/// <summary>
/// 创建带范畴限定的选择器
/// </summary>
/// <param name="expression">选择器表达式</param>
/// <param name="scope">范畴限定，上溯时不超出此范畴</param>
/// <returns>带范畴限定的层叠选择器</returns>
public static ISelector Create(IHtmlContainer scope, string expression)
{
if (scope == null)
{
throw new ArgumentNullException("scope");
}
if (expression == null)
{
throw new ArgumentNullException("expression");
}
return(CssCasecadingSelector.Create(new CssAncetorRelativeSelector(new ContainerRestrict(scope)), CssParser.ParseSelector(expression)));
}
/// <summary>
/// 合并两个关系选择器
/// </summary>
/// <param name="left">左关系选择器</param>
/// <param name="right">右关系选择器</param>
/// <returns>合并后的关系选择器</returns>
public static CssRelativeSelector Combine(CssRelativeSelector left, CssRelativeSelector right)
{
if (left == null)
{
throw new ArgumentNullException("left");
}
if (right == null)
{
throw new ArgumentNullException("right");
}
var selector = right.LeftSelector;
var combinator = right.Combinator;
var casecadingSelector = selector as CssCasecadingSelector;
if (casecadingSelector != null) //如果右边关系选择器的左选择器是一个层叠选择器
{
return(CreateRelativeSelector(CssCasecadingSelector.Combine(left, casecadingSelector), combinator)); //将层叠选择器与左边的关系选择器合并，得到一个新的层叠选择器，再根据结合符创建新的关系选择器。
}
/*
* 举例说明如下：
* 假设左关系选择器是 p>，右关系选择器是 div>ul>li+
* 则右关系选择器的左选择器(selector)是div>ul>li，结合符(combinator)是+。
* 将selector与左边的关系选择器合并，得到：p>div>ul>li，再与结合符结合得到新的关系选择器：p>div>ul>li+
*/
var elementSelector = selector as CssElementSelector;
if (elementSelector != null)
{
return(CreateRelativeSelector(new CssCasecadingSelector(left, elementSelector), combinator));
}
throw new NotSupportedException();
}
/// <summary>
/// 在元素集所有子代元素中使用 CSS 选择器选出符合要求的元素
/// </summary>
/// <param name="elements">作为选择范围的元素集</param>
/// <param name="expression">CSS 选择器表达式</param>
/// <returns>符合选择器的所有子代</returns>
public static IEnumerable <IHtmlElement> Find(this IEnumerable <IHtmlElement> elements, string expression)
{
if (!elements.Any())
{
return(Enumerable.Empty <IHtmlElement>());
}
if (elements.IsSingle())
{
return(elements.Single().Find(expression));
}
var document = elements.First().Document;
if (elements.Any(e => !e.Document.Equals(document)))
{
throw new InvalidOperationException("不支持在不同的文档中搜索");
}
var selector = CssCasecadingSelector.Create(elements, expression);
return(selector.Filter(document.Descendants()));
}
/// <summary>
/// 合并关系选择器和层叠选择器
/// </summary>
/// <param name="relativeSelector">关系选择器</param>
/// <param name="selector">层叠选择器</param>
/// <returns></returns>
internal static CssCasecadingSelector Combine(CssRelativeSelector relativeSelector, CssCasecadingSelector selector)
{
relativeSelector = Combine(relativeSelector, selector.RelativeSelector);
return(new CssCasecadingSelector(relativeSelector, selector.LastSelector));
}
/// <summary>
/// 创建层叠选择器
/// </summary>
/// <param name="leftSelector">左选择器</param>
/// <param name="combanitor">结合符</param>
/// <param name="rightSelector">右选择器</param>
/// <returns>层叠选择器</returns>
private static ISelector CreateCasecadingSelector(ISelector leftSelector, char combanitor, CssElementSelector rightSelector)
{
return(CssCasecadingSelector.Create(leftSelector, combanitor, rightSelector));
}
public static ISelector Combine(CssRelativeSelector relativeSelector, CssMultipleSelector multipleSelector)
{
return(new CssMultipleSelector(multipleSelector._selectors.Select(selector => CssCasecadingSelector.Create(relativeSelector, selector)).ToArray()));
}
/// <summary>
/// 合并关系选择器和层叠选择器
/// </summary>
/// <param name="relativeSelector">关系选择器</param>
/// <param name="selector">层叠选择器</param>
/// <returns></returns>
internal static CssCasecadingSelector Combine( CssRelativeSelector relativeSelector, CssCasecadingSelector selector )
{
relativeSelector = Combine( relativeSelector, selector.RelativeSelector );
return new CssCasecadingSelector( relativeSelector, selector.LastSelector );
}
