refactor: centralize raw frame identity derivation

modules/core/ingest-facts/src/main/java/com/lingniu/ingest/facts/RawFrameIdentity.java

@@ -0,0 +1,43 @@
+package com.lingniu.ingest.facts;
+
+import com.lingniu.ingest.api.ProtocolId;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.time.Instant;
+import java.util.HexFormat;
+
+public record RawFrameIdentity(
+        String checksum,
+        String vehicleKey,
+        String frameId
+) {
+    public RawFrameIdentity {
+        checksum = checksum == null ? "" : checksum;
+        vehicleKey = vehicleKey == null ? "" : vehicleKey;
+        frameId = frameId == null ? "" : frameId;
+    }
+
+    public static RawFrameIdentity derive(ProtocolId protocol,
+                                          String vin,
+                                          String phone,
+                                          String rawIdentitySeed,
+                                          int messageId,
+                                          int subType,
+                                          Instant receivedAt,
+                                          byte[] rawBytes) {
+        String checksum = "sha256:" + sha256(rawBytes);
+        String vehicleKey = VehicleKey.derive(protocol, vin, phone, rawIdentitySeed);
+        String frameId = FactIds.rawFrameId(protocol, vehicleKey, messageId, subType, receivedAt, checksum);
+        return new RawFrameIdentity(checksum, vehicleKey, frameId);
+    }
+
+    private static String sha256(byte[] value) {
+        try {
+            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+            return HexFormat.of().formatHex(digest.digest(value == null ? new byte[0] : value));
+        } catch (NoSuchAlgorithmException e) {
+            throw new IllegalStateException("SHA-256 is unavailable", e);
+        }
+    }
+}

modules/core/ingest-facts/src/test/java/com/lingniu/ingest/facts/RawFrameIdentityTest.java

@@ -0,0 +1,36 @@
+package com.lingniu.ingest.facts;
+
+import com.lingniu.ingest.api.ProtocolId;
+import org.junit.jupiter.api.Test;
+
+import java.time.Instant;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class RawFrameIdentityTest {
+
+    @Test
+    void derivesChecksumVehicleKeyAndFrameIdTogether() {
+        RawFrameIdentity identity = RawFrameIdentity.derive(
+                ProtocolId.JT808,
+                "",
+                "13307795425",
+                "1782900000000000",
+                0x0200,
+                0,
+                Instant.parse("2026-07-01T10:00:00Z"),
+                new byte[]{0x7e, 0x02, 0x00, 0x7e});
+
+        assertThat(identity.checksum()).startsWith("sha256:");
+        assertThat(identity.vehicleKey()).isEqualTo("jt808:13307795425");
+        assertThat(identity.frameId())
+                .isEqualTo(FactIds.rawFrameId(
+                        ProtocolId.JT808,
+                        "jt808:13307795425",
+                        0x0200,
+                        0,
+                        Instant.parse("2026-07-01T10:00:00Z"),
+                        identity.checksum()))
+                .startsWith("rf_");
+    }
+}