api/telegram/bot: Go package for Telegram API Bot

1 files changed, 71 insertions, 0 deletions

diff --git a/api/telegram/bot/command.go b/api/telegram/bot/command.go
new file mode 100644
index 00000000..6d80343a
--- /dev/null
+++ b/api/telegram/bot/command.go
@@ -0,0 +1,71 @@
+// Copyright 2020, Shulhan <m.shulhan@gmail.com>. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package bot
+
+import (
+	"fmt"
+)
+
+//
+// Command represents a bot command.
+//
+type Command struct {
+	// Text of the command, 1-32 characters. Can contain only lowercase
+	// English letters, digits and underscores.
+	Command string `json:"command"`
+
+	// Description of the command, 3-256 characters.
+	Description string `json:"description"`
+
+	// Function that will be called when Bot receive the command.
+	// Handler can read command and its arguments through Message.Command
+	// and Message.CommandArgs.
+	Handler UpdateHandler `json:"-"`
+}
+
+//
+// validate will return an error if command is not valid.
+//
+func (cmd *Command) validate() error {
+	if len(cmd.Command) == 0 || len(cmd.Command) > 32 {
+		return errCommandLength(cmd.Command)
+	}
+	for x := 0; x < len(cmd.Command); x++ {
+		b := cmd.Command[x]
+		if b >= 'a' && b <= 'z' {
+			continue
+		}
+		if b >= '0' && b <= '9' {
+			continue
+		}
+		if b == '_' {
+			continue
+		}
+		return errCommandValue(cmd.Command)
+	}
+	if len(cmd.Description) < 3 || len(cmd.Description) > 256 {
+		return errDescLength(cmd.Command)
+	}
+	if cmd.Handler == nil {
+		return errHandlerNil(cmd.Command)
+	}
+	return nil
+}
+
+func errCommandLength(cmd string) error {
+	return fmt.Errorf("%q: the Command length must be between 1-32 characters", cmd)
+}
+
+func errCommandValue(cmd string) error {
+	return fmt.Errorf("%q: command can contain only lowercase English letter, digits, and underscores", cmd)
+}
+
+func errDescLength(cmd string) error {
+	return fmt.Errorf("%q: the Description length must be between 3-256 characters", cmd)
+}
+
+func errHandlerNil(cmd string) error {
+	return fmt.Errorf("%q: the Command's Handler is not set", cmd)
+}