///<summary>
/// Finds path from start to end by building a graph using BFS traversal
///</summary>
public async Task <Models.Race> FindPath(string startUrl, string endUrl)
{
var visited = new HashSet <string>();
var startArticleTitle = ParseTitle(startUrl);
var endArticleTitle = ParseTitle(endUrl);
visited.Add(startArticleTitle);
var queue = new Queue <Models.Article>();
queue.Enqueue(new Models.Article()
{
Title = startArticleTitle,
Parent = null
});
Models.Article currentArticle = null;
int numberOfArticlesTraversed = 0;
while (queue.Count > 0)
{
currentArticle = queue.Dequeue();
visited.Add(currentArticle.Title);
if (++numberOfArticlesTraversed >= _maxNumberOfArticlesTraversed)
{
throw new Exception("Maximm number of articles traversed reached");
}
var links = await _proxy.GetArticleLinks(currentArticle.Title);
foreach (var link in links)
{
if (!visited.Contains(link))
{
var linkedArticle = new Models.Article()
{
Title = link,
Parent = currentArticle
};
queue.Enqueue(linkedArticle);
if (link == endArticleTitle)
{
return(new Models.Race()
{
Start = startUrl,
End = endUrl,
Path = _pathConstructor.ConstructPath(linkedArticle)
});
}
}
}
}
throw new Exception("Path does not exist");
}
public List <string> ConstructPath(Models.Article currentArticle)
{
var path = new List <string>();
while (currentArticle != null)
{
path.Add(_ArticleUrl + currentArticle.Title);
currentArticle = currentArticle.Parent;
}
//since we traverse from the end back to start we need to reverse the path
path.Reverse();
return(path);
}
