Harden vehicle detection and prompt

src/main/kotlin/com/android/trisolarisserver/component/DocumentExtractionService.kt

@@ -25,14 +25,22 @@ class DocumentExtractionService(
                         imageUrl,
                         "IS THIS A VEHICLE NUMBER PLATE PHOTO? Answer YES or NO only."
                     )
-                    isYes(results["isVehiclePhoto"])
-                },
-                handle = {
-                    results["vehicleNumber"] = llamaClient.ask(
+                    if (!isYes(results["isVehiclePhoto"])) return@Detection false
+                    val candidate = llamaClient.ask(
                         imageUrl,
                         "VEHICLE NUMBER PLATE? Reply only number or NONE."
                     )
-                }
+                    val cleaned = cleanedValue(candidate)
+                    if (cleaned != null && isLikelyVehicleNumber(cleaned)) {
+                        results["vehicleNumber"] = cleaned
+                        true
+                    } else {
+                        results["vehicleNumber"] = "NONE"
+                        results["isVehiclePhoto"] = "NO"
+                        false
+                    }
+                },
+                handle = {}
             ),
             Detection(
                 detect = {
@@ -217,6 +225,13 @@ class DocumentExtractionService(
         return value.orEmpty().contains("YES", ignoreCase = true)
     }
 
+    private fun isLikelyVehicleNumber(value: String): Boolean {
+        val normalized = value.uppercase().replace(Regex("[\\s-]"), "")
+        if (normalized.length == 12 && normalized.all { it.isDigit() }) return false
+        if (normalized.length < 6) return false
+        return standardPlateRegex.matches(normalized) || bhPlateRegex.matches(normalized)
+    }
+
     private fun computeDocType(results: Map<String, String>, handled: Boolean): String {
         if (!handled) return "GENERAL"
         return when {
@@ -308,3 +323,6 @@ private fun cleanedValue(value: String?): String? {
     if (upper == "NONE" || upper == "N/A" || upper == "NA" || upper == "NULL") return null
     return trimmed
 }
+
+private val standardPlateRegex = Regex("^[A-Z]{2}\\d{1,2}[A-Z]{1,3}\\d{3,4}$")
+private val bhPlateRegex = Regex("^\\d{2}BH\\d{4}[A-Z]{1,2}$")

src/main/kotlin/com/android/trisolarisserver/component/LlamaClient.kt

@@ -26,7 +26,7 @@ class LlamaClient(
     private val topK: Int
 ) {
     private val systemPrompt =
-        "Look only at visible text. " +
+        "Read extremely carefully. Look only at visible text. " +
             "Return the exact text you can read verbatim. " +
             "If the text is unclear, partial, or inferred, return NOT CLEARLY VISIBLE. " +
             "Do not guess. Do not explain."