.kokoro

#!/bin/bash
#
# Copyright 2017-present The Material Components for iOS 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.

# Fail on any error
set -e
COCOAPODS_VERSION="1.6.0"

# Fix permissions issue with Ruby Gems (b/128326105)
if [ -n "$KOKORO_BUILD_NUMBER" ]; then
  sudo chown -Rh $(whoami) /Library/Ruby/Gems
fi

if [ -n "$KOKORO_BUILD_NUMBER" ]; then
  repo_dir='github/repo'
else
  repo_dir="$(dirname $0)"
fi

repo_dir="$(cd $repo_dir; pwd)"
scripts_dir="${repo_dir}/scripts/lib"

source "${scripts_dir}/github_comments.sh"
source "${scripts_dir}/select_xcode.sh"
source "${scripts_dir}/package_managers.sh"

# To install homebrew formulas at specific versions we need to point directly
# to the desired sha in the homebrew formula repository.
# See https://danepowell.com/blog/homebrew-formula-versions for more details.
# This currently points to version 0.21.3, the last version that supports Xcode 9
SOURCEKITTEN_FORMULA="https://raw.githubusercontent.com/Homebrew/homebrew-core/c5a8a094f9e1dd8e41ed24785acef07ef7092d0d/Formula/sourcekitten.rb"

fix_bazel_imports() {
  echo "Rewriting imports for bazel..."

  private_components() {
    find "components/private" -type d | cut -d'/' -f3 | sort | uniq
  }
  
  rewrite_tests() {
    find "${stashed_dir}"components/private/*/tests -type f -name '*.swift' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/*/tests -type f -name '*.swift' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/*/tests -type f -name '*.m' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/schemes/*/tests -type f -name '*.m' -exec perl -pi -e "$1" {} + || true
  }
  rewrite_examples() {
    find "${stashed_dir}"components/private/*/examples -type f -name '*.swift' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/private/*/examples -type f -name '*.h' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/private/*/examples -type f -name '*.m' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/*/examples -type f -name '*.swift' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/*/examples -type f -name '*.h' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/*/examples -type f -name '*.m' -exec perl -pi -e "$1" {} + || true
  }
  rewrite_source() {
    find "${stashed_dir}"components/private/*/src -type f -name '*.h' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/private/*/src -type f -name '*.m' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/*/src -type f -name '*.h' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/*/src -type f -name '*.m' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/schemes/*/src -type f -name '*.h' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"components/schemes/*/src -type f -name '*.m' -exec perl -pi -e "$1" {} + || true
  }
  rewrite_catalogs() {
    find "${stashed_dir}"catalog/MDC* -type f -name '*.swift' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"catalog/MDC* -type f -name '*.m' -exec perl -pi -e "$1" {} + || true
    find "${stashed_dir}"catalog/MDC* -type f -name '*.h' -exec perl -pi -e "$1" {} + || true
  }

