#!/bin/bash

# Copyright 2015 The Kubernetes 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
#
# 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.

# Checkout a PR from GitHub. (Yes, this is sitting in a Git tree. How
# meta.) Assumes you care about pulls from remote "upstream" and
# checks them out to a branch named:
# automated-cherry-pick-of-<pr>-<target branch>-<timestamp>

set -o errexit
set -o nounset
set -o pipefail

declare -r REPO_ROOT="$(git rev-parse --show-toplevel)"
cd "${REPO_ROOT}"

declare -r STARTINGBRANCH=$(git symbolic-ref --short HEAD)
declare -r REBASEMAGIC="${REPO_ROOT}/.git/rebase-apply"
DRY_RUN=${DRY_RUN:-""}
UPSTREAM_REMOTE=${UPSTREAM_REMOTE:-upstream}
FORK_REMOTE=${FORK_REMOTE:-origin}
MAIN_REPO_NAME=${MAIN_REPO_NAME:-"python"}
MAIN_REPO_ORG=${MAIN_REPO_ORG:-"kubernetes-client"}

if [[ -z ${GITHUB_USER:-} ]]; then
echo "Please export GITHUB_USER=<your-user> (or GH organization, if that's where your fork lives)"
 exit 1
fi

if ! which hub > /dev/null; then
echo "Can't find 'hub' tool in PATH, please install from https://github.com/github/hub"
 exit 1
fi

if [[ "$#" -lt 2 ]]; then
echo "${0} <remote branch> <pr-number>...: cherry pick one or more <pr> onto <remote branch> and leave instructions for proposing pull request"
 echo
 echo " Checks out <remote branch> and handles the cherry-pick of <pr> (possibly multiple) for you."
 echo " Examples:"
 echo " 0ドル upstream/release-3.14 12345 # Cherry-picks PR 12345 onto upstream/release-3.14 and proposes that as a PR."
 echo " 0ドル upstream/release-3.14 12345 56789 # Cherry-picks PR 12345, then 56789 and proposes the combination as a single PR."
 echo
 echo " Set the DRY_RUN environment var to skip git push and creating PR."
 echo " This is useful for creating patches to a release branch without making a PR."
 echo " When DRY_RUN is set the script will leave you in a branch containing the commits you cherry-picked."
 echo
 echo " Set UPSTREAM_REMOTE (default: upstream) and FORK_REMOTE (default: origin)"
 echo " To override the default remote names to what you have locally."
 exit 2
fi

if git_status=$(git status --porcelain --untracked=no 2>/dev/null) && [[ -n "${git_status}" ]]; then
echo "!!! Dirty tree. Clean up and try again."
 exit 1
fi

if [[ -e "${REBASEMAGIC}" ]]; then
echo "!!! 'git rebase' or 'git am' in progress. Clean up and try again."
 exit 1
fi

declare -r BRANCH="1ドル"
shift 1
declare -r PULLS=( "$@" )

function join { local IFS="1ドル"; shift; echo "$*"; }
declare -r PULLDASH=$(join - "${PULLS[@]/#/#}") # Generates something like "#12345-#56789"
declare -r PULLSUBJ=$(join " " "${PULLS[@]/#/#}") # Generates something like "#12345 #56789"

echo "+++ Updating remotes..."
git remote update "${UPSTREAM_REMOTE}" "${FORK_REMOTE}"

if ! git log -n1 --format=%H "${BRANCH}" >/dev/null 2>&1; then
echo "!!! '${BRANCH}' not found. The second argument should be something like ${UPSTREAM_REMOTE}/release-0.21."
 echo " (In particular, it needs to be a valid, existing remote branch that I can 'git checkout'.)"
 exit 1
fi

declare -r NEWBRANCHREQ="automated-cherry-pick-of-${PULLDASH}" # "Required" portion for tools.
declare -r NEWBRANCH="$(echo "${NEWBRANCHREQ}-${BRANCH}" | sed 's/\//-/g')"
declare -r NEWBRANCHUNIQ="${NEWBRANCH}-$(date +%s)"
echo "+++ Creating local branch ${NEWBRANCHUNIQ}"

cleanbranch=""
prtext=""
gitamcleanup=false
function return_to_kansas {
 if [[ "${gitamcleanup}" == "true" ]]; then
echo
 echo "+++ Aborting in-progress git am."
 git am --abort >/dev/null 2>&1 || true
fi

 # return to the starting branch and delete the PR text file
 if [[ -z "${DRY_RUN}" ]]; then
echo
 echo "+++ Returning you to the ${STARTINGBRANCH} branch and cleaning up."
 git checkout -f "${STARTINGBRANCH}" >/dev/null 2>&1 || true
if [[ -n "${cleanbranch}" ]]; then
git branch -D "${cleanbranch}" >/dev/null 2>&1 || true
fi
 if [[ -n "${prtext}" ]]; then
rm "${prtext}"
 fi
 fi
}
trap return_to_kansas EXIT

