add postgress user handling support

database.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"context"
+	"crypto/subtle"
+	"errors"
+
+	"github.com/jackc/pgx/v5"
+)
+
+var dbConnection *pgx.Conn
+
+func InitDatabase(ctx context.Context) {
+	conn, err := pgx.Connect(ctx, "postgres://master:secret@localhost:5432")
+	if err != nil {
+		panic(err)
+	}
+
+	_, err = conn.Exec(ctx, `
+		CREATE TABLE IF NOT EXISTS users (
+		    id SERIAL PRIMARY KEY,
+		    name VARCHAR(20) UNIQUE NOT NULL,
+		    pass_hash VARCHAR(255) NOT NULL,
+		    color VARCHAR(3) NOT NULL
+		)
+	`)
+	if err != nil {
+		panic(err)
+	}
+	dbConnection = conn
+}
+
+func AddNewUser(ctx context.Context, user User) (uint, error) {
+	if len(user.name) == 0 || len(user.name) > 20 {
+		return 0, errors.New("username bad length")
+	}
+	if user.isPasswordHashed {
+		if len(user.password) != 255 {
+			return 0, errors.New("password bad length")
+		}
+	} else {
+		// TODO
+	}
+	if len(user.color) != 1 && len(user.color) != 3 {
+		return 0, errors.New("color invalid")
+	}
+	var id uint
+	err := dbConnection.QueryRow(ctx, `
+        INSERT INTO users (name, pass_hash, color)
+        VALUES ($1, $2, $3)
+        RETURNING id
+    `, user.name, user.isPasswordHashed, user.color).Scan(&id)
+	return id, err
+}
+
+func CheckPassword(ctx context.Context, id string, hash string) bool {
+	var controlHash string
+	err := dbConnection.QueryRow(ctx, "SELECT pass_hash FROM users WHERE id = $1", id).Scan(&controlHash)
+	if err != nil {
+		return false
+	}
+	return subtle.ConstantTimeCompare([]byte(controlHash), []byte(hash)) == 1
+}
+
+func GetUserData(ctx context.Context, id string) (User, error) {
+	var user User
+	err := dbConnection.QueryRow(ctx, "SELECT id, name, pass_hash, color FROM users WHERE id = $1", id).
+		Scan(&user.id, &user.name, &user.password, &user.color)
+	if err != nil {
+		return User{}, err
+	}
+	user.isPasswordHashed = true
+	return user, nil
+}