# Adapted with modifications from tensorflow/third_party/py/
"""Repository rule for Python autoconfiguration.

`python_configure` depends on the following environment variables:

  * `PYTHON_BIN_PATH`: location of python binary.
  * `PYTHON_LIB_PATH`: Location of python libraries.
"""

_BAZEL_SH = "BAZEL_SH"
_PYTHON_BIN_PATH = "PYTHON_BIN_PATH"
_PYTHON_LIB_PATH = "PYTHON_LIB_PATH"
_PYTHON_CONFIG_REPO = "PYTHON_CONFIG_REPO"


def _tpl(repository_ctx, tpl, substitutions={}, out=None):
    if not out:
        out = tpl
    repository_ctx.template(out, Label("//third_party/py:%s.tpl" % tpl),
                            substitutions)


def _fail(msg):
    """Output failure message when auto configuration fails."""
    red = "\033[0;31m"
    no_color = "\033[0m"
    fail("%sPython Configuration Error:%s %s\n" % (red, no_color, msg))


def _is_windows(repository_ctx):
    """Returns true if the host operating system is windows."""
    os_name = repository_ctx.os.name.lower()
    return os_name.find("windows") != -1


def _execute(repository_ctx,
             cmdline,
             error_msg=None,
             error_details=None,
             empty_stdout_fine=False):
    """Executes an arbitrary shell command.

    Args:
        repository_ctx: the repository_ctx object
        cmdline: list of strings, the command to execute
        error_msg: string, a summary of the error if the command fails
        error_details: string, details about the error or steps to fix it
        empty_stdout_fine: bool, if True, an empty stdout result is