Reject duplicate guest documents by hash

src/main/kotlin/com/android/trisolarisserver/controller/GuestDocuments.kt

@@ -28,6 +28,7 @@ import java.time.OffsetDateTime
 import java.nio.file.Files
 import java.nio.file.Paths
 import java.util.UUID
+import java.security.MessageDigest
 
 @RestController
 @RequestMapping("/properties/{propertyId}/guests/{guestId}/documents")
@@ -82,6 +83,17 @@ class GuestDocuments(
         }
 
         val stored = storage.store(propertyId, guestId, bookingId, file)
+        val fileHash = hashFile(stored.storagePath)
+        if (fileHash != null && guestDocumentRepo.existsByPropertyIdAndGuestIdAndBookingIdAndFileHash(
+                propertyId,
+                guestId,
+                bookingId,
+                fileHash
+            )
+        ) {
+            Files.deleteIfExists(Paths.get(stored.storagePath))
+            throw ResponseStatusException(HttpStatus.CONFLICT, "Duplicate document")
+        }
         val document = GuestDocument(
             property = property,
             guest = guest,
@@ -90,7 +102,8 @@ class GuestDocuments(
             originalFilename = stored.originalFilename,
             contentType = stored.contentType,
             sizeBytes = stored.sizeBytes,
-            storagePath = stored.storagePath
+            storagePath = stored.storagePath,
+            fileHash = fileHash
         )
         val saved = guestDocumentRepo.save(document)
         runExtraction(saved.id!!, propertyId, guestId)
@@ -236,6 +249,27 @@ class GuestDocuments(
         }
     }
 
+    private fun hashFile(storagePath: String): String? {
+        return try {
+            val path = Paths.get(storagePath)
+            if (!Files.exists(path)) return null
+            val digest = MessageDigest.getInstance("SHA-256")
+            Files.newInputStream(path).use { input ->
+                val buffer = ByteArray(DEFAULT_BUFFER_SIZE)
+                var read = input.read(buffer)
+                while (read >= 0) {
+                    if (read > 0) {
+                        digest.update(buffer, 0, read)
+                    }
+                    read = input.read(buffer)
+                }
+            }
+            digest.digest().joinToString("") { "%02x".format(it) }
+        } catch (_: Exception) {
+            null
+        }
+    }
+
 }
 
 data class GuestDocumentResponse(