}
/* generate a JavaScript parser, if requested */
if (config.outfd) {
fs.writeSync(config.outfd, api.toSource(config.lite, config.funcName));
if (config.lite) {
console.log(`\napg-lite grammar object generated: ${config.outFilename}`);
} else {
console.log(`\napg-js grammar object generated: ${config.outFilename}`);
}
}
} catch (e) {
let msg = 'EXCEPTION THROWN: ';
if (e instanceof Error) {
msg += `${e.name}: ${e.message}`;
} else if (typeof e === 'string') {
msg += e;
} else {
msg += '\n';
msg += util.inspect(e, {
showHidden: true,
depth: null,
colors: true,
});
}
console.log(msg);
}
};