  stashed_dir=""
  rewrite_tests "s/import MaterialComponents.Material(.+)_(.+)/import components_\1_\2/"
  rewrite_tests "s/import MaterialComponentsBeta.Material(.+)Beta/import components_\1_\1Beta \/\/ BetaSplit/"
  rewrite_tests "s/import MaterialComponents.Material(.+)Scheme/import components_schemes_\1_\1/"
  rewrite_catalogs "s/import MaterialCatalog/import catalog_MaterialCatalog/"
  rewrite_catalogs "s/import MaterialComponents.MaterialIcons_(.+)/import components_private_Icons_icons_\1_\1/"
  rewrite_catalogs "s/import MaterialComponents.Material(.+)_(.+)/import components_\1_\2/"
  rewrite_catalogs "s/import MaterialComponents.Material(.+)Scheme/import components_schemes_\1_\1/"
  rewrite_examples "s/import <MaterialComponentsBeta\/(.+)>/import\/\*Material beta framework import\*\/ \"\1\"/"
  rewrite_examples "s/import MaterialComponents.Material(.+)_Private/import components_\1_Private/"
  rewrite_examples "s/import MaterialComponents.Material(.+)_(.+)/import components_\1_\2/"
  rewrite_examples "s/import MaterialComponentsBeta.Material(.+)Beta/import components_\1_\1Beta \/\/ BetaSplit/"
  rewrite_examples "s/import MaterialComponents.Material(.+)Scheme/import components_schemes_\1_\1/"
  private_components | while read private_component; do
    if [ -z "$private_component" ]; then
      continue
    fi
    rewrite_tests "s/import MaterialComponents.Material$private_component/import components_private_${private_component}_${private_component}/"
    rewrite_examples "s/import MaterialComponents.Material$private_component/import components_private_${private_component}_${private_component}/"
    rewrite_catalogs "s/import MaterialComponents.Material$private_component\\b/import components_private_${private_component}_${private_component}/"
  done
  rewrite_tests "s/import MaterialComponentsBeta.Material(.+)_(.+)/import components_\1_\2 \/\/ Beta/"
  rewrite_tests "s/import MaterialComponentsBeta.Material(.+)/import components_\1_\1 \/\/ Beta/"
  rewrite_tests "s/import MaterialComponents.Material(.+)/import components_\1_\1/"
  rewrite_catalogs "s/import MaterialComponentsBeta.Material(.+)_(.+)/import components_\1_\2 \/\/ Beta/"
  rewrite_catalogs "s/import MaterialComponentsBeta.Material(.+)/import components_\1_\1 \/\/ Beta/"
  rewrite_catalogs "s/import MaterialComponents.Material(.+)/import components_\1_\1/"
  rewrite_catalogs "s/import CatalogByConvention/import catalog_by_convention_CatalogByConvention/"
  rewrite_catalogs "s/import MDFInternationalization/import material_internationalization_ios_MDFInternationalization/"
  rewrite_catalogs "s/import MDFTextAccessibility/import material_text_accessibility_ios_MDFTextAccessibility/"
  rewrite_catalogs "s/import <CatalogByConvention\/CatalogByConvention\.h>/import\/\*Material prefix framework import\*\/ \"CatalogByConvention.h\"/"
  rewrite_examples "s/import <MaterialComponents\/Material(.+)\.h>/import\/\*Material prefix framework import\*\/ \"Material\1.h\"/"
  rewrite_examples "s/import MaterialComponentsBeta.Material(.+)_(.+)/import components_\1_\2 \/\/ Beta/"
  rewrite_examples "s/import MaterialComponentsBeta.Material(.+)/import components_\1_\1 \/\/ Beta/"
  rewrite_examples "s/import MaterialComponents.Material(.+)/import components_\1_\1/"
  rewrite_examples "s/import MDFTextAccessibility/import material_text_accessibility_ios_MDFTextAccessibility/"
  rewrite_source "s/import <MaterialComponentsBeta\/(.+)>/import\/\*Material beta framework import\*\/ \"\1\"/"
  rewrite_source "s/import <Motion(.+)\/Motion.+\.h>/import \"Motion\1.h\"/"
  rewrite_source "s/import <MDFTextAccessibility\/MDFTextAccessibility\.h>/import \"MDFTextAccessibility.h\"/"
  rewrite_source "s/import <MaterialComponents\/Material(.+)\.h>/import\/\*Material prefix framework import\*\/ \"Material\1.h\"/"
  rewrite_source "s/import <MaterialComponents\/MDC(.+)\.h>/import\/\*MDC prefix framework import\*\/ \"MDC\1.h\"/"
  rewrite_tests "s/import <MaterialComponentsBeta\/Material(.+)Beta\.h>/import\/\*Material beta prefix framework import\*\/ \"Material\1Beta.h\"/"
  rewrite_tests "s/import <MaterialComponents\/Material(.+)\.h>/import\/\*Material prefix framework import\*\/ \"Material\1.h\"/"
  rewrite_tests "s/import MDFTextAccessibility/import material_text_accessibility_ios_MDFTextAccessibility/"
  rewrite_tests "s/import MDFInternationalization/import material_internationalization_ios_MDFInternationalization/"
  stashed_dir="$(pwd)/"
  reset_imports() {
    echo "Undoing import rewrites for bazel..."

