#!/usr/bin/env bash
# Copyright 2014 The Flutter Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.


# ---------------------------------- NOTE ---------------------------------- #
#
# Please keep the logic in this file consistent with the logic in the
# `shared.bat` script in the same directory to ensure that Flutter & Dart continue
# to work across all platforms!
#
# -------------------------------------------------------------------------- #

set -e

# Needed because if it is set, cd may print the path it changed to.
unset CDPATH

function retry_upgrade {
  local total_tries="10"
  local remaining_tries=$((total_tries - 1))
  while [[ "$remaining_tries" -gt 0 ]]; do
    (cd "$FLUTTER_TOOLS_DIR" && "$PUB" upgrade "$VERBOSITY" --no-precompile) && break
    echo "Error: Unable to 'pub upgrade' flutter tool. Retrying in five seconds... ($remaining_tries tries left)"
    remaining_tries=$((remaining_tries - 1))
    sleep 5
  done

  if [[ "$remaining_tries" == 0 ]]; then
    echo "Command 'pub upgrade' still failed after $total_tries tries, giving up."
    return 1
  fi
  return 0
}

# Trap function for removing any remaining lock file at exit.
function _rmlock () {
  [ -n "$FLUTTER_UPGRADE_LOCK" ] && rm -rf "$FLUTTER_UPGRADE_LOCK"
}

# Determines which lock method to use, based on what is available on the system.
# Returns a non-zero value if the lock was not acquired, zero if acquired.
function _lock () {
  if hash flock 2>/dev/null; then
    flock --nonblock --exclusive 7 2>/dev/null
  else
    mkdir "$1" 2>/dev/null
  fi
}

# Waits for an update lock to be acquired.
#
# To ensure that we don't simultaneously update Dart in multiple parallel
# instances, we try to obtain an exclusive lock on this file descriptor (and
# thus this script's source file) while we are updating Dart and compiling the
# script. To do this, we try to use the command line program "flock", which is
# available on many Unix-like platforms, in particular on most Linux
# distributions. You give it a file descriptor, and it locks the corresponding
# file, having inherited the file descriptor from the shell.
#
# Complicating matters, there are two major scenarios where this will not
# work.
#
# The first is if the platform doesn't have "flock", for example on macOS. There
# is not a direct equivalent, so on platforms that don't have flock, we fall
# back to using mkdir as an atomic operation to create a lock directory. If
# mkdir is able to create the directory, then the lock is acquired. To determine
# if we have "flock" available, we use the "hash" shell built-in.
#
# The second complication is NFS. On NFS, to obtain an exclusive lock you need a
# file descriptor that is open for writing. Thus, we ignore errors from flock by
# redirecting all output to /dev/null, since users will typically not care about
# errors from flock and are more likely to be confused by them than helped.
#
# The upgrade_flutter function calling _wait_for_lock is executed in a subshell
# with a redirect that pipes the source of this script into file descriptor 7.
# A flock lock is released when this subshell exits and file descriptor 7 is
# closed. The mkdir lock is released via an exit trap from the subshell that
# deletes the lock directory.
function _wait_for_lock () {
  FLUTTER_UPGRADE_LOCK="$FLUTTER_ROOT/bin/cache/.upgrade_lock"
  local waiting_message_displayed
  while ! _lock "$FLUTTER_UPGRADE_LOCK"; do
    if [[ -z $waiting_message_displayed ]]; then
      # Print with a return so that if the Dart code also prints this message
      # when it does its own lock, the message won't appear twice. Be sure that
      # the clearing printf below has the same number of space characters.
      printf "Waiting for another flutter command to release the startup lock...\r";
      waiting_message_displayed="true"
    fi
    sleep .1;
  done
  # Clear the waiting message so it doesn't overlap any following text.
  printf "                                                                  \r";
  unset waiting_message_displayed
  # If the lock file is acquired, make sure that it is removed on exit.
  trap _rmlock INT TERM EXIT
}

# This function is always run in a subshell. Running the function in a subshell
# is required to make sure any lock directory is cleaned up by the exit trap in
# _wait_for_lock.
function upgrade_flutter () (
  mkdir -p "$FLUTTER_ROOT/bin/cache"

  # Waits for the update lock to be acquired.
  _wait_for_lock

  local revision="$(cd "$FLUTTER_ROOT"; git rev-parse HEAD)"

