diff --git a/tools/releasetools/ota_from_target_files.py b/tools/releasetools/ota_from_target_files.py
index f474a6c..d6c50dc 100755
--- a/tools/releasetools/ota_from_target_files.py
+++ b/tools/releasetools/ota_from_target_files.py
@@ -527,12 +527,7 @@
   if target_info.oem_props and not OPTIONS.oem_no_mount:
     target_info.WriteMountOemScript(script)
 
-  metadata = {
-      "post-build": target_info.fingerprint,
-      "pre-device": target_info.device,
-      "post-timestamp": target_info.GetBuildProp("ro.build.date.utc"),
-      "ota-type" : "BLOCK",
-  }
+  metadata = GetPackageMetadata(target_info)
 
   device_specific = common.DeviceSpecificParams(
       input_zip=input_zip,
@@ -711,6 +706,57 @@
     metadata["post-timestamp"] = post_timestamp
 
 
+def GetPackageMetadata(target_info, source_info=None):
+  """Generates and returns the metadata dict.
+
+  It generates a dict() that contains the info to be written into an OTA
+  package (META-INF/com/android/metadata). It also handles the detection of
+  downgrade / timestamp override / data wipe based on the global options.
+
+  Args:
+    target_info: The BuildInfo instance that holds the target build info.
+    source_info: The BuildInfo instance that holds the source build info, or
+        None if generating full OTA.
+
+  Returns:
+    A dict to be written into package metadata entry.
+  """
+  assert isinstance(target_info, BuildInfo)
+  assert source_info is None or isinstance(source_info, BuildInfo)
+
+  metadata = {
+      'post-build' : target_info.fingerprint,
+      'post-build-incremental' : target_info.GetBuildProp(
+          'ro.build.version.incremental'),
+  }
+
+  if target_info.is_ab:
+    metadata['ota-type'] = 'AB'
+    metadata['ota-required-cache'] = '0'
+  else:
+    metadata['ota-type'] = 'BLOCK'
+
+  if OPTIONS.wipe_user_data:
+    metadata['ota-wipe'] = 'yes'
+
+  is_incremental = source_info is not None
+  if is_incremental:
+    metadata['pre-build'] = source_info.fingerprint
+    metadata['pre-build-incremental'] = source_info.GetBuildProp(
+        'ro.build.version.incremental')
+    metadata['pre-device'] = source_info.device
+  else:
+    metadata['pre-device'] = target_info.device
+
+  # Detect downgrades, or fill in the post-timestamp.
+  if is_incremental:
+    HandleDowngradeMetadata(metadata, target_info, source_info)
+  else:
+    metadata['post-timestamp'] = target_info.GetBuildProp('ro.build.date.utc')
+
+  return metadata
+
+
 def WriteBlockIncrementalOTAPackage(target_zip, source_zip, output_zip):
   target_info = BuildInfo(OPTIONS.target_info_dict, OPTIONS.oem_dicts)
   source_info = BuildInfo(OPTIONS.source_info_dict, OPTIONS.oem_dicts)
@@ -728,12 +774,7 @@
     if not OPTIONS.oem_no_mount:
       source_info.WriteMountOemScript(script)
 
-  metadata = {
-      "pre-device": source_info.device,
-      "ota-type": "BLOCK",
-  }
-
-  HandleDowngradeMetadata(metadata, target_info, source_info)
+  metadata = GetPackageMetadata(target_info, source_info)
 
   device_specific = common.DeviceSpecificParams(
       source_zip=source_zip,
@@ -745,13 +786,6 @@
       metadata=metadata,
       info_dict=source_info)
 
-  metadata["pre-build"] = source_info.fingerprint
-  metadata["post-build"] = target_info.fingerprint
-  metadata["pre-build-incremental"] = source_info.GetBuildProp(
-      "ro.build.version.incremental")
-  metadata["post-build-incremental"] = target_info.GetBuildProp(
-      "ro.build.version.incremental")
-
   source_boot = common.GetBootableImage(
       "/tmp/boot.img", "boot.img", OPTIONS.source_tmp, "BOOT", source_info)
   target_boot = common.GetBootableImage(
@@ -1070,24 +1104,7 @@
     source_info = None
 
   # Metadata to comply with Android OTA package format.
-  metadata = {
-      "post-build" : target_info.fingerprint,
-      "post-build-incremental" : target_info.GetBuildProp(
-          "ro.build.version.incremental"),
-      "ota-required-cache" : "0",
-      "ota-type" : "AB",
-  }
-
-  if source_file is not None:
-    metadata["pre-device"] = source_info.device
-    metadata["pre-build"] = source_info.fingerprint
-    metadata["pre-build-incremental"] = source_info.GetBuildProp(
-        "ro.build.version.incremental")
-
-    HandleDowngradeMetadata(metadata, target_info, source_info)
-  else:
-    metadata["pre-device"] = target_info.device
-    metadata["post-timestamp"] = target_info.GetBuildProp("ro.build.date.utc")
+  metadata = GetPackageMetadata(target_info, source_info)
 