    # Undoes our source changes from above.
    rewrite_tests "s/import\/\*Material beta prefix framework import\*\/ \"Material(.+).h\"/import <MaterialComponentsBeta\/Material\1\.h>/"
    rewrite_tests "s/import components_(.+)_\1 \/\/ Beta/import MaterialComponentsBeta.Material\1/"
    rewrite_tests "s/import components_schemes_(.+)_.+/import MaterialComponents.Material\1Scheme/"
    rewrite_tests "s/import components_private_(.+)_.+/import MaterialComponents.Material\1/"
    rewrite_tests "s/import components_(.+)_\1/import MaterialComponents.Material\1/"
    rewrite_tests "s/import components_(.+)_\1Beta \/\/ BetaSplit/import MaterialComponentsBeta.Material\1Beta/"
    rewrite_tests "s/import components_(.+)_(.+) \/\/ Beta/import MaterialComponentsBeta.Material\1_\2/"
    rewrite_tests "s/import components_(.+)_(.+)/import MaterialComponents.Material\1_\2/"
    rewrite_catalogs "s/import\/\*Material prefix framework import\*\/ \"CatalogByConvention\.h\"/import <CatalogByConvention\/CatalogByConvention\.h>/"
    rewrite_catalogs "s/import catalog_MaterialCatalog/import MaterialCatalog/"
    rewrite_catalogs "s/import components_private_Icons_icons_(.+)_\1/import MaterialComponents.MaterialIcons_\1/"
    rewrite_catalogs "s/import components_(.+)_\1 \/\/ Beta/import MaterialComponentsBeta.Material\1/"
    rewrite_catalogs "s/import components_schemes_(.+)_.+/import MaterialComponents.Material\1Scheme/"
    rewrite_catalogs "s/import components_private_(.+)_.+/import MaterialComponents.Material\1/"
    rewrite_catalogs "s/import components_(.+)_\1/import MaterialComponents.Material\1/"
    rewrite_catalogs "s/import components_(.+)_(.+) \/\/ Beta/import MaterialComponentsBeta.Material\1_\2/"
    rewrite_catalogs "s/import components_(.+)_(.+)/import MaterialComponents.Material\1_\2/"
    rewrite_catalogs "s/import catalog_by_convention_CatalogByConvention/import CatalogByConvention/"
    rewrite_catalogs "s/import material_internationalization_ios_MDFInternationalization/import MDFInternationalization/"
    rewrite_catalogs "s/import material_text_accessibility_ios_MDFTextAccessibility/import MDFTextAccessibility/"
    rewrite_examples "s/import\/\*Material beta framework import\*\/ \"(.+)\"/import <MaterialComponentsBeta\/\1>/"
    rewrite_examples "s/import components_(.+)_\1Beta \/\/ BetaSplit/import MaterialComponentsBeta.Material\1Beta/"
    rewrite_examples "s/import components_(.+)_\1 \/\/ Beta/import MaterialComponentsBeta.Material\1/"
    rewrite_examples "s/import components_schemes_(.+)_.+/import MaterialComponents.Material\1Scheme/"
    rewrite_examples "s/import components_private_(.+)_.+/import MaterialComponents.Material\1/"
    rewrite_examples "s/import components_(.+)_Private/import MaterialComponents.Material\1_Private/"
    rewrite_examples "s/import components_(.+)_\1/import MaterialComponents.Material\1/"
    rewrite_examples "s/import components_(.+)_(.+) \/\/ Beta/import MaterialComponentsBeta.Material\1_\2/"
    rewrite_examples "s/import components_(.+)_(.+)/import MaterialComponents.Material\1_\2/"
    rewrite_examples "s/import material_text_accessibility_ios_MDFTextAccessibility/import MDFTextAccessibility/"
    rewrite_examples "s/import\/\*Material prefix framework import\*\/ \"Material(.+)\.h\"/import <MaterialComponents\/Material\1\.h>/"
    rewrite_source "s/import\/\*Material beta framework import\*\/ \"(.+)\"/import <MaterialComponentsBeta\/\1>/"
    rewrite_source "s/import \"Motion(.+)\.h\"/import <Motion\1\/Motion\1.h>/"
    rewrite_source "s/import \"MDFTextAccessibility\.h\"/import <MDFTextAccessibility\/MDFTextAccessibility.h>/"
    rewrite_source "s/import\/\*Material prefix framework import\*\/ \"Material(.+)\.h\"/import <MaterialComponents\/Material\1\.h>/"
    rewrite_source "s/import\/\*MDC prefix framework import\*\/ \"MDC(.+)\.h\"/import <MaterialComponents\/MDC\1\.h>/"
    rewrite_tests "s/import\/\*Material prefix framework import\*\/ \"Material(.+)\.h\"/import <MaterialComponents\/Material\1\.h>/"
    rewrite_tests "s/import material_text_accessibility_ios_MDFTextAccessibility/import MDFTextAccessibility/"
    rewrite_tests "s/import material_internationalization_ios_MDFInternationalization/import MDFInternationalization/"
  }
  trap reset_imports EXIT
}

move_derived_data_to_tmp() {
  targetDir="${HOME}/Library/Developer/Xcode/DerivedData"
  if [[ -d "$targetDir" ]]; then
    mv "$targetDir" /tmpfs/
    ln -sf /tmpfs/DerivedData "$targetDir"
  fi
}

