/*
Copyright 2014 The Camlistore Authors.

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.
*/

goog.provide('cam.reactUtil');

goog.require('goog.string');

// A React prop validator that enforces a property has the specified duck type.
// @param Object iface An object that describes the required interface. Each property should itself be a React prop validator describing the corresponding required member.
cam.reactUtil.quacksLike = function(iface) {
	var validator = function(props, propName, componentName) {
		componentName += '.' + propName;
		if (propName in props) {
			var thing = props[propName];
			for (var p in iface) {
				iface[p](thing, p, componentName);
			}
		}
	};

	validator.isRequired = function(props, propName, componentName) {
		if (!(propName in props)) {
			throw new Error(goog.string.subs('Required prop %s is not present', propName));
		}
		validator(props, propName, componentName);
	};

	return validator;
};

// Returns the appropriate vendor prefixed style property name. This is figured out by testing the presence of various property names on an actual DOM style object.
// The returned property is of the form 'fooBar' (if no prefix is needed), or 'WebkitFooBar' if a prefix is needed, which is the form React expects.
// @param {string} prop The property name to find.
// @param {CSSStyleDeclaration=} style A style object to test on. This can be any DOM style object, e.g., document.body.style.
// @return {?string} The appropriate property name to use, or null if the property is not supported in this environment.
cam.reactUtil.getVendorProp = function(prop, opt_testStyle) {
	if (!goog.isDef(opt_testStyle)) {
		opt_testStyle = document.body.style;
	}

	if (goog.isDef(opt_testStyle[prop])) {
		return prop;
	}

	var prefixes = ['webkit', 'moz', 'ie'];
	for (var i = 0, p; p = prefixes[i]; i++) {
		var candidate = p + goog.string.toTitleCase(prop);
		if (goog.isDef(opt_testStyle[candidate])) {
			// React expects vendor prefixed property names to be TitleCase.
			return goog.string.toTitleCase(candidate);
		}
	}

	return null;
};

// Like cam.object.extend(), except that special care is taken to also merge together some known child properties that are part of React specifications.
// @param Object parentSpec
// @param Object childSpec
// @return Object merged spec
cam.reactUtil.extend = function(parentSpec, childSpec) {
	var result = cam.object.extend(parentSpec, childSpec);
	if (childSpec.propTypes) {
		result.propTypes = cam.object.extend(parentSpec.propTypes, childSpec.propTypes);
	}
	return result;
}