Introduce Oppia proto API v1: Android

BUILD

@@ -0,0 +1,35 @@
+"""
+TODO: fill in
+"""
+
+package_group(
+    name = "api_visibility",
+    packages = [
+        "//",
+    ],
+)
+
+package_group(
+    name = "proto_impl_visibility",
+    packages = [
+        "//proto/...",
+    ],
+)
+
+java_library(
+    name = "android_java_protos",
+    visibility = ["//visibility:public"],
+    exports = [
+      "//proto/v1/api:android_java_proto",
+      "//proto/v1/structure:structure_java_proto",
+    ],
+)
+
+java_library(
+    name = "android_java_lite_protos",
+    visibility = ["//visibility:public"],
+    exports = [
+      "//proto/v1/api:android_java_proto_lite",
+      "//proto/v1/structure:structure_java_proto_lite",
+    ],
+)

README.md

@@ -1,2 +1,42 @@
-# oppia-android-api
-Published Android-specific API for the Oppia backend.
+# oppia-proto-api
+Published common proto API for the Oppia server/client.
+
+This API governs the transfer of data between the Oppia Python server and the Android app. 
+
+### API Versions
+Each version of this API is formatted as a major & minor version (e.g. 1.0) and corresponds to a separate release.
+
+- The major version is represented directly in the directory structure (e.g. 'v1'), and is only incremented if a breaking change must be introduced into the API. (Note that this repository might house multiple major versions, in order to maintain long-term backward compatibility with older API versions.)
+- The minor version is incremented whenever a compatible change to the API is released. It is only ever represented in the release numbers, and never in code form.
+
+Because protobuf is backward/forward interoperable, incompatibilities are unlikely as long as proto versions are respected (though, even in those cases, there should be potential for graceful failures). 
+
+### Content Versions
+Content versions represent the version of the corresponding entity instance (e.g. a topic, skill, or exploration). These are used to track whether a particular structure has content updates. They map to the versions stored in the corresponding structure's VersionedModel in the backend.
+
+### Proto Versions
+Proto versions correspond to the proto structures defined in this repository. They only need to be incremented when a proto structure is updated in such a way that the default data will break existing logical assumptions (thus requiring a data migration). Such upgrades should always happen in a compatible way (except for major API version upgrades -- see the "API Version" section above).
+
+Three notes:
+
+1. Some proto versions correspond to **groups** of substructures (such as SubtitledHtml, or other language-based substructures), because these substructures are shared across high-level structures.
+2. There is no need to version interactions separately. This is because their structure and how they relate to the exploration/question experience is implied as part of State's structure version.
+3. If any changes happen in the proto structure which are getting tracked, the version specified in the comment must be incremented.
+
+The following are the list of structure types whose versions are tracked:
+- TopicSummaryProtoVersion
+- RevisionCardProtoVersion
+- ConceptCardProtoVersion
+- ExplorationProtoVersion
+- QuestionProtoVersion
+- StateProtoVersion
+- LanguageProtosVersion
+- ImageProtoVersion
+
+## Support
+If you have any feature requests or bug reports, please log them on our [issue tracker](https://github.com/oppia/oppia-proto-api/issues/new?title=Describe%20your%20feature%20request%20or%20bug%20report%20succinctly&body=If%20you%27d%20like%20to%20propose%20a%20feature,%20describe%20what%20you%27d%20like%20to%20see.%0A%0AIf%20you%27re%20reporting%20a%20bug,%20please%20be%20sure%20to%20include%20the%20expected%20behaviour,%20the%20observed%20behaviour,%20and%20steps%20to%20reproduce%20the%20problem.%20Console%20copy-pastes%20and%20any%20background%20on%20the%20environment%20would%20also%20be%20helpful.%0A%0AThanks!).
+
+Please report security issues directly to [email protected].
+
+## Licence
+The Oppia-Proto-API code is released under the [Apache v2 license](https://github.com/oppia/oppia-proto-api/blob/master/LICENSE).