# Uploads all of the bazel test artifacts to Kokoro's artifacts storage.
upload_bazel_test_artifacts() {
  logs_dir="$KOKORO_ARTIFACTS_DIR/bazel_test_logs"
  mkdir -p "$logs_dir"

  # Copies each file from stdin to $KOKORO_ARTIFACTS_DIR and preserves the directory structure
  copy_to_artifacts() {
    cat - | while read file; do
      directory="$logs_dir/$(dirname $file)"
      mkdir -p "$directory"
      cp "$file" "$logs_dir/$file"
    done
  }

  brew_install rename

  # rename all test.log to sponge_log.log and then copy them to the kokoro
  # artifacts directory.
  find -L . -name "test.log" -type f -exec rename 's/test.log/sponge_log.log/' {} \;
  find -L . -name "sponge_log.log" -type f | copy_to_artifacts

  # rename all test.xml to sponge_log.xml and then copy them to kokoro
  # artifacts directory.
  find -L . -name "test.xml" -type f -exec rename 's/test.xml/sponge_log.xml/' {} \;
  find -L . -name "sponge_log.xml" -type f | copy_to_artifacts
}

# Upgrades kokoro's current bazel version to at least 0.20.0
upgrade_kokoro_bazel_if_needed() {
  bazel version

  if [ -f "$KOKORO_GFILE_DIR/use_bazel.sh" ]; then
    bash "$KOKORO_GFILE_DIR/use_bazel.sh" 0.20.0
  else
    use_bazel.sh 0.20.0
  fi
  bazel version
}

run_bazel_affected() {
  echo "Checking affected targets..."
  if [ -z "$COMMAND" ]; then
    COMMAND="test"
  fi
  if [ -z "$TARGET" ]; then
    if [ "$COMMAND" == "test" ]; then
      # Only return test targets.
      bazel_kind="test"
    else
      # Return all affected targets.
      bazel_kind="rule"
    fi

    if [ -n "$KOKORO_BUILD_NUMBER" ]; then
      pushd github/repo >> /dev/null
    fi

    # `target_branch` is either the Pull Request destination branch (where it will be merged) or if
    # none can be determined, defaults to `develop`.
    if [ -n "$KOKORO_GITHUB_PULL_REQUEST_TARGET_BRANCH" ]; then
      target_branch="$KOKORO_GITHUB_PULL_REQUEST_TARGET_BRANCH"
    else
      target_branch=develop
    fi

    # `base_sha` is the merge base of `target_branch` and the current HEAD.
    base_sha=$(git merge-base "$target_branch" HEAD)

    # We must upgrade bazel prior to running bazel query because we rely on features in bazel
    # 0.20.
    if [ -n "$KOKORO_BUILD_NUMBER" ]; then
      upgrade_kokoro_bazel_if_needed
    fi
    
    # Output the affected targets to the logs. This also gives the affected_targets script the
    # opportunity to fail.
    scripts/affected_targets "$bazel_kind" "$base_sha...HEAD"

    # `TARGET` is then all bazel targets affected by changes in the commit range between `base_sha`
    # and `HEAD`.  By default, that becomes all changes between the `develop` branch and the latest
    #  commit.
    TARGET="$(scripts/affected_targets $bazel_kind $base_sha...HEAD)"

    if [ -n "$KOKORO_BUILD_NUMBER" ]; then
      popd >> /dev/null
    fi
  fi
  
  if [ -z "$TARGET" ]; then
    echo "Nothing to build."
    exit 0
  fi
  
  comment_identifier="affected-targets"

  if [ -z "$TARGET" ]; then
    echo "Nothing to build."

