Added leave-message command

commands/leave-message.js

+const errors = require('../errors.json');
+const config = require('../config.json');
+
+exports.run = async (client, message, args, connection) => {
+    if(!message.member.hasPermission('ADMINISTRATOR')) {
+            message.channel.send(errors.insufficient_permission_for_user).catch(e => {
+            return;
+        });
+    };
+    if (!args.join(' ')) {
+        message.channel.send(`${errors.insufficient_args}`).catch(e => {
+            return;
+        });
+        return;
+    };
+    const prefixdb = await new Promise((resolve, reject) => {
+        connection.query(`SELECT prefix FROM prefixes WHERE guild ='${message.guild.id}'`, function (err, result) {
+            if (err)
+                reject(err);
+            resolve(result);
+        });
+    });
+    var prefix;
+    if(prefixdb.length < 1) {
+        prefix = config.prefix;
+        } else {
+        prefix = prefixdb[0].prefix;
+    };
+
+    connection.query(`SELECT message FROM leave_message WHERE guild ='${message.guild.id}'`, function (err, result) {
+        if (err) {
+            throw err;
+        };
+        if (result.length < 1) {
+            if (args[0] == "reset") {
+                message.channel.send(errors.not_existing_on_db).catch(e => {
+                    return;
+                });
+                return;
+            };
+            connection.query(`INSERT INTO leave_message (guild, message) VALUES ('${message.guild.id}', '${args.join(' ')}')`, function (err, result) {
+                if (err) {
+                    throw err;
+                };
+            });
+            message.channel.send('Successful!').catch(e => {
+                return;
+            });
+        } else {
+            if (args[0] == "reset") {
+                connection.query(`DELETE FROM leave_message WHERE guild ='${message.guild.id}'`, function (err, result) {
+                    if (err) {
+                        throw err;
+                    };
+                });
+                message.channel.send('Resetting...').catch(e => {
+                    return;
+                });    
+            } else {
+                message.channel.send(`Leave message is already existing. To reset type \`${prefix}leave-message reset\`.`).catch(e => {
+                    return;
+                });
+            };
+        };
+    });
+};
+
+module.exports.help = {
+    name: 'leave-message',
+    aliases: ['leave_message', 'leavemessage']
+};