# diamond

### a golang ORM for mongodb that rocks 🎸~♬

# usage

## installation

run the following command in your terminal...

```shell
go get rockfic.com/orm
```

...and import the package at the top of your file(s) like so:

```go
package tutorial

import "rockfic.com/orm"
```

## Connect to the database

```go
package tutorial

import "rockfic.com/orm"

func main() {
	orm.Connect("mongodb://127.0.0.1", "your_database")
}
```

this will create a connection and store it in the `DB` global variable. This global variable is used internally to
interact with the underlying database.

if you need to <sub><sub>~~why?~~</sub></sub>, you may also access the mongoDB client directly via the `orm.Client`
variable.

## Create a Model

to create a new model, you need to define a struct like this:

```go
package tutorial

import "rockfic.com/orm"

type User struct {
	orm.Document `bson:",inline" coll:"collection"`
  ID int64 `bson:"_id"`
	Username     string `bson:"username"`
	Email        string `bson:"email"`
	Friends      []User `bson:"friends"`
}
```

this on its own is useless. to actually do anything useful with it, you need to *register* this struct as a model:

```go
package tutorial

import "rockfic.com/orm"

func main() {
	/* ~ snip ~ */
	orm.ModelRegistry.Model(User{})
}
```

you can also pass multiple arguments to `orm.Model`, so long as they embed the `Document` struct.

you can access the newly created model like this:

```go
package tutorial

import "rockfic.com/orm"

func main() {
  /* ~ snip ~ */
  userModel := orm.ModelRegistry.Get("User")
}
```

## Documents

any struct can be used as a document, so long as it embeds the `Document` struct. the `Document` struct is special, in
that it turns any structs which embed it into `IDocument` implementors.
`Document` should be embedded with a `bson:",inline" tag, otherwise you will end up with something like this in the
database:

```bson
{
  "document": {
    "createdAt": ISODate('2001-09-11T05:37:18.742Z'),
    "updatedAt": ISODate('2001-09-11T05:37:18.742Z')
  },
  _id: 1,
  username: "foobar",
  email: "test@testi.ng",
  friends: []
}
```

a `coll` or `collection` tag is also required, to assign the model to a mongodb collection. this tag is only valid on
the embedded `Document` field, and each document can only have one collection associated with it.
<sub>obviously.</sub>
<sub><sub>i mean seriously, who'd want to store one thing in two places?</sub></sub>

the recommended way to create a new document instance is via the `orm.Create` method:

```go
package tutorial

import "rockfic.com/orm"

func main() {
  /* ~ snip ~ */
  user := orm.Create(User{}).(*User)
}
```

similarly, to create a slice of documents, call `orm.CreateSlice`:

```go
package tutorial

import "rockfic.com/orm"

func main() {
  /* ~ snip ~ */
  users := orm.CreateSlice[User](User{})
}
```

lastly, let's implement the `HasID` interface on our document:

```go
package tutorial

import "rockfic.com/orm"

func (u *User) GetId() any {
  return u.ID
}

func (u *User) SetId(id any) {
  u.ID = id.(int64)
}
```

#### but why do i need to implement this? :(

other ORMs rudely assume that you want your `_id`s to be mongodb ObjectIDs, which are **fucking ugly**, but also, more
importantly, *may not match your existing schema.*
by doing things this way, you can set your _id to be any of the following types:

- int
- int32
- int64
- uint
- uint32
- uint64
- string
- ObjectId
  
  <sub>(if you hate yourself that much)</sub>

## finding/querying

`Find`, `FindOne`, `FindByID`, and `FindPaged` all return an `*orm.Query` object.
to get the underlying value, simply call `.Exec()`, passing to it a pointer to the variable in which you wish to store
the results.

### `Find` example

```go
package tutorial

import (
  "go.mongodb.org/mongo-driver/bson"
  "rockfic.com/orm"
)

func main() {
  /* ~ snip ~ */
  userModel := orm.ModelRegistry.Get("User")
  if userModel != nil {
    res := orm.CreateSlice(User{})
    jq, _ := userModel.Find(bson.M{"username": "foobar"})
    q.Exec(&res)
  }
}

```

## saving/updating

to save a document, simply call the `Save()` method. if the document doesn't exist, the ORM will create it, otherwise it
replaces the existing one.

