#!/usr/bin/env bash
# Copyright 2019 The Wire Authors
#
# 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
#
#     https://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.

# This script checks to see if there are any incompatible API changes on the
# current branch relative to the upstream branch.
# It fails if it finds any, unless there is a commit with BREAKING_CHANGE_OK
# in the first line of the commit message.

# This script expects:
# a) to be run at the root of the repository
# b) HEAD is pointing to a commit that merges between the pull request and the
#    upstream branch (GITHUB_BASE_REF).

set -euo pipefail

UPSTREAM_BRANCH="${GITHUB_BASE_REF:-master}"
echo "Checking for incompatible API changes relative to ${UPSTREAM_BRANCH}..."

MASTER_CLONE_DIR="$(mktemp -d)"
PKGINFO_BRANCH=$(mktemp)
PKGINFO_MASTER=$(mktemp)

function cleanup() {
  rm -rf "$MASTER_CLONE_DIR"
  rm -f "$PKGINFO_BRANCH"
  rm -f "$PKGINFO_MASTER"
}
trap cleanup EXIT

# Install apidiff.
go install golang.org/x/exp/cmd/apidiff@latest

git clone -b "$UPSTREAM_BRANCH" . "$MASTER_CLONE_DIR" &> /dev/null

incompatible_change_pkgs=()
PKGS=$(cd "$MASTER_CLONE_DIR"; go list ./... | grep -v test | grep -v internal)
for pkg in $PKGS; do
  echo "  Testing ${pkg}..."

  # Compute export data for the current branch.
  package_deleted=0
  apidiff -w "$PKGINFO_BRANCH" "$pkg" || package_deleted=1
  if [[ $package_deleted -eq 1 ]]; then
    echo "  Package ${pkg} was deleted! Recording as an incompatible change.";
    incompatible_change_pkgs+=(${pkg});
    continue;
  fi

  # Compute export data for master@HEAD.
  (cd "$MASTER_CLONE_DIR"; apidiff -w "$PKGINFO_MASTER" "$pkg")

  # Print all changes for posterity.
  apidiff "$PKGINFO_MASTER" "$PKGINFO_BRANCH"

  # Note if there's an incompatible change.
  ic=$(apidiff -incompatible "$PKGINFO_MASTER" "$PKGINFO_BRANCH")
  if [ ! -z "$ic" ]; then
    incompatible_change_pkgs+=("$pkg");
  fi
done

if [ ${#incompatible_change_pkgs[@]} -eq 0 ]; then
  # No incompatible changes, we are good.
  echo "OK: No incompatible changes found."
  exit 0;
fi
echo "Found breaking API change(s) in: ${incompatible_change_pkgs[*]}."

# Found incompatible changes; see if they were declared as OK via a commit.
if git cherry -v master | grep -q "BREAKING_CHANGE_OK"; then
  echo "Allowing them due to a commit message with BREAKING_CHANGE_OK.";
  exit 0;
fi

echo "FAIL. If this is expected and OK, you can pass this check by adding a commit with BREAKING_CHANGE_OK in the first line of the message."
exit 1