1 files changed, 259 insertions, 0 deletions
diff --git a/lua/buffer_browser.lua b/lua/buffer_browser.lua
new file mode 100644
index 0000000..0683f4b
--- /dev/null
+++ b/lua/buffer_browser.lua
@@ -0,0 +1,259 @@
+--[[
+BUFFER BROWSER
+Author: Marc Coquand
+
+The comments below the code can be used to test the functions. Run them in `lua %` or with a code runner, like sniprun.
+]]
+local api = vim.api
+
+--[[ STATE MANAGEMENT
+We make use of a Zipper to keep track of the state of the buffers
+(https://stackoverflow.com/questions/380438/what-is-the-zipper-data-structure-and-should-i-be-using-it)
+]]
+local function matchesFilter(filters, name)
+	if filters == nil then
+		return false
+	end
+
+	for _, filter in ipairs(filters) do
+		if name == filter then
+			return true
+		end
+	end
+	return false
+end
+
+
+local function StateAppend(bufNr, stateFiletype, state, filters)
+	if (state.current == bufNr) then
+		return state
+	end
+
+	-- if filters matches the filetype of the buffer we change from, don't add it to history
+	if (stateFiletype ~= nil and matchesFilter(filters, stateFiletype)) then
+		state.current = bufNr
+		return state
+	else
+		state.future = {}
+		table.insert(state.previous, 1, state.current)
+		state.current = bufNr
+
+		return state
+	end
+end
+
+local function StateGoBack(state)
+	-- Go back in the state by setting current to the first element of previous, and appending the current to the future
+	-- Check if past is empty, if so return state as is
+	if #state.previous == 0 then
+		return state
+	end
+
+	table.insert(state.future, 1, state.current)
+	state.current = table.remove(state.previous, 1)
+	return state
+end
+-- local state = { current = 1, previous = { 2, 3 }, future = { 4, 5 } }
+-- print(StateGoBack(StateGoBack(StateGoBack(state)))['current'])
+-- > 3
+
+local function StateGoForward(state)
+	-- Go forward in the state by setting current to the first element of future, and appending the current to the previous
+
+	-- Check if future is empty, if so return state as is
+	if #state.future == 0 then
+		return state
+	end
+
+	table.insert(state.previous, 1, state.current)
+	state.current = table.remove(state.future, 1)
+
+	return state
+end
+-- local state = { current = 1, previous = { 2, 3 }, future = { 4, 5 } }
+-- print(StateGoForward(StateGoForward(StateGoForward(state)))['current'])
+
+local function StateDelete(state, bufNr)
+	-- Delete bufNr from state.previous
+	for i, v in ipairs(state.previous) do
+		if v == bufNr then
+			table.remove(state.previous, i)
+		end
+	end
+
+	-- Delete bufNr from state.future
+	for i, v in ipairs(state.future) do
+		if v == bufNr then
+			table.remove(state.future, i)
+		end
+	end
+
+	-- If bufNr is current, set current to the first element of previous
+	if state.current == bufNr and #state.previous > 0 then
+		state.current = table.remove(state.previous, 1)
+		return state
+	end
+
+	-- If bufNr is current and we have a future
+	if state.current == bufNr and #state.future > 0 then
+		state.current = table.remove(state.future, 1)
+		return state
+	end
+
+	-- If bufNr is current, set current to the first element of future
+	if state.current == bufNr then
+		state.current = nil
+		return state
+	end
+	return state
+end
+-- local state = { current = 1, previous = { 2, 3 }, future = { 4, 5 } }
+-- print(StateDelete(state, 1)['current'])
+-- -- > 2
+
+local function stateIsEmpty(state)
+	return (state.current == nil and state.previous == nil and state.future == nil)
+end
+
+
+-- [[ EFFECTS ]]
+local function setState(state)
+	vim.w.buffer_browser_previous = state.previous
+	vim.w.buffer_browser_current = state.current
+	vim.w.buffer_browser_future = state.future
+end
+
+local function getState()
+	local current = vim.w.buffer_browser_current
+	local previous = vim.w.buffer_browser_previous
+	local future = vim.w.buffer_browser_future
+	return {
+		current = current,
+		previous = previous,
+		future = future,
+	}
+end
+
+local function initState(bufNr)
+	vim.w.buffer_browser_current = bufNr
+	vim.w.buffer_browser_previous = {}
+	vim.w.buffer_browser_future = {}
+end
+
+local function getBufNr()
+	local winnr = api.nvim_tabpage_get_win(0)
+	return api.nvim_win_get_buf(winnr)
+end
+
+local function getFiletype(bufnr)
+	if (bufnr == nil) then
+		return ''
+	end
+	return vim.bo[bufnr].filetype
+end
+
+--[[ AUTO COMMANDS ]]
+function BufferBrowserBufferEnter(args)
+	local bufNr = args.buf
+	local filters = vim.g.buffer_browser_filters
+
+	local state = getState()
+	if stateIsEmpty(state) then
+		initState(bufNr)
+	else
+		if (state.current ~= bufNr) then
+			local stateFiletype = getFiletype(state.current)
+			StateAppend(bufNr, stateFiletype, state, filters)
+			setState(state)
+		end
+	end
+end
+
+function BufferBrowserBufferWipeOut(args)
+	local buf = args.buf
+	local state = getState()
+	if not stateIsEmpty(state) then
+		StateDelete(state, buf)
+		setState(state)
+	end
+end
+
+local BufferBrowserGroup = api.nvim_create_augroup('BufferBrowser', { clear = true })
+
+api.nvim_create_autocmd({ 'WinEnter', 'BufEnter' },
+	{
+		group = BufferBrowserGroup,
+		pattern = '*',
+		callback = function(args)
+			BufferBrowserBufferEnter(args)
+		end
+	}
+)
+
+-- BufWipeout is called before deletion
+api.nvim_create_autocmd('BufWipeout',
+	{
+		group = BufferBrowserGroup,
+		pattern = '*',
+		callback = function(args)
+			BufferBrowserBufferWipeOut(args)
+		end
+	}
+)
+
+
+--[[ COMMANDS ]]
+local function next()
+	local bufnr = getBufNr()
+	local state = getState()
+
+	if stateIsEmpty(state) then
+		initState(bufnr)
+	else
+		StateGoForward(state)
+		setState(state)
+	end
+	api.nvim_command('buffer ' .. state.current)
+end
+
+local function prev()
+	local bufnr = getBufNr()
+	local state = getState()
+
+	if stateIsEmpty(state) then
+		initState(bufnr)
+	else
+		StateGoBack(state)
+		setState(state)
+	end
+	api.nvim_command('buffer ' .. state.current)
+end
+
+--[[ DEBUG ]]
+local function printBrowserHistory()
+	local state = getState()
+	print('Browser State Previous: ' .. vim.inspect(state.previous))
+	print('Browser State Current: ' .. vim.inspect(state.current))
+	print('Browser State Future: ' .. vim.inspect(state.future))
+end
+
+
+--[[ SETUP ]]
+local function setup(opts)
+	if (opts == nil) then
+		local default = {
+			'', 'netrw', 'gitcommit', 'TelescopePrompt'
+		}
+		vim.g.buffer_browser_filters = default
+	else
+		-- Filter is based on filetype
+		vim.g.buffer_browser_filters = opts.filetype_filters
+	end
+end
+
+return {
+	next = next,
+	prev = prev,
+	printBrowserHistory = printBrowserHistory,
+	setup = setup
+}