private String substituteVars()

in ratis-common/src/main/java/org/apache/ratis/conf/RaftProperties.java [149:218]
65 lines of code
20 McCabe index (conditional complexity)

  private String substituteVars(String expr) {
    if (expr == null) {
      return null;
    }
    String eval = expr;
    Set<String> evalSet = null;
    for(int s = 0; s < MAX_SUBST; s++) {
      final int[] varBounds = findSubVariable(eval);
      if (varBounds[SUB_START_IDX] == -1) {
        return eval;
      }
      final String var = eval.substring(varBounds[SUB_START_IDX],
          varBounds[SUB_END_IDX]);
      String val = null;
      try {
        if (var.startsWith("env.") && 4 < var.length()) {
          String v = var.substring(4);
          int i = 0;
          for (; i < v.length(); i++) {
            char c = v.charAt(i);
            if (c == ':' && i < v.length() - 1 && v.charAt(i + 1) == '-') {
              val = getenv(v.substring(0, i));
              if (val == null || val.length() == 0) {
                val = v.substring(i + 2);
              }
              break;
            } else if (c == '-') {
              val = getenv(v.substring(0, i));
              if (val == null) {
                val = v.substring(i + 1);
              }
              break;
            }
          }
          if (i == v.length()) {
            val = getenv(v);
          }
        } else {
          val = getProperty(var);
        }
      } catch(SecurityException se) {
        LOG.warn("Unexpected SecurityException in Configuration", se);
      }
      if (val == null) {
        val = getRaw(var);
      }
      if (val == null) {
        return eval; // return literal ${var}: var is unbound
      }

      // prevent recursive resolution
      //
      final int dollar = varBounds[SUB_START_IDX] - "${".length();
      final int afterRightBrace = varBounds[SUB_END_IDX] + "}".length();
      final String refVar = eval.substring(dollar, afterRightBrace);
      if (evalSet == null) {
        evalSet = new HashSet<>();
      }
      if (!evalSet.add(refVar)) {
        return expr; // return original expression if there is a loop
      }

      // substitute
      eval = eval.substring(0, dollar)
             + val
             + eval.substring(afterRightBrace);
    }
    throw new IllegalStateException("Variable substitution depth too large: "
                                    + MAX_SUBST + " " + expr);
  }