#!/usr/bin/env bash

# https://www.tldp.org/LDP/abs/html/options.html#AEN19601
# https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html
set -u -e -E -o pipefail

BOLD='printf \e[1m'
RESET_STYLES='printf \e[0m'
LIGHT_CYAN='printf \e[96m'
LIGHT_MAGENTA='printf \e[95m'
GREEN='printf \e[32m'
RED='printf \e[31m'

BASEDIR=$(dirname "$0")
BASEDIR=`(cd $BASEDIR; pwd)`

PR_NUMBER=0
PUSH_UPSTREAM=1
FORCE=0
while [[ $# -gt 0 ]]
do
  key="$1"

  case $key in
      --dryrun)
      PUSH_UPSTREAM=0
      shift # past argument
      ;;
      --force)
      FORCE=1
      shift # past argument
      ;;
      *)    # unknown option
      PR_NUMBER="$1" # save it in an array for later
      shift # past argument
      ;;
  esac
done

if [ "$PR_NUMBER" -eq 0 ]; then
  echo "Merge github PR into the target branches if status is green"
  echo
  echo "$0 PR_NUMBER [--dryrun] [--force]"
  echo
  echo    --dryrun   Performs all operations but does not push the merge back to git@github.com:angular/angular.git.
  echo    --force    Continues even if PR status is not green.
  exit 0
fi

if [ -z ${TOKEN:-''} ]; then
    $RED
    echo "############################################################"
    echo "############################################################"
    echo "WARNING: you should set the TOKEN variable to a github token"
    echo "############################################################"
    echo "############################################################"
    $RESET_STYLES
    GH_AUTH=""
else
    GH_AUTH="Authorization: token $TOKEN"
fi

PULL_JSON=`curl -H "$GH_AUTH" -s https://api.github.com/repos/angular/angular/pulls/$PR_NUMBER`
PR_SHA_COUNT=`node $BASEDIR/utils/json_extract.js commits <<< """$PULL_JSON"""`
STATUS_JSON_URL=`node $BASEDIR/utils/json_extract.js _links.statuses.href <<< """$PULL_JSON"""`
STATUS=`curl -H "$GH_AUTH" -s $STATUS_JSON_URL | node $BASEDIR/utils/json_extract.js description | cut -d '|' -f1`
PR_LABELS=`curl -H "$GH_AUTH" -s https://api.github.com/repos/angular/angular/issues/$PR_NUMBER/labels`
PR_ACTION=`echo "$PR_LABELS" | node $BASEDIR/utils/json_extract.js "name=^PR action:"`
PR_TARGET=`echo "$PR_LABELS"  | node $BASEDIR/utils/json_extract.js "name=^PR target:"`
PR_CLA=`echo "$PR_LABELS"  | node $BASEDIR/utils/json_extract.js "name=^cla"`
MASTER_BRANCH='master'

if [[ ! "$PR_ACTION" =~ "PR action: merge" ]]; then
  $RED
  echo The PR is missing 'PR action: merge(-assistance)' label, found: $PR_ACTION
  $RESET_STYLES
  exit 1
fi

if [[ "$PR_CLA" != "cla: yes" ]]; then
  $RED
  echo The PR is missing 'cla: Yes' label, found: $PR_CLA
  $RESET_STYLES
  exit 1
fi

if [[ "$STATUS" != "All checks passed!" ]]; then
  echo PR $PR_NUMBER is failing with: $STATUS
  if [[ $FORCE == 1 ]]; then
    $BOLD
    $LIGHT_MAGENTA
    echo FORCING: --force flag used to ignore PR status.
    $RESET_STYLES
  else
    echo Exiting...
    exit 1
  fi
fi

if [[ $PR_TARGET == "PR target: master & patch" ]]; then
  MERGE_MASTER=1
  MERGE_PATCH=1
elif [[ $PR_TARGET == "PR target: master-only" ]]; then
  MERGE_MASTER=1
  MERGE_PATCH=0
elif [[ $PR_TARGET == "PR target: patch-only" ]]; then
  MERGE_MASTER=0
  MERGE_PATCH=1
else
  $RED
  echo "Unknown PR target format: $PR_TARGET"
  $RESET_STYLES
  exit 1;
fi

CURRENT_BRANCH=`git rev-parse --abbrev-ref HEAD`
PATCH_BRANCH=`git ls-remote --heads  git@github.com:angular/angular.git | grep -E 'refs\/heads\/[0-9]+\.[0-9]+\.x' | cut -d '/' -f3 | sort -r | head -n1`

CHECKOUT_MASTER="git checkout merge_pr_master"
CHECKOUT_PATCH="git checkout merge_pr_patch"
RESTORE_BRANCH="git checkout $CURRENT_BRANCH"