## referencing other documents

it's possible to store references to other documents/structs, or slices to other documents. given the `User` struct we
defined above, which contains a slice (`Friends`) referencing other `User`s, we could change the `Friends` field in the
`User` type to be populateable, like so:

```diff
type User struct {
	orm.Document `bson:",inline" coll:"collection"`
	ID           int64  `bson:"_id"`
	Username     string `bson:"username"`
	Email        string `bson:"email"`
-	Friends      []User `bson:"friends"`
+   Friends      []User `bson:"friends" ref:"User"`
}
```

assuming we've filled a user's `Friends` with a few friends...

```go
package tutorial

import "rockfic.com/orm"

func main() {
  /* ~ snip ~ */
  user := orm.Create(User{}).(*User)
  for i := 0; i < 10; i++ {
    friend := orm.Create(User{ID: int64(i + 2)}).(*User)
    user.Friends = append(user.Friends, friend)
  }
}

```

...in the database, `friends` will be stored like this:

```json5
{
  // ~ snip ~ //
  friends: [
    2,
    3,
    4,
    5,
    6,
    7,
    8,
    9,
    10,
    11
  ]
}
```

after retrieving a `User` from the database, you can load their `Friends` and their info by using the `Populate`function
on the returned `Query` pointer, like in the following example:

```go
package tutorial

import (
  "fmt"
  "go.mongodb.org/mongo-driver/bson"
  "rockfic.com/orm"
)

func main() {
  /* ~ snip ~ */
  query, err := userModel.FindOne(bson.M{"_id": 1})
  if err == nil {
    result := orm.Create(User{}).(*User)
    query.Populate("Friends").Exec(result)
    fmt.Printf("%+v", result)
  }
}

```

### Models vs Documents: what's the difference?

a **`Model`** is a static type that contains information about a given Document-like type. a **`Document`**, on the
other hand, is a full-fledged instances with its own set of methods.
if you come from an object-oriented programming background, you can envision the relationship between a `Model` and
`Document` something like this (using Java as an example):

```java
public class Document {
    public void Pull(field String, elements ...Document) {
        // ...
    }
    public void Append(field String, elements ...Document) {
        // ...
    }
    public void Save() {
        //... 
    }
    public void Delete() {
        //...
    }

    // model methods //
    public static Document FindOne(HashMap<String, Object> query, MongoOptions options) {
        // ...
    }
    public static ArrayList<Document> FindAll(HashMap<String, Object> query, MongoOptions options) {
        // ...
    } 
}
```

## Struct Tags

the following tags are recognized by the ORM:

### `ref`

the syntax of the `ref` tag is:

```
`ref:"struct_name"`
```

where `struct_name` is the name of the struct you're referencing, as shown
in [Referencing other documents](#referencing-other-documents).

### `gridfs`

you can load files stored in [gridfs](https://www.mongodb.com/docs/manual/core/gridfs/) directly into your structs using
this tag, which has the following syntax:

```
`gridfs:"bucket_name,file_fmt"
```

where:

- `bucket_name` is the name of the gridfs bucket
- `file_fmt` is a valid [go template string](https://pkg.go.dev/text/template) that resolves to the unique file name.
  all exported methods and fields in the surrounding struct can be referenced in this template.

currently, the supported field types for the `gridfs` tag are:

- `string`
- `[]byte`

### `idx`/`index`

indexes can be defined using this tag on the field you want to create the index for. the syntax is as follows:

`idx:{field || field1,field2,...},keyword1,keyword2,...`

supported keywords are `unique` and `sparse`.
`background` is technically allowed, but it's deprecated, and so will essentially be a no-op on mongodb 4.2+.

## acknowledgements

- [goonode/mogo](https://github.com/goonode/mogo), the project which largely inspired this one

# Further reading

see the [godocs]("https://git.tablet.sh/tablet/diamond-orm/src/branch/main/godoc.html") for more details :)