go: Implement invite code creation

It is now possible to create invite code using '!invite <validation code>'

GoBot/.gitignore

@@ -1 +1,2 @@
 token.txt
+terraocean.db

GoBot/db.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"database/sql"
+	"errors"
+
+	//Import this driver to be used by the SQL package.
+	_ "github.com/mattn/go-sqlite3"
+)
+
+var db *sql.DB
+
+var errNotFound = errors.New("db: the requested entry was not found")
+var errAlreadyExists = errors.New("db: attempting to write to an entry that already exists")
+var errInviteUsed = errors.New("db: the requested invite has already been used")
+
+func init() {
+	var err error
+	db, err = sql.Open("sqlite3", "terraocean.db")
+	if err != nil {
+		panic(err)
+	}
+	_, err = db.Exec("CREATE TABLE IF NOT EXISTS invite (code TEXT, owner TEXT, used BOOLEAN)")
+	if err != nil {
+		panic(err)
+	}
+}
+
+func getInviteOwner(inviteCode string) (string, error) {
+	rows, err := db.Query("SELECT owner, used FROM invite WHERE code=?", inviteCode)
+	if err != nil {
+		return "", err
+	}
+	if rows.Next() {
+		var owner string
+		var used bool
+		err := rows.Scan(&owner, &used)
+		if err != nil {
+			return "", err
+		}
+		if used {
+			return "", errInviteUsed
+		}
+		return owner, nil
+	}
+	return "", errNotFound
+}
+
+func setInviteOwner(inviteCode, owner string) error {
+	_, err := getInviteOwner(inviteCode)
+	if err == nil {
+		return errAlreadyExists
+	}
+	if err != errNotFound {
+		return err
+	}
+	_, err = db.Exec("INSERT INTO invite(code, owner, used) VALUES(?,?,?)", inviteCode, owner, false)
+	return err
+}
+
+func useInvite(inviteCode string) error {
+	owner, err := getInviteOwner(inviteCode)
+	if err != nil {
+		return err
+	}
+	_, err = db.Exec("REPLACE INTO invite(code, owner, used) VALUES(?,?,?)", inviteCode, owner, true)
+	return err
+}

GoBot/go.mod

@@ -2,4 +2,7 @@ module TerraOceanBot
 
 go 1.13
 
-require github.com/bwmarrin/discordgo v0.19.0
+require (
+	github.com/bwmarrin/discordgo v0.19.0
+	github.com/mattn/go-sqlite3 v1.11.0
+)

GoBot/go.sum

@@ -2,5 +2,7 @@ github.com/bwmarrin/discordgo v0.19.0 h1:kMED/DB0NR1QhRcalb85w0Cu3Ep2OrGAqZH1R5a
 github.com/bwmarrin/discordgo v0.19.0/go.mod h1:O9S4p+ofTFwB02em7jkpkV8M3R0/PUVOwN61zSZ0r4Q=
 github.com/gorilla/websocket v1.4.0 h1:WDFjx/TMzVgy9VdMMQi2K2Emtwi2QcUQsztZ/zLaH/Q=
 github.com/gorilla/websocket v1.4.0/go.mod h1:E7qHFY5m1UJ88s3WnNqhKjPHQ0heANvMoAMk2YaljkQ=
+github.com/mattn/go-sqlite3 v1.11.0 h1:LDdKkqtYlom37fkvqs8rMPFKAMe8+SgjbwZ6ex1/A/Q=
+github.com/mattn/go-sqlite3 v1.11.0/go.mod h1:FPy6KqzDD04eiIsT53CuJW3U88zkxoIYsOqkbpncsNc=
 golang.org/x/crypto v0.0.0-20181030102418-4d3f4d9ffa16 h1:y6ce7gCWtnH+m3dCjzQ1PCuwl28DDIc3VNnvY29DlIA=
 golang.org/x/crypto v0.0.0-20181030102418-4d3f4d9ffa16/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=

