public string GetArgument()

in vsintegration/src/FSharp.LanguageService.Base/ExpansionProvider.cs [653:715]
57 lines of code
19 McCabe index (conditional complexity)

        public string GetArgument(int index) {
            if (args == null || args.Length == 0 || index > args.Length) return null;
            string arg = args[index];
            if (arg == null) return null;
            int i = arg.IndexOf('$');
            if (i >= 0) {
                StringBuilder sb = new StringBuilder();
                int len = arg.Length;
                int start = 0;

                while (i >= 0 && i + 1 < len) {
                    sb.Append(arg.Substring(start, i - start));
                    start = i;
                    i++;
                    if (arg[i] == '$') {
                        sb.Append('$');
                        start = i + 1; // $$ is resolved to $.
                    } else {
                        // parse name of variable.
                        int j = i;
                        for (; j < len; j++) {
                            if (!Char.IsLetterOrDigit(arg[j]))
                                break;
                        }
                        if (j == len) {
                            // terminating '$' not found.
                            sb.Append('$');
                            start = i;
                            break;
                        } else if (arg[j] == '$') {
                            string name = arg.Substring(i, j - i);
                            string value;
                            if (GetFieldValue(name, out value)) {
                                sb.Append(value);
                            } else {
                                // just return the unresolved variable.
                                sb.Append('$');
                                sb.Append(name);
                                sb.Append('$');
                            }
                            start = j + 1;
                        } else {
                            // invalid syntax, e.g. "$US 23.45" or some such thing                            
                            sb.Append('$');
                            sb.Append(arg.Substring(i, j - i));
                            start = j;
                        }
                    }
                    i = arg.IndexOf('$', start);
                }
                if (start < len) {
                    sb.Append(arg.Substring(start, len - start));
                }
                arg = sb.ToString();
            }
            // remove quotes around string literals.
            if (arg.Length > 2 && arg[0] == '"' && arg[arg.Length - 1] == '"') {
                arg = arg.Substring(1, arg.Length - 2);
            } else if (arg.Length > 2 && arg[0] == '\'' && arg[arg.Length - 1] == '\'') {
                arg = arg.Substring(1, arg.Length - 2);
            }
            return arg;
        }