# Architectural concepts

Vikunja was built with a maximum flexibility in mind while developing. To achive this, I built a set of easy-to-use
functions and respective web handlers, all represented through interfaces.

## CRUDable

This interface defines methods to Create/Read/ReadAll/Update/Delete something. In order to use the common web
handler, the struct must implement this and the `rights` interface.

The interface is defined as followed:

```go
type CRUDable interface {
	Create(*User) error
	ReadOne() error
	ReadAll(*User) (interface{}, error)
	Update() error
	Delete() error
}
```

Each of these methods is called on an instance of a struct like so:

```go
func (l *List) ReadOne() (err error) {
	*l, err = GetListByID(l.ID)
	return
}
```

In that case, it takes the `ID` saved in the struct instance, gets the full list object and fills the original object with it.
(See parambinder to understand where that `ID` is coming from).

All functions should behave like this, if they create or update something, they should return the created/updated struct
instance. The only exception is `ReadAll()` which returns an interface. Usually this is an array, because, well you cannot
make an array of a set type (If you know a way to do this, don't hesitate to drop me a message).

## Rights

This interface defines methods to check for rights on structs. They accept a `User` as parameter and usually return a `bool`.

The interface is defined as followed:

```go
type Rights interface {
	IsAdmin(*User) bool
	CanWrite(*User) bool
	CanRead(*User) bool
	CanDelete(*User) bool
	CanUpdate(*User) bool
	CanCreate(*User) bool
}
```

When using the standard web handler, all methods except `CanRead()` are called before their `CRUD` counterparts. `CanRead()`
is called after `Read()` was invoked as this would otherwise mean getting an object from the db to check if the user has the
right to see it and then getting it again if thats the case. Calling the function afterwards means we only have to get the
object once. 

## Standard web handler