Function find_json_start

core/src/llm/structured.rs:451–482

Find the byte offset where JSON content starts in a text stream. Skips leading prose/whitespace to find `{` or `[` that isn't inside a string.

(text: &str)

/// Find the byte offset where JSON content starts in a text stream.
/// Skips leading prose/whitespace to find `{` or `[` that isn't inside a string.
fn find_json_start(text: &str) -> Option<usize> {
    // Skip past code fence markers if present
    let (search_text, offset) = if let Some(rest) = text.strip_prefix("```json") {
        (rest, 7)
    } else if let Some(rest) = text.strip_prefix("```") {
        (rest, 3)
    } else {
        (text, 0)
    };

    let mut in_string = false;
    let mut escape_next = false;
    for (i, &b) in search_text.as_bytes().iter().enumerate() {
        if escape_next {
            escape_next = false;
            continue;
        }
        match b {
            b'\\' if in_string => {
                escape_next = true;
            }
            b'"' => {
                in_string = !in_string;
            }
            b'{' | b'[' if !in_string => {
                return Some(offset + i);
            }
            _ => {}
        }
    }
    None
}

// ---------------------------------------------------------------------------
// Partial JSON parsing (for streaming)