SUBJECTS=()
function make-a-pr() {
 local rel="$(basename "${BRANCH}")"
 echo
 echo "+++ Creating a pull request on GitHub at ${GITHUB_USER}:${NEWBRANCH}"

 # This looks like an unnecessary use of a tmpfile, but it avoids
 # https://github.com/github/hub/issues/976 Otherwise stdin is stolen
 # when we shove the heredoc at hub directly, tickling the ioctl
 # crash.
 prtext="$(mktemp -t prtext.XXXX)" # cleaned in return_to_kansas
 cat >"${prtext}" <<EOF
Automated cherry pick of ${PULLSUBJ}

Cherry pick of ${PULLSUBJ} on ${rel}.

$(printf '%s\n' "${SUBJECTS[@]}")
EOF

hub pull-request -F "${prtext}" -h "${GITHUB_USER}:${NEWBRANCH}" -b "${MAIN_REPO_ORG}:${rel}"
}

git checkout -b "${NEWBRANCHUNIQ}" "${BRANCH}"
cleanbranch="${NEWBRANCHUNIQ}"

gitamcleanup=true
for pull in "${PULLS[@]}"; do
echo "+++ Downloading patch to /tmp/${pull}.patch (in case you need to do this again)"

 curl -o "/tmp/${pull}.patch" -sSL "https://github.com/${MAIN_REPO_ORG}/${MAIN_REPO_NAME}/pull/${pull}.patch"
 echo
 echo "+++ About to attempt cherry pick of PR. To reattempt:"
 echo " $ git am -3 /tmp/${pull}.patch"
 echo
git am -3 "/tmp/${pull}.patch" || {
 conflicts=false
while unmerged=$(git status --porcelain | grep ^U) && [[ -n ${unmerged} ]] \
 || [[ -e "${REBASEMAGIC}" ]]; do
conflicts=true # <-- We should have detected conflicts once
 echo
 echo "+++ Conflicts detected:"
 echo
 (git status --porcelain | grep ^U) || echo "!!! None. Did you git am --continue?"
 echo
 echo "+++ Please resolve the conflicts in another window (and remember to 'git add / git am --continue')"
 read -p "+++ Proceed (anything but 'y' aborts the cherry-pick)? [y/n] " -r
 echo
if ! [[ "${REPLY}" =~ ^[yY]$ ]]; then
echo "Aborting." >&2
 exit 1
 fi
 done

 if [[ "${conflicts}" != "true" ]]; then
echo "!!! git am failed, likely because of an in-progress 'git am' or 'git rebase'"
 exit 1
 fi
 }

 # set the subject
 subject=$(grep -m 1 "^Subject" "/tmp/${pull}.patch" | sed -e 's/Subject: \[PATCH//g' | sed 's/.*] //')
 SUBJECTS+=("#${pull}: ${subject}")

 # remove the patch file from /tmp
 rm -f "/tmp/${pull}.patch"
done
gitamcleanup=false

if [[ -n "${DRY_RUN}" ]]; then
echo "!!! Skipping git push and PR creation because you set DRY_RUN."
 echo "To return to the branch you were in when you invoked this script:"
 echo
 echo " git checkout ${STARTINGBRANCH}"
 echo
 echo "To delete this branch:"
 echo
 echo " git branch -D ${NEWBRANCHUNIQ}"
 exit 0
fi

if git remote -v | grep ^${FORK_REMOTE} | grep {$MAIN_REPO_ORG}/{$MAIN_REPO_NAME}.git; then
echo "!!! You have ${FORK_REMOTE} configured as your {$MAIN_REPO_ORG}/{$MAIN_REPO_NAME}.git"
 echo "This isn't normal. Leaving you with push instructions:"
 echo
 echo "+++ First manually push the branch this script created:"
 echo
 echo " git push REMOTE ${NEWBRANCHUNIQ}:${NEWBRANCH}"
 echo
 echo "where REMOTE is your personal fork (maybe ${UPSTREAM_REMOTE}? Consider swapping those.)."
 echo "OR consider setting UPSTREAM_REMOTE and FORK_REMOTE to different values."
 echo
make-a-pr
 cleanbranch=""
 exit 0
fi

echo
echo "+++ I'm about to do the following to push to GitHub (and I'm assuming ${FORK_REMOTE} is your personal fork):"
echo
echo " git push ${FORK_REMOTE}${NEWBRANCHUNIQ}:${NEWBRANCH}"
echo
read -p "+++ Proceed (anything but 'y' aborts the cherry-pick)? [y/n] " -r
if ! [[ "${REPLY}" =~ ^[yY]$ ]]; then
echo "Aborting." >&2
 exit 1
fi

git push "${FORK_REMOTE}" -f "${NEWBRANCHUNIQ}:${NEWBRANCH}"
make-a-pr