From 7cb95de38967a3d2dd403ede97213ae5b22d630d Mon Sep 17 00:00:00 2001
From: Thomas Vanbesien <tvanbesi@proton.me>
Date: Sun, 7 Jun 2026 16:48:18 +0200
Subject: feat(nvim): support custom snippets

---
 .config/nvim/after/ftplugin/lua.lua   | 11 +++++
 .config/nvim/plugin/50-completion.lua | 80 +++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+)

(limited to '.config/nvim')

diff --git a/.config/nvim/after/ftplugin/lua.lua b/.config/nvim/after/ftplugin/lua.lua
index 05e4978..b7d29c1 100644
--- a/.config/nvim/after/ftplugin/lua.lua
+++ b/.config/nvim/after/ftplugin/lua.lua
@@ -28,7 +28,18 @@ vim.opt_local.textwidth = vim.g.dotfiles.textwidth.lua -- gw wraps at this value
 vim.opt_local.colorcolumn = "+1" -- Highlight one column after 'textwidth'
 vim.opt_local.complete = {
 	"o", -- 'omnifunc'
+	"F", -- 'completefunc' (snippet source, see plugin/50-completion.lua)
 }
 
 vim.b.autoformat = true
 vim.b.format_func = format
+
+------------------------------------------------------------------------------------------------------------------------
+-- Snippets
+------------------------------------------------------------------------------------------------------------------------
+-- Trigger word -> LSP snippet body. `$1` mirrors the `${1:X}` placeholder, so the variable is typed once.
+-- Surfaced in the completion menu via the "F" source in 'complete' above (see plugin/50-completion.lua).
+vim.b.snippets = {
+	["debug_print"] = 'vim.print("${1:X} = " .. vim.inspect($1))',
+}
+vim.bo.completefunc = "v:lua.dotfiles_snippet_source"
diff --git a/.config/nvim/plugin/50-completion.lua b/.config/nvim/plugin/50-completion.lua
index 56c99d7..f21b1f4 100644
--- a/.config/nvim/plugin/50-completion.lua
+++ b/.config/nvim/plugin/50-completion.lua
@@ -91,6 +91,86 @@ snippet.expand = function(input)
 	end
 end
 
+------------------------------------------------------------------------------------------------------------------------
+-- Snippet completion source
+------------------------------------------------------------------------------------------------------------------------
+-- Exposes `vim.b.snippets` (trigger word -> LSP snippet body) as a 'complete' function source. A filetype opts in from
+-- its ftplugin by setting `vim.b.snippets`, pointing 'completefunc' at this function, and appending "F" to 'complete'.
+-- Must be a global so `v:lua` can reach it; see `:help complete-functions` and `:help v:lua-call`.
+
+-- Render a snippet to preview text: resolve placeholders and their mirrors to the placeholder's default value.
+local function render_snippet(s)
+	local defaults = {}
+	for n, d in s:gmatch("%${(%d+):([^{}]*)}") do
+		defaults[n] = d
+	end
+	local prev
+	repeat
+		prev = s
+		s = s:gsub("%$(%b{})", function(group)
+			local body = group:sub(2, -2)
+			local choice = body:match("^%d+|(.*)|$")
+			if choice then
+				return (choice:gsub(",.*$", "")) -- first choice
+			end
+			local default = body:match("^[%w_]+:(.*)$")
+			if default then
+				return default -- ${n:default} / ${VAR:default}
+			end
+			return defaults[body] or "" -- ${n} / ${VAR}
+		end)
+	until s == prev
+	s = s:gsub("%$(%d+)", function(n)
+		return defaults[n] or "" -- $n mirror
+	end)
+	s = s:gsub("%$[%w_]+", "") -- bare $VAR
+	s = s:gsub("\\([%$}{|,\\])", "%1") -- unescape
+	return s
+end
+
+function _G.dotfiles_snippet_source(findstart, base)
+	local snippets = vim.b.snippets or {}
+	local line = vim.api.nvim_get_current_line()
+	local col = vim.api.nvim_win_get_cursor(0)[2]
+	if findstart == 1 then
+		-- Walk back over trigger characters to find the range the match replaces.
+		local start = col
+		while start > 0 and line:sub(start, start):match("[%w_]") do
+			start = start - 1
+		end
+		return start
+	end
+	local items = {}
+	for trigger, body in pairs(snippets) do
+		if vim.startswith(trigger, base) then
+			items[#items + 1] = {
+				word = trigger,
+				kind = "Snippet",
+				menu = "[snippet]",
+				info = render_snippet(body),
+				user_data = { snippet = body },
+			}
+		end
+	end
+	return items
+end
+
+-- Expand the snippet once one of the items above is accepted (its trigger word is inserted first, so remove it).
+vim.api.nvim_create_autocmd("CompleteDone", {
+	desc = "Expand accepted snippet completion",
+	group = vim.g.dotfiles.augroup,
+	callback = function()
+		local item = vim.v.completed_item
+		local data = item.user_data
+		if type(data) ~= "table" or not data.snippet then
+			return
+		end
+		local row, col = unpack(vim.api.nvim_win_get_cursor(0))
+		vim.api.nvim_buf_set_text(0, row - 1, col - #item.word, row - 1, col, { "" })
+		vim.snippet.expand(data.snippet)
+	end,
+})
+
 ------------------------------------------------------------------------------------------------------------------------
 -- Command-line mode completion
 ------------------------------------------------------------------------------------------------------------------------
-- 
cgit v1.3.1