tribe.storage/indexeddb/indexes.js

Efficient, portable, extensible object storage.

module.exports = {
    indexName: function (expression) {
        if (expression.constructor === Array) {
            var paths = [];
            for (var i = 0, l = expression.length; i < l; i++)
                if(paths.indexOf(expression[i].p) === -1)
                    paths.push(expression[i].p);
            return paths.join('_');
        }
        return expression.p;
    },
    convertExpression: function (expression) {
        if (expression.constructor === Array) {
            var upperBounds = [],
                lowerBounds = [];
            for (var i = 0, l = expression.length; i < l; i++) {
                var bounds = convertExpression(expression[i]);
                lowerBounds.push(bounds.lower);
                upperBounds.push(bounds.upper);
            }
            return IDBKeyRange.bound(lowerBounds, upperBounds);
        }

        var bounds = convertExpression(expression);
        return IDBKeyRange.bound(bounds.lower, bounds.upper);
    }
};

function convertExpression(expression) {
    var conversion = getConversion(expression.v);

    switch (expression.o) {
        case '=':
        case undefined:
            return { lower: expression.v, upper: expression.v };
        case '<=':
            return { lower: conversion.lower, upper: expression.v };
        case '<':
            return { lower: conversion.lower, upper: conversion.nextLower() };
        case '>=':
            return { lower: expression.v, upper: conversion.upper };
        case '>':
            return { lower: conversion.nextHigher(), upper: conversion.upper };
    }

    throw new Error('Unsupported expression type: ' + expression.o);
}

function getConversion(value) {
    var conversions = {
        'default': {
            lower: value,
            upper: value,
            nextLower: function () { return value; },
            nextHigher: function () { return value; }
        },
        'number': {
            lower: Number.MIN_VALUE,
            upper: Number.MAX_VALUE,
            nextLower: function () {
                return value - 1;
            },
            nextHigher: function () {
                return value + 1;
            }
        },
        'string': {
            lower: String.fromCharCode(0),
            upper: String.fromCharCode(65535),
            nextLower: function () {
                return value && (value.substring(0, value.length - 1) + String.fromCharCode(value.charCodeAt(value.length - 1) + 1));
            },
            nextHigher: function () {
                return value + String.fromCharCode(0);
            }
        }
    };

    return conversions[typeof value] || conversions.default;
}

function sortByName(source) {
    return source.sort(function (a, b) {
        return a.p > b.p;
    });
}