How to Build a Go Web App with Gin, MongoDB, and AI

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mkdir mflix
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cd mflix

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go mod init mflix

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go get github.com/gin-gonic/gin
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go get go.mongodb.org/mongo-driver/mongo

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package main
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import (
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    "github.com/gin-gonic/gin"
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)
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func main() {
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    r := gin.Default()
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    r.GET("/", func(c *gin.Context) {
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        c.JSON(200, gin.H{
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            "message": "Hello World",
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        })
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    })
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    r.Run()
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}

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package main
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import (
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    // Add required Go packages
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    "context"
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    "log"
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    "github.com/gin-gonic/gin"
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    // Add the MongoDB driver packages 
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    "go.mongodb.org/mongo-driver/mongo"
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    "go.mongodb.org/mongo-driver/mongo/options"
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)
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// Your MongoDB Atlas Connection String
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const uri = "YOUR-CONNECTION-STRING-HERE"
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// A global variable that will hold a reference to the MongoDB client
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var mongoClient *mongo.Client
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// The init function will run before our main function to establish a connection to MongoDB. If it cannot connect it will fail and the program will exit.
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func init() {
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    if err := connect_to_mongodb(); err != nil {
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        log.Fatal("Could not connect to MongoDB")
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    }
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}
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func main() {
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    r := gin.Default()
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    r.GET("/", func(c *gin.Context) {
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        c.JSON(200, gin.H{
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            "message": "Hello World",
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        })
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    })
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    r.Run()
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}
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// Our implementation logic for connecting to MongoDB
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func connect_to_mongodb() error {
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    serverAPI := options.ServerAPI(options.ServerAPIVersion1)
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    opts := options.Client().ApplyURI(uri).SetServerAPIOptions(serverAPI)
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    client, err := mongo.Connect(context.TODO(), opts)
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    if err != nil {
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        panic(err)
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    }
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    err = client.Ping(context.TODO(), nil)
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    mongoClient = client
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    return err
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}

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// GET /movies - Get all movies
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func getMovies(c *gin.Context) {
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    // Find movies
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    cursor, err := mongoClient.Database("sample_mflix").Collection("movies").Find(context.TODO(), bson.D{{}})
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    if err != nil {
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        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
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        return
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    }
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    // Map results
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    var movies []bson.M
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    if err = cursor.All(context.TODO(), &movies); err != nil {
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        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
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        return
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    }
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    // Return movies
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    c.JSON(http.StatusOK, movies)
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}

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// GET /movies/:id - Get movie by ID
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func getMovieByID(c *gin.Context) {
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    // Get movie ID from URL
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    id := c.Param("id")
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    // Find movie by ID
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    var movie bson.M
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    err := mongoClient.Database("sample_mflix").Collection("movies").FindOne(context.TODO(), bson.D{{"_id", id}}).Decode(&movie)
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    if err != nil {
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        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
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        return
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    }
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    // Return movie
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    c.JSON(http.StatusOK, movie)
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}

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// POST /movies/aggregations - Run aggregations on movies
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func aggregateMovies(c *gin.Context) {
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    // Get aggregation pipeline from request body
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    var pipeline interface{}
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    if err := c.ShouldBindJSON(&pipeline); err != nil {
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        c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
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        return
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    }
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    // Run aggregations
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    cursor, err := mongoClient.Database("sample_mflix").Collection("movies").Aggregate(context.TODO(), pipeline)
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    if err != nil {
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        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
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        return
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    }
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    // Map results
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    var result []bson.M
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    if err = cursor.All(context.TODO(), &result); err != nil {
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        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
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        return
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    }
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    // Return result
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    c.JSON(http.StatusOK, result)
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}

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func main() {
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	r := gin.Default()
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	r.GET("/", func(c *gin.Context) {
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		c.JSON(200, gin.H{
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			"message": "Hello World",
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		})
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	})
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	r.GET("/movies", getMovies)
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	r.GET("/movies/:id", getMovieByID)
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	r.POST("/movies/aggregations", aggregateMovies)
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	r.Run()
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}

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func getMovieByID(c *gin.Context) {
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	// Get movie ID from URL
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	idStr := c.Param("id")
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	// Convert id string to ObjectId
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	id, err := primitive.ObjectIDFromHex(idStr)
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	if err != nil {
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		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
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		return
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	}
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	// Find movie by ObjectId
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	var movie bson.M
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	err = mongoClient.Database("sample_mflix").Collection("movies").FindOne(context.TODO(), bson.D{{"_id", id}}).Decode(&movie)
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	if err != nil {
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		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
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		return
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	}
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	// Return movie
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	c.JSON(http.StatusOK, movie)
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}