    if [ -n "$GITHUB_API_TOKEN" ]; then
      delete_comment "$comment_identifier"
    fi

    exit 0
  else
    if [ -n "$GITHUB_API_TOKEN" ]; then
      comment_tmp_path=$(mktemp -d)
      comment_tmp_file="$comment_tmp_path/comment.tmp"
      echo "bazel detected changes to the following targets:" > "$comment_tmp_file"
      echo >> "$comment_tmp_file"
      echo '```' >> "$comment_tmp_file"
      echo "$TARGET" >> "$comment_tmp_file"
      echo '```' >> "$comment_tmp_file"

      post_comment "$comment_identifier" "$comment_tmp_file"
    fi
  fi

  run_bazel
}

run_bazel() {
  echo "Running bazel builds..."

  if [ -n "$KOKORO_BUILD_NUMBER" ]; then
    move_derived_data_to_tmp
  fi

  if [ -n "$KOKORO_BUILD_NUMBER" ]; then
    upgrade_kokoro_bazel_if_needed
  fi

  if [ -n "$VERBOSE_OUTPUT" ]; then
    verbosity_args="-s"
  fi

  if [ -z "$COMMAND" ]; then
    COMMAND="test"
  fi
  if [ -z "$TARGET" ]; then
    TARGET="//..."
  fi

  if [ -n "$KOKORO_BUILD_NUMBER" ]; then
    select_xcode "$XCODE_VERSION"

    # Move into our cloned repo
    cd github/repo
  fi

  # Run against whichever Xcode is currently selected.
  selected_xcode_developer_path=$(xcode-select -p)
  selected_xcode_contents_path=$(dirname "$selected_xcode_developer_path")

  xcode_version=$(cat "$selected_xcode_contents_path/version.plist" \
    | grep "CFBundleShortVersionString" -A1 \
    | grep string \
    | cut -d'>' -f2 \
    | cut -d'<' -f1)

  if [ "$COMMAND" == "build" ]; then
    echo "🏗️  $COMMAND with Xcode $xcode_version..."
  elif [ "$COMMAND" == "test" ]; then
    echo "🛠️  $COMMAND with Xcode $xcode_version..."

    if [ -n "$VERBOSE_OUTPUT" ]; then
      extra_args="--test_output=all"
    else
      extra_args="--test_output=errors"
    fi
  fi

  fix_bazel_imports
  if [ -n "$KOKORO_ARTIFACTS_DIR" ]; then
    # Especially in the event of failure, we want our test artifacts to be uploaded.
    trap upload_bazel_test_artifacts EXIT
  fi

  snapshot_dir="${repo_dir}/snapshot_test_goldens/goldens"
  tmp_img_dir="$(mktemp -d)"

  # Install git lfs if we're performing tests on kokoro
  if [ -n "$KOKORO_BUILD_NUMBER" ]; then
    if [ "$COMMAND" == "test" ]; then
      brew_install git-lfs
      git lfs install
      git lfs pull

      # Reset the simulators to prepare for hosted snapshot tests
      sim_cleaner_tmp=$(mktemp -d)
      git clone https://github.com/material-foundation/ios-simulator-utils.git "$sim_cleaner_tmp"
      source "${sim_cleaner_tmp}/scripts/cleanup_simulators.sh"
      perform_pre_test_cleanup "iPhone"
    fi
  fi

  bazel $COMMAND $TARGET --xcode_version $xcode_version --ios_minimum_os=9.0 \
    --ios_multi_cpus=i386,x86_64 $extra_args $verbosity_args \
    --test_env="FB_REFERENCE_IMAGE_DIR=$snapshot_dir" \
    --test_env="IMAGE_DIFF_DIR=$tmp_img_dir"
}

run_cocoapods() {
  echo "Running cocoapods builds..."

  if [ -n "$KOKORO_BUILD_NUMBER" ]; then
    move_derived_data_to_tmp
  fi

  if [ -n "$KOKORO_BUILD_NUMBER" ]; then
    select_xcode "$XCODE_VERSION"

    # Move into our cloned repo
    cd github/repo

    gem_install xcpretty 
    # TODO(https://github.com/material-components/material-components-ios/issues/6356 ): Move to 1.6
    gem install cocoapods -v "$COCOAPODS_VERSION"
    pod --version

    # Install git-lfs
    brew_install git-lfs
    git lfs install
    git lfs pull
  fi

  if [ "$DEPENDENCY_SYSTEM" = "cocoapods" ]; then
    bash scripts/prep_all
    bash scripts/build_all --verbose
    if [ -n "$IS_RELEASE" ]; then
      bash scripts/test_all
    else
      bash scripts/test_all catalog/MDCCatalog.xcworkspace:MDCCatalog
    fi
  elif [ "$DEPENDENCY_SYSTEM" = "cocoapods-podspec" ]; then
    pod lib lint MaterialComponents.podspec --skip-tests
  fi

  if [ -n "$CODECOV_TOKEN" ]; then
    bash <(curl -s https://codecov.io/bash)
  fi
}

