spoiler-bot.lua

local http = require("coro-http")
local discordia = require("discordia")
local client = discordia.Client()

local function starts_with( str, start )
	return str:sub(1, #start) == start
end

local prefix = "!"

client:on("ready", function()
	client:info("Logged in as ".. client.user.username)
end)

local commands = setmetatable({}, { __index = function( t, k )
	if k == "squeak" then
		return { call = function( message, arg )
			message:reply("🐁 squeak!")
		end }
	end
	return {
		brief = "no such command",
		call = function( message, arg )
			-- ignore unrecognized command
		end
	}
end})

local function fetch( attachments )
	local res = {}
	for idx, v in ipairs(attachments) do
		local _, body = http.request("GET", v.url)
		res[idx] = {"SPOILER_" .. v.filename, body}
	end
	return res
end

commands.spoiler = {
	brief = "replace this message with all attachments marked as spoilers",
	example = "[MESSAGE_WITH_ATTACHMENTS] " .. prefix
		.. "spoiler REST_OF_YOUR_MESSAGE",
	call = function( message, arg )
		if not message.attachments then return end
		local data = fetch(message.attachments)
		message:reply({
			mention = message.author,
			content = "posted: " .. arg,
			-- allowed_mentions = {
			-- 	parse = {}
			-- },
			files = data
		})
		message:delete()
	end
}

commands.remove = {
	brief = "remove a spoiler post created from your own message",
	example = prefix .. "remove BOT_MESSAGE_ID",
	call = function( message, arg )
		local found = message.channel:getMessage(arg)
		if not found then
			message:reply(
				"could not find message " .. arg .. " in this channel")
			return
		end
		if found.author ~= client.user then
			message:reply("target message is not a bot message")
			return
		end
		local firstMention = found.mentionedUsers.first
		if message.author ~= firstMention then
			message:reply("you are not the originator of the target message")
			return
		end
		found:delete()
		message:delete()
	end
}

commands.info = {
	brief = "display bot information",
	call = function( message, arg )
		local answer = { embed = {
			author = {
				name = "Spoiler Bot",
				icon_url = client.user.avatarURL,
			},
			description =
				"A helper bot for marking images as spoiler on mobile.\n"
				.. "Source code available [here](https://gist.github.com"
				.. "/Siapran/42a14232bbf56f2f956d9978b4c3507e)."
		}}
		message:reply(answer)
	end
}

commands.help = {
	brief = "display a list of available commands, "
		.. "or help for a particular command",
	example = prefix .. "help spoiler",
	call = function( message, arg )
		if arg == "" then
			local fields = {}
			for key,value in pairs(commands) do
				table.insert(fields, {
					name = key,
					value = value.brief or ""
				})
			end
			local answer = { embed = {
				title = "available commands",
				fields = fields
			}}
			message:reply(answer)
		else
			local command = commands[arg]
			local fields = {}
			if command.brief then
				table.insert(fields, {
					name = "brief",
					value = command.brief
				})
			end
			if command.example then
				table.insert(fields, {
					name = "example",
					value = "`" .. command.example .. "`"
				})
			end
			local answer = { embed = {
				title = arg,
				fields = fields
			}}
			message:reply(answer)
		end
	end
}

client:on("messageCreate", function( message )
	if message.author.bot then return end
	if not starts_with(message.content, prefix) then return end
	local cmd, arg =
		message.content
		:sub(prefix:len() + 1)
		:match("(%S+)%s*(.*)")
	if cmd then
		client:info(tostring(message.author) .. ": "
			.. tostring(message.content))
		commands[cmd].call(message, arg)
	end
end)

if not args[2] then
	client:error("Please provide a bot token via commandline arguments.")
	return
end

client:run("Bot " .. args[2])