#!/usr/bin/env bash

set -eu
set -o pipefail
# This setting enables the desired behavior in the "for corefile in ${core_directory}/${SEARCH_PATTERN_NON_TRACKED}; do" loop
# more details at https://gist.github.com/springmeyer/6dd234ff89ba306a73608a6f45cb5506
shopt -s nullglob

PLATFORM_UNAME=$(uname -s)
REQUIRED_FILENAME="core"
LOGBT_VERSION="v2.0.3"
BASE_CORE_DIRECTORY=/tmp/logbt-coredumps

if [[ ${PLATFORM_UNAME} == "Linux" ]]; then
  REQUIRED_PATTERN="${REQUIRED_FILENAME}.%p.%E"
  DEBUGGER="gdb"
elif [[ ${PLATFORM_UNAME} == "Darwin" ]]; then
  # Recommend running with the following setting to only show crashes
  # in the notification center
  # defaults write com.apple.CrashReporter UseUNC 1
  REQUIRED_PATTERN="${REQUIRED_FILENAME}.%P"
  DEBUGGER="lldb"
else
  error "Unsupported platform: ${PLATFORM_UNAME}"
fi

function error() {
  >&2 echo "[logbt] $@"
  exit 1
}

function process_core() {
  local program=${1}
  local corefile=${2}
  local debugger=${3}
  if [[ ${debugger} =~ "lldb" ]]; then
    lldb --core ${corefile} --batch -o "thread backtrace all" -o "quit"
  else
    gdb ${program} --core ${corefile} -ex "set pagination 0" -ex "thread apply all bt" --batch
  fi
  # note: on OS X the -f avoids a hang on prompt "remove write-protected regular file?"
  rm -f ${corefile}
}

function find_core_by_pid() {
  local program=${1}
  local core_directory=${2}
  local debugger=${3}
  local child_pid=${4}
  if [[ ${PLATFORM_UNAME} == "Darwin" ]]; then
    local single_corefile="${core_directory}/${REQUIRED_FILENAME}.${child_pid}"
    if [ -e ${single_corefile} ]; then
      echo "[logbt] Found corefile at ${single_corefile}"
      process_core ${program} ${single_corefile} ${debugger}
    fi
  else
    local SEARCH_PATTERN_BY_PID="${REQUIRED_FILENAME}.${child_pid}.*"
    # note: this for loop depends on the `shopt -s nullglob` above
    for corefile in ${core_directory}/${SEARCH_PATTERN_BY_PID}; do
      echo "[logbt] Found corefile at ${corefile}"
      # extract program name from corefile
      filename=$(basename "${corefile}")
      binary_program=/$(echo ${filename##*.\!} | tr "!" "/")
      process_core ${binary_program} ${corefile} ${debugger}
    done
  fi  
}

function find_remaining_cores() {
  local program=${1}
  local core_directory=${2}
  local debugger=${3}
  local SEARCH_PATTERN_NON_TRACKED="${REQUIRED_FILENAME}.*"
  local hit=false
  for corefile in ${core_directory}/${SEARCH_PATTERN_NON_TRACKED}; do
    echo "[logbt] Found corefile (non-tracked) at ${corefile}"
    hit=true
  done
  if [[ ${hit} == true ]]; then
    echo "[logbt] Processing cores..."
  fi
  for corefile in ${core_directory}/${SEARCH_PATTERN_NON_TRACKED}; do
    # below two lines are linux specific, but harmless to run on osx
    filename=$(basename "${corefile}")
    binary_program=/$(echo ${filename##*.\!} | tr "!" "/")
    process_core ${binary_program} ${corefile} ${debugger}
  done
}

function snapshot {
  local program=${1}
  local debugger=${2}
  local child_pid=${3}
  echo "[logbt] snapshotting ${program} (${child_pid})"
  if [[ ${debugger} =~ "lldb" ]]; then
    lldb -p ${child_pid} --batch -o "thread backtrace all" -o "quit"
  else
    gdb --pid ${child_pid} -ex "set pagination 0" -ex "thread apply all bt" --batch
  fi
}

