#!/bin/bash

# Copyright 2023 Google Inc. All rights reserved.
#
# 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.

set -eu

main() {
    # Check if the last commit included changes to a .gn or .gni file, which need
    # to be reflected in a .patch
    if git diff --name-only HEAD~..HEAD | egrep -q '[.]gni?$'; then
        echo "INFO: changes to a .gn|.gni file detected."
    else
        # no patch needed
        exit 0
    fi

    # HACK: checking for the existence of rebase-merge may not always work as
    # expected.
    # TODO: find a better solution. One option is to parse `git status` output and
    # grep for the "rebase in progress" string.
    if [[ -d "$(git rev-parse --git-dir)/rebase-merge" ]]; then
        # interactive rebase in progress.
        echo "WARNING! .patch files are not updated during interactive rebase"
        exit 0
    fi

    # There is no flag to skip the post-commit hook (--no-verify only works for
    # pre-commit and commit-msg hooks). Briefly remove the executable
    # permission to prevent recursion.
    chmod -x .git/hooks/post-commit
    # Ensure chmod +x is always run, even when script exits early
    trap "chmod +x .git/hooks/post-commit" EXIT

    # Remove any existing .patch files from the commit
    local -r patches_dir="${ANDROID_BUILD_TOP}/external/cronet/patches"
    git reset HEAD~ -- "${patches_dir}/*.patch"
    git -c "advice.ignoredHook=false" commit --amend --no-edit

    # Create patch (which only reflects changes to .gn and .gni files).
    local -r number_of_patches=$(git ls-tree -r HEAD~ -- "${patches_dir}" | wc -l)
    local -r patch_name=$(git format-patch -1 -N --start-number "${number_of_patches}" -o "${patches_dir}" HEAD -- "*.gn" "*.gni")
    git add "${patch_name}"
    git -c "advice.ignoredHook=false" commit --amend --no-edit

    echo "INFO: a .patch file was added to your CL"
}

main "$@"; exit