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

Parser for Falcor Path Syntax

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

/**
 * The indexer is all the logic that happens in between
 * the '[', opening bracket, and ']' closing bracket.
 */
module.exports = function range(tokenizer, openingToken, state, out) {
    var token = tokenizer.peek();
    var dotCount = 1;
    var done = false;
    var inclusive = true;

    // Grab the last token off the stack.  Must be an integer.
    var idx = state.indexer.length - 1;
    var from = Tokenizer.toNumber(state.indexer[idx]);
    var to;

    if (isNaN(from)) {
        E.throwError(E.range.precedingNaN, tokenizer);
    }

    // Why is number checking so difficult in javascript.

    while (!done && !token.done) {

        switch (token.type) {

            // dotSeparators at the top level have no meaning
            case TokenTypes.dotSeparator:
                if (dotCount === 3) {
                    E.throwError(E.unexpectedToken, tokenizer);
                }
                ++dotCount;

                if (dotCount === 3) {
                    inclusive = false;
                }
                break;

            case TokenTypes.token:
                // move the tokenizer forward and save to.
                to = Tokenizer.toNumber(tokenizer.next().token);

                // throw potential error.
                if (isNaN(to)) {
                    E.throwError(E.range.suceedingNaN, tokenizer);
                }

                done = true;
                break;

            default:
                done = true;
                break;
        }

        // Keep cycling through the tokenizer.  But ranges have to peek
        // before they go to the next token since there is no 'terminating'
        // character.
        if (!done) {
            tokenizer.next();

            // go to the next token without consuming.
            token = tokenizer.peek();
        }

        // break and remove state information.
        else {
            break;
        }
    }

    state.indexer[idx] = {from: from, to: inclusive ? to : to - 1};
};