Add nvim stacc plugin (task stack with locations)

vim/plugin/stacc.lua

@@ -0,0 +1,51 @@
+-- A simple per-session task stack.
+-- Allows pushing locations with a note and returning to them later.
+
+local ns = vim.api.nvim_create_namespace("stacc")
+
+local locations = {}
+
+local stacc = {}
+
+--- Pushes a new location to the stack
+--- @param description string A message to display when returning to this location
+function stacc.push(description)
+	local bufnr = vim.fn.bufnr()
+	local line, column = unpack(vim.api.nvim_win_get_cursor(0))
+	line = line - 1 -- 0-based :help api-indexing
+	local id = vim.api.nvim_buf_set_extmark(bufnr, ns, line, column, {})
+	table.insert(locations, {bufnr, id, description, vim.fn.line(".")})
+end
+
+--- Pops a given number of items from the task stack
+--- Jumps to the last removed item and displays its description
+--- @param count number How many items to pop from the stack
+--- @return string description The description of the current task
+function stacc.pop(count)
+	if count > #locations then
+		error("stack only has "..#locations.." elements.")
+	end
+	local description
+	local final = vim.api.nvim_win_get_cursor(0)
+	for _=1, count do
+		local bufnr, id
+		bufnr, id, description = unpack(table.remove(locations))
+		final = vim.api.nvim_buf_get_extmark_by_id(bufnr, ns, id, {})
+		vim.api.nvim_buf_del_extmark(bufnr, ns, id)
+		final[1] = final[1] + 1 -- Make line 1-indexed
+		final.bufnr = bufnr
+	end
+	vim.api.nvim_set_current_buf(final.bufnr or 0)
+	final.bufnr = nil
+	vim.api.nvim_win_set_cursor(0, final)
+	return description
+end
+
+vim.api.nvim_create_user_command("StaccPush", function(params)
+	stacc.push(params.args)
+end, {nargs="?"})
+
+vim.api.nvim_create_user_command("StaccPop", function(params)
+	local message = stacc.pop(tonumber(params.args) or 1)
+	print(message)
+end, {nargs="?"})