add the ability to rotate logs

This feature allows users to delete logs periodically while choosing the retention time.
It will help servers located in Europe to comply with GDPR and to keep the logging channels clean.

Author: Equinox4

module_logs.lua

@@ -2,50 +2,109 @@
 -- This file is part of the "Not a Bot" application
 -- For conditions of distribution and use, see copyright notice in LICENSE
 
-local client = Client
-local discordia = Discordia
-local bot = Bot
-local enums = discordia.enums
+local Bot = Bot
+local Discordia = Discordia
+local Clock = Discordia.Clock
+local Date = Discordia.Date
+
 
 Module.Name = "logs"
 
+local messagesToDelete = {}
+
 function Module:GetConfigTable()
 	return {
 		{
 			Name = "ChannelManagementLogChannel",
 			Description = "Where channel created/updated/deleted should be logged",
-			Type = bot.ConfigType.Channel,
+			Type = Bot.ConfigType.Channel,
 			Optional = true
 		},
 		{
 			Name = "DeletedMessageChannel",
 			Description = "Where deleted messages should be logged",
-			Type = bot.ConfigType.Channel,
+			Type = Bot.ConfigType.Channel,
 			Optional = true
 		},
+		{
+			Name = "EnableLogRotation",
+			Description = "Enable log rotation",
+			Type = Bot.ConfigType.Boolean,
+			Default = false
+		},
+		{
+			Name = "LogRetentionPeriod",
+			Description = "The retention period of logs",
+			Type = Bot.ConfigType.Duration,
+			Default = 2 * 365 * 24 * 60 * 60 -- 2 years
+		},
 		{
 			Name = "IgnoredDeletedMessageChannels",
 			Description = "Messages deleted in those channels will not be logged",
-			Type = bot.ConfigType.Channel,
+			Type = Bot.ConfigType.Channel,
 			Array = true,
 			Default = {}
 		},
 		{
 			Name = "NicknameChangedLogChannel",
 			Description = "Where nickname changes should be logged",
-			Type = bot.ConfigType.Channel,
+			Type = Bot.ConfigType.Channel,
 			Optional = true
 		},
 		{
 			Global = true,
 			Name = "PersistentMessageCacheSize",
 			Description = "How many of the last messages of every text channel should stay in bot memory?",
-			Type = bot.ConfigType.Integer,
+			Type = Bot.ConfigType.Integer,
 			Default = 50
 		},
 	}
 end
 
+
+function Module:OnLoaded()
+	self.RotationClock = Clock()
+	self.RotationClock:on("day", function ()
+		self:ForEachGuild(function (guildId, config, data, persistentData)
+			local guild = Client:getGuild(guildId)
+			if (guild) then
+				local config = self:GetConfig(guild)
+				if not config.EnableLogRotation then
+					return
+				end
+
+				Module:RotateLogs(guild,
+					config.LogRetentionPeriod,
+					{
+						config.ChannelManagementLogChannel,
+						config.DeletedMessageChannel,
+						config.NicknameChangedLogChannel,
+					}
+				)
+			end
+		end)
+	end)
+
+	self.DeletionClock = Clock()
+	self.DeletionClock:on("sec", function ()
+		if next(messagesToDelete) then
+			table.remove(messagesToDelete):delete()
+		end
+	end)
+
+	return true
+end
+
+function Module:OnUnload()
+	self.RotationClock:stop()
+	self.DeletionClock:stop()
+end
+
+function Module:OnReady()
+	self.RotationClock:start()
+	self.DeletionClock:start()
+end
+
 function Module:OnEnable(guild)
 	local data = self:GetData(guild)
 
@@ -96,7 +155,7 @@ function Module:OnChannelDelete(channel)
 		embed = {
 			title = "Channel deleted",
 			description = channel.name,
-			timestamp = discordia.Date():toISO('T', 'Z')
+			timestamp = Date():toISO('T', 'Z')
 		}
 	})
 end
@@ -123,7 +182,7 @@ function Module:OnChannelCreate(channel)
 		embed = {
 			title = "Channel created",
 			description = "<#" .. channel.id .. ">",
-			timestamp = discordia.Date():toISO('T', 'Z')
+			timestamp = Date():toISO('T', 'Z')
 		}
 	})
 end
@@ -154,7 +213,7 @@ function Module:OnMemberUpdate(member)
 			embed = {
 				title = "Nickname changed",
 				description = string.format("%s - `%s` → `%s`", member.mentionString, data.nicknames[member.id], member.name),
-				timestamp = discordia.Date():toISO('T', 'Z')
+				timestamp = Date():toISO('T', 'Z')
 			}
 		})
 	end
@@ -164,7 +223,7 @@ function Module:OnMemberUpdate(member)
 			embed = {
 				title = "Username changed",
 				description = string.format("%s - `%s` → `%s`", member.mentionString, data.usernames[member.id], member.user.username),
-				timestamp = discordia.Date():toISO('T', 'Z')
+				timestamp = Date():toISO('T', 'Z')
 			}
 		})
 	end
@@ -199,7 +258,7 @@ function Module:OnMessageDelete(message)
 	embed.footer = {
 		text = string.format("Author ID: %s | Message ID: %s", message.author.id, message.id)
 	}
-	embed.timestamp = discordia.Date():toISO('T', 'Z')
+	embed.timestamp = Date():toISO('T', 'Z')
 
 	logChannel:send({
 		embed = embed
@@ -231,7 +290,7 @@ function Module:OnMessageDeleteUncached(channel, messageId)
 			footer = {
 				text = string.format("Message ID: %s", messageId)
 			},
-			timestamp = discordia.Date():toISO('T', 'Z')
+			timestamp = Date():toISO('T', 'Z')
 		}
 	})
 end
@@ -257,3 +316,47 @@ function Module:OnMessageCreate(message)
 		table.remove(cachedMessages, 1)
 	end
 end
+
+local function isMessageTooOld(message, logRetentionPeriod)
+	local messageTimestamp = Date.fromSnowflake(message.id):toSeconds()
+	return os.difftime(os.time(), messageTimestamp) > logRetentionPeriod
+end
+
+local function scheduleOldMessagesToDeletion(firstMessage, channel, logRetentionPeriod)
+	local buf = {}
+
+	repeat
+		-- Sort by id to keep the temporal order
+		local messages = channel:getMessagesAfter(firstMessage.id, 100):toArray("id")
+		table.insert(messages, 1, firstMessage)
+
+		for _, msg in ipairs(messages) do
+			if msg.author.id == Client.user.id
+			and (msg.embed and msg.embed.description and msg.embed.description:match("Deleted message"))
+			and isMessageTooOld(msg, logRetentionPeriod) then
+				table.insert(buf, msg)
+			end
+		end
+
+		firstMessage = messages[#messages]
+	until next(buf) or messages == nil
+
+	messagesToDelete = buf
+end
+
+function Module:RotateLogs(guild, logRetentionPeriod, logChannels)
+	local done = {}
+	for _, logChannelId in pairs(logChannels) do
+		if not done[logChannelId] then
+			local logChannel = guild:getChannel(logChannelId)
+			local firstMessage = logChannel:getFirstMessage()
+
+			if firstMessage then
+				scheduleOldMessagesToDeletion(firstMessage, logChannel, logRetentionPeriod)
+			end
+
+			done[logChannelId] = true
+		end
+	end
+end
+