WORKSPACE

@@ -0,0 +1,60 @@
+"""
+This file lists and imports all external dependencies needed to build Oppia Proto API.
+"""
+
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+# Set up Python (as a prerequisite dependency for Protobuf).
+
+PYTHON_SHA256_HASH = "934c9ceb552e84577b0faf1e5a2f0450314985b4d8712b2b70717dc679fdc01b"
+PYTHON_VERSION = "0.3.0"
+
+http_archive(
+    name = "rules_python",
+    url = "https://github.com/bazelbuild/rules_python/releases/download/{0}/rules_python-{0}.tar.gz".format(PYTHON_VERSION),
+    sha256 = PYTHON_SHA256_HASH,
+)
+
+# Set up proto & its toolchain.
+
+PROTOBUF_SHA256_HASH = "c6003e1d2e7fefa78a3039f19f383b4f3a61e81be8c19356f85b6461998ad3db"
+PROTOBUF_VERSION = "3.17.3"
+
+http_archive(
+    name = "com_google_protobuf",
+    sha256 = PROTOBUF_SHA256_HASH,
+    strip_prefix = "protobuf-%s" % PROTOBUF_VERSION,
+    urls = ["https://github.com/protocolbuffers/protobuf/archive/v%s.tar.gz" % PROTOBUF_VERSION]
+)
+
+# Set up rules_proto to allow defining proto libraries.
+
+# Note that rules_proto doesn't have any shipped versions, so the workspace needs to pin to a
+# specific commit hash.
+RULES_PROTO_VERSION = "97d8af4dc474595af3900dd85cb3a29ad28cc313"
+RULES_PROTO_SHA256_HASH = "602e7161d9195e50246177e7c55b2f39950a9cf7366f74ed5f22fd45750cd208"
+
+http_archive(
+    name = "rules_proto",
+    sha256 = RULES_PROTO_SHA256_HASH,
+    strip_prefix = "rules_proto-%s" % RULES_PROTO_VERSION,
+    urls = ["https://github.com/bazelbuild/rules_proto/archive/%s.tar.gz" % RULES_PROTO_VERSION],
+)
+
+load("@rules_proto//proto:repositories.bzl", "rules_proto_dependencies", "rules_proto_toolchains")
+rules_proto_dependencies()
+rules_proto_toolchains()
+
+# Set up rules_java to enable the Java proto & Java proto lite rules.
+RULES_JAVA_VERSION = "0.1.1"
+RULES_JAVA_SHA256_HASH = "220b87d8cfabd22d1c6d8e3cdb4249abd4c93dcc152e0667db061fb1b957ee68"
+
+http_archive(
+    name = "rules_java",
+    sha256 = RULES_JAVA_SHA256_HASH,
+    url = "https://github.com/bazelbuild/rules_java/releases/download/{0}/rules_java-{0}.tar.gz".format(RULES_JAVA_VERSION),
+)
+
+load("@rules_java//java:repositories.bzl", "rules_java_dependencies", "rules_java_toolchains")
+rules_java_dependencies()
+rules_java_toolchains()

proto/BUILD

@@ -0,0 +1,3 @@
+"""
+TODO: fill in
+"""

proto/v1/BUILD

@@ -0,0 +1,3 @@
+"""
+TODO: fill in
+"""

proto/v1/api/BUILD

@@ -0,0 +1,30 @@
+"""
+This library contains the proto_library(), java_lite_proto_library() and java_proto_library rules.
+The proto_library() rule creates a proto file library for the android API 
+proto file to be used in multiple languages. 
+The java_lite_proto_library() rule takes in a proto_library target and generates Java code.
+The java_proto_library() rule takes in a proto_library target and generates Java code.
+"""
+
+load("@rules_java//java:defs.bzl", "java_lite_proto_library", "java_proto_library")
+load("@rules_proto//proto:defs.bzl", "proto_library")
+
+proto_library(
+    name = "android_proto",
+    srcs = ["android.proto"],
+    deps = [
+      "//proto/v1/structure:structure_proto"
+    ],
+)
+
+java_proto_library(
+    name = "android_java_proto",
+    visibility = ["//:api_visibility"],
+    deps = [":android_proto"],
+)
+
+java_lite_proto_library(
+    name = "android_java_proto_lite",
+    visibility = ["//:api_visibility"],
+    deps = [":android_proto"],
+)