FETCH_PR="git fetch git@github.com:angular/angular.git pull/$PR_NUMBER/head:merge_pr heads/$MASTER_BRANCH:merge_pr_master heads/$PATCH_BRANCH:merge_pr_patch -f"
BASE_PR="git checkout merge_pr~$PR_SHA_COUNT -B merge_pr_base"
SQUASH_PR="git rebase --autosquash --interactive merge_pr_base merge_pr"
REWRITE_MESSAGE="git filter-branch -f --msg-filter \"$BASEDIR/utils/github_closes.js $PR_NUMBER\" merge_pr_base..merge_pr"
PUSH_BRANCHES="git push git@github.com:angular/angular.git merge_pr_master:$MASTER_BRANCH merge_pr_patch:$PATCH_BRANCH"
CHERRY_PICK_PR="git cherry-pick merge_pr_base..merge_pr"

# Checks that each PR branch to be merged upstream contains SHAs of commits that significantly changed our CI infrastructure.
#
# This check is used to enforce that we don't merge PRs that have not been rebased recently and could result in merging
# of non-approved or otherwise bad changes.
REQUIRED_BASE_SHA_MASTER="a03a9236f2aed5d00012d25f032aa43a046d91da" # pullapprove => CODEOWNERS migration
REQUIRED_BASE_SHA_PATCH="a03a9236f2aed5d00012d25f032aa43a046d91da"  # pullapprove => CODEOWNERS migration
if [[ $MERGE_MASTER == 1 ]]; then
  REQUIRED_BASE_SHA="$REQUIRED_BASE_SHA_MASTER"
# check patch only if patch-only PR
elif [[ $MERGE_PATCH == 1 ]]; then
  REQUIRED_BASE_SHA="$REQUIRED_BASE_SHA_PATCH"
fi
CHECK_IF_PR_REBASED="git branch --quiet merge_pr --contains $REQUIRED_BASE_SHA"

$BOLD
$LIGHT_CYAN
echo "======================"
echo "GitHub Merge PR Steps"
echo "======================"
echo "   $FETCH_PR"
echo "   $BASE_PR"
echo "   $CHECK_IF_PR_REBASED"
echo "   $SQUASH_PR"
echo "   $REWRITE_MESSAGE"
if [[ $MERGE_MASTER == 1 ]]; then
  echo "   $CHECKOUT_MASTER && $CHERRY_PICK_PR"
fi
if [[ $MERGE_PATCH == 1 ]]; then
  echo "   $CHECKOUT_PATCH && $CHERRY_PICK_PR"
fi
echo "   $PUSH_BRANCHES"
echo "   $RESTORE_BRANCH"
echo "----------------------"
$RESET_STYLES
$BOLD
echo ""
echo ">>> Fetch PR: $FETCH_PR"
$RESET_STYLES
$FETCH_PR
$BOLD
echo ""
echo ">>> Mark base: $BASE_PR"
$RESET_STYLES
$BASE_PR
$BOLD
echo ""
echo ">>> Check if PR rebased: $CHECK_IF_PR_REBASED"
$RESET_STYLES
if [[ $($CHECK_IF_PR_REBASED) != "" ]]; then
  $GREEN
  echo "The PR is sufficiently rebased!"
  $RESET_STYLES
else
  $RED
  echo ""
  echo ""
  echo "Failed to merge pull request #${PR_NUMBER} because it hasn't been rebased recently and could be bypassing new or updated CI checks!"
  echo ""
  echo "Please rebase the PR and try again."
  echo ""|
  $RESET_STYLES
  $RESTORE_BRANCH
  exit 1
fi
$BOLD
echo ""
echo ">>> Autosquash: $SQUASH_PR"
$RESET_STYLES
GIT_EDITOR=echo $SQUASH_PR
$BOLD
echo ""
echo ">>> Rewrite message: $REWRITE_MESSAGE"
# Next line should work, but it errors, hence copy paste the command.
# $REWRITE_MESSAGE
$RESET_STYLES
git filter-branch -f --msg-filter "$BASEDIR/utils/github_closes.js $PR_NUMBER" merge_pr_base..merge_pr
if [[ $MERGE_MASTER == 1 ]]; then
  $BOLD
  echo
  echo ">>> Cherry pick to master: $CHECKOUT_MASTER && $CHERRY_PICK_PR"
  $RESET_STYLES
  $CHECKOUT_MASTER
  $CHERRY_PICK_PR
fi
if [[ $MERGE_PATCH == 1 ]]; then
  $BOLD
  echo
  echo ">>> Cherry pick to patch: $CHECKOUT_PATCH && $CHERRY_PICK_PR"
  $RESET_STYLES
  $CHECKOUT_PATCH
  $CHERRY_PICK_PR
fi
$RESTORE_BRANCH

if [[ $PUSH_UPSTREAM == 1 ]]; then
  $BOLD
  echo
  echo ">>> Push branches to angular repo"
  $RESET_STYLES
  $PUSH_BRANCHES
fi
$BOLD
$GREEN
echo
echo ">>>>>> SUCCESS <<<<<< PR#$PR_NUMBER merged."
$RESET_STYLES