function backtrace {
  local program=${1}
  local core_directory=${2}
  local debugger=${3}
  local child_pid=${4}
  local child_return=${5}
  find_core_by_pid ${program} ${core_directory} ${debugger} ${child_pid}
  find_remaining_cores ${program} ${core_directory} ${debugger}
}

function warn_on_existing_cores() {
  local core_directory=${1}
  local SEARCH_PATTERN_NON_TRACKED="${REQUIRED_FILENAME}.*"
  for corefile in ${core_directory}/${SEARCH_PATTERN_NON_TRACKED}; do
    echo "[logbt] WARNING: Found corefile (existing) at ${corefile}"
  done
}

function error_on_existing_cores() {
  local core_directory=${1}
  local SEARCH_PATTERN_NON_TRACKED="${REQUIRED_FILENAME}.*"
  for corefile in ${core_directory}/${SEARCH_PATTERN_NON_TRACKED}; do
    error "Error: Found corefile (unexpected) at ${corefile}"
  done  
}

function ensure_directory_is_writeable() {
  # ensure we can write to the directory, otherwise
  # core files might not be able to be written
  WRITE_RETURN=0
  touch ${core_directory}/test.txt || WRITE_RETURN=$?
  if [[ ${WRITE_RETURN} != 0 ]]; then
    error "Permissions problem: unable to write to ${core_directory} (exited with ${WRITE_RETURN})"
  else
    # cleanup from test
    rm ${core_directory}/test.txt
  fi  
}

function get_target_core_pattern() {
  echo ${BASE_CORE_DIRECTORY}/${REQUIRED_PATTERN}
}

function get_core_pattern() {
  if [[ ${PLATFORM_UNAME} == "Linux" ]]; then
    local core_pattern=$(cat /proc/sys/kernel/core_pattern)
  elif [[ ${PLATFORM_UNAME} == "Darwin" ]]; then
    # Recommend running with the following setting to only show crashes
    # in the notification center
    # defaults write com.apple.CrashReporter UseUNC 1
    local core_pattern=$(sysctl -n kern.corefile)
  fi
  echo ${core_pattern}
}

function validate_core_pattern() {
  local core_pattern=${1}
  if [[ ! ${core_pattern} =~ ${REQUIRED_PATTERN} ]]; then
    error "unexpected core_pattern: ${core_pattern}"
  fi  
}

function generic_signal_handler() {
  local code=$?
  local program=${1}
  local child_pid=${2}
  local sig=${3}
  # Bug note: On darwin ${code} will be incorrectly 0 after snapshot here
  # so we ignore ${code} and instead get it from the signal
  code=$(($(kill -l ${sig})+128))
  echo "[logbt] received signal:${code} (${sig})"
  echo "[logbt] sending SIGTERM to ${program} (${child_pid})"
  # sleep here to help the stdout show in the right
  # order (accounts for an intermittant case where the above lines print after
  # the child outputs stdout during shutdown)
  sleep 1
  KILL_RETURN=0
  kill -TERM ${child_pid} || KILL_RETURN=$?
  if [[ ${KILL_RETURN} != 0 ]]; then
    echo "[logbt] could not terminate child process (kill returned ${KILL_RETURN})"
  else
    CHILD_EXIT=0
    wait ${child_pid} || CHILD_EXIT=$?
    if [[ ${CHILD_EXIT} != 143 ]]; then
      error "child process exited abnormally: ${CHILD_EXIT}"
    fi
  fi
  echo "[logbt] exiting with ${code}"
  exit ${code}
}


: '
NOTE: SIGINT (aka ctrl-c) is special. First of all SIGINT is sent to the whole process group
automatically in bash (http://stackoverflow.com/a/6804155). This means we do not need to reap
the child process manually. And if logbt is a "foreground" process then SIGINT is ignored if
sent directly with ./bin/logbt <args> & kill -INT $! (http://stackoverflow.com/a/14697034).
So the only way to send SIGINT is with ctrl-c or via another terminal that has a different
process group.
'

function sigint_handler() {
  local code=$?
  local program=${1}
  local child_pid=${2}
  local sig=${3}
  echo "[logbt] received signal:${code} (${sig})"
  CHILD_EXIT=0
  wait ${child_pid} || CHILD_EXIT=$?
  if [[ ${CHILD_EXIT} != 130 ]]; then
    echo "[logbt] child process exited with:${CHILD_EXIT}"
  fi
  exit ${code}
}

function launch_and_wait() {

  local program=${1}
  local core_pattern=$(get_core_pattern)
  validate_core_pattern ${core_pattern}

  local core_directory=$(dirname ${core_pattern})
  echo "[logbt] using corefile location: ${core_directory}"
  echo "[logbt] using core_pattern: $(basename ${core_pattern})"

