Class ChunkTokenizer

core/src/main/java/feign/template/Template.java:261–330

Splits a Uri into Chunks that exists inside and outside of an expression, delimited by curly braces "{}". Nested expressions are treated as literals, for example "foo{bar{baz}}" will be treated as "foo, {bar{baz}}". Inspired by Apache CXF Jax-RS.

   * treated as "foo, {bar{baz}}". Inspired by Apache CXF Jax-RS.
   */
  static class ChunkTokenizer {

    private List<String> tokens = new ArrayList<>();
    private int index;

    ChunkTokenizer(String template) {
      boolean outside = true;
      int level = 0;
      int lastIndex = 0;
      int idx;

      /* loop through the template, character by character */
      for (idx = 0; idx < template.length(); idx++) {
        if (template.charAt(idx) == '{') {
          /* start of an expression */
          if (outside) {
            /* outside of an expression */
            if (lastIndex < idx) {
              /* this is the start of a new token */
              tokens.add(template.substring(lastIndex, idx));
            }
            lastIndex = idx;

            /*
             * no longer outside of an expression, additional characters will be treated as in an
             * expression
             */
            outside = false;
          } else {
            /* nested braces, increase our nesting level */
            level++;
          }
        } else if (template.charAt(idx) == '}' && !outside) {
          /* the end of an expression */
          if (level > 0) {
            /*
             * sometimes we see nested expressions, we only want the outer most expression
             * boundaries.
             */
            level--;
          } else {
            /* outermost boundary */
            if (lastIndex < idx) {
              /* this is the end of an expression token */
              tokens.add(template.substring(lastIndex, idx + 1));
            }
            lastIndex = idx + 1;

            /* outside an expression */
            outside = true;
          }
        }
      }
      if (lastIndex < idx) {
        /* grab the remaining chunk */
        tokens.add(template.substring(lastIndex, idx));
      }
    }