Create separate python libraries for the following logic and refactor SBOM generation script accordingly.

1) writer classes of generating SBOM in different SPDX formats
2) data classes to model the SBOM structure in SPDX

Bug: 272358880
Test: CIs
Test: build/soong/tests/sbom_test.sh
Test: atest --host sbom_writers_test

Change-Id: I1175cf0d99864bc4304559a59484ef0ba401cd64

tools/sbom/sbom_data.py

@@ -0,0 +1,120 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2023 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Define data classes that model SBOMs defined by SPDX. The data classes could be
+written out to different formats (tagvalue, JSON, etc) of SPDX with corresponding
+writer utilities.
+
+Rrefer to SPDX 2.3 spec: https://spdx.github.io/spdx-spec/v2.3/ and go/android-spdx for details of
+fields in each data class.
+"""
+
+from dataclasses import dataclass, field
+from typing import List
+
+SPDXID_DOC = 'SPDXRef-DOCUMENT'
+SPDXID_PRODUCT = 'SPDXRef-PRODUCT'
+SPDXID_PLATFORM = 'SPDXRef-PLATFORM'
+
+PACKAGE_NAME_PRODUCT = 'PRODUCT'
+PACKAGE_NAME_PLATFORM = 'PLATFORM'
+
+
+class PackageExternalRefCategory:
+  SECURITY = 'SECURITY'
+  PACKAGE_MANAGER = 'PACKAGE-MANAGER'
+  PERSISTENT_ID = 'PERSISTENT-ID'
+  OTHER = 'OTHER'
+
+
+class PackageExternalRefType:
+  cpe22Type = 'cpe22Type'
+  cpe23Type = 'cpe23Type'
+
+
+@dataclass
+class PackageExternalRef:
+  category: PackageExternalRefCategory
+  type: PackageExternalRefType
+  locator: str
+
+
+@dataclass
+class Package:
+  name: str
+  id: str
+  version: str = None
+  supplier: str = None
+  download_location: str = None
+  files_analyzed: bool = False
+  verification_code: str = None
+  file_ids: List[str] = field(default_factory=list)
+  external_refs: List[PackageExternalRef] = field(default_factory=list)
+
+
+@dataclass
+class File:
+  id: str
+  name: str
+  checksum: str
+
+
+class RelationshipType:
+  DESCRIBES = 'DESCRIBES'
+  VARIANT_OF = 'VARIANT_OF'
+  GENERATED_FROM = 'GENERATED_FROM'
+
+
+@dataclass
+class Relationship:
+  id1: str
+  relationship: RelationshipType
+  id2: str
+
+
+@dataclass
+class DocumentExternalReference:
+  id: str
+  uri: str
+  checksum: str
+
+
+@dataclass
+class Document:
+  name: str
+  namespace: str
+  id: str = SPDXID_DOC
+  describes: str = SPDXID_PRODUCT
+  creators: List[str] = field(default_factory=list)
+  created: str = None
+  external_refs: List[DocumentExternalReference] = field(default_factory=list)
+  packages: List[Package] = field(default_factory=list)
+  files: List[File] = field(default_factory=list)
+  relationships: List[Relationship] = field(default_factory=list)
+
+  def add_external_ref(self, external_ref):
+    if not any(external_ref.uri == ref.uri for ref in self.external_refs):
+      self.external_refs.append(external_ref)
+
+  def add_package(self, package):
+    if not any(package.id == p.id for p in self.packages):
+      self.packages.append(package)
+
+  def add_relationship(self, rel):
+    if not any(rel.id1 == r.id1 and rel.id2 == r.id2 and rel.relationship == r.relationship
+               for r in self.relationships):
+      self.relationships.append(rel)