# `ToonEx.Decode.StructuralParserV2`
[🔗](https://github.com/ohhi-vn/toon_ex/blob/v1.1.0/lib/toon_ex/decode/structural_parser_v2.ex#L1)

Structural parser for TOON format that handles indentation-based nesting.

This parser processes TOON input by analyzing indentation levels and building
a hierarchical structure from the flat text representation.

## Performance Design (Jason-level efficiency)

This parser is optimized for single-pass, zero-copy decoding:

1. **Binary pattern matching** replaces `String.starts_with?`, `String.contains?`,
   `String.ends_with?`, and regex calls in hot paths with O(1) byte checks.
2. **Sub-binary references** via `binary_part/3` avoid copying — BEAM shares
   the underlying binary when slicing.
3. **Tail-recursive accumulators** with `:lists.reverse/1` instead of appending.
4. **`@compile {:inline, ...}`** for hot functions to eliminate call overhead.
5. **Struct pattern matching** in function heads replaces `cond` + map access.
6. **`binary_part/3`** for slicing instead of `String.slice/3` (avoids UTF-8 scan).

# `line_info`

```elixir
@type line_info() :: %{
  content: String.t(),
  indent: non_neg_integer(),
  line_number: non_neg_integer(),
  original: String.t(),
  is_blank: boolean()
}
```

# `parse_metadata`

```elixir
@type parse_metadata() :: %{
  quoted_keys: MapSet.t(String.t()),
  key_order: [String.t()]
}
```

# `parse`

```elixir
@spec parse(String.t(), map()) ::
  {:ok, {term(), parse_metadata()}} | {:error, ToonEx.DecodeError.t()}
```

Parses TOON input string into a structured format.

Returns a tuple of {result, metadata} where metadata contains quoted_keys and key_order.

---

*Consult [api-reference.md](api-reference.md) for complete listing*