   # 1. Generate payload.
   payload_file = common.MakeTempFile(prefix="payload-", suffix=".bin")
diff --git a/tools/releasetools/test_ota_from_target_files.py b/tools/releasetools/test_ota_from_target_files.py
index 0948c61..5f6c5d0 100644
--- a/tools/releasetools/test_ota_from_target_files.py
+++ b/tools/releasetools/test_ota_from_target_files.py
@@ -19,7 +19,7 @@
 
 import common
 from ota_from_target_files import (
-    _LoadOemDicts, BuildInfo, WriteFingerprintAssertion)
+    _LoadOemDicts, BuildInfo, GetPackageMetadata, WriteFingerprintAssertion)
 
 
 class MockScriptWriter(object):
@@ -300,3 +300,179 @@
       self.assertEqual('foo', oem_dict['xyz'])
       self.assertEqual('bar', oem_dict['a.b.c'])
       self.assertEqual('{}'.format(i), oem_dict['ro.build.index'])
+
+
+class OtaFromTargetFilesTest(unittest.TestCase):
+
+  TEST_TARGET_INFO_DICT = {
+      'build.prop' : {
+          'ro.product.device' : 'product-device',
+          'ro.build.fingerprint' : 'build-fingerprint-target',
+          'ro.build.version.incremental' : 'build-version-incremental-target',
+          'ro.build.date.utc' : '1500000000',
+      },
+  }
+
+  TEST_SOURCE_INFO_DICT = {
+      'build.prop' : {
+          'ro.product.device' : 'product-device',
+          'ro.build.fingerprint' : 'build-fingerprint-source',
+          'ro.build.version.incremental' : 'build-version-incremental-source',
+          'ro.build.date.utc' : '1400000000',
+      },
+  }
+
+  def setUp(self):
+    # Reset the global options as in ota_from_target_files.py.
+    common.OPTIONS.incremental_source = None
+    common.OPTIONS.downgrade = False
+    common.OPTIONS.timestamp = False
+    common.OPTIONS.wipe_user_data = False
+
+  def test_GetPackageMetadata_abOta_full(self):
+    target_info_dict = copy.deepcopy(self.TEST_TARGET_INFO_DICT)
+    target_info_dict['ab_update'] = 'true'
+    target_info = BuildInfo(target_info_dict, None)
+    metadata = GetPackageMetadata(target_info)
+    self.assertDictEqual(
+        {
+            'ota-type' : 'AB',
+            'ota-required-cache' : '0',
+            'post-build' : 'build-fingerprint-target',
+            'post-build-incremental' : 'build-version-incremental-target',
+            'post-timestamp' : '1500000000',
+            'pre-device' : 'product-device',
+        },
+        metadata)
+
+  def test_GetPackageMetadata_abOta_incremental(self):
+    target_info_dict = copy.deepcopy(self.TEST_TARGET_INFO_DICT)
+    target_info_dict['ab_update'] = 'true'
+    target_info = BuildInfo(target_info_dict, None)
+    source_info = BuildInfo(self.TEST_SOURCE_INFO_DICT, None)
+    common.OPTIONS.incremental_source = ''
+    metadata = GetPackageMetadata(target_info, source_info)
+    self.assertDictEqual(
+        {
+            'ota-type' : 'AB',
+            'ota-required-cache' : '0',
+            'post-build' : 'build-fingerprint-target',
+            'post-build-incremental' : 'build-version-incremental-target',
+            'post-timestamp' : '1500000000',
+            'pre-device' : 'product-device',
+            'pre-build' : 'build-fingerprint-source',
+            'pre-build-incremental' : 'build-version-incremental-source',
+        },
+        metadata)
+
+  def test_GetPackageMetadata_nonAbOta_full(self):
+    target_info = BuildInfo(self.TEST_TARGET_INFO_DICT, None)
+    metadata = GetPackageMetadata(target_info)
+    self.assertDictEqual(
+        {
+            'ota-type' : 'BLOCK',
+            'post-build' : 'build-fingerprint-target',
+            'post-build-incremental' : 'build-version-incremental-target',
+            'post-timestamp' : '1500000000',
+            'pre-device' : 'product-device',
+        },
+        metadata)
+
+  def test_GetPackageMetadata_nonAbOta_incremental(self):
+    target_info = BuildInfo(self.TEST_TARGET_INFO_DICT, None)
+    source_info = BuildInfo(self.TEST_SOURCE_INFO_DICT, None)
+    common.OPTIONS.incremental_source = ''
+    metadata = GetPackageMetadata(target_info, source_info)
