Better logging, new preview.lua plugin.

When an exception is caught, info will be printed to the config.log_chat or the console.
/preview will give an "unlinked" preview for the link.
youtube.lua now uses config.google_api_key.
youtube.lua now uses unlinked previews.
lastfm.lua gives more informative error messages.
New utility: handle_exception().

plugins/lastfm.lua

@@ -69,7 +69,7 @@ local action = function(msg)
 
 	local jdat = JSON.decode(jstr)
 	if jdat.error then
-		sendReply(msg, config.errors.results)
+		sendReply(msg, 'Please specify your last.fm username or set it with /fmset.')
 		return
 	end
 

plugins/preview.lua

@@ -0,0 +1,47 @@
+local command = 'preview <link>'
+local doc = [[```
+/preview <link>
+Returns a full-message, "unlinked" preview.
+```]]
+
+local triggers = {
+	'^/preview'
+}
+
+local action = function(msg)
+
+	local input = msg.text:input()
+
+	if not input then
+		sendMessage(msg.chat.id, doc, true, nil, true)
+		return
+	end
+
+	input = get_word(input, 1)
+	if not input:match('^https?://.+') then
+		input = 'http://' .. input
+	end
+
+	local res = HTTP.request(input)
+	if not res then
+		sendReply(msg, 'Please provide a valid link.')
+		return
+	end
+
+	if res:len() == 0 then
+		sendReply(msg, 'Sorry, the link you provided is not letting us make a preview.')
+		return
+	end
+
+	-- Invisible zero-width, non-joiner.
+	local output = '[​](' .. input .. ')'
+	sendMessage(msg.chat.id, output, false, nil, true)
+
+end
+
+return {
+	action = action,
+	triggers = triggers,
+	doc = doc,
+	command = command
+}

plugins/wikipedia.lua

@@ -42,7 +42,7 @@ local action = function(msg)
 		sendReply(msg, config.errors.results)
 		return
 	end
-
+--
 	local url = jdat.responseData.results[1].url
 	local title = jdat.responseData.results[1].titleNoFormatting:gsub(' %- Wikipedia, the free encyclopedia', '')
 
@@ -79,6 +79,13 @@ local action = function(msg)
 	end
 
 	sendMessage(msg.chat.id, output, true, nil, true)
+--
+--[[ Comment the previous block and uncomment this one for full-message,
+ -- "unlinked" link previews.
+	-- Invisible zero-width, non-joiner.
+	local output = '[​](' .. jdat.responseData.results[1].url .. ')'
+	sendMessage(msg.chat.id, output, false, nil, true)
+]]--
 
 end
 

plugins/youtube.lua

@@ -1,5 +1,11 @@
  -- Thanks to @TiagoDanin for writing the original plugin.
 
+if not config.google_api_key then
+	print('Missing config value: google_api_key.')
+	print('youtube.lua will not be enabled.')
+	return
+end
+
 local command = 'youtube <query>'
 local doc = [[```
 /youtube <query>
@@ -25,7 +31,7 @@ local action = function(msg)
 		end
 	end
 
-	local url = 'https://www.googleapis.com/youtube/v3/search?key=AIzaSyAfe7SI8kwQqaoouvAmevBfKumaLf-3HzI&type=video&part=snippet&maxResults=1&q=' .. URL.escape(input)
+	local url = 'https://www.googleapis.com/youtube/v3/search?key=' .. config.google_api_key .. '&type=video&part=snippet&maxResults=1&q=' .. URL.escape(input)
 
 	local jstr, res = HTTPS.request(url)
 	if res ~= 200 then
@@ -35,9 +41,9 @@ local action = function(msg)
 
 	local jdat = JSON.decode(jstr)
 
-	local message = 'https://www.youtube.com/watch?v=' .. jdat.items[1].id.videoId
+	local output = '[​](https://www.youtube.com/watch?v=' .. jdat.items[1].id.videoId .. ')'
 
-	sendMessage(msg.chat.id, message, false, msg.message_id)
+	sendMessage(msg.chat.id, output, false, nil, true)
 
 end