Prevent dice overflow

rand.Int() would panic when the max value is <= 0, which happens when
big.NewInt() was fed with a too large number. Avoid this by validating
the big.NewInt() return beforehand. Add error handling to all callers to
both gracefully return to IRC and to log an error message.
Rename the shadowed "max" variable whilst at it to avoid confusion.

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

config.example.yaml

@@ -1,4 +1,5 @@
 watbot:
+  database: wat.db  # wat.db (in the working directory) is the default
   server:
     host: irc.casa  # mandatory, no default
     port: 6697

main.go

@@ -20,6 +20,7 @@ type Config struct {
 }
 
 type watConfig struct {
+	Database	string		`default:"wat.db" yaml:"database"`
 	Nick		string		`yaml:"nick"`
 	Pass		string		`yaml:"pass"`
 	User		string		`yaml:"user"`
@@ -99,6 +100,7 @@ func main() {
 		Name: config.Name,
 	}
 	watConfig := wat.WatConfig{
+		DatabasePath:      config.Database,
 		AutoJoinChannels:  config.Channels.Join,
 		PermittedChannels: config.Channels.Permitted,
 		IgnoredHosts:      config.Ignores.Hosts,

wat/bot.go

@@ -20,6 +20,7 @@ type WatBot struct {
 }
 
 type WatConfig struct {
+	DatabasePath      string
 	BotHosts          []string
 	BotGames          BotGameConfig
 	AdminHosts        []string
@@ -30,7 +31,7 @@ type WatConfig struct {
 
 func NewWatBot(config *irc.ClientConfig, watConfig *WatConfig, serverConn *tls.Conn) *WatBot {
 	wat := WatBot{conn: serverConn, Nick: config.Nick, c: watConfig}
-	wat.Db = NewWatDb()
+	wat.Db = NewWatDb(watConfig.DatabasePath)
 	wat.game = NewWatGame(&wat, wat.Db)
 	wat.integration = NewWatIntegration(&wat, wat.Db, &WatIntegrationConfig{BotHosts: watConfig.BotHosts, BotGames: watConfig.BotGames})
 	config.Handler = irc.HandlerFunc(wat.HandleIrcMsg)

wat/db.go

@@ -52,10 +52,10 @@ type WatDb struct {
 	db *gorm.DB
 }
 
-func NewWatDb() *WatDb {
+func NewWatDb(dbpath string) *WatDb {
 	w := WatDb{}
         var err error
-	w.db, err = gorm.Open(sqlite.Open("wat.db"), &gorm.Config{})
+	w.db, err = gorm.Open(sqlite.Open(dbpath), &gorm.Config{})
 	if err != nil {
 		panic(err)
 	}