nvf/modules/plugins/lsp/presets/clangd.nix

{
  config,
  lib,
  pkgs,
  ...
}: let
  inherit (lib.meta) getExe';
  inherit (lib.modules) mkIf;
  inherit (lib.options) mkEnableOption;
  inherit (lib.generators) mkLuaInline;

  cfg = config.vim.lsp.presets.clangd;
in {
  options.vim.lsp.presets.clangd = {
    enable = mkEnableOption "the Clangd Language Server";
  };

  config = mkIf cfg.enable {
    vim.lsp.servers.clangd = {
      enable = true;
      cmd = [(getExe' pkgs.clang-tools "clangd")];
      root_markers = [
        ".git"
        ".clangd"
        ".clang-tidy"
        ".clang-format"
        "compile_commands.json"
        "compile_flags.txt"
        "configure.ac"
      ];
      capabilities = {
        textDocument = {
          completion = {
            editsNearCursor = true;
          };
        };
        offsetEncoding = ["utf-8" "utf-16"];
      };
      on_attach = mkLuaInline ''
        function(client, bufnr)
          local function switch_source_header(bufnr)
            local method_name = "textDocument/switchSourceHeader"
            local client = vim.lsp.get_clients({ bufnr = bufnr, name = "clangd", })[1]
            if not client then
              return vim.notify(('method %s is not supported by any servers active on the current buffer'):format(method_name))
            end
            local params = vim.lsp.util.make_text_document_params(bufnr)
            client.request(method_name, params, function(err, result)
              if err then
                error(tostring(err))
              end
              if not result then
                vim.notify('corresponding file cannot be determined')
                return
              end
              vim.cmd.edit(vim.uri_to_fname(result))
            end, bufnr)
          end

          local function symbol_info()
            local bufnr = vim.api.nvim_get_current_buf()
            local clangd_client = vim.lsp.get_clients({ bufnr = bufnr, name = "clangd" })[1]
            if not clangd_client or not clangd_client:supports_method 'textDocument/symbolInfo' then
              return vim.notify('Clangd client not found', vim.log.levels.ERROR)
            end
            local win = vim.api.nvim_get_current_win()
            local params = vim.lsp.util.make_position_params(win, clangd_client.offset_encoding)
            clangd_client:request('textDocument/symbolInfo', params, function(err, res)
              if err or #res == 0 then
                -- Clangd always returns an error, there is not reason to parse it
                return
              end
              local container = string.format('container: %s', res[1].containerName) ---@type string
              local name = string.format('name: %s', res[1].name) ---@type string
              vim.lsp.util.open_floating_preview({ name, container }, "", {
                height = 2,
                width = math.max(string.len(name), string.len(container)),
                focusable = false,
                focus = false,
                border = 'single',
                title = 'Symbol Info',
              })
            end, bufnr)
          end

          vim.api.nvim_buf_create_user_command(
            bufnr,
            "ClangdSwitchSourceHeader",
            function(arg)
              switch_source_header(0)
            end,
            {desc = "Switch between source/header"}
          )

          vim.api.nvim_buf_create_user_command(
            bufnr,
            "ClangdShowSymbolInfo",
            function(arg)
              symbol_info()
            end,
            {desc = "Show symbol info"}
          )
        end
      '';
    };
  };
}