  # Invalidate cache if:
  #  * SNAPSHOT_PATH is not a file, or
  #  * STAMP_PATH is not a file with nonzero size, or
  #  * Contents of STAMP_PATH is not our local git HEAD revision, or
  #  * pubspec.yaml last modified after pubspec.lock
  if [[ ! -f "$SNAPSHOT_PATH" || ! -s "$STAMP_PATH" || "$(cat "$STAMP_PATH")" != "$revision" || "$FLUTTER_TOOLS_DIR/pubspec.yaml" -nt "$FLUTTER_TOOLS_DIR/pubspec.lock" ]]; then
    rm -f "$FLUTTER_ROOT/version"
    touch "$FLUTTER_ROOT/bin/cache/.dartignore"
    "$FLUTTER_ROOT/bin/internal/update_dart_sdk.sh"
    VERBOSITY="--verbosity=error"

    echo Building flutter tool...
    if [[ "$CI" == "true" || "$BOT" == "true" || "$CONTINUOUS_INTEGRATION" == "true" || "$CHROME_HEADLESS" == "1" ]]; then
      PUB_ENVIRONMENT="$PUB_ENVIRONMENT:flutter_bot"
      VERBOSITY="--verbosity=normal"
    fi
    export PUB_ENVIRONMENT="$PUB_ENVIRONMENT:flutter_install"

    if [[ -d "$FLUTTER_ROOT/.pub-cache" ]]; then
      export PUB_CACHE="${PUB_CACHE:-"$FLUTTER_ROOT/.pub-cache"}"
    fi

    retry_upgrade

    "$DART" --disable-dart-dev $FLUTTER_TOOL_ARGS --snapshot="$SNAPSHOT_PATH" --packages="$FLUTTER_TOOLS_DIR/.packages" --no-enable-mirrors "$SCRIPT_PATH"
    echo "$revision" > "$STAMP_PATH"
  fi
  # The exit here is extraneous since the function is run in a subshell, but
  # this serves as documentation that running the function in a subshell is
  # required to make sure any lock directory created by mkdir is cleaned up.
  exit $?
)

# This function is intended to be executed by entrypoints (e.g. `//bin/flutter`
# and `//bin/dart`). PROG_NAME and BIN_DIR should already be set by those
# entrypoints.
function shared::execute() {
  export FLUTTER_ROOT="$(cd "${BIN_DIR}/.." ; pwd -P)"

  FLUTTER_TOOLS_DIR="$FLUTTER_ROOT/packages/flutter_tools"
  SNAPSHOT_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.snapshot"
  STAMP_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.stamp"
  SCRIPT_PATH="$FLUTTER_TOOLS_DIR/bin/flutter_tools.dart"
  DART_SDK_PATH="$FLUTTER_ROOT/bin/cache/dart-sdk"

  DART="$DART_SDK_PATH/bin/dart"
  PUB="$DART_SDK_PATH/bin/pub"

  # If running over git-bash, overrides the default UNIX executables with win32
  # executables
  case "$(uname -s)" in
    MINGW32*)
      DART="$DART.exe"
      PUB="$PUB.bat"
      ;;
  esac

  # Test if running as superuser – but don't warn if running within Docker
  if [[ "$EUID" == "0" && ! -f /.dockerenv ]]; then
    echo "   Woah! You appear to be trying to run flutter as root."
    echo "   We strongly recommend running the flutter tool without superuser privileges."
    echo "  /"
    echo "📎"
  fi

  # Test if Git is available on the Host
  if ! hash git 2>/dev/null; then
    echo "Error: Unable to find git in your PATH."
    exit 1
  fi
  # Test if the flutter directory is a git clone (otherwise git rev-parse HEAD
  # would fail)
  if [[ ! -e "$FLUTTER_ROOT/.git" ]]; then
    echo "Error: The Flutter directory is not a clone of the GitHub project."
    echo "       The flutter tool requires Git in order to operate properly;"
    echo "       to install Flutter, see the instructions at:"
    echo "       https://flutter.dev/get-started"
    exit 1
  fi

  # To debug the tool, you can uncomment the following lines to enable checked
  # mode and set an observatory port:
  # FLUTTER_TOOL_ARGS="--enable-asserts $FLUTTER_TOOL_ARGS"
  # FLUTTER_TOOL_ARGS="$FLUTTER_TOOL_ARGS --observe=65432"

  upgrade_flutter 7< "$PROG_NAME"

  BIN_NAME="$(basename "$PROG_NAME")"
  case "$BIN_NAME" in
    flutter*)
      # FLUTTER_TOOL_ARGS aren't quoted below, because it is meant to be
      # considered as separate space-separated args.
      "$DART" --disable-dart-dev --packages="$FLUTTER_TOOLS_DIR/.packages" $FLUTTER_TOOL_ARGS "$SNAPSHOT_PATH" "$@"
      ;;
    dart*)
      "$DART" "$@"
      ;;
    *)
      echo "Error! Executable name $BIN_NAME not recognized!"
      exit 1
      ;;
  esac
}