Basic CRUD handlers and services.

.env

@@ -0,0 +1,2 @@
+DATABASE_URI=mongodb://localhost:27017
+DATABASE_NAME=mydb

db.go

@@ -0,0 +1,39 @@
+package grf
+
+import (
+	"context"
+	"log"
+	"os"
+	"time"
+
+	"github.com/joho/godotenv"
+	"go.mongodb.org/mongo-driver/mongo"
+	"go.mongodb.org/mongo-driver/mongo/options"
+)
+
+func SetupDatabase() (*mongo.Database, func(), error) {
+	connectionString, dbname := GetDBDetails()
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	client, err := mongo.Connect(ctx, options.Client().ApplyURI(connectionString))
+
+	disconnect := func() {
+		cancel()
+		if err := client.Disconnect(ctx); err != nil {
+			panic(err)
+		}
+	}
+	db := client.Database(dbname)
+
+	return db, disconnect, err
+}
+
+func GetDBDetails() (uri, dbname string) {
+	err := godotenv.Load()
+	if err != nil {
+		log.Fatal("Error loading .env file")
+	}
+
+	uri = os.Getenv("DATABASE_URI")
+	dbname = os.Getenv("DATABASE_NAME")
+	return
+}

example/.env

@@ -0,0 +1,2 @@
+DATABASE_URI=mongodb://localhost:27017
+DATABASE_NAME=mydb

example/example.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"context"
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"time"
+
+	grf "github.com/Jyothis-P/go-rest-framework"
+	"github.com/gorilla/mux"
+)
+
+// 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"`
+}
+
+func main() {
+
+	// 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.
+	r := mux.NewRouter().StrictSlash(true)
+
+	// Register routes for the model.
+	grf.RegisterCRUDRoutes[Todo]("/todo", r, &appContext)
+
+	// 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)
+}

go.mod

@@ -1,3 +1,22 @@
 module github.com/Jyothis-P/go-rest-framework
 
 go 1.22.3
+
+require (
+	github.com/gorilla/mux v1.8.1
+	github.com/joho/godotenv v1.5.1
+	go.mongodb.org/mongo-driver v1.15.0
+)
+
+require (
+	github.com/golang/snappy v0.0.1 // indirect
+	github.com/klauspost/compress v1.13.6 // indirect
+	github.com/montanaflynn/stats v0.0.0-20171201202039-1bf9dbcd8cbe // indirect
+	github.com/xdg-go/pbkdf2 v1.0.0 // indirect
+	github.com/xdg-go/scram v1.1.2 // indirect
+	github.com/xdg-go/stringprep v1.0.4 // indirect
+	github.com/youmark/pkcs8 v0.0.0-20181117223130-1be2e3e5546d // indirect
+	golang.org/x/crypto v0.17.0 // indirect
+	golang.org/x/sync v0.1.0 // indirect
+	golang.org/x/text v0.14.0 // indirect
+)

go.sum

@@ -0,0 +1,56 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/golang/snappy v0.0.1 h1:Qgr9rKW7uDUkrbSmQeiDsGa8SjGyCOGtuasMWwvp2P4=
+github.com/golang/snappy v0.0.1/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
+github.com/google/go-cmp v0.5.2 h1:X2ev0eStA3AbceY54o37/0PQ/UWqKEiiO2dKL5OPaFM=
+github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/gorilla/mux v1.8.1 h1:TuBL49tXwgrFYWhqrNgrUNEY92u81SPhu7sTdzQEiWY=
+github.com/gorilla/mux v1.8.1/go.mod h1:AKf9I4AEqPTmMytcMc0KkNouC66V3BtZ4qD5fmWSiMQ=
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+github.com/xdg-go/pbkdf2 v1.0.0 h1:Su7DPu48wXMwC3bs7MCNG+z4FhcyEuz5dlvchbq0B0c=
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+github.com/xdg-go/scram v1.1.2 h1:FHX5I5B4i4hKRVRBCFRxq1iQRej7WO3hhBuJf+UUySY=
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+github.com/youmark/pkcs8 v0.0.0-20181117223130-1be2e3e5546d h1:splanxYIlg+5LfHAM6xpdFEAYOk8iySO56hMFq6uLyA=
+github.com/youmark/pkcs8 v0.0.0-20181117223130-1be2e3e5546d/go.mod h1:rHwXgn7JulP+udvsHwJoVG1YGAP6VLg4y9I5dyZdqmA=
+github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
+go.mongodb.org/mongo-driver v1.15.0 h1:rJCKC8eEliewXjZGf0ddURtl7tTVy1TK3bfl0gkUSLc=
+go.mongodb.org/mongo-driver v1.15.0/go.mod h1:Vzb0Mk/pa7e6cWw85R4F/endUC3u0U9jGcNU603k65c=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
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grf.go

