typingspeed: added typingspeed plugin (#47)

This plugin displays your current typing speed in characters per minute
and words per minute in the status bar.
I tried to keep the logic very simple, so instead of using real accurate
values, it counts characters/words in the current minute and adds
the value of the previous minute multiplied by the percentage needed to
'complete' the current minute (so it basically always displays the value
for one minute, but the part of it that falls into the last minute uses
the average):
```
words_last * (1 - (t.sec) / 60) + words
```
This should give fairly good results without the need for complicated code
or falling back to 0 after every minute.

2 files changed, 94 insertions, 0 deletions

diff --git a/README.md b/README.md
index 61fe45c..c508037 100644
--- a/README.md
+++ b/README.md
@@ -144,6 +144,7 @@ to something other than a raw file it should be marked with an asterisk.*
 | [`titleize`](plugins/titleize.lua?raw=1)                                                                       | Titleizes selected string (`hello world` => `Hello World`)                                                                                                                                                                                                                                      |
 | [`todotreeview`](https://github.com/drmargarido/TodoTreeView)\*                                                | Todo tree viewer for annotations in code like `TODO`, `BUG`, `FIX`, `IMPROVEMENT`                                                                                                                                                                                                               |
 | [`togglesnakecamel`](plugins/togglesnakecamel.lua?raw=1)                                                       | Toggles symbols between `snake_case` and `camelCase`                                                                                                                                                                                                                                            |
+| [`typingspeed`](plugins/typingspeed.lua?raw=1)                                                                 | Displays your current typing speed in characters and words per minute in the status bar                                                                                                                                                                                                         |
 | [`unboundedscroll`](plugins/unboundedscroll.lua?raw=1)                                                         | Allows scrolling outside the bounds of a document                                                                                                                                                                                                                                               |
 | [`updatechecker`](https://github.com/vincens2005/lite-xl-updatechecker)\*                                      | Automatically checks for updates and notifies you                                                                                                                                                                                                                                               |
 | [`vibe`](https://github.com/eugenpt/lite-xl-vibe)\*                                                            | VI(vim?) bindings with a hint of DOOM Emacs, for lite-xl                                                                                                                                                                                                                                        |
diff --git a/plugins/typingspeed.lua b/plugins/typingspeed.lua
new file mode 100644
index 0000000..62e44ef
--- /dev/null
+++ b/plugins/typingspeed.lua
@@ -0,0 +1,93 @@
+-- mod-version:2
+
+local core = require "core"
+local style = require "core.style"
+local common = require "core.common"
+local config = require "core.config"
+local DocView = require "core.docview"
+
+if common["merge"] then
+	config.plugins.typingspeed = common.merge({
+		-- characters that should be counted as word boundary
+		word_boundaries = "[%p%s]",
+	}, config.plugins.keystats)
+else
+	config.plugins.typingspeed = {
+		-- characters that should be counted as word boundary
+		word_boundaries = "[%p%s]",
+	}
+end
+
+local chars = 0
+local chars_last = 0
+local words = 0
+local words_last = 0
+local time_last = 0
+local started_word = false
+local cpm = 0
+local wpm = 0
+
+core.add_thread(function()
+	while true do
+		local t = os.date("*t")
+		if t.sec <= time_last then
+			words_last = words
+			words = 0
+			chars_last = chars
+			chars = 0
+			time_last = t.sec
+		end
+		wpm = words_last * (1-(t.sec)/60) + words
+		cpm = chars_last * (1-(t.sec)/60) + chars
+		coroutine.yield(1)
+	end
+end)
+
+local on_text_input = DocView.on_text_input
+function DocView:on_text_input(text, idx)
+	chars = chars + 1
+	if string.find(text, config.plugins.typingspeed.word_boundaries) then
+		if started_word then
+			words = words + 1
+			started_word = false
+		end
+	else
+		started_word = true
+	end
+	on_text_input(self, text, idx)
+end
+
+if core.status_view["add_item"] then
+	core.status_view:add_item(
+		function()
+			return core.active_view and getmetatable(core.active_view) == DocView
+		end,
+		"keystats:stats",
+		core.status_view.Item.RIGHT,
+		function()
+			return {
+				style.text,
+				string.format("%.0f CPM / %.0f WPM", cpm, wpm)
+			}
+		end,
+		nil,
+		1,
+		"characters / words per minute"
+	).separator = core.status_view.separator2
+else
+	local get_items = core.status_view.get_items
+	function core.status_view:get_items()
+		local left, right = get_items(self)
+
+		local t = {
+			style.text, string.format("%.0f CPM / %.0f WPM", cpm, wpm),
+			style.dim, self.separator2
+		}
+
+		for i, item in ipairs(t) do
+			table.insert(right, i, item)
+		end
+
+		return left, right
+	end
+end