feat: initialize the generator

README.md

@@ -1,3 +1,17 @@
 # Google CloudEvents – Java
 
 This repository contains types for CloudEvents issued by Google.
+
+## Prerequisites
+
+- Java 7 (or higher)
+
+## Generate
+
+Generate libraries:
+
+```sh
+./gen.sh
+```
+
+Observe the new files in `src/`.

gen.sh

@@ -0,0 +1,67 @@
+#!/bin/bash
+# Script to generate the Protobuf classes from googleapis/google-cloudevents
+set -e
+
+echo "~ START"
+PROTOBUF_VERSION=3.12.3
+
+# protoc is a native application, so we need to download different zip files
+# and use different binaries depending on the OS.
+echo "- Determining OS type"
+case "$OSTYPE" in
+  darwin*)
+    PROTOBUF_PLATFORM=osx-x86_64
+    PROTOC=tmp/protobuf/bin/protoc
+    ;;
+  linux*)
+    PROTOBUF_PLATFORM=linux-x64_64
+    PROTOC=tmp/protobuf/bin/protoc
+    ;;
+  win* | msys* | cygwin*)
+    PROTOBUF_PLATFORM=win64
+    PROTOC=tmp/protobuf/bin/protoc.exe
+    ;;
+  *)
+    echo "Unknown OSTYPE: $OSTYPE"
+    exit 1
+esac
+
+echo "- Cloning github.com/googleapis/google-cloudevents into tmp"
+# For the moment, just clone google-cloudevents. Later we might make
+# it a submodule. We clone quietly, and only with a depth of 1
+# as we don't need history.
+rm -rf tmp
+mkdir -p tmp
+git clone https://github.com/googleapis/google-cloudevents tmp/google-cloudevents -q --depth 1
+
+# We download a specific version rather than using package managers
+# for portability and being able to rely on the version being available
+# as soon as it's released on GitHub.
+echo "- Downloading protobuf tools"
+cd tmp
+curl -sSL \
+  https://github.com/protocolbuffers/protobuf/releases/download/v$PROTOBUF_VERSION/protoc-$PROTOBUF_VERSION-$PROTOBUF_PLATFORM.zip \
+  --output protobuf.zip
+(mkdir -p protobuf && cd protobuf && unzip -q ../protobuf.zip)
+cd ..
+chmod +x $PROTOC
+
+echo "- Generating src/ from scratch"
+
+# First delete any previously-generated files if present
+rm -rf src 2>/dev/null
+mkdir src
+
+# Generate using protoc
+$PROTOC \
+  --java_out=src/ \
+  -I tmp/protobuf/include \
+  -I tmp/google-cloudevents/third_party/googleapis \
+  -I tmp/google-cloudevents/proto \
+  $(find tmp/google-cloudevents/proto -name data.proto)
+
+# Delete temp directory
+echo "- Removing tmp/"
+rm -rf tmp
+
+echo "~ DONE ✓"