# Copyright 2016 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Initialize gdb for debugging fuchsia code."""

import gdb
import os
import sys


_FUCHSIA_SYS_PATH = "scripts/gdb"
_FUCHSIA_GDB_FILE = _FUCHSIA_SYS_PATH + "/fuchsia/gdb/__init__.py"


def _get_sys_path(fuchsia_gdb_file):
  """Return sys.path entry for gdb support.

  Arguments:
    fuchsia_gdb_file: The absolute path to _FUCHSIA_GDB_FILE.

  Returns:
    Path to add to sys.path.
  """

  # /foo/bar/fuchsia/gdb/__init__.py -> /foo/bar
  return os.path.dirname(os.path.dirname(os.path.dirname(fuchsia_gdb_file)))


def _find_file(file):
  """Look for file in current directory and every parent.

  Returns:
    Absolute path of found file or None if not found.
  """

  cwd = os.getcwd()

  while cwd != "/":
    trial = os.path.join(cwd, file)
    if os.path.exists(trial):
      return trial
    # Protect against unknown failure modes.
    new_cwd = os.path.dirname(cwd)
    if new_cwd == cwd:
      print "Trouble with file system trying to find: %s" % (file)
      sys.exit(1)
    cwd = new_cwd
  return None


def _append_sys_path(path):
  """Append path to sys.path if not already present."""
  # Python2 canonicalizes directories in sys.path, so we do too.
  path = os.path.abspath(path)
  if os.path.exists(path) and \
      path not in sys.path:
    sys.path.append(path)


def _try_bootstrap():
  """Try to find Fuchsia support and load it.

  Most of Fuchsia support comes with the Fuchsia tree in the scripts repo.
  We just need to find it.
  """

  fuchsia_gdb_file = _find_file(_FUCHSIA_GDB_FILE)
  if fuchsia_gdb_file != None:
    _append_sys_path(_get_sys_path(fuchsia_gdb_file))
    # TODO(dje): Catch certain exceptions?
    import fuchsia.gdb
    fuchsia.gdb.initialize()
  else:
    print "Unable to find Fuchsia support. In Fuchsia tree?"
    print "Looking for file: %s" % (_FUCHSIA_GDB_FILE)


# This message is quite helpful for debugging issues with the python support.
print "Hi, this is fuchsia.py. Adding Fuchsia support."

_try_bootstrap()