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import (
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	"context"
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	"log"
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	"net/http"
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	"github.com/gin-gonic/gin"
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	"go.mongodb.org/mongo-driver/bson"
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	"go.mongodb.org/mongo-driver/bson/primitive"
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	"go.mongodb.org/mongo-driver/mongo"
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	"go.mongodb.org/mongo-driver/mongo/options"
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)

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[
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    {"$match": {"genres": "Comedy"}},
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    {"$group": {
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        "_id": "$year", 
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        "count": {"$sum": 1}
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    }},
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    {"$sort": {"count": -1}}
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]

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[
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    {
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        "_id": 2014,
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        "count": 287
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    },
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    {
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        "_id": 2013,
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        "count": 286
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    },
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    {
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        "_id": 2009,
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        "count": 268
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    },
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    {
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        "_id": 2011,
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        "count": 263
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    },
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    {
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        "_id": 2006,
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        "count": 260
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    },
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    ...
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]

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// Declare the entry point into our application
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package main
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// Add our dependencies from the standard library, Gin, and MongoDB
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import (
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    "context"
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    "fmt"
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    "log"
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    "net/http"
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    "github.com/gin-gonic/gin"
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    "go.mongodb.org/mongo-driver/bson"
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    "go.mongodb.org/mongo-driver/bson/primitive"
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    "go.mongodb.org/mongo-driver/mongo"
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    "go.mongodb.org/mongo-driver/mongo/options"
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)
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// Define your MongoDB connection string
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const uri = "{YOUR-CONNECTION-STRING-HERE}"
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// Create a global variable to hold our MongoDB connection
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var mongoClient *mongo.Client
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// This function runs before we call our main function and connects to our MongoDB database. If it cannot connect, the application stops.
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func init() {
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    if err := connect_to_mongodb(); err != nil {
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        log.Fatal("Could not connect to MongoDB")
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    }
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}
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// Our entry point into our application
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func main() {
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    // The simplest way to start a Gin application using the frameworks defaults
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    r := gin.Default()
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    // Our route definitions
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    r.GET("/", func(c *gin.Context) {
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        c.JSON(200, gin.H{
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            "message": "Hello World",
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        })
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    })
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    r.GET("/movies", getMovies)
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    r.GET("/movies/:id", getMovieByID)
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    r.POST("/movies/aggregations", aggregateMovies)
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    // The Run() method starts our Gin server
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    r.Run()
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}
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// Implemention of the /movies route that returns all of the movies from our movies collection.
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func getMovies(c *gin.Context) {
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    // Find movies
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    cursor, err := mongoClient.Database("sample_mflix").Collection("movies").Find(context.TODO(), bson.D{{}})
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    if err != nil {
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        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
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        return
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    }
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    // Map results
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    var movies []bson.M
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    if err = cursor.All(context.TODO(), &movies); err != nil {
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        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
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        return
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    }
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    // Return movies
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    c.JSON(http.StatusOK, movies)
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}
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// The implementation of our /movies/{id} endpoint that returns a single movie based on the provided ID
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func getMovieByID(c *gin.Context) {
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    // Get movie ID from URL
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    idStr := c.Param("id")
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    // Convert id string to ObjectId
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    id, err := primitive.ObjectIDFromHex(idStr)
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    if err != nil {
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        c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
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        return
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    }
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    // Find movie by ObjectId
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    var movie bson.M
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    err = mongoClient.Database("sample_mflix").Collection("movies").FindOne(context.TODO(), bson.D{{"_id", id}}).Decode(&movie)
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    if err != nil {
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        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
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        return
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    }
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    // Return movie
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    c.JSON(http.StatusOK, movie)
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}
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// The implementation of our /movies/aggregations endpoint that allows a user to pass in an aggregation to run our the movies collection.
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func aggregateMovies(c *gin.Context) {
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    // Get aggregation pipeline from request body
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    var pipeline interface{}
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    if err := c.ShouldBindJSON(&pipeline); err != nil {
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        c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
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        return
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    }
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    // Run aggregations
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    cursor, err := mongoClient.Database("sample_mflix").Collection("movies").Aggregate(context.TODO(), pipeline)
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    if err != nil {
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        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
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        return
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    }
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    // Map results
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    var result []bson.M
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    if err = cursor.All(context.TODO(), &result); err != nil {
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        c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
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        return
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    }
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    // Return result
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    c.JSON(http.StatusOK, result)
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}
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// Our implementation code to connect to MongoDB at startup
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func connect_to_mongodb() error {
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    serverAPI := options.ServerAPI(options.ServerAPIVersion1)
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    opts := options.Client().ApplyURI(uri).SetServerAPIOptions(serverAPI)
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    client, err := mongo.Connect(context.TODO(), opts)
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    if err != nil {
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        panic(err)
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    }
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    err = client.Ping(context.TODO(), nil)
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    mongoClient = client
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    return err
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}