Bot: Added a Prefixer API which breaks the old Prefix string API

_example/advanced_bot/main.go

@@ -18,7 +18,7 @@ func main() {
 	commands := &Bot{}
 
 	wait, err := bot.Start(token, commands, func(ctx *bot.Context) error {
-		ctx.Prefix = "!"
+		ctx.HasPrefix = bot.NewPrefix("!", "~")
 
 		// Subcommand demo, but this can be in another package.
 		ctx.MustRegisterSubcommand(&Debug{})

_example/simple/main.go

@@ -29,8 +29,6 @@ func main() {
 		log.Fatalln("Failed to connect:", err)
 	}
 
-	defer s.Close()
-
 	u, err := s.Me()
 	if err != nil {
 		log.Fatalln("Failed to get myself:", err)
@@ -38,7 +36,7 @@ func main() {
 
 	log.Println("Started as", u.Username)
 
-	// Block until a fatal error or SIGINT.
+	// Block until a fatal error or SIGINT. Wait also calls Close().
 	if err := s.Wait(); err != nil {
 		log.Fatalln("Gateway fatal error:", err)
 	}

_example/undeleter/main.go

@@ -39,8 +39,6 @@ func main() {
 		log.Fatalln("Failed to connect:", err)
 	}
 
-	defer s.Close()
-
 	u, err := s.Me()
 	if err != nil {
 		log.Fatalln("Failed to get myself:", err)
@@ -48,7 +46,7 @@ func main() {
 
 	log.Println("Started as", u.Username)
 
-	// Block until a fatal error or SIGINT.
+	// Block until a fatal error or SIGINT. Wait also calls Close().
 	if err := s.Wait(); err != nil {
 		log.Fatalln("Gateway fatal error:", err)
 	}

bot/ctx.go

@@ -12,6 +12,23 @@ import (
 	"github.com/pkg/errors"
 )
 
+// Prefixer checks a message if it starts with the desired prefix. By default,
+// NewPrefix() is used.
+type Prefixer func(*gateway.MessageCreateEvent) (prefix string, ok bool)
+
+// NewPrefix creates a simple prefix checker using strings. As the default
+// prefix is "!", the function is called as NewPrefix("!").
+func NewPrefix(prefixes ...string) Prefixer {
+	return func(msg *gateway.MessageCreateEvent) (string, bool) {
+		for _, prefix := range prefixes {
+			if strings.HasPrefix(msg.Content, prefix) {
+				return prefix, true
+			}
+		}
+		return "", false
+	}
+}
+
 // TODO: add variadic arguments
 
 // Context is the bot state for commands and subcommands.
@@ -56,8 +73,9 @@ type Context struct {
 	// Descriptive help body
 	Description string
 
-	// The prefix for commands
+	// Called to check a message's prefix. The default prefix is "!". Refer to
-	Prefix string
+	// NewPrefix().
+	HasPrefix Prefixer
 
 	// FormatError formats any errors returned by anything, including the method
 	// commands or the reflect functions. This also includes invalid usage
@@ -152,7 +170,7 @@ func New(s *state.State, cmd interface{}) (*Context, error) {
 	ctx := &Context{
 		Subcommand: c,
 		State:      s,
-		Prefix:     "~",
+		HasPrefix:  NewPrefix("~"),
 		FormatError: func(err error) string {
 			// Escape all pings, including @everyone.
 			return strings.Replace(err.Error(), "@", "@\u200b", -1)
@@ -176,6 +194,8 @@ func (ctx *Context) Wait() error {
 	return ctx.Session.Wait()
 }
 
+// Subcommands returns the slice of subcommands. To add subcommands, use
+// RegisterSubcommand().
 func (ctx *Context) Subcommands() []*Subcommand {
 	// Getter is not useless, refer to the struct doc for reason.
 	return ctx.subcommands
@@ -348,7 +368,7 @@ func (ctx *Context) help(hideAdmin bool) string {
 			continue
 		}
 
-		help.WriteString(indent + ctx.Prefix + cmd.Command)
+		help.WriteString(indent + cmd.Command)
 
 		switch {
 		case len(cmd.Usage()) > 0:
@@ -364,7 +384,7 @@ func (ctx *Context) help(hideAdmin bool) string {
 	var subcommands = ctx.Subcommands()
 
 	for _, sub := range subcommands {
-		if help := sub.Help(ctx.Prefix, indent, hideAdmin); help != "" {
+		if help := sub.Help(indent, hideAdmin); help != "" {
 			subHelp.WriteString(help)
 		}
 	}

bot/ctx_call.go

@@ -114,13 +114,13 @@ func (ctx *Context) callCmd(ev interface{}) error {
 
 func (ctx *Context) callMessageCreate(mc *gateway.MessageCreateEvent) error {
 	// check if prefix
-	if !strings.HasPrefix(mc.Content, ctx.Prefix) {
+	pf, ok := ctx.HasPrefix(mc)
-		// not a command, ignore
+	if !ok {
 		return nil
 	}
 
