#!/bin/bash

# Copyright 2017 The Bazel Authors. 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.


@@GENERATED_MESSAGE@@

set -euo pipefail

RUNNER_LABEL=@@RUNNER_LABEL@@
GAZELLE_SHORT_PATH=@@GAZELLE_SHORT_PATH@@
GAZELLE_LABEL=@@GAZELLE_LABEL@@
ARGS=@@ARGS@@

# find_repo_root prints the absolute path to the repository root. This is
# discovered by locating the WORKSPACE file in a parent directory, and
# deferencing symlinks. If no WORKSPACE file is found, this function prints
# an error and exits.
function find_repo_root {
  pushd . &>/dev/null
  while [ $(pwd) != / -a ! -f WORKSPACE ]; do
    cd ..
  done
  if [ ! -f WORKSPACE ]; then
    echo "error: could not find WORKSPACE file in any parent directory" >&2
    exit 1
  fi
  if [ "$is_bazel_run" = true ]; then
    dirname $(readlink WORKSPACE)
  else
    pwd
  fi
  popd &>/dev/null
}

# bazel_build_get_path builds a given target and prints the absolute path
# to the generated binary. This only works for rules that produce a single file.
function bazel_build_get_path {
  local build_log=$(mktemp gazelle_build.XXXX.json --tmpdir)
  bazel build --build_event_json_file="$build_log" "$1"
  grep "^{\"id\":{\"targetCompleted\":{\"label\":\"$1\"" "$build_log" | \
    sed -e 's!^.*file://\([^"]*\).*$!\1!'
  rm -f "$build_log"
}

# Check whether the script was executed by Bazel. The gazelle macro prepends
# an argument that tells us this.
is_bazel_run=false
if [ "${1-}" = "-bazel_run" ]; then
  is_bazel_run=true
  shift
fi

# If arguments were provided on the command line, use those instead of the
# arguments generated by the rule.
if [ $# -ne 0 ]; then
  ARGS=("$@")
fi

if [ "$is_bazel_run" = true ]; then
  # If the script was invoked by "bazel run", jump out of the execroot, into
  # the workspace before running Gazelle.
  # TODO(jayconrod): detect when a command can't be run this way.
  gazelle_short_path=$(readlink "$GAZELLE_SHORT_PATH")
  cd $(find_repo_root)
  "$gazelle_short_path" "${ARGS[@]}"
else
  # If the script was invoked directly, check whether the script is out of
  # date before proceeding.
  new_runner_script=$(bazel_build_get_path "$RUNNER_LABEL")
  if ! diff "$new_runner_script" "$0" &>/dev/null; then
    cat - >&2 <<EOF
error: $0: script is out of date. Refresh it with the command:
  bazel build $RUNNER_LABEL && cp -fv "$new_runner_script" "$0"
EOF
    exit 1
  fi

  # Rebuild and run Gazelle.
  gazelle_exe=$(bazel_build_get_path "$GAZELLE_LABEL")
  "$gazelle_exe" "${ARGS[@]}"
fi