# README

go-rest-framework

An opinionated Go web framework with MongoDB support for rapid REST API development. Simply define your models and get started with your basic CRUD routes.

Features

Provides a new Handler adapter which can passes an Application Context to your handler functions. This way, you can access. your DB from any package without a lot of global variables.

Based on this article: Custom Handlers and Avoiding Globals in Go Web Applications
Provides ready to use generic services for CRUD from your mongodb.
Provides ready to use generic handlers for CRUD from your mongodb.

Getting started

Environment setup.

GRF expects that you have mongodb set up with Replicasets in your environment. This is to avail the transaction capabilities of the database and ensure ACID transactions. If you're looking for a quick and easy way to set it up, I'd recommend checking out run-rs.

Once the db is setup, please add the following variables to your .env file at the project root.
```
DATABASE_URI=<Your mongodb connection string>
DATABASE_NAME=<Your database name>
```

Create an App Context with a DB connection.

We need a *mongo.Database object that we can pass in the Application context to the handlers. You can use the SetupDatabase() function to ease this up.

import grf "github.com/Jyothis-P/go-rest-framework"

// Setup database.
db, cancel, err := grf.SetupDatabase()
defer cancel()
if err != nil {
	log.Println("Error setting up the database.", err)
	return
}

// Create App context.
appContext := grf.Ctx{
	DB: db,
}

Create a router. [Currently modelled for gorilla/mux will be generalising to add support for anything that supports http/Handler]
```
// Create a router.
r := mux.NewRouter().StrictSlash(true)
```
Create your model.

Make sure to add json and bson struct tags to help configure marshalling. Showing a model to store TODO objects. bson struct tags are used for attribute names in the db. json struct tags are used to determine the json parameters during http requests.
```
// Create a model
// Make sure to give json and bson structs as necessary.
type Todo struct {
	Title     string `json:"title" bson:"title"`
	Completed bool   `json:"completed" bson:"completed"`
}
```
Register the CRUD routes.

RegisterCRUDRoutes is a generic that takes the model as the type parameter. It creates a subrouter with the given path. This router can be optionally returned if further routes are need on it.
```
// Register routes for the model.
grf.RegisterCRUDRoutes[Todo]("/todo", r, &appContext)
```
That’s it! This function will take care of the services and handlers required for all the basic CRUD REST endpoints for your model.

The data will be saved in a collection with the plural form of your model’s name. The collection name will be todos for this example.

Setup and start the webserver.

// Set up server.
const PORT string = "8001"
srv := &http.Server{
	Addr:         "0.0.0.0:" + PORT,
	WriteTimeout: time.Second * 15,
	ReadTimeout:  time.Second * 15,
	IdleTimeout:  time.Second * 60,
	Handler:      r,
}

// Start the server.
go func() {
	log.Println("Starting web server on " + PORT)
	if err := srv.ListenAndServe(); err != nil {
		log.Println("Error with the web server.")
		log.Println(err)
	}
}()

// Graceful shutdown of the server in case of os interrupts.
c := make(chan os.Signal, 1)
signal.Notify(c, os.Interrupt)
<-c

ctx, cancel := context.WithTimeout(context.Background(), time.Second*15)
defer cancel()

srv.Shutdown(ctx)
log.Println("Shutting down.")
os.Exit(0)

Writing your custom handle functions with App Context

Create the handler as usual with the addition of *grf.Ctx in the parameters.

// Customer Handler function using the generic Delete service.
func customDeleteHandler(appCtx *grf.Ctx, w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)

	// You can use any of the generic service functions or your own custom service.
	err := grf.Delete[Todo](appCtx.DB, vars["id"])
	if err != nil {
		http.Error(w, "Error deleting TODO.", http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusOK)
	fmt.Fprintln(w, "Group deleted.")
}

Make sure you are wrapping this in the adapter when registering the route.

// Earlier code to generate the crud routes that returns a subrouted.
todoRouter := grf.RegisterCRUDRoutes[Todo]("/todo", r, &appContext)

// Register the new customer handler as a new route in the subrouter.
todoRouter.Handle("/{id}/customDeleteTodo", grf.H{Ctx: &appContext, Fn: customDeleteHandler}).Methods("DELETE")

Custom services

Even when writing your own service, you can pass the db context as a parameter instead of using global variables.


// Custom Handler with a custom service making use of the db connection passed from context.
func markComplete(appCtx *grf.Ctx, w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	err := finisherService(appCtx.DB, vars["id"])
	if err != nil {
		http.Error(w, "Error completing TODO.", http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusOK)
	fmt.Fprintln(w, "Marked complete!")
}

func finisherService(db *mongo.Database, id string) error {
	collection := db.Collection("todos")

	// Converting the group id from the hex string to the ObjectID format that mongo use
	objectID, err := primitive.ObjectIDFromHex(id)
	if err != nil {
		log.Println("Error converting id to ObjectId:", err)
		return err
	}

	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()
	filter := bson.D{{Key: "_id", Value: objectID}}
	update := bson.M{"$set": bson.M{"completed": true}}
	res, err := collection.UpdateOne(ctx, filter, update)
	if err != nil || res.ModifiedCount < 1 {
		log.Println("Error Marking complete:", err)
		log.Println("Matched Count: ", res.MatchedCount)
		log.Println("Modified Count: ", res.ModifiedCount)
		return err
	}
	return nil
}