# For local runs, you must set the following environment variables:
#
#   DANGER_GITHUB_API_TOKEN -> Create a token here: https://github.com/settings/tokens.
#                              Must have public_repo scope.
#   DANGER_TEST_PR="###"    -> The PR # you want to test danger against.
#
# And you'll likely have to install danger:
#
#   yarn add danger
#
run_danger() {
  if [ -n "$KOKORO_BUILD_NUMBER" ]; then
    # Move into our cloned repo
    cd github/repo

    export DANGER_TEST_PR="$KOKORO_GITHUB_PULL_REQUEST_NUMBER"

    # Install danger
    yarn add danger
  fi

  # We're not a supported CI, so we have to pretend to be one.
  export DANGER_FAKE_CI="YEP"
  export DANGER_TEST_REPO="material-components/material-components-ios"

  # Run Danger
  yarn danger ci
}

generate_website() {
  if [ -n "$KOKORO_BUILD_NUMBER" ]; then
    # Move into our cloned repo
    cd github/repo

    ./scripts/build_site.sh

    gem_install bundler
    brew_install yarn --ignore-dependencies
    
    # The above installations update node to v10, but the docsite generator
    # relies on v8.
    brew unlink node
    brew install node@8
    # Required because node@8 is keg-only, meaning it isn't linked automatically.
    brew link --force --overwrite node@8
  fi

  cd docsite-generator
  bundle install
  yarn install
  cd ../

  TMP_PATH=$(mktemp -d)
  ./scripts/build_site.sh 2>&1 | tee "$TMP_PATH/output"

  if [[ $(grep "^Error:" "$TMP_PATH/output") ]]; then
    # Make site generation errors be script failures. build_site.sh always exits with 0
    # unfortunately.
    exit 1
  fi
}

# Will generate an API diff between the current branch and the merge-base from develop.
# The result will be posted to GitHub as a comment.
#
# For local runs, you must set the following environment variables:
#
#   GITHUB_API_TOKEN -> Create a token here: https://github.com/settings/tokens.
#                       Must have public_repo scope.
#   KOKORO_GITHUB_PULL_REQUEST_NUMBER="###" -> The PR # you want to post the API diff results to.
#
# And you'll likely have to install sourcekitten:
#
#   brew install sourcekitten
#
generate_apidiff() {
  if [ -n "$KOKORO_BUILD_NUMBER" ]; then
    select_xcode "$XCODE_VERSION"

    # Move into our cloned repo
    cd github/repo

    # Install sourcekitten, a dependency of the apidiff tool
    brew_install "$SOURCEKITTEN_FORMULA"

    sourcekitten version
  fi

  usage() {
    echo "Usage: $0 -d apidiff"
    echo
    echo "Will generate an API diff between the current branch and the merge-base from develop."
    echo "The result will be posted to GitHub as a comment."
    echo
    echo "Must set the following environment variables to run locally:"
    echo
    echo "GITHUB_API_TOKEN -> Create a token here: https://github.com/settings/tokens."
    echo "                    Must have public_repo scope."
    echo "KOKORO_GITHUB_PULL_REQUEST_NUMBER=\"###\" -> The PR # you want to post the API diff results to."
  }

  if [ -z "$GITHUB_API_TOKEN" ]; then
    echo "GITHUB_API_TOKEN must be set to a github token with public_repo scope."
    usage
    exit 1
  fi

  if [ -z "$KOKORO_GITHUB_PULL_REQUEST_NUMBER" ]; then
    echo "KOKORO_GITHUB_PULL_REQUEST_NUMBER must be set to a github pull request number."
    usage
    exit 1
  fi

  BUILDS_TMP_PATH=$(mktemp -d)
  base_sha=$(git merge-base origin/develop HEAD)

