/// <summary>
///
/// </summary>
/// <param name="str"></param>
/// <param name="cursor"></param>
/// <returns></returns>
public static bool TryParse(string str, out NavigationCursor cursor)
{
if (null == str)
{
throw new ArgumentNullException(nameof(str));
}
if (0 < str.Length)
{
var stream = new MemoryStream(Base64UrlTextEncoder.Decode(str));
if (TryRead(stream, out var dir, out var id, out var count))
{
var direction = Enum.ToObject(typeof(NavigationCursorDirection), dir);
cursor = new NavigationCursor((NavigationCursorDirection)direction, id, count);
return(true);
}
}
cursor = null;
return(false);
}
public static string ToEncodedString(NavigationCursor cursor)
{
var stream = new MemoryStream();
Write(stream, Convert.ToSByte(cursor.Direction), cursor.Id, cursor.Count);
return(Base64UrlTextEncoder.Encode(stream.ToArray()));
}
/// <summary>
///
/// </summary>
/// <param name="entities"></param>
/// <param name="backward"></param>
/// <param name="forward"></param>
/// <returns></returns>
public static IPagedQueryResult <TEntity> Success(
IEnumerable <TEntity> entities,
NavigationCursor backward = null,
NavigationCursor forward = null)
{
var list = new List <TEntity>(entities);
var collection = new ReadOnlyCollection <TEntity>(list);
return(new PagedQueryResult <TEntity>(collection, backward, forward));
}
/// <summary>
///
/// </summary>
/// <param name="entities"></param>
/// <param name="backward"></param>
/// <param name="forward"></param>
public PagedQueryResult(
IReadOnlyCollection <TEntity> entities,
NavigationCursor backward = null,
NavigationCursor forward = null)
{
this.entities = entities;
exceptions = null;
Backward = backward;
Forward = forward;
}
/// <summary>
///
/// </summary>
/// <param name="stories"></param>
/// <param name="authors"></param>
/// <param name="backward"></param>
/// <param name="forward"></param>
/// <returns></returns>
public static PagedStoriesQueryResult Create(
IReadOnlyCollection <Story> stories,
IReadOnlyCollection <Author> authors,
NavigationCursor backward = null,
NavigationCursor forward = null)
{
return(new PagedStoriesQueryResult
{
stories = stories,
authors = authors,
Backward = backward,
Forward = forward
});
}
private static NavigationCursor GetForwardCursor(IList <Story> stories, int pageSize)
{
if (0 == stories.Count)
{
return(null);
}
if (pageSize > stories.Count)
{
return(null);
}
var id = stories[stories.Count - 1].Id;
return(NavigationCursor.Forward(id, pageSize));
}
private static NavigationCursor GetBackwardCursor(long?firstId, IList <Story> stories, int pageSize)
{
if (0 == stories.Count)
{
return(null);
}
var id = stories[0].Id;
if (firstId >= id)
{
return(null);
}
return(NavigationCursor.Backward(id - pageSize, pageSize));
}
public async Task <IActionResult> Get(string page, [FromCommaSeparatedQuery(Name = "include")] IEnumerable <string> includes)
{
var flags = EnumFlags.Parse <StoryIncludes>(includes);
var query = new GetStoriesListQuery(User)
{
IncludeAuthors = StoryIncludes.Authors == (flags & StoryIncludes.Authors),
IncludeComments = StoryIncludes.Comments == (flags & StoryIncludes.Comments),
Cursor = (null != page && NavigationCursorEncoder.TryParse(page, out var cursor))
? cursor
: NavigationCursor.Forward(0, blogSettings.PageSize)
};
var result = await mediator.Send(query, HttpContext.RequestAborted);
if (false == result.IsSuccess())
{
foreach (var exception in result.Exceptions)
{
logger.LogError(exception, "[StoriesController.Get]");
}
return(BadRequest(result.Exceptions));
}
var include = EnumFlags.ToQueryString(flags);
string backward = null;
string forward = null;
if (null != result.Backward)
{
backward = Url.Action("Get", "Stories", new
{
page = NavigationCursorEncoder.ToEncodedString(result.Backward),
include = include.ToString()
});
}
if (null != result.Forward)
{
forward = Url.Action("Get", "Stories", new
{
page = NavigationCursorEncoder.ToEncodedString(result.Forward),
include = include.ToString()
});
}
return(Ok(new ListResult <StoryModel, ResourcesMetaInfo>
{
Data = result.Select(story =>
{
var model = mapper.Map <StoryModel>(story);
model.Author = result.Authors.FindIndex(story.Author);
return model;
}),
Meta = new ResourcesMetaInfo
{
Resources = new AuthorsResource
{
Authors = result.Authors.Select(author => mapper.Map <AuthorModel>(author))
},
Navigation = new Navigation
{
Previous = backward,
Next = forward
}
}
}));
}
}
