albe / node-event-storage / 26529902254

const BYTE_QUOTE = 0x22;

const BYTE_ESCAPE = 0x5c;

const BYTE_OPEN_OBJECT = 0x7b;

const BYTE_CLOSE_OBJECT = 0x7d;

const BYTE_OPEN_ARRAY = 0x5b;

const BYTE_CLOSE_ARRAY = 0x5d;

const BYTE_COMMA = 0x2c;

/**

 * Find the position of `pattern` within `buffer` at depth 0 (the top-level object), starting

 * from `startOffset`.  It scans character-by-character tracking JSON nesting depth and string

 * quoting.  If `matchPosition` arrives at depth > 0 it means the pattern is inside a nested

 * object/array, so the scan continues searching for the next candidate at depth 0.  Returns -1

 * when no such position exists before the end of the buffer or when a closing brace reduces depth

 * below zero (the top-level object has ended).

 */

function indexOfSameLevel(buffer, pattern, startOffset = 0, matchPosition) {

    /* c8 ignore start */

    // Defensive fallback: public call path precomputes an initial candidate in preCheck.

    if (matchPosition === undefined) {

        matchPosition = buffer.indexOf(pattern, startOffset);

    }

    if (matchPosition === -1) {

        return -1;

    }

    /* c8 ignore stop */

    let depth = 0;

    let inString = false;

    let i = startOffset;

    while (i < buffer.length) {

        if (inString) {

            if (buffer[i] === BYTE_ESCAPE) { // '\\'

                i += 2;

                continue;

            }

            if (buffer[i] === BYTE_QUOTE) { // '"'

                inString = false;

            }

            i++;

            continue;

        }

        const ch = buffer[i];

        if (ch === BYTE_OPEN_OBJECT || ch === BYTE_OPEN_ARRAY) { // '{' or '['

            depth++;

            i++;

            continue;

        } else if (ch === BYTE_CLOSE_OBJECT || ch === BYTE_CLOSE_ARRAY) { // '}' or ']'

            depth--;

            if (depth < 0) {

                return -1;

            }

            i++;

            continue;

        } else if (ch === BYTE_QUOTE) { // '"'

            inString = true;

        }

        if (i >= matchPosition) {

            if (i === matchPosition && ch === BYTE_QUOTE && depth === 0) { // '"'

                const end = i + pattern.length;

                if (pattern[pattern.length - 1] === BYTE_OPEN_OBJECT) { // '{'

                    return i;

                }

                if (buffer[end] === BYTE_COMMA || buffer[end] === BYTE_CLOSE_OBJECT || buffer[end] === BYTE_CLOSE_ARRAY) { // ',' or '}' or ']'

                    return i;

                }

            }

            matchPosition = buffer.indexOf(pattern, matchPosition + 1);

            if (matchPosition < 0) {

                return -1;

            }

        }

        i++;

    }

    /* c8 ignore next */

    return -1;

}

export { BYTE_OPEN_OBJECT, indexOfSameLevel };