GoBot/invite.go

@@ -0,0 +1,52 @@
+package main
+
+import "github.com/bwmarrin/discordgo"
+
+func createInvite(s *discordgo.Session, m *discordgo.MessageCreate, command []string) {
+	if !enforceDM(s, m) {
+		return
+	}
+	if !membersOnly(s, m) {
+		return
+	}
+	if len(command) < 2 {
+		s.ChannelMessageSend(m.ChannelID, "指令的使用方法是`!invite <你所要设置的验证码>`.\nUsage: `!invite <validation code>`")
+		return
+	}
+	if len(command) > 2 {
+		s.ChannelMessageSend(m.ChannelID, "所提供的验证码不得有任何空格。\nThe provided validation code cannot contain any spaces.")
+		return
+	}
+
+	err := setInviteOwner(command[1], m.Author.ID)
+	switch err {
+	case errAlreadyExists:
+		owner, _ := getInviteOwner(command[1])
+		if owner == m.Author.ID {
+			s.ChannelMessageSend(
+				m.ChannelID,
+				"这个验证码归你所有，它仍然未被使用。请把它告诉你要邀请的人。\nThis validation code belongs to you. Please give it to the person you want to invite.",
+			)
+			return
+		}
+		s.ChannelMessageSend(
+			m.ChannelID,
+			"这个验证码已被其他会员注册。请使用别的验证码。\nThis validation code is already registered. Please try another one.",
+		)
+	case errInviteUsed:
+		s.ChannelMessageSend(
+			m.ChannelID,
+			"这个验证码已被使用。请使用别的验证码。\nThis validation code has already been used. Please try another one.",
+		)
+	case nil:
+		s.ChannelMessageSend(
+			m.ChannelID,
+			"这个验证码现在属于你了。请好好保管并把它交给你要邀请的人。\nThis validation code now belongs to you! Pass it on to the person you want to invite.",
+		)
+	default:
+		s.ChannelMessageSend(
+			m.ChannelID,
+			"不明错误已发生，请把这个错误信息发在群里。\nAn unknown error has occurred. Please pass this error message on.\n"+err.Error(),
+		)
+	}
+}

GoBot/main.go

@@ -41,5 +41,7 @@ func messageCreate(s *discordgo.Session, m *discordgo.MessageCreate) {
 		sendAs(s, m, command)
 	case "!editas":
 		editAs(s, m, command)
+	case "!invite":
+		createInvite(s, m, command)
 	}
 }

GoBot/messageUtil.go

@@ -0,0 +1,40 @@
+package main
+
+import "github.com/bwmarrin/discordgo"
+
+const guildID = "626424729234046987"
+const memberRoleID = "626434632614805526"
+
+func enforceDM(s *discordgo.Session, m *discordgo.MessageCreate) bool {
+	if m.GuildID != "" {
+		//This command can only be used in DM to protect the invite creator.
+		s.ChannelMessageDelete(m.ChannelID, m.ID)
+		s.ChannelMessageSend(
+			m.ChannelID,
+			m.Author.Mention()+"，这个指令只能在私信中使用。\n"+m.Author.Mention()+", this command can only be used in DM.",
+		)
+		return false
+	}
+	return true
+}
+
+func membersOnly(s *discordgo.Session, m *discordgo.MessageCreate) bool {
+	member, err := s.GuildMember(guildID, m.Author.ID)
+	if err != nil {
+		s.ChannelMessageSend(
+			m.ChannelID,
+			m.Author.Mention()+"，请在成为会员后才使用这个指令。\n"+m.Author.Mention()+", please use this command after you become a member.",
+		)
+		return false
+	}
+	for _, v := range member.Roles {
+		if v == memberRoleID {
+			return true
+		}
+	}
+	s.ChannelMessageSend(
+		m.ChannelID,
+		m.Author.Mention()+"，请在成为会员后才使用这个指令。\n"+m.Author.Mention()+", please use this command after you become a member.",
+	)
+	return false
+}