#!/usr/bin/env bash

set -eou pipefail

help() {
    echo "Sync merge commits from bitcoin-core/secp256k1 into secp256k1-zkp."
    echo
    echo "Usage:"
    echo "  $0 [-b <branch>] range [end]"
    echo "      Merges every merge commit present in upstream/master and missing in <branch>"
    echo "      (default: master). If the optional [end] commit is provided, only merges"
    echo "      up to and including [end]."
    echo
    echo "  $0 [-b <branch>] select <commit> ... <commit>"
    echo "      Merges every selected merge commit into <branch> (default: master)."
    echo
    echo "This tool creates a temporary branch and attempts to merge the upstream commits."
    echo "If there are merge conflicts, resolve them and run tests, then use the generated"
    echo "script contrib/gh-pr-create.sh to create the PR (requires the gh tool)."
    echo
    echo "Setup:"
    echo "  Requires a remote named 'upstream' pointing to bitcoin-core/secp256k1."
    echo "  The script will fetch it automatically, and offer to create it if missing."
    echo "  To add manually: git remote add upstream git@github.com:bitcoin-core/secp256k1.git"
    echo
    echo "Listing upstream merge commits:"
    echo "  To list merge commits in upstream/master that are missing from <branch> (oldest first):"
    echo "    git log --oneline --merges \$(git merge-base upstream/master <branch>)..upstream/master | tac"
    echo "  Use these for [end] in 'range' or as arguments to 'select'."
    exit 1
}

REMOTE=upstream
REMOTE_BRANCH="$REMOTE/master"
LOCAL_BRANCH="master"
# Makes sure you have a remote "upstream" that is up-to-date
setup() {
    ret=0
    git fetch "$REMOTE" &> /dev/null || ret="$?"
    if [ ${ret} == 0 ]; then
        return
    fi
    echo "Adding remote \"$REMOTE\" with URL git@github.com:bitcoin-core/secp256k1.git. Continue with y"
    read -r yn
    case $yn in
        [Yy]* ) ;;
        * ) exit 1;;
    esac
    git remote add "$REMOTE" git@github.com:bitcoin-core/secp256k1.git &> /dev/null
    git fetch "$REMOTE" &> /dev/null
}

range() {
    RANGESTART_COMMIT=$(git merge-base "$REMOTE_BRANCH" "$LOCAL_BRANCH")
    RANGEEND_COMMIT=$(git rev-parse "$REMOTE_BRANCH")
    if [ "$#" = 1 ]; then
        RANGEEND_COMMIT=$1
    fi

    COMMITS=$(git --no-pager log --oneline --merges "$RANGESTART_COMMIT".."$RANGEEND_COMMIT")
    COMMITS=$(echo "$COMMITS" | tac | awk '{ print $1 }' ORS=' ')
    echo "Merging $COMMITS. Continue with y"
    read -r yn
    case $yn in
        [Yy]* ) ;;
        * ) exit 1;;
    esac
}

# Process -b <branch> argument
while getopts "b:" opt; do
  case $opt in
    b)
      LOCAL_BRANCH=$OPTARG
      ;;
    \?)
      echo "Invalid option: -$OPTARG" >&2
      ;;
  esac
done

# Shift off the processed options
shift $((OPTIND -1))

if [ "$#" -lt 1 ]; then
    help
fi

case $1 in
    range)
        shift
        setup
        range "$@"
        REPRODUCE_COMMAND="$0 -b $LOCAL_BRANCH range $RANGEEND_COMMIT"
        ;;
    select)
        shift
        setup
        COMMITS=$*
        REPRODUCE_COMMAND="$0 -b $LOCAL_BRANCH select $@"
        ;;
    help)
        help
        ;;
    *)
        help
esac

TITLE="Upstream PRs"
BODY=""
for COMMIT in $COMMITS
do
    PRNUM=$(git log -1 "$COMMIT" --pretty=format:%s | sed s/'Merge \(bitcoin-core\/secp256k1\)\?#\([0-9]*\).*'/'\2'/)
    TITLE="$TITLE $PRNUM,"
    BODY=$(printf "%s\n%s" "$BODY" "$(git log -1 "$COMMIT" --pretty=format:%s | sed s/'Merge \(bitcoin-core\/secp256k1\)\?#\([0-9]*\)'/'[bitcoin-core\/secp256k1#\2]'/)")
done
# Remove trailing ","
TITLE=${TITLE%?}
BODY+=$(cat <<EOF


This PR can be recreated with \`$REPRODUCE_COMMAND\`.

Tips:
 * Use \`git show --remerge-diff <pr-branch>\` to show the conflict resolution in the merge commit.
 * Use \`git read-tree --reset -u <pr-branch>\` to replay these resolutions during the conflict resolution stage when recreating the PR branch locally.
   Be aware that this may discard your index as well as the uncommitted changes and untracked files in your worktree.
EOF
)

echo "-----------------------------------"
echo "$TITLE"
echo "-----------------------------------"
echo "$BODY"
echo "-----------------------------------"
# Create branch from PR commit and create PR
git checkout "$LOCAL_BRANCH"
git pull --autostash
git checkout -b temp-merge-"$PRNUM"

# Escape single quote
# ' -> '\''
quote() {
    local quoted=${1//\'/\'\\\'\'}
    printf "%s" "$quoted"
}
TITLE=$(quote "$TITLE")
BODY=$(quote "$BODY")

BASEDIR=$(dirname "$0")
FNAME="$BASEDIR/gh-pr-create.sh"
cat <<EOT > "$FNAME"
#!/bin/sh
gh pr create -t '$TITLE' -b '$BODY' --web
# Remove temporary branch
git checkout "$LOCAL_BRANCH"
git branch -D temp-merge-"$PRNUM"
EOT
chmod +x "$FNAME"
echo Run "$FNAME" after solving the merge conflicts

git merge --no-edit -m "Merge commits '$COMMITS' into temp-merge-$PRNUM" $COMMITS