+    self.assertDictEqual(
+        {
+            'ota-type' : 'BLOCK',
+            'post-build' : 'build-fingerprint-target',
+            'post-build-incremental' : 'build-version-incremental-target',
+            'post-timestamp' : '1500000000',
+            'pre-device' : 'product-device',
+            'pre-build' : 'build-fingerprint-source',
+            'pre-build-incremental' : 'build-version-incremental-source',
+        },
+        metadata)
+
+  def test_GetPackageMetadata_wipe(self):
+    target_info = BuildInfo(self.TEST_TARGET_INFO_DICT, None)
+    common.OPTIONS.wipe_user_data = True
+    metadata = GetPackageMetadata(target_info)
+    self.assertDictEqual(
+        {
+            'ota-type' : 'BLOCK',
+            'ota-wipe' : 'yes',
+            'post-build' : 'build-fingerprint-target',
+            'post-build-incremental' : 'build-version-incremental-target',
+            'post-timestamp' : '1500000000',
+            'pre-device' : 'product-device',
+        },
+        metadata)
+
+  @staticmethod
+  def _test_GetPackageMetadata_swapBuildTimestamps(target_info, source_info):
+    (target_info['build.prop']['ro.build.date.utc'],
+     source_info['build.prop']['ro.build.date.utc']) = (
+         source_info['build.prop']['ro.build.date.utc'],
+         target_info['build.prop']['ro.build.date.utc'])
+
+  def test_GetPackageMetadata_unintentionalDowngradeDetected(self):
+    target_info_dict = copy.deepcopy(self.TEST_TARGET_INFO_DICT)
+    source_info_dict = copy.deepcopy(self.TEST_SOURCE_INFO_DICT)
+    self._test_GetPackageMetadata_swapBuildTimestamps(
+        target_info_dict, source_info_dict)
+
+    target_info = BuildInfo(target_info_dict, None)
+    source_info = BuildInfo(source_info_dict, None)
+    common.OPTIONS.incremental_source = ''
+    self.assertRaises(RuntimeError, GetPackageMetadata, target_info,
+                      source_info)
+
+  def test_GetPackageMetadata_downgrade(self):
+    target_info_dict = copy.deepcopy(self.TEST_TARGET_INFO_DICT)
+    source_info_dict = copy.deepcopy(self.TEST_SOURCE_INFO_DICT)
+    self._test_GetPackageMetadata_swapBuildTimestamps(
+        target_info_dict, source_info_dict)
+
+    target_info = BuildInfo(target_info_dict, None)
+    source_info = BuildInfo(source_info_dict, None)
+    common.OPTIONS.incremental_source = ''
+    common.OPTIONS.downgrade = True
+    common.OPTIONS.wipe_user_data = True
+    metadata = GetPackageMetadata(target_info, source_info)
+    self.assertDictEqual(
+        {
+            'ota-downgrade' : 'yes',
+            'ota-type' : 'BLOCK',
+            'ota-wipe' : 'yes',
+            'post-build' : 'build-fingerprint-target',
+            'post-build-incremental' : 'build-version-incremental-target',
+            'pre-device' : 'product-device',
+            'pre-build' : 'build-fingerprint-source',
+            'pre-build-incremental' : 'build-version-incremental-source',
+        },
+        metadata)
+
+  def test_GetPackageMetadata_overrideTimestamp(self):
+    target_info_dict = copy.deepcopy(self.TEST_TARGET_INFO_DICT)
+    source_info_dict = copy.deepcopy(self.TEST_SOURCE_INFO_DICT)
+    self._test_GetPackageMetadata_swapBuildTimestamps(
+        target_info_dict, source_info_dict)
+
+    target_info = BuildInfo(target_info_dict, None)
+    source_info = BuildInfo(source_info_dict, None)
+    common.OPTIONS.incremental_source = ''
+    common.OPTIONS.timestamp = True
+    metadata = GetPackageMetadata(target_info, source_info)
+    self.assertDictEqual(
+        {
+            'ota-type' : 'BLOCK',
+            'post-build' : 'build-fingerprint-target',
+            'post-build-incremental' : 'build-version-incremental-target',
+            'post-timestamp' : '1500000001',
+            'pre-device' : 'product-device',
+            'pre-build' : 'build-fingerprint-source',
+            'pre-build-incremental' : 'build-version-incremental-source',
+        },
+        metadata)