extractFirstJsonStringValue static method

String? extractFirstJsonStringValue(String rawBuffer)

Extracts the first JSON string value from a single-key object fragment, e.g. { "thought": "Hello -> returns Hello (best-effort, supports partial).

This is used for Thinking delta-args where the payload is always a key/value pair but we don't want to show { "key": " in the UI.

Implementation

static String? extractFirstJsonStringValue(String rawBuffer) {
  try {
    if (rawBuffer.trim().isEmpty) return rawBuffer;
    final int firstKeyQuote = rawBuffer.indexOf('"');
    if (firstKeyQuote < 0) return null;
    final int colonIndex = rawBuffer.indexOf(':', firstKeyQuote + 1);
    if (colonIndex < 0) return null;
    final int firstValueQuote = rawBuffer.indexOf('"', colonIndex + 1);
    if (firstValueQuote < 0) return null;

    final StringBuffer value = StringBuffer();
    bool escaped = false;
    for (int i = firstValueQuote + 1; i < rawBuffer.length; i++) {
      final String ch = rawBuffer[i];
      if (escaped) {
        switch (ch) {
          case 'n':
            value.write('\n');
            break;
          case 'r':
            value.write('\r');
            break;
          case 't':
            value.write('\t');
            break;
          case '"':
            value.write('"');
            break;
          case '\\':
            value.write('\\');
            break;
          default:
            value.write(ch);
            break;
        }
        escaped = false;
        continue;
      }
      if (ch == '\\') {
        escaped = true;
        continue;
      }
      if (ch == '"') {
        break;
      }
      value.write(ch);
    }

    final String result = value.toString();
    return result.trim().isEmpty ? rawBuffer : result;
  } catch (e) {
    return rawBuffer;
  }
}