 	// trim the prefix before splitting, this way multi-words prefices work
-	content := mc.Content[len(ctx.Prefix):]
+	content := mc.Content[len(pf):]
 
 	if content == "" {
 		return nil // just the prefix only
@@ -197,7 +197,6 @@ func (ctx *Context) callMessageCreate(mc *gateway.MessageCreateEvent) error {
 				return &ErrUnknownCommand{
 					Command: args[1],
 					Parent:  args[0],
-					Prefix:  ctx.Prefix,
 					ctx:     s.Commands,
 				}
 			}
@@ -213,7 +212,6 @@ func (ctx *Context) callMessageCreate(mc *gateway.MessageCreateEvent) error {
 
 		return &ErrUnknownCommand{
 			Command: args[0],
-			Prefix:  ctx.Prefix,
 			ctx:     ctx.Commands,
 		}
 	}
@@ -293,7 +291,6 @@ func (ctx *Context) callMessageCreate(mc *gateway.MessageCreateEvent) error {
 
 		return &ErrInvalidUsage{
 			Args:  args,
-			Prefix: ctx.Prefix,
 			Index: len(args) - 1,
 			Err:   err,
 			Ctx:   cmd,
@@ -307,7 +304,6 @@ func (ctx *Context) callMessageCreate(mc *gateway.MessageCreateEvent) error {
 		if err != nil {
 			return &ErrInvalidUsage{
 				Args:  args,
-				Prefix: ctx.Prefix,
 				Index: i,
 				Err:   err.Error(),
 				Ctx:   cmd,

bot/error.go

@@ -8,8 +8,6 @@ type ErrUnknownCommand struct {
 	Command string
 	Parent  string
 
-	Prefix string
-
 	// TODO: list available commands?
 	// Here, as a reminder
 	ctx []*CommandContext
@@ -20,7 +18,7 @@ func (err *ErrUnknownCommand) Error() string {
 }
 
 var UnknownCommandString = func(err *ErrUnknownCommand) string {
-	var header = "Unknown command: " + err.Prefix
+	var header = "Unknown command: "
 	if err.Parent != "" {
 		header += err.Parent + " " + err.Command
 	} else {
@@ -32,8 +30,6 @@ var UnknownCommandString = func(err *ErrUnknownCommand) string {
 
 type ErrInvalidUsage struct {
 	Args  []string
-	Prefix string
-
 	Index int
 	Err   string
 
@@ -55,16 +51,13 @@ var InvalidUsageString = func(err *ErrInvalidUsage) string {
 		return "Missing arguments. Refer to help."
 	}
 
-	body := "Invalid usage at " + err.Prefix
+	body := "Invalid usage at " +
-
 		// Write the first part
-	body += strings.Join(err.Args[:err.Index], " ")
+		strings.Join(err.Args[:err.Index], " ") +
-
 		// Write the wrong part
-	body += " __" + err.Args[err.Index] + "__ "
+		" __" + err.Args[err.Index] + "__ " +
-
 		// Write the last part
-	body += strings.Join(err.Args[err.Index+1:], " ")
+		strings.Join(err.Args[err.Index+1:], " ")
 
 	if err.Err != "" {
 		body += "\nError: " + err.Err

bot/subcommand.go

@@ -173,7 +173,7 @@ func (sub *Subcommand) ChangeCommandInfo(methodName, cmd, desc string) bool {
 	return false
 }
 
-func (sub *Subcommand) Help(prefix, indent string, hideAdmin bool) string {
+func (sub *Subcommand) Help(indent string, hideAdmin bool) string {
 	if sub.Flag.Is(AdminOnly) && hideAdmin {
 		return ""
 	}
@@ -205,8 +205,7 @@ func (sub *Subcommand) Help(prefix, indent string, hideAdmin bool) string {
 			continue
 		}
 
-		commands += indent + indent +
+		commands += indent + indent + sub.Command + " " + cmd.Command
-			prefix + sub.Command + " " + cmd.Command
 
 		switch {
 		case len(cmd.Usage()) > 0: