falcor-path-syntax/src/parse-tree/head.js

Parser for Falcor Path Syntax

var TokenTypes = require('./../TokenTypes');
var E = require('./../exceptions');
var indexer = require('./indexer');

/**
 * The top level of the parse tree.  This returns the generated path
 * from the tokenizer.
 */
module.exports = function head(tokenizer) {
    var token = tokenizer.next();
    var state = {};
    var out = [];

    while (!token.done) {

        switch (token.type) {
            case TokenTypes.token:
                var first = +token.token[0];
                if (!isNaN(first)) {
                    E.throwError(E.invalidIdentifier, tokenizer);
                }
                out[out.length] = token.token;
                break;

            // dotSeparators at the top level have no meaning
            case TokenTypes.dotSeparator:
                if (out.length === 0) {
                    E.throwError(E.unexpectedToken, tokenizer);
                }
                break;

            // Spaces do nothing.
            case TokenTypes.space:
                // NOTE: Spaces at the top level are allowed.
                // titlesById  .summary is a valid path.
                break;


            // Its time to decend the parse tree.
            case TokenTypes.openingBracket:
                indexer(tokenizer, token, state, out);
                break;

            default:
                E.throwError(E.unexpectedToken, tokenizer);
                break;
        }

        // Keep cycling through the tokenizer.
        token = tokenizer.next();
    }

    if (out.length === 0) {
        E.throwError(E.invalidPath, tokenizer);
    }

    return out;
};