degesch: add a "fancy-prompt" plugin

So that the client looks at least a tiny bit decent if needed.

plugins/degesch/fancy-prompt.lua

@@ -0,0 +1,97 @@
+--
+-- fancy-prompt.lua: the fancy multiline prompt you probably want
+--
+-- Copyright (c) 2016, Přemysl Janouch <p.janouch@gmail.com>
+--
+-- Permission to use, copy, modify, and/or distribute this software for any
+-- purpose with or without fee is hereby granted, provided that the above
+-- copyright notice and this permission notice appear in all copies.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+-- SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+-- OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+-- CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+--
+-- Beware that it is a hack and only goes about 90% of the way, which is why
+-- this functionality is only available as a plugin in the first place
+-- (well, and also for customizability).
+--
+-- The biggest problem is that the way we work with Readline is incompatible
+-- with multiline prompts, and normal newlines just don't work.  This is being
+-- circumvented by using an overflowing single-line prompt with a specially
+-- crafted character in the rightmost column that prevents the bar's background
+-- from spilling all over the last line.
+--
+-- There is also a problem with C-r search rendering not clearing out the
+-- background but to really fix that mode, we'd have to fully reimplement it
+-- since its alternative prompt very often gets overriden by accident anyway.
+
+local prompt = degesch.hook_prompt (function (hook)
+	local current = degesch.current_buffer
+	local chan = current.channel
+	local s = current.server
+
+	local current_n = 0
+	local active = ""
+	for i, buffer in ipairs (degesch.buffers) do
+		if buffer == current then
+			current_n = i
+		elseif buffer.new_messages_count ~= buffer.new_unimportant_count then
+			if active ~= "" then active = active .. "," end
+			if buffer.highlighted then active = active .. "!" end
+			active = active .. i
+		end
+	end
+	if active ~= "" then active = "(" .. active .. ")" end
+	local x = current_n .. ":" .. current.name
+	if chan then
+		local param = ""
+		for mode, param in pairs (chan.param_modes) do
+			param = param .. " +" .. mode .. " " .. param
+		end
+		local modes = chan.no_param_modes .. param:sub (2)
+		if modes ~= "" then x = x .. "(+" .. modes .. ")" end
+		if chan.users_len ~= 0 then x = x .. "{" .. chan.users_len .. "}" end
+	end
+	if current.hide_unimportant then x = x .. "<H>" end
+
+	local lines, cols = degesch.get_screen_size ()
+	x = x .. " " .. active .. string.rep (" ", cols)
+
+	-- Cut off extra characters and apply formatting, including the hack.
+	-- Note that this doesn't count with full-width or zero-width characters.
+	local overflow = utf8.offset (x, cols - 1)
+	if overflow then x = x:sub (1, overflow) end
+	x = "\x01\x1b[0;4;1;38;5;16m\x1b[48;5;255m\x02" ..
+		x ..  "\x01\x1b[0;4;1;7;38;5;255m\x02 \x01\x1b[0;1m\x02"
+
+	local user_prefix = function (chan, user)
+		for i, chan_user in ipairs (chan.users) do
+			if chan_user.user == user then return chan_user.prefixes end
+		end
+		return ""
+	end
+	if s then
+		x = x .. "["
+		local state = s.state
+		if state == "disconnected" or state == "connecting" then
+			x = x .. "(" .. state .. ")"
+		elseif state ~= "registered" then
+			x = x .. "(unregistered)"
+		else
+			local user, modes = s.user, s.user_mode
+			if chan then x = x .. user_prefix (chan, user) end
+			x = x .. user.nickname
+			if modes ~= "" then x = x .. "(" .. modes .. ")" end
+		end
+		x = x .. "] "
+	else
+		-- There needs to be at least one character so that the cursor
+		-- doesn't get damaged by our hack in that last column
+		x = x .. "> "
+	end
+	return x
+end)