Sieve/README.md

# Sieve
⚗️ Sieve is a simple, clean, and extensible framework for .NET Core that **adds sorting, filtering, and pagination functionality out of the box**. 
Most common use case would be for serving ASP.NET Core GET queries.

[![NuGet Release](https://img.shields.io/nuget/v/Sieve.svg?style=flat-square)](https://www.nuget.org/packages/Sieve)

[Get Sieve on nuget](https://www.nuget.org/packages/Sieve/)

## Usage for ASP.NET Core

In this example, consider an app with a `Post` entity. 
We'll use Sieve to add sorting, filtering, and pagination capabilities when GET-ing all available posts.

### 1. Add required services

Inject the `SieveProcessor` service. So in `Startup.cs` add:
```
services.AddScoped<SieveProcessor>();
```

### 2. Tell Sieve which properties you'd like to sort/filter in your models

Sieve will only sort/filter properties that have the attribute `[Sieve(CanSort = true, CanFilter = true)]` on them (they don't have to be both true).
So for our `Post` entity model example:
```
public int Id { get; set; }

[Sieve(CanFilter = true, CanSort = true)]
public string Title { get; set; }

[Sieve(CanFilter = true, CanSort = true)]
public int LikeCount { get; set; }

[Sieve(CanFilter = true, CanSort = true)]
public int CommentCount { get; set; }

[Sieve(CanFilter = true, CanSort = true, Name = "created")]
public DateTimeOffset DateCreated { get; set; } = DateTimeOffset.UtcNow;

```
There is also the `Name` parameter that you can use to have a different name for use by clients.

Alternatively, you can use Fluent API to do the same. This is especially useful if you don't want to use attributes or have multiple APIs. [More on Sieve's Fluent API here](https://github.com/Biarity/Sieve/issues/4#issuecomment-364629048).

### 3. Get sort/filter/page queries by using the Sieve model in your controllers

In the action that handles returning Posts, use `SieveModel` to get the sort/filter/page query. 
Apply it to your data by injecting `SieveProcessor` into the controller and using its `ApplyAll<TEntity>` method. So for instance:
```
[HttpGet]
public JsonResult GetPosts(SieveModel sieveModel) 
{
    var result = _dbContext.Posts.AsNoTracking(); // Makes read-only queries faster
    result = _sieveProcessor.ApplyAll(sieveModel, result); // Returns `result` after applying the sort/filter/page query in `SieveModel` to it
    return Json(result.ToList());
}
```
There are also `ApplySorting`, `ApplyFiltering`, and `ApplyPagination` methods.

### 4. Send a request

[Send a request](#send-a-request)

### Add custom sort/filter methods

If you want to add custom sort/filter methods, inject `ISieveCustomSortMethods` or `ISieveCustomFilterMethods` with the implementation being a class that has custom sort/filter methods that Sieve will search through.

For instance:
```
services.AddScoped<ISieveCustomSortMethods, SieveCustomSortMethods>();
services.AddScoped<ISieveCustomFilterMethods, SieveCustomFilterMethods>();
```
Where `SieveCustomSortMethodsOfPosts` for example is:
```
public class SieveCustomSortMethods : ISieveCustomSortMethods
{
    public IQueryable<Post> Popularity(IQueryable<Post> source, bool useThenBy, bool desc) // The method is given an indicator of weather to use ThenBy(), and if the query is descending 
    {
        var result = useThenBy ?
            ((IOrderedQueryable<Post>)source).ThenBy(p => p.LikeCount) : // ThenBy only works on IOrderedQueryable<TEntity>
            source.OrderBy(p => p.LikeCount)
            .ThenBy(p => p.CommentCount)
            .ThenBy(p => p.DateCreated);

        return result; // Must return modified IQueryable<TEntity>
    }
}
```
And `SieveCustomFilterMethods`:
```
public class SieveCustomFilterMethods : ISieveCustomFilterMethods
{
    public IQueryable<Post> IsNew(IQueryable<Post> source, string op, string value) // The method is given the {Operator} & {Value}
    {
        var result = source.Where(p => p.LikeCount < 100 &&
                                        p.CommentCount < 5);

        return result; // Must return modified IQueryable<TEntity>
    }
}
```

## Handle Sieve's exceptions

Sieve can throw 2 kinds of custom exceptions:

* `SieveMethodNotFoundException` with a `MethodName`
* `SieveIncompatibleMethodException` with a `MethodName`, an `ExpectedType` and an `ActualType`

It is recommended that you write exception-handling middleware to globally handle Sieve's exceptions when using it with ASP.NET Core.

## Configure Sieve
Use the [ASP.NET Core options pattern](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/options) with `SieveOptions` to tell Sieve where to look for configuration. For example:
```
services.Configure<SieveOptions>(Configuration.GetSection("Sieve"));
```
Then you can add the configuration:
```
{
    "Sieve": {
        "CaseSensitive": `boolean: should property names be case-sensitive? Defaults to false`,
        "DefaultPageSize": `number: optional number to fallback to when no page argument is given`
    }
}
```

## Send a request

With all the above in place, you can now send a GET request that includes a sort/filter/page query.
An example:
```
GET /GetPosts

?sorts=     LikeCount,CommentCount,-created         // sort by likes, then comments, then descendingly by date created 
&filters=   LikeCount>10, Title@=awesome title,     // filter to posts with more than 10 likes, and a title that contains the phrase "awesome title"
&page=      1                                       // get the first page...
&pageSize=  10                                      // ...which contains 10 posts

```
More formally:
* `sorts` is a comma-delimited ordered list of property names to sort by. Adding a `-` before the name switches to sorting descendingly.
* `filters` is a comma-delimited list of `{Name}{Operator}{Value}` where
    * `{Name}` is the name of a property with the Sieve attribute or the name of a custom filter method for TEntity
    * `{Operator}` is one of the [Operators](#operators)
    * `{Value}` is the value to use for filtering
* `page` is the number of page to return
* `pageSize` is the number of items returned per page 

Notes:
* Don't forget to remove commas from any `{Value}` fields
* You can have spaces anywhere except *within* `{Name}` or `{Operator}` fields
* Here's a [good example on how to work with arrays](https://github.com/Biarity/Sieve/issues/2)

### Creating your own DSL
You can replace this DSL with your own (eg. use JSON instead) by implementing an [ISieveModel](https://github.com/Biarity/Sieve/blob/master/Sieve/Models/ISieveModel.cs). You can use the default [SieveModel](https://github.com/Biarity/Sieve/blob/master/Sieve/Models/SieveModel.cs) for reference.

### Operators
| Operator   | Meaning                  |
|------------|--------------------------|
| `==`       | Equals                   |
| `!=`       | Not equals               |
| `>`        | Greater than             |
| `<`        | Less than                |
| `>=`       | Greater than or equal to |
| `<=`       | Less than or equal to    |
| `@=`       | Contains                 |
| `_=`       | Starts with              |
| `@=*`      | Case-insensitive string Contains |
| `_=*`      | Case-insensitive string Starts with |
| `==*`      | Case-insensitive string Equals |

### Example project
You can find an example project incorporating most Sieve concepts in [SieveTests](https://github.com/Biarity/Sieve/tree/master/SieveTests).

## License & Contributing
Sieve is licensed under Apache 2.0. Any contributions highly appreciated!