如何根据两个部分Uri和一个假设反向计算Url /Uri

Question

我在数据库字段中存储了一个相对路径。它看起来是这样的：

/images/2012-6/file.jpg

我可以通过以下方式访问绝对Url：

http://www.blah.com/images/2012-6/file.jpg

缩略图相对路径未存储在数据库表中。然而，我知道它可以在以下位置找到：

http://www.blah.com/images/thumbnails/2012-6/file.jpg

假设我知道http://www.blah.com/和/images/2012-6/file.jpg，那么确定以下内容的最佳算法是什么：

http://www.blah.com/images/thumbnails/2012-6/file.jpg

注意:命名方案可以是相对路径和缩略图文件夹根路径上的多个文件夹。即/images/whatever/something/thumbnails/"。

您可以做的一个也是唯一的假设是，两者都将从相同的第一个段(文件夹)开始。即/images/。

这是在一个控制台应用程序中(如果我可以的话没有System.Web )。这是到目前为止的the best I have come up：

public static void Main()
{
    var test = GetThumbnail("http://www.blah.com/", "/images/folder/subfolder/test/again/filename.jpg", "/images/extra/thumbnails/");
    Console.WriteLine(test);
}

private static string GetThumbnail(string baseUriString, string relativePath, string thumbsPath)
{
    var root = new Uri(baseUriString, UriKind.Absolute);
    var absolute = new Uri(root, relativePath);
    var segments = absolute.Segments;

    var thumbnailUri = new Uri(root, thumbsPath);
    var thumbSegments = thumbnailUri.Segments;

    var matchedRoot = Array.IndexOf(segments, thumbSegments[1]);

    var builder = new UriBuilder(root);

    for (var j = 1; j < segments.Length; j++)
    {
        if (j == matchedRoot)
        {
            for (var k = 1; k < thumbSegments.Length; k++)
            {
                builder.Path += thumbSegments[k];
            }
        }
        else
        {
            builder.Path += segments[j];
        }
    }

    return builder.Uri.ToString();
}

这似乎令人费解。有没有更好的方法呢？

Answer 1

如果我正确地理解了您的需求，您基本上想要：

找到重叠的第一个片段

2. 将所有的拇指片段插入到Uri中的那个点。

您的代码已经做到了这一点，但我相信下面的代码会让这些步骤变得更加清晰：

    private static string GetThumbnail(string baseUriString, string relativePath, string thumbsPath)
    {
        // 1. Break the paths into segments
        // the trim here is important to prevent empty list items or "//" when we rebuild later.
        List<string> relativeSegments = relativePath.Trim('/').Split('/').ToList();
        List<string> thumbsSegments = thumbsPath.Trim('/').Split('/').ToList();

        // 2. Find the first segment of thumbs in the relative segments
        int sharedSegmentIndex = relativeSegments.IndexOf(thumbsSegments[0]);

        // 3. Insert all the thumbs segments into that spot in the Uri.
        // remove the overlapping segment (because we're adding it again below)
        relativeSegments.RemoveAt(sharedSegmentIndex);
        // insert the thumbs segment
        relativeSegments.InsertRange(sharedSegmentIndex, thumbsSegments);

        // build up the full path.
        var root = new Uri(baseUriString, UriKind.Absolute);
        var builder = new UriBuilder(root);
        builder.Path += string.Join("/", relativeSegments);

        return builder.Uri.ToString();
    }

此外，这里是我的快速和肮脏的测试套件，所以你可以检查我做出了正确的期望输出，以及任何其他想要修补的人。

    public static void Main()
    {
        RunTest("http://www.blah.com/", "/images/2012-6/file.jpg", "/images/thumbnails/", "http://www.blah.com/images/thumbnails/2012-6/file.jpg");
        RunTest("http://www.blah.com/", "/images/folder/subfolder/test/again/filename.jpg", "/images/extra/thumbnails/", "http://www.blah.com/images/extra/thumbnails/folder/subfolder/test/again/filename.jpg");
        RunTest("http://www.blah.com/", "/myapp/images/folder/subfolder/test/again/filename.jpg", "/images/extra/thumbnails/", "http://www.blah.com/myapp/images/extra/thumbnails/folder/subfolder/test/again/filename.jpg");
    }

    public static void RunTest(string baseUriString, string relativePath, string thumbsPath, string expected)
    {
        var result = GetThumbnail(baseUriString, relativePath, thumbsPath);
        Debug.Assert(result == expected);
    }