fix: avoid StackOverflowError when parsing upload payload

.cursor/rules/Chinese.mdc

@@ -1,6 +0,0 @@
----
-alwaysApply: true
----
-
-Please execute the generate commit message command in Chinese.
-生成 Git 提交信息（Commit Message）时，必须强制使用中文。

code/src/main/java/RedisClipSync.java

@@ -51,7 +51,6 @@ public class RedisClipSync {
     // 公共上传通道
     private static final String UPLOAD_CHANNEL = "global_clip_upload";
     private static final String UNKNOWN_SLAVE_ID = "unknown";
-    private static final Pattern UPLOAD_PAYLOAD_PATTERN = Pattern.compile("\\{\"slaveId\":\"((?:\\\\.|[^\"])*)\",\"content\":\"((?:\\\\.|[^\"])*)\",\"timestamp\":(\\d+)\\}");
     private static final String MASTER_TO_SLAVE_LOG_FILE = "master_to_slave.log";
     private static final String SLAVE_TO_MASTER_LOG_FILE = "slave_to_master.log";
     private static final String LOG_ENTRY_SEPARATOR = "\n\n------------------\n\n";
@@ -551,14 +550,112 @@ public class RedisClipSync {
             return null;
         }
 
-        Matcher matcher = UPLOAD_PAYLOAD_PATTERN.matcher(message);
-        if (!matcher.matches()) {
+        // Avoid regex here: large clipboard payloads can trigger deep backtracking and StackOverflowError.
+        // We only need to parse a fixed JSON shape produced by buildUploadPayload().
+        try {
+            String trimmed = message.trim();
+            if (!trimmed.startsWith("{") || !trimmed.endsWith("}")) {
+                return null;
+            }
+
+            String slaveIdRaw = extractJsonStringField(trimmed, "slaveId");
+            String contentRaw = extractJsonStringField(trimmed, "content");
+            // timestamp is optional for parsing; we just validate it exists and is numeric when present
+            if (!hasJsonNumberField(trimmed, "timestamp")) {
+                return null;
+            }
+
+            String slaveId = unescapeJson(slaveIdRaw);
+            String content = unescapeJson(contentRaw);
+            return new UploadMessage(slaveId, content);
+        } catch (Exception ignored) {
             return null;
         }
+    }
 
-        String slaveId = unescapeJson(matcher.group(1));
-        String content = unescapeJson(matcher.group(2));
-        return new UploadMessage(slaveId, content);
+    static String extractJsonStringField(String json, String fieldName) {
+        int namePos = indexOfJsonFieldName(json, fieldName);
+        if (namePos < 0) {
+            throw new IllegalArgumentException("missing field: " + fieldName);
+        }
+
+        int colon = json.indexOf(':', namePos);
+        if (colon < 0) {
+            throw new IllegalArgumentException("bad json: missing colon for " + fieldName);
+        }
+
+        int i = colon + 1;
+        while (i < json.length() && Character.isWhitespace(json.charAt(i))) {
+            i++;
+        }
+        if (i >= json.length() || json.charAt(i) != '"') {
+            throw new IllegalArgumentException("bad json: expected string for " + fieldName);
+        }
+
+        return parseJsonStringBody(json, i);
+    }
+
+    static boolean hasJsonNumberField(String json, String fieldName) {
+        int namePos = indexOfJsonFieldName(json, fieldName);
+        if (namePos < 0) {
+            return false;
+        }
+        int colon = json.indexOf(':', namePos);
+        if (colon < 0) {
+            return false;
+        }
+
+        int i = colon + 1;
+        while (i < json.length() && Character.isWhitespace(json.charAt(i))) {
+            i++;
+        }
+        int start = i;
+        while (i < json.length()) {
+            char c = json.charAt(i);
+            if (c < '0' || c > '9') {
+                break;
+            }
+            i++;
+        }
+        return i > start;
+    }
+
+    static int indexOfJsonFieldName(String json, String fieldName) {
+        // Find: "fieldName" (as a JSON string token)
+        String needle = "\"" + fieldName + "\"";
+        return json.indexOf(needle);
+    }
+
+    /**
+     * Parse JSON string starting at the opening quote and return the raw (escaped) body.
+     * Example input: "a\\n\"b" -> returns: a\\n\"b (without surrounding quotes)
+     */
+    static String parseJsonStringBody(String json, int openingQuoteIndex) {
+        if (openingQuoteIndex < 0 || openingQuoteIndex >= json.length() || json.charAt(openingQuoteIndex) != '"') {
+            throw new IllegalArgumentException("bad json: expected opening quote");
+        }
+
+        StringBuilder rawEscaped = new StringBuilder();
+        int i = openingQuoteIndex + 1;
+        while (i < json.length()) {
+            char c = json.charAt(i);
+            if (c == '"') {
+                return rawEscaped.toString();
+            }
+            if (c == '\\') {
+                if (i + 1 >= json.length()) {
+                    throw new IllegalArgumentException("bad json: trailing backslash");
+                }
+                rawEscaped.append('\\').append(json.charAt(i + 1));
+                i += 2;
+                continue;
+            }
+
+            rawEscaped.append(c);
+            i++;
+        }
+
+        throw new IllegalArgumentException("bad json: unterminated string");
     }
 
     static String escapeJson(String value) {