cspj-application/server/internal/db/db.go

package db

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"net/http"

	"github.com/jackc/pgx/v5/pgxpool"
)

// db connection info
// !MIGHT CHANGE
const (
	host     = "localhost"
	port     = 5432
	user     = "asdfuser"
	password = "asdfpassword"
	dbname   = "asdfdb"
)

var DbPool *pgxpool.Pool
var allowedUsernames map[string]bool

// initialize connection to db
func ConnectToDb() (*pgxpool.Pool, error) {
	// this server is intended to be ran on the same system as the db
	dbUrl := fmt.Sprintf("postgresql://%s:%s@%s:%d/%s", user, password, host, port, dbname)
	config, err := pgxpool.ParseConfig((dbUrl))
	if err != nil {
		return nil, fmt.Errorf("unable to parse data URL: %w", err)
	}

	pool, err := pgxpool.NewWithConfig(context.Background(), config)
	if err != nil {
		return nil, fmt.Errorf("unable to create connection pool: %w", err)
	}

	log.Println("Connected to DB :)")
	return pool, nil
}

// setup demo db
func SetupDemoDb(w http.ResponseWriter, r *http.Request) {
	// create table and insert demo data
	createTableSQL := `
	CREATE TABLE IF NOT EXISTS users (
	id SERIAL PRIMARY KEY,
	username VARCHAR(50) UNIQUE NOT NULL,
	email VARCHAR(100) NOT NULL,
	password VARCHAR(100) NOT NULL
);`

	// also avoid duplicate entries
	insertDataSQL := `
	INSERT INTO users (username, email, password) VALUES
	('alice', 'alice@example.com', 'asdfalicepassword'),
	('bob', 'bob@example.com', 'asdfbobpassword'),
	('charlie', 'charlie@example.com', 'asdfcharliepassword')
	ON CONFLICT (username) DO NOTHING;`

	// execute create table
	_, err := DbPool.Exec(context.Background(), createTableSQL)
	if err != nil {
		http.Error(w, "Failed to create table", http.StatusInternalServerError)
		log.Printf("Error creating table: %v", err)
		return
	}

	// execute insert demo data
	_, err = DbPool.Exec(context.Background(), insertDataSQL)
	if err != nil {
		http.Error(w, "Failed to insert demo data", http.StatusInternalServerError)
		log.Printf("Error inserting demo data: %v", err)
		return
	}

	// response back to client
	w.WriteHeader(http.StatusOK)
	w.Write([]byte("Database setup complete with demo data"))
	log.Println("Demo database setup completed successfully")
}

// nuke the db
func NukeDb(w http.ResponseWriter, r *http.Request) {
	// drop user table
	dropTableSQL := `
	DROP TABLE IF EXISTS users CASCADE;
	`

	// execute the command
	_, err := DbPool.Exec(context.Background(), dropTableSQL)
	if err != nil {
		http.Error(w, "Failed to drop table", http.StatusInternalServerError)
		log.Printf("Error dropping table: %v", err)
		return
	}

	w.WriteHeader(http.StatusOK)
	w.Write([]byte("Bye bye"))
	log.Println("Database nuked")
}

// fetch existing usernames from db
func FetchUsernames() (map[string]bool, error) {
	usernames := make(map[string]bool)

	rows, err := DbPool.Query(context.Background(), "SELECT username FROM users")
	if err != nil {
		return nil, fmt.Errorf("error querying users: %w", err)
	}
	defer rows.Close()

	for rows.Next() {
		var username string
		if err := rows.Scan(&username); err != nil {
			return nil, fmt.Errorf("error scanning username: %w", err)
		}
		usernames[username] = true
	}

	log.Println("Fetched usernames:", usernames)
	return usernames, nil
}

// fetch all users for demo
func FetchAllUsers(w http.ResponseWriter, r *http.Request) {
	// construct sql query to select all users
	query := "SELECT * FROM users"

	// execute the query
	rows, err := DbPool.Query(context.Background(), query)
	if err != nil {
		http.Error(w, "Failed to retrieve users", http.StatusInternalServerError)
		log.Printf("Error executing query: %v", err)
		return
	}
	defer rows.Close()

	// define a slice to hold user data
	users := []map[string]interface{}{}

	// get column names
	columnNames := rows.FieldDescriptions()

	// iterate over the rows and build the result set
	for rows.Next() {
		// create a slice to hold the values for each row
		values := make([]interface{}, len(columnNames))
		valuePointers := make([]interface{}, len(columnNames))
		for i := range values {
			valuePointers[i] = &values[i]
		}

		// scan the row into slice of interfaces
		if err := rows.Scan(valuePointers...); err != nil {
			http.Error(w, "Failed to scan user data", http.StatusInternalServerError)
			log.Printf("Error scanning row: %v", err)
			return
		}

		// create a map for the row data
		user := make(map[string]interface{})
		for i, col := range columnNames {
			user[string(col.Name)] = values[i]
		}

		// append the user map to the users slice
		users = append(users, user)
	}

	// check for any errors encountered during the iteration
	if err = rows.Err(); err != nil {
		http.Error(w, "Internal server error", http.StatusInternalServerError)
		log.Printf("Error encountered during iteration of rows: %v", err)
		return
	}

	log.Printf("All Users Data: %v", users)

	// Encode the users slice as JSON and write it to the response
	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(users); err != nil {
		http.Error(w, "Failed to encode response as JSON", http.StatusInternalServerError)
		log.Printf("Error encoding response: %v", err)
		return
	}

	log.Println("Response successfully written to client")
}