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Copy pathparser.js
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101 lines (93 loc) · 3.34 KB
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module.exports = Parser;
var util = require('util'), stream = require('stream');
util.inherits(module.exports, stream.Transform);
function Parser(options) {
stream.Transform.call(this, options);
this._writableState.objectMode = true;
this._readableState.objectMode = true;
this._state = 'newStmt';
this._stmtstack = [];
this._statements = [];
}
function last(a) { return a[a.length - 1]; }
Parser.prototype._transform = function(token, _enc, cb) {
try {
this._innerTransform(token);
} catch (e) {
this.emit('err', e);
this._innerTransform = function(){};
}
cb();
};
Parser.prototype._innerTransform = function(token) {
switch (this._state) {
case 'newStmt':
switch(token.type) {
case 'END':
this._statements.push({type: 'END'});
this._state = 'EOL';
break;
case 'PRINT':
this._statements.push({type: 'PRINT'});
this._state = 'stringExpr';
break;
case 'FOR':
this._statements.push({type: 'FOR'});
this._state = 'forVar';
break;
case 'NEXT':
var forBody = this._statements;
if (this._stmtstack.length === 0) throw new Error('no matching FOR for NEXT');
this._statements = this._stmtstack.pop();
var forStatement = last(this._statements);
forStatement.body = forBody;
this._state = 'EOL';
break;
default: throw new Error('unknown statement type ' +JSON.stringify(token));
}
break;
case 'forVar':
last(this._statements).varName = token.type;
this._state = 'forAssignment';
break;
case 'forAssignment':
if(token.data !== '=') throw new Error('expected = ; found ' + JSON.stringify(token));
this._state = 'forInit';
break;
case 'forInit':
if(token.type !== 'num') throw token;
last(this._statements).init = token.data;
this._state = 'to';
break;
case 'to':
if(token.type!=='TO') throw token;
this._state = 'forStep';
break;
case 'forStep':
if(token.type!=='num') throw token;
last(this._statements).limit = token.data;
last(this._statements).step = 1;
this._stmtstack.push(this._statements);
this._statements = [];
this._state = 'EOL';
break;
case 'stringExpr':
if(token.type!=='string') throw token;
last(this._statements).expr = token;
this._state = 'EOL';
break;
case 'EOL':
if(token.type !== 'lineBreak') throw token;
if(this._stmtstack.length === 0) {
this._statements.forEach(this.push.bind(this));
this._statements = [];
}
this._state = 'newStmt';
break;
default: throw token;
}
};
Parser.prototype._flush = function(cb) {
if(this._stmtstack.length !== 0) this.emit('err', new Error('unclosed ' + last(last(this._stmtstack)).type));
cb();
}