# ArelToolkit

## Overview

- [![Build Status](https://travis-ci.com/mvgijssel/arel_toolkit.svg?branch=master)](https://travis-ci.com/mvgijssel/arel_toolkit)
- [![Maintainability](https://api.codeclimate.com/v1/badges/3ef13d1649a00a98562d/maintainability)](https://codeclimate.com/github/mvgijssel/arel_toolkit/maintainability)
- [![Test Coverage](https://api.codeclimate.com/v1/badges/3ef13d1649a00a98562d/test_coverage)](https://codeclimate.com/github/mvgijssel/arel_toolkit/test_coverage)
- [![Gem Version](https://badge.fury.io/rb/arel_toolkit.svg)](https://badge.fury.io/rb/arel_toolkit)
- [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
- ![](http://ruby-gem-downloads-badge.herokuapp.com/arel_toolkit?type=total)
- ![](http://ruby-gem-downloads-badge.herokuapp.com/arel_toolkit?label=downloads-current-version)
- [Coverage report](https://mvgijssel.github.io/arel_toolkit/)

## Installation

Add this line to your application's Gemfile:

```ruby
gem 'arel_toolkit'
```

And then execute:

    $ bundle

Or install it yourself as:

    $ gem install arel_toolkit

## sql_to_arel

Convert your (PostgreSQL) SQL into an Arel AST.

```ruby
[1] > sql = 'SELECT id FROM users'
=> "SELECT id FROM users;"
[2] > arel = Arel.sql_to_arel(sql)
=> #<Arel::SelectManager:0x00007fe4e39823d8>
[3] > arel.to_sql
=> "SELECT \"id\" FROM \"users\""
```

## Extensions

Adds missing Arel nodes and extends the existing visitors, [lib/arel/extensions](https://github.com/mvgijssel/arel_toolkit/tree/master/lib/arel/extensions) for a full list.

## Middleware

The middleware sits between ActiveRecord and the database, which allows you to mutate or log queries before they hit the database. Multiple middleware are supported by passing the results from a finished middleware to the next. User defined context will be passed, which can contains things like the `current_user_id`.

### Example

Create an initializer in Rails which loads the Arel::Middleware **after** ActiveRecord:

```ruby
ActiveSupport.on_load :active_record do
  Arel::Middleware::Railtie.insert_postgresql
end
```

Create some middleware (can be any Ruby object which responds to `call`):

```ruby
class ReorderMiddleware
  def self.call(arel, _context)
    arel.order(Post.arel_table[:id].asc)
  end
end

class LoggingMiddleware
  def self.call(arel, context)
    puts "User executing query: `#{context[:current_user_id]}`"
    puts "Original SQL: `#{context[:original_sql]}`"
    puts "Modified SQL: `#{arel.to_sql}`"
    arel
  end
end
```

Run a query with middleware applied

```ruby
[1] > Arel.middleware.apply([ReorderMiddleware, LoggingMiddleware]).context(current_user_id: 1) { Post.all.load }
User executing query: `1`
Original SQL: `SELECT "posts".* FROM "posts" ORDER BY "posts"."id" DESC`
Modified SQL: `SELECT "posts".* FROM "posts" ORDER BY "posts"."id" DESC, "posts"."id" ASC`
Post Load (4.1ms)  SELECT "posts".* FROM "posts" ORDER BY "posts"."id" DESC, "posts"."id" ASC
=> []
```

There are more methods available to help with ordering and modifying of the current applied middleware:

- `Arel.middleware.apply([SomeMiddleware]) { ... }`
- `Arel.middleware.only([OnlyMe]) { ... }`
- `Arel.middleware.none { ... }`
- `Arel.middleware.except(RemoveMe) { ... }`
- `Arel.middleware.insert_before(RunBefore, ThisMiddleware) { ... }`
- `Arel.middleware.insert_after(RunAfter, ThisMiddleware) { ... }`

## Development

After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).

## Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/arel_toolkit. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.

## License

The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).

## Code of Conduct

Everyone interacting in the ArelToolkit project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the [code of conduct](https://github.com/[USERNAME]/arel_toolkit/blob/master/CODE_OF_CONDUCT.md).