  # ensure we have a debugger installed
  if ! which ${DEBUGGER} > /dev/null; then
    error "Could not find required command '${DEBUGGER}'"
  fi

  if [[ ! -d ${core_directory} ]]; then
    echo "[logbt] creating directory for core files at '${core_directory}'"
    mkdir -p -m a+w ${core_directory}
  fi

  ensure_directory_is_writeable ${core_directory}

  warn_on_existing_cores ${core_directory}

  # Enable corefile generation
  ulimit -c unlimited

  # Run the child process in a background process
  # in order to get the PID
  if [[ ${LD_PRELOAD:-} ]] && [[ ${PLATFORM_UNAME} == 'Darwin' ]]; then
      # on os x DYLD_INSERT_LIBRARIES is blocked from being inherited
      # so we accept LD_PRELOAD and foreward along
      DYLD_INSERT_LIBRARIES=${LD_PRELOAD} LOGBT_PID=$$ "$@" & CHILD_PID=$!
  else
      LOGBT_PID=$$ "$@" & CHILD_PID=$!
  fi

  # Hook up function to run when logbt received signal
  trap "snapshot ${program} ${DEBUGGER} ${CHILD_PID}" USR1
  trap "generic_signal_handler ${program} ${CHILD_PID} TERM" TERM
  trap "generic_signal_handler ${program} ${CHILD_PID} HUP" HUP
  trap "sigint_handler ${program} ${CHILD_PID} INT" INT

  # Wait for child and attempt to generate a backtrace if child exits in non-zero way
  wait_for_child ${program} ${core_directory} ${DEBUGGER} ${CHILD_PID}
}

function wait_for_child() {
  local program=${1}
  local core_directory=${2}
  local debugger=${3}
  local child_pid=${4}
  CHILD_RETURN=0
  wait ${child_pid} || CHILD_RETURN=$?
  # Bug note: on linux USR1 will trigger an exit which makes it looks like the child
  # has returned when it has not. So the below code ensures we stay alive and watching
  # the child if USR1 is hit
  if [[ $(uname -s) == 'Linux' ]] && [[ $(kill -l ${CHILD_RETURN}) == USR1 ]]; then
    wait_for_child ${program} ${core_directory} ${debugger} ${child_pid}
  fi
  if [[ ${CHILD_RETURN} == 127 ]]; then
    # command not found : http://www.tldp.org/LDP/abs/html/exitcodes.html
    echo "[logbt] command not found: ${program}"
  elif [[ ${CHILD_RETURN} != 0 ]]; then
    local exit_msg="saw '${program}' exit with code:${CHILD_RETURN}"
    exit_msg="${exit_msg} ($(kill -l ${CHILD_RETURN}))"
    echo "[logbt] ${exit_msg}"
    backtrace ${program} ${core_directory} ${DEBUGGER} ${child_pid} ${CHILD_RETURN}
  fi
  # exit logbt with the same code as the child
  exit ${CHILD_RETURN}
}

function setup_logbt() {
  local settable_core_pattern=$(get_target_core_pattern)
  if [[ ${PLATFORM_UNAME} == "Linux" ]]; then
    echo "[logbt] setting $(cat /proc/sys/kernel/core_pattern) -> ${settable_core_pattern}"
    # write new value to /proc/sys/kernel/core_pattern
    echo "${settable_core_pattern}" > /proc/sys/kernel/core_pattern
  elif [[ ${PLATFORM_UNAME} == "Darwin" ]]; then
    echo "[logbt] setting $(sysctl -n kern.corefile) -> ${settable_core_pattern}"
    sysctl kern.corefile=${settable_core_pattern}
  fi

