lsp/gopls.lua
---
-- @file lsp/gopls.lua
--
-- @brief
-- The configuration file for the Go LSP
--
-- @author Tanuharja, R.A.
-- @date 2025-07-25
--

local mod_cache = nil
local std_lib = nil

local function identify_go_dir(custom_args, on_complete)
	local cmd = { "go", "env", custom_args.envvar_id }
	vim.system(cmd, { text = true }, function(output)
		local res = vim.trim(output.stdout or "")
		if output.code == 0 and res ~= "" then
			if custom_args.custom_subdir and custom_args.custom_subdir ~= "" then
				res = res .. custom_args.custom_subdir
			end
			on_complete(res)
		else
			vim.schedule(function()
				vim.notify(
					("[gopls] identify " .. custom_args.envvar_id .. " dir cmd failed with code %d: %s\n%s"):format(
						output.code,
						vim.inspect(cmd),
						output.stderr
					)
				)
			end)
			on_complete(nil)
		end
	end)
end

local function get_std_lib_dir()
	if std_lib and std_lib ~= "" then
		return std_lib
	end

	identify_go_dir({ envvar_id = "GOROOT", custom_subdir = "/src" }, function(dir)
		if dir then
			std_lib = dir
		end
	end)
	return std_lib
end

local function get_mod_cache_dir()
	if mod_cache and mod_cache ~= "" then
		return mod_cache
	end

	identify_go_dir({ envvar_id = "GOMODCACHE" }, function(dir)
		if dir then
			mod_cache = dir
		end
	end)
	return mod_cache
end

local function get_root_dir(fname)
	if mod_cache and fname:sub(1, #mod_cache) == mod_cache then
		local clients = vim.lsp.get_clients({ name = "gopls" })
		if #clients > 0 then
			return clients[#clients].config.root_dir
		end
	end
	if std_lib and fname:sub(1, #std_lib) == std_lib then
		local clients = vim.lsp.get_clients({ name = "gopls" })
		if #clients > 0 then
			return clients[#clients].config.root_dir
		end
	end
	return vim.fs.root(fname, "go.work") or vim.fs.root(fname, "go.mod") or vim.fs.root(fname, ".git")
end

return {

	filetypes = { "go", "gomod", "gowork", "gotmpl" },

	cmd = { "gopls" },

	root_dir = function(bufnr, on_dir)
		local fname = vim.api.nvim_buf_get_name(bufnr)
		get_mod_cache_dir()
		get_std_lib_dir()
		on_dir(get_root_dir(fname))
	end,
}
