'use strict';
var isArray = Array.isArray;
var load = require('./loader');

function classListHelper(arg, classNames) {
    var len;

    if (arg) {
        if (typeof arg === 'string') {
            classNames.push(arg);
        } else if (typeof (len = arg.length) === 'number') {
            for (var i=0; i<len; i++) {
                classListHelper(arg[i], classNames);
            }
        } else if (typeof arg === 'object') {
            for (var name in arg) {
                if (arg.hasOwnProperty(name)) {
                    var value = arg[name];
                    if (value) {
                        classNames.push(name);
                    }
                }
            }
        }
    }
}

function classList(classList) {
    var classNames = [];
    classListHelper(classList, classNames);
    return classNames.join(' ');
}

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);
}

function LoopStatus(len) {
    this.i = 0;
    this.len = len;
}

LoopStatus.prototype = {
    getLength: function() {
        return this.len;
    },
    isLast: function() {
        return this.i === this.len - 1;
    },
    isFirst: function() {
        return this.i === 0;
    },
    getIndex: function() {
        return this.i;
    }
};

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.toString();
    },

    /**
     * Internal helper method to handle loops with a status variable
     * @private
     */
    fv: function (array, callback) {
        if (!array) {
            return;
        }
        if (!array.forEach) {
            array = [array];
        }

        var len = array.length;
        var loopStatus = new LoopStatus(len);

        for (; loopStatus.i < len; loopStatus.i++) {
            var o = array[loopStatus.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 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]);
            }
        }
    },

    /**
     * Helper to load a custom tag
     */
    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;
        }
    },

    /**
     * Merges object properties
     * @param  {[type]} object [description]
     * @param  {[type]} source [description]
     * @return {[type]}        [description]
     */
    m: function(into, source) {
        for (var k in source) {
            if (source.hasOwnProperty(k) && !into.hasOwnProperty(k)) {
                into[k] = source[k];
            }
        }
        return into;
    },

    /**
     * classList(a, b, c, ...)
     * Joines a list of class names with spaces. Empty class names are omitted.
     *
     * classList('a', undefined, 'b') --> 'a b'
     *
     */
    cl: function() {
        return classList(arguments);
    },

    /**
     * Loads a template (__helpers.l --> marko_loadTemplate(path))
     */
    l: load
};