  local core_pattern=$(get_core_pattern)
  validate_core_pattern ${core_pattern}
  local core_directory=$(dirname ${core_pattern})

  if [[ ! -d ${core_directory} ]]; then
    echo "[logbt] creating directory for core files at '${core_directory}'"
    mkdir -p -m a+w ${core_directory}
  fi

  error_on_existing_cores ${core_directory}

}

function test_logbt() {
  ulimit -c unlimited
  # First we create a program that crashes itself
  # We use bash to avoid needing an external dep on some runtime

  # Due to https://github.com/mapbox/logbt/issues/29 we need to copy the bash
  # exe on OS X to a new location since coredumps are disabled for /bin/bash for
  # reasons I don't understand
  if [[ ${PLATFORM_UNAME} == "Darwin" ]]; then
      # first touch file to create it with writable permissions for this user
      # such that we can cleanup after
      # then copy the system bash there
      cp --no-preserve=all $(which bash) /tmp/tmp-bash
      chmod +x /tmp/tmp-bash
      echo '#!/tmp/tmp-bash' > /tmp/crasher.sh
  else
    # on linux the default bash is okay
      echo '#!/usr/bin/env bash' > /tmp/crasher.sh
  fi
  echo 'kill -SIGSEGV $$' >> /tmp/crasher.sh
  chmod +x /tmp/crasher.sh
  # run it in logbt
  RETURN=0
  ${BASH_SOURCE} -- /tmp/crasher.sh >/tmp/logbt-stdout 2>/tmp/logbt-stderr || RETURN=$?
  local err_message
  if [[ ${RETURN} != 139 ]] || [[ ! $(cat /tmp/logbt-stdout) =~ "Found corefile at" ]]; then
    cat /tmp/logbt-stdout
    cat /tmp/logbt-stderr
    err_message="Expected return code of 139 and a corefile to be generated"
  fi
  if [[ ! $(cat /tmp/logbt-stdout) =~ "Found corefile at" ]]; then
    cat /tmp/logbt-stdout
    cat /tmp/logbt-stderr
    err_message="Expected a corefile to be generated"
  fi
  # cleanup
  rm -f /tmp/logbt-stderr
  rm -f /tmp/logbt-stdout
  rm -f /tmp/crasher.sh
  rm -f /tmp/tmp-bash
  if [[ ${err_message:-} ]]; then
    error ${err_message}
  else
    echo "[logbt] test success (coredumps are working with core pattern: '$(get_core_pattern)')"
  fi
}

function usage() {
  >&2 echo "Usage for logbt:"
  >&2 echo ""
  >&2 echo "Setup logbt (requires root privileges):"
  >&2 echo ""
  >&2 echo "$ sudo logbt --setup"
  >&2 echo ""
  >&2 echo "Test logbt is setup correctly"
  >&2 echo ""
  >&2 echo "$ logbt --test"
  >&2 echo ""
  >&2 echo "Launch a program with logbt:"
  >&2 echo ""
  >&2 echo "$ logbt -- ./program"
  >&2 echo ""
  >&2 echo "Other commands are:"
  >&2 echo ""
  >&2 echo " --current-pattern"
  >&2 echo " --target-pattern"
  >&2 echo " --version"
  exit 1
}

function get_version() {
  echo ${LOGBT_VERSION}
}

if [[ ! ${1:-} ]]; then
  usage
fi

# https://stackoverflow.com/questions/192249/how-do-i-parse-command-line-arguments-in-bash
for i in "$@"
do
case $i in
    --)
    if [[ ! ${2:-} ]]; then
      usage
    fi
    shift
    launch_and_wait "$@"
    ;;
    --setup)
    setup_logbt
    shift
    ;;
    --test)
    test_logbt
    shift
    ;;
    --current-pattern)
    get_core_pattern
    ;;
    --target-pattern)
    get_target_core_pattern
    ;;
    -v | --version)
    get_version
    shift
    ;;
    -h | --help)
    usage
    shift
    ;;
    *)
    usage
    ;;
esac
done