proto/v1/api/android.proto

@@ -0,0 +1,116 @@
+syntax = "proto3";
+
+package org.oppia.proto.v1.api;
+
+import "proto/v1/structure/concept_card.proto";
+import "proto/v1/structure/exploration.proto";
+import "proto/v1/structure/question.proto";
+import "proto/v1/structure/revision_card.proto";
+import "proto/v1/structure/topic_summary.proto";
+import "proto/v1/structure/versions.proto";
+
+option java_package = "org.oppia.proto.v1.api";
+option java_multiple_files = true;
+
+message TopicListRequest {
+  TopicListRequestResponseProtoVersion proto_version = 1;
+
+  ClientContext client_context = 2;
+  ClientCompatibilityContext compatibility_context = 3;
+  ClientDownloadStateContext download_context = 4;
+}
+
+message TopicListResponse {
+  TopicListRequestResponseProtoVersion proto_version = 1;
+
+  // All topic summaries that are newer & compatible with the client.
+  repeated org.oppia.proto.v1.structure.TopicSummary topic_summaries = 2;
+}
+
+message TopicContentRequest {
+  TopicContentRequestResponseProtoVersion proto_version = 1;
+
+  ClientContext client_context = 2;
+  repeated DownloadRequestStructureIdentifier identifiers = 3;
+  int32 requested_max_payload_size = 4;
+}
+
+message TopicContentResponse {
+  TopicContentRequestResponseProtoVersion proto_version = 1;
+
+  repeated DownloadResult download_results = 2;
+
+  // Structure corresponds to TopicContentRequestResponseProtoVersion.
+  message DownloadResult {
+    DownloadRequestStructureIdentifier identifier = 1;
+
+    oneof structure_type {
+      // Indicates that the request corresponding to this particular identifier was skipped
+      // and suggested to retry by the Oppia backend. Note that the presence of this value in the 
+      // oneof is sufficient to indicate its state, and its actual value does not matter.
+      bool skipped = 2;
+      org.oppia.proto.v1.structure.RevisionCard revision_card = 3;
+      org.oppia.proto.v1.structure.ConceptCard concept_card = 4;
+      org.oppia.proto.v1.structure.Exploration exploration = 5;
+      QuestionIdList question_id_list = 6;
+      org.oppia.proto.v1.structure.Question question = 7;
+    }
+  }
+
+  // Structure corresponds to TopicContentRequestResponseProtoVersion.
+  message QuestionIdList {
+    repeated string question_ids = 1;
+  }
+}
+
+message ClientContext {
+  string version_name = 1;
+  int64 version_code = 2;
+}
+
+message ClientCompatibilityContext {
+  org.oppia.proto.v1.structure.TopicSummaryProtoVersion topic_summary_proto_version = 1;
+  org.oppia.proto.v1.structure.RevisionCardProtoVersion revision_card_proto_version = 2;
+  org.oppia.proto.v1.structure.ConceptCardProtoVersion concept_card_proto_version = 3;
+  org.oppia.proto.v1.structure.ExplorationProtoVersion exploration_proto_version = 4;
+  org.oppia.proto.v1.structure.QuestionProtoVersion question_proto_version = 5;
+  org.oppia.proto.v1.structure.StateProtoVersion state_proto_version = 6;
+  org.oppia.proto.v1.structure.LanguageProtosVersion language_proto_version = 7;
+  org.oppia.proto.v1.structure.ImageProtoVersion thumbnail_proto_version = 8;
+}
+
+message ClientDownloadStateContext {
+  message DownloadState {
+    int32 content_version = 1;
+    oneof structure_type {
+      string topic_id = 2;
+      org.oppia.proto.v1.structure.SubtopicId revision_card_id = 3;
+      string concept_card_id = 4;
+      string story_id = 5; 
+      string exploration_id = 6; 
+      string question_id = 7;
+      string skill_id = 8;
+    }
+  }
+
+  repeated DownloadState current_downloads = 1;
+}
+
+// This structure's version corresponds to TopicContentRequestResponseProtoVersion.
+message DownloadRequestStructureIdentifier {
+  oneof structure_type {
+    org.oppia.proto.v1.structure.SubtopicId revision_card_id = 1;
+    string concept_card_id = 2;
+    string exploration_id = 3;
+    string question_list_skill_id = 4;
+    string question_id = 5;
+  }
+}
+
+message TopicListRequestResponseProtoVersion {
+  int32 version = 1;
+}
+
+message TopicContentRequestResponseProtoVersion {
+  int32 version = 1;
+}