@@ -0,0 +1,24 @@
+package grf
+
+import (
+	"net/http"
+
+	"go.mongodb.org/mongo-driver/mongo"
+)
+
+// Application Context struct. This is made available to your handler functions as a parameter.
+// Handy for keeping values like database connections.
+type Ctx struct {
+	DB *mongo.Database
+}
+
+// An adapter for handler functions with an added app context passed in.
+// Implements http.Handler.
+type H struct {
+	*Ctx
+	Fn func(*Ctx, http.ResponseWriter, *http.Request)
+}
+
+func (appHandler H) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	appHandler.Fn(appHandler.Ctx, w, r)
+}

handlers.go

@@ -0,0 +1,150 @@
+package grf
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"strings"
+
+	"github.com/gorilla/mux"
+)
+
+// Function to register the basic CRUD routes given a model.
+// User can register individual routes from the generic handlers.
+// Or they can use this function to generate teh default REST endpoints.
+// Problem comes when it is mongodb which does not support CASCADE delete out of the box and you need a better logic for deleting.
+// Maybe add an optional callback function?
+// Putting a pin on it. [This can be good for atomics]
+// [For objects with more complex dependencies, use the handlers you need and create the rest yourself]
+func RegisterCRUDRoutes[T any](pathPrefix string, r *mux.Router, ctx *Ctx) *mux.Router {
+	subRouter := r.PathPrefix(pathPrefix).Subrouter()
+	subRouter.Handle("/", H{Ctx: ctx, Fn: GetAllHandler[T]}).Methods("GET")
+	subRouter.Handle("/{id}", H{Ctx: ctx, Fn: GetHandler[T]}).Methods("GET")
+	subRouter.Handle("/", H{Ctx: ctx, Fn: CreateHandler[T]}).Methods("POST")
+	subRouter.Handle("/{id}", H{Ctx: ctx, Fn: DeleteHandler[T]}).Methods("DELETE")
+	return subRouter
+}
+
+func GetHandler[K any](ctx *Ctx, w http.ResponseWriter, r *http.Request) {
+	vars := mux.Vars(r)
+	var object K
+	err := ReadOne(ctx.DB, &object, vars["id"])
+	if err != nil {
+		log.Print("Error retrieving object.")
+		log.Print(err.Error())
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	b, err := json.Marshal(object)
+	if err != nil {
+		log.Print("Error marshalling.")
+		log.Print(err.Error())
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	w.WriteHeader(http.StatusOK)
+	fmt.Fprintln(w, string(b))
+}
+
+func GetAllHandler[K any](ctx *Ctx, w http.ResponseWriter, r *http.Request) {
+	var objects []K
+	err := Read(ctx.DB, &objects)
+	log.Println(objects)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		fmt.Fprintln(w, "Error getting all objects.")
+		return
+	}
+
+	log.Println(objects)
+	b, err := json.Marshal(objects)
+	if err != nil {
+		log.Print("Error marshalling.")
+		log.Print(err.Error())
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	w.WriteHeader(http.StatusOK)
+	fmt.Fprintln(w, string(b))
+}
+
+func CreateHandler[T any](ctx *Ctx, w http.ResponseWriter, r *http.Request) {
+	decoder := json.NewDecoder(r.Body)
+	decoder.DisallowUnknownFields()
+
+	var object T
+	err := decoder.Decode(&object)
+
+	// Let the gatekeeping begin.
+	if err != nil {
+		log.Println("Error decoding the object from the request.")
+		msg, statusCode := validateJsonError(err)
+		http.Error(w, msg, statusCode)
+		log.Println(msg)
+		return
+	}
+
+	log.Println("Decoded object: ", object)
+
+	// Attempting to save the object to the db.
+	res, err := Create(ctx.DB, object)
+
+	if err != nil {
+		log.Print("Error saving object to db.")
+		log.Print(err.Error())
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	w.WriteHeader(http.StatusOK)
+	fmt.Fprintf(w, "Object created!, id: %s", *res)
+}
+
+func DeleteHandler[T any](ctx *Ctx, w http.ResponseWriter, r *http.Request) {
+	vars := mux.Vars(r)
+
+	// Adding additional checks in this generic function would be difficult.
+	// If you need more validation and dependency checking, please use a seperate handler for the same.
+	err := Delete[T](ctx.DB, vars["id"])
+	if err != nil {
+		http.Error(w, "Error deleting object.", http.StatusInternalServerError)
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	fmt.Fprintln(w, "Object deleted.")
+}
+
+func validateJsonError(err error) (string, int) {
+	msg := ""
+	var statusCode int
+	var unmarshallError *json.UnmarshalTypeError
+	var syntaxError *json.SyntaxError
+	switch {
+	case errors.As(err, &syntaxError):
+		msg = fmt.Sprintf("Request body contains badly-formed JSON (at position %d)", syntaxError.Offset)
+		statusCode = http.StatusBadRequest
+	case errors.As(err, &unmarshallError):
+		msg = fmt.Sprintf("Request body contains an invalid value for the %q field (at position %d)", unmarshallError.Field, unmarshallError.Offset)
+		statusCode = http.StatusBadRequest
+	case errors.Is(err, io.ErrUnexpectedEOF):
+		msg = "Request body contains badly-formed JSON"
+		statusCode = http.StatusBadRequest
+	case strings.HasPrefix(err.Error(), "json: unknown field "):
+		fieldName := strings.TrimPrefix(err.Error(), "json: unknown field ")
+		msg = fmt.Sprintf("Request body contains unknown field %s", fieldName)
+		statusCode = http.StatusBadRequest
+	case errors.Is(err, io.EOF):
+		msg = "Request body must not be empty"
+		statusCode = http.StatusBadRequest
+	case err.Error() == "http: request body too large":
+		msg = "Request body must not be larger than 1MB"
+		statusCode = http.StatusRequestEntityTooLarge
+	default:
+		msg = http.StatusText(http.StatusInternalServerError)
+		statusCode = http.StatusInternalServerError
+	}
+	return msg, statusCode
+}