#!/usr/bin/env bash
#
# prune-pick.sh automates cherry-picking commits that should be modified to omit the presence of a
# given directory.

if [ -n "$VERBOSE" ]; then
  set -x
fi
set -eo pipefail

function usage() {
  echo "Usage:   ./cherry-pick.sh <commit-range> <prune-dir>"
  echo "Example: ./cherry-pick.sh 9819020b..3e91245c ./enterprise"
  echo 'Debug:   Set VERBOSE=1'
}

function pickOne() {
  set +e
  COMMIT=$1
  PRUNE_DIR=$2
  if [ -z "$COMMIT" ] || [ -z "$PRUNE_DIR" ]; then
    echo "Unexpected error" 1>&2
    exit 1
  fi

  if (git cherry-pick "$COMMIT" &>/dev/null); then
    set -e
    PRUNE_DIR_EXISTED=$(
      test -d "$PRUNE_DIR"
      echo $?
    )

    # clean cherry-pick
    rm -rf "$PRUNE_DIR" && (git add "$PRUNE_DIR" 2>/dev/null || true)
    git commit --amend --no-edit --allow-empty 1>/dev/null
    if [ -z "$(git diff HEAD^..HEAD)" ]; then
      git reset --hard HEAD^ &>/dev/null
      echo "$COMMIT omit (empty after removing $PRUNE_DIR/)"
    else
      if [ "$PRUNE_DIR_EXISTED" = "0" ]; then
        echo "$COMMIT cherry-pick + remove $PRUNE_DIR/"
      else
        echo "$COMMIT cherry-pick"
      fi
    fi
  else
    set -e
    # dirty cherry-pick
    rm -rf "$PRUNE_DIR" && (git add "$PRUNE_DIR" 2>/dev/null || true)
    #
    # Ignoring https://github.com/koalaman/shellcheck/wiki/SC2143 because "pipefail" option is set above.
    #
    # shellcheck disable=SC2143
    if [ -n "$(git status --porcelain | grep -v '^M')" ]; then
      echo "Failed to cherry-pick commit $COMMIT. This script is aborting and leaving the working directory in an intermediate state."
      echo 'You must either "git cherry-pick --abort" OR manually resolve the conflict and run "git cherry-pick --continue".'
      exit 1
    fi
    set +e
    if ! (git -c core.editor=true cherry-pick --continue &>/dev/null); then
      set -e
      #
      # Ignoring https://github.com/koalaman/shellcheck/wiki/SC2143 because "pipefail" option is set above.
      #
      # shellcheck disable=SC2143
      if [ -z "$(git status --porcelain | grep -v '^M')" ]; then
        git -c core.editor=true commit --allow-empty
        git reset --hard HEAD^ &>/dev/null
      fi
    fi
    set -e

    echo "$COMMIT cherry-pick, removed $PRUNE_DIR/"
  fi
}

COMMIT_RANGE=$1
PRUNE_DIR=$2
if [ -z "$COMMIT_RANGE" ] || [ -z "$PRUNE_DIR" ]; then
  usage
  exit 1
fi

COMMITS="$COMMIT_RANGE"
if [[ "$COMMIT_RANGE" == *".."* ]]; then
  COMMITS=$(git rev-list --reverse "$COMMIT_RANGE")
fi

set -e

# cc @beyang - what are the possible values of
# $COMMIT_RANGE ?
# shellcheck disable=SC2116
for rev in $(echo "$COMMITS"); do
  pickOne "$rev" "$PRUNE_DIR"
done