refactor(nvim): rewrite formatter plugin

1 files changed, 59 insertions, 0 deletions

diff --git a/lua/dotfiles/format.lua b/lua/dotfiles/format.lua
new file mode 100644
index 0000000..72d0248
--- /dev/null
+++ b/lua/dotfiles/format.lua
@@ -0,0 +1,59 @@
+-- Format engine. Features register a stdin formatter command per filetype; the engine runs the
+-- registered formatter over the buffer on write, when formatting is enabled for it (vim.b.format,
+-- toggled by :FormatToggle). Formatters are registered in plugin/50-format.lua.
+--
+-- API:
+--   register(filetype, cmd) — `cmd` is a command list run with the buffer contents on stdin; its
+--                             stdout replaces the buffer. Call once per filetype to share a command.
+
+local M = {}
+
+-- Registered formatter commands, keyed by filetype.
+M.formatters = {}
+
+-- Run `cmd` with `lines` piped on stdin; return its stdout as a list of lines, or nil on failure.
+local function run(cmd, lines)
+	local r = vim.system(cmd, { stdin = lines, text = true }):wait()
+	if r.code ~= 0 then
+		vim.notify(cmd[1] .. " error:\n" .. r.stderr, vim.log.levels.WARN)
+		return nil
+	end
+	return vim.split(r.stdout, "\n", { trimempty = true })
+end
+
+-- Register the stdin formatter command `cmd` for `filetype`.
+function M.register(filetype, cmd)
+	assert(type(filetype) == "string", "format.register: filetype must be a string")
+	assert(type(cmd) == "table", "format.register: cmd must be a command list")
+	M.formatters[filetype] = cmd
+end
+
+-- Format buffer `ev.buf` with its filetype's formatter when formatting is enabled for it.
+-- Meant as a 'BufWritePre' handler; preserves the cursor/window view across the rewrite.
+local function format_buffer(ev)
+	if vim.b[ev.buf].format ~= true then
+		return
+	end
+	local ft = vim.bo[ev.buf].filetype
+	local cmd = M.formatters[ft]
+	if not cmd then
+		vim.notify("No formatter registered for " .. ft, vim.log.levels.ERROR)
+		return
+	end
+	local lines_in = vim.api.nvim_buf_get_lines(ev.buf, 0, -1, false)
+	local lines_out = run(cmd, lines_in)
+	if not lines_out or vim.deep_equal(lines_in, lines_out) then
+		return
+	end
+	local view = vim.fn.winsaveview()
+	vim.api.nvim_buf_set_lines(ev.buf, 0, -1, false, lines_out)
+	vim.fn.winrestview(view)
+end
+
+vim.api.nvim_create_autocmd("BufWritePre", {
+	desc = "Format buffer",
+	group = vim.g.dotfiles.augroup,
+	callback = format_buffer,
+})
+
+return M