backend: Don't fail if an hint is already opened

backend/hint.go

@@ -42,7 +42,7 @@ func treatOpeningHint(pathname string, team *fic.Team) {
 		log.Printf("%s [!!!] The team asks to open an hint whereas it doesn't have access to the exercice\n", id)
 	} else if !team.CanSeeHint(hint) {
 		log.Printf("%s [!!!] The team asks to open an hint whereas it doesn't have access to it due to hint dependencies\n", id)
-	} else if err = team.OpenHint(hint); err != nil {
+	} else if err = team.OpenHint(hint); err != nil && !fic.DBIsDuplicateKeyError(err) { // Skip DUPLICATE KEY errors
 		log.Printf("%s [ERR] Unable to open hint: %s\n", id, err)
 	} else {
 		// Write event

libfic/db.go

@@ -2,11 +2,13 @@ package fic
 
 import (
 	"database/sql"
-	_ "github.com/go-sql-driver/mysql"
+	"errors"
 	"log"
 	"os"
 	"strings"
 	"time"
+
+	"github.com/go-sql-driver/mysql"
 )
 
 // db stores the connection to the database
@@ -47,6 +49,11 @@ func DSNGenerator() string {
 	return db_user + ":" + db_password + "@" + db_host + "/" + db_db
 }
 
+func DBIsDuplicateKeyError(err error) bool {
+	var mysqlErr *mysql.MySQLError
+	return errors.As(err, &mysqlErr) && mysqlErr.Number == 1062
+}
+
 // DBInit establishes the connection to the database
 func DBInit(dsn string) (err error) {
 	if db, err = sql.Open("mysql", dsn+"?parseTime=true&foreign_key_checks=1"); err != nil {