  ./scripts/release apidiff "$base_sha" | tee "$BUILDS_TMP_PATH/api_diff"
  changelog_path=$(cat "$BUILDS_TMP_PATH/api_diff" | grep "Changelog=" | cut -d'=' -f2)
  error_path=$(cat "$BUILDS_TMP_PATH/api_diff" | grep "Errors=" | cut -d'=' -f2)

  if [ ! -f scripts/external/github-comment/.git ]; then
    git submodule update --init --recursive scripts/external/github-comment
  fi

  pushd scripts/external/github-comment >> /dev/null

  if [ -f "$changelog_path" ]; then
    echo "## API diff detected the following changes" > "$changelog_path.tmp"
    cat "$changelog_path" >> "$changelog_path.tmp"

    swift run github-comment \
      --repo=material-components/material-components-ios \
      --github_token="$GITHUB_API_TOKEN" \
      --pull_request_number="$KOKORO_GITHUB_PULL_REQUEST_NUMBER" \
      --identifier=apidiff \
      --comment_body="$changelog_path.tmp"

  else
    # No changelog, so delete any existing comment
    swift run github-comment \
      --repo=material-components/material-components-ios \
      --github_token="$GITHUB_API_TOKEN" \
      --pull_request_number="$KOKORO_GITHUB_PULL_REQUEST_NUMBER" \
      --identifier=apidiff \
      --delete
  fi

  popd >> /dev/null

  if [ -f "$error_path" ]; then
    nested_error_path=$(cat "$error_path" | grep "stderr output is available in" | cut -d' ' -f6)
    if [ -f "$nested_error_path" ]; then
      echo
      echo "Potential build errors:"
      cat "$nested_error_path"
    fi
  fi
}

# This command can be used when a pull request should always be put into a failure state.
# For example, we do not want to allow pull requests to be merged into stable.
fail_immediately() {
  exit 1
}

# This command protects the stable branch from being merged with anything other than
# release-candidate branches.
protect_stable_from_undesired_merges() {
  if [ -z "$KOKORO_GITHUB_PULL_REQUEST_NUMBER" ]; then
    echo "KOKORO_GITHUB_PULL_REQUEST_NUMBER has not been defined."
    echo "Please set this variable to a valid GitHub pull request number."
    exit 1
  fi

  pull_request_api_url="https://api.github.com/repos/material-components/material-components-ios/pulls/$KOKORO_GITHUB_PULL_REQUEST_NUMBER"

  tmp_path=$(mktemp -d)
  pull_request_metadata_file="$tmp_path/output"

  curl -s "$pull_request_api_url" > "$pull_request_metadata_file"

  if ! grep --quiet '^    "label": "material-components:stable",$' "$pull_request_metadata_file"; then
    echo "This job should only be used to validate pull requests to stable."
    exit 1;
  fi

  if ! grep --quiet '^    "label": "material-components:release-candidate",$' "$pull_request_metadata_file"; then
    echo "Only release-candidate branches can be merged into stable."
    exit 1;
  fi

  echo "Validated that this branch is a release-candidate being merged in to stable."
}

# The fall-through case for unknown jobs.
unknown_job() {
  if [ -n "$DEPENDENCY_SYSTEM" ]; then
    echo "The following job is unknown and will not be run: $DEPENDENCY_SYSTEM"
  else
    echo "You must provide a depenency system with '-d' or the environment "
    echo "variable 'DEPENDENCY_SYSTEM'."
  fi
  exit 1
}

POSITIONAL=()
while [[ $# -gt 0 ]]; do
  key="$1"

  case $key in
  -v|--verbose)
    VERBOSE_OUTPUT="1"
    shift
    ;;
  -d|--dependency_system)
    DEPENDENCY_SYSTEM="$2"
    shift
    shift
    ;;
  -c|--command)
    COMMAND="$2"
    shift
    shift
    ;;
  -t|--target)
    TARGET="$2"
    shift
    shift
    ;;
  *)
    POSITIONAL+=("$1")
    shift
    ;;
  esac
done
set -- "${POSITIONAL[@]}" # restore positional parameters

if [ -n "$VERBOSE_OUTPUT" ]; then
  # Display commands to stderr.
  set -x
fi

case "$DEPENDENCY_SYSTEM" in
  "bazel")      run_bazel ;;
  "bazel-affected")      run_bazel_affected ;;
  "cocoapods")  run_cocoapods ;;
  "cocoapods-podspec")  run_cocoapods ;;
  "website")    generate_website ;;
  "danger")     run_danger ;;
  "apidiff")    generate_apidiff ;;
  "fail")       fail_immediately ;;
  "protect-stable-from-undesired-merges") protect_stable_from_undesired_merges ;;

  *)            unknown_job ;;
esac

echo "Success!"