proto/v1/structure/BUILD

@@ -0,0 +1,38 @@
+"""
+This library contains the proto_library(), java_lite_proto_library() and java_proto_library rules.
+The proto_library() rule creates a proto file library for the core proto files to be used in multiple languages. 
+The java_lite_proto_library() rule takes in a proto_library target and generates Java code.
+The java_proto_library() rule takes in a proto_library target and generate Java code.
+"""
+
+load("@rules_java//java:defs.bzl", "java_lite_proto_library", "java_proto_library")
+load("@rules_proto//proto:defs.bzl", "proto_library")
+
+proto_library(
+    name = "structure_proto",
+    srcs = [
+        "concept_card.proto",
+        "exploration.proto",
+        "image.proto",
+        "languages.proto",
+        "objects.proto",
+        "question.proto",
+        "revision_card.proto",
+        "state.proto",
+        "topic_summary.proto",
+        "versions.proto",
+    ],
+    visibility = ["//:proto_impl_visibility"],
+)
+
+java_proto_library(
+    name = "structure_java_proto",
+    visibility = ["//:api_visibility"],
+    deps = [":structure_proto"],
+)
+
+java_lite_proto_library(
+    name = "structure_java_proto_lite",
+    visibility = ["//:api_visibility"],
+    deps = [":structure_proto"],
+)

proto/v1/structure/concept_card.proto

@@ -0,0 +1,49 @@
+syntax = "proto3";
+
+package org.oppia.proto.v1.structure;
+
+import "proto/v1/structure/image.proto";
+import "proto/v1/structure/languages.proto";
+import "proto/v1/structure/versions.proto";
+
+option java_package = "org.oppia.proto.v1.structure";
+option java_multiple_files = true;
+
+// NOTE: Update ConceptCardProtoVersion if the structure of this proto is modified. The current
+// version is 1.
+// Proto of a single concept card that can be displayed for a specific skill.
+message ConceptCard {
+  ConceptCardProtoVersion proto_version = 1;
+
+  // The ID corresponding to the skill this concept is representing.
+  string skill_id = 2;
+
+  //A human-readable description for the skill.
+  string description = 3;
+
+  // The explanation of the skill that is shown in the concept card.
+  SubtitledHtml explanation = 4;
+
+  // A list of worked examples to present to the learner.
+  repeated WorkedExample worked_examples = 5;
+
+  // The recorded audio to play SubtitledHTML subfields of this concept card. 
+  RecordedVoiceovers recorded_voiceovers = 6;
+
+  // The translations of SubtitledHTML subfields of this concept card.
+  WrittenTranslations written_translations = 7;
+
+  // The list of all images that are included within SubtitledHTML and WorkedExample 
+  // subfields of this concept card.
+  ReferencedImageList referenced_image_list = 8;
+
+  // The worked example is an example of question and answer shown in a concept card.
+  message WorkedExample {
+
+    // The question for this worked example.
+    SubtitledHtml question = 1;
+
+    // The explanation for how to solve this worked example.
+    SubtitledHtml explanation = 2;
+  }
+}