fix(nvim): live highlight TODO strings

Previously, extended marks for TODO strings were only set once on
`'FileType'`.

1 files changed, 37 insertions, 13 deletions

diff --git a/.config/nvim/plugin/50-extmarks.lua b/.config/nvim/plugin/50-extmarks.lua
index c11d10c..1324da0 100644
--- a/.config/nvim/plugin/50-extmarks.lua
+++ b/.config/nvim/plugin/50-extmarks.lua
@@ -37,7 +37,7 @@ end
 local function pmatches(lines, pattern)
 	local col1, col2, row = nil, nil, 1
 	return function()
-		while row < #lines do
+		while row <= #lines do
 			col1, col2 = string.find(lines[row], pattern, (col2 or 0) + 1)
 			if col1 then
 				return { col1 = col1, col2 = col2, row = row }
@@ -55,18 +55,18 @@ end
 --     predicate: is passed row and col, if true then set the mark
 --     hl_group: highlight group
 --  }
-local function set_extmarks(next_pos, opts)
+local function set_extmarks(buf, next_pos, opts)
 	for pos in next_pos do
 		local marks = vim.api.nvim_buf_get_extmarks(
-			0,
+			buf,
 			opts.ns,
 			{ pos.row - 1, pos.col1 - 1 },
 			{ pos.row - 1, pos.col2 - 1 },
 			{}
 		)
-		if #marks == 0 and opts.predicate(pos.row - 1, pos.col1 - 1) then
+		if #marks == 0 and opts.predicate(buf, pos.row - 1, pos.col1 - 1) then
 			vim.api.nvim_buf_set_extmark(
-				0,
+				buf,
 				opts.ns,
 				pos.row - 1,
 				pos.col1 - 1,
@@ -79,11 +79,11 @@ end
 -- TODO a better way to do this:
 -- For code, only check in "comment" node ranges
 -- For non-code, do it per type. For Markdown, only check "paragraph" nodes
-local function hl_todo_predicate(row, col)
-	if vim.o.filetype == "markdown" or vim.treesitter.get_parser() == nil then
+local function hl_todo_predicate(buf, row, col)
+	if vim.bo[buf].filetype == "markdown" or vim.treesitter.get_parser(buf) == nil then
 		return true
 	end
-	local node = assert(vim.treesitter.get_node({ pos = { row, col } }))
+	local node = assert(vim.treesitter.get_node({ bufnr = buf, pos = { row, col } }))
 	return node_within_type(node, "comment")
 end
 
@@ -94,12 +94,36 @@ local extmarks_todo_opts = {
 	predicate = hl_todo_predicate,
 }
 
--- Initialize extmarks
+local function scan(buf, first, last)
+	local lines = vim.api.nvim_buf_get_lines(buf, first, last, false)
+	local iter = pmatches(lines, patterns.todo)
+	set_extmarks(buf, function()
+		local pos = iter()
+		if pos then
+			pos.row = pos.row + first
+		end
+		return pos
+	end, extmarks_todo_opts)
+end
+
 vim.api.nvim_create_autocmd("FileType", {
-	desc = "Initialize extmarks",
+	desc = "Initialize and watch TODO extmarks",
 	group = vim.g.dotfiles.augroup,
-	callback = function()
-		local lines = vim.api.nvim_buf_get_lines(0, 0, -1, false)
-		set_extmarks(pmatches(lines, patterns.todo), extmarks_todo_opts)
+	callback = function(args)
+		local buf = args.buf
+		scan(buf, 0, -1)
+		if vim.b[buf].dotfiles_todo_attached then
+			return
+		end
+		vim.b[buf].dotfiles_todo_attached = true
+		vim.api.nvim_buf_attach(buf, false, {
+			on_lines = function(_, b, _, first, _, last_new)
+				vim.schedule(function()
+					if vim.api.nvim_buf_is_valid(b) then
+						scan(b, first, last_new)
+					end
+				end)
+			end,
+		})
 	end,
 })