marko/runtime/helpers.js

/*
* Copyright 2011 eBay Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*    http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

'use strict';
var escapeXml = require('raptor-util/escapeXml');
var escapeXmlAttr = escapeXml.attr;
var runtime = require('./'); // Circular dependency, but that is okay
var extend = require('raptor-util/extend');
var attr = require('raptor-util/attr');
var attrs = require('raptor-util/attrs');
var isArray = Array.isArray;

function notEmpty(o) {
    if (o == null) {
        return false;
    } else if (Array.isArray(o)) {
        return !!o.length;
    } else if (o === '') {
        return false;
    }

    return true;
}

function createDeferredRenderer(handler) {
    function deferredRenderer(input, out) {
        deferredRenderer.renderer(input, out);
    }

    // This is the initial function that will do the rendering. We replace
    // the renderer with the actual renderer func on the first render
    deferredRenderer.renderer = function(input, out) {
        var rendererFunc = handler.renderer || handler.render;
        if (typeof rendererFunc !== 'function') {
            throw new Error('Invalid tag handler: ' + handler);
        }
        // Use the actual renderer from now on
        deferredRenderer.renderer = rendererFunc;
        rendererFunc(input, out);
    };

    return deferredRenderer;
}

function resolveRenderer(handler) {
    var renderer = handler.renderer;

    if (renderer) {
        return renderer;
    }

    if (typeof handler === 'function') {
        return handler;
    }

    if (typeof (renderer = handler.render) === 'function') {
        return renderer;
    }

    // If the user code has a circular function then the renderer function
    // may not be available on the module. Since we can't get a reference
    // to the actual renderer(input, out) function right now we lazily
    // try to get access to it later.
    return createDeferredRenderer(handler);
}

module.exports = {
    /**
     * Internal helper method to prevent null/undefined from being written out
     * when writing text that resolves to null/undefined
     * @private
     */
    s: function(str) {
        return (str == null) ? '' : str;
    },
    /**
     * Internal helper method to handle loops with a status variable
     * @private
     */
    fv: function (array, callback) {
        if (!array) {
            return;
        }
        if (!array.forEach) {
            array = [array];
        }
        var i = 0;
        var len = array.length;
        var loopStatus = {
                getLength: function () {
                    return len;
                },
                isLast: function () {
                    return i === len - 1;
                },
                isFirst: function () {
                    return i === 0;
                },
                getIndex: function () {
                    return i;
                }
            };
        for (; i < len; i++) {
            var o = array[i];
            callback(o, loopStatus);
        }
    },
    /**
     * Internal helper method to handle loops without a status variable
     * @private
     */
    f: function forEach(array, callback) {
        if (isArray(array)) {
            for (var i=0; i<array.length; i++) {
                callback(array[i]);
            }
        } else if (typeof array === 'function') {
            // Also allow the first argument to be a custom iterator function
            array(callback);
        }
    },
    /**
     * Internal helper method to handle native for loops
     * @private
     */
    fl: function (array, func) {
        if (array != null) {
            if (!Array.isArray(array)) {
                array = [array];
            }
            func(array, 0, array.length);
        }
    },
    /**
     * Internal helper method for looping over the properties of any object
     * @private
     */
    fp: function (o, func) {
        if (!o) {
            return;
        }
        for (var k in o) {
            if (o.hasOwnProperty(k)) {
                func(k, o[k]);
            }
        }
    },
    /**
     * Internal method to check if an object/array is empty
     * @private
     */
    e: function (o) {
        return !notEmpty(o);
    },
    /**
     * Internal method to check if an object/array is not empty
     * @private
     */
    ne: notEmpty,
    /**
     * Internal method to escape special XML characters
     * @private
     */
    x: escapeXml,
    /**
     * Internal method to escape special XML characters within an attribute
     * @private
     */
    xa: escapeXmlAttr,
    /**
     * Internal helper to prevent an object from being escaped
     * @private
     */
    nx: function (str) {
        return {
            toString: function () {
                return str;
            }
        };
    },
    /**
     * Internal method to render a single HTML attribute
     * @private
     */
    a: attr,

    /**
     * Internal method to render multiple HTML attributes based on the properties of an object
     * @private
     */
    as: attrs,
    /**
     * Loads a template
     */
    l: function(path) {
        if (typeof path === 'string') {
            return runtime.load(path);
        } else {
            // Assume it is already a pre-loaded template
            return path;
        }
    },

    // ----------------------------------
    // The helpers listed below require an out
    // ----------------------------------


    /**
     * Invoke a tag handler render function
     */
    t: function (renderer, targetProperty, isRepeated, hasNestedTags) {
        if (renderer) {
            renderer = resolveRenderer(renderer);
        }

        if (targetProperty || hasNestedTags) {
            return function(input, out, parent, renderBody) {
                // Handle nested tags
                if (renderBody) {
                    renderBody(out, input);
                }

                if (targetProperty) {
                    // If we are nested tag then we do not have a renderer
                    if (isRepeated) {
                        var existingArray = parent[targetProperty];
                        if (existingArray) {
                            existingArray.push(input);
                        } else {
                            parent[targetProperty] = [input];
                        }
                    } else {
                        parent[targetProperty] = input;
                    }
                } else {
                    // We are a tag with nested tags, but we have already found
                    // our nested tags by rendering the body
                    renderer(input, out);
                }
            };
        } else {
            return renderer;
        }
    },

    /**
     * Internal helper method that captures the output of rendering.
     * This function works by swapping out the underlying writer to
     * a temporary writer that buffers a string. The provided function
     * is executed and the old writer is restored. Finally, the buffered
     * string is returned.
     */
    c: function (out, func) {
        var output = out.captureString(func);
        return {
            toString: function () {
                return output;
            }
        };
    },
    /**
     * Internal method to handle includes/partials
     * @private
     */
    i: function(out, path, data) {
        if (!path) {
            return;
        }

        if (typeof path === 'string') {
            runtime.render(path, data, out);
        } else if (typeof path.render === 'function') {
            path.render(data, out);
        } else {
            throw new Error('Invalid template');
        }

        return this;
    },
    /**
     * Internal helper method to do a shallow copy of the properties of one object to another.
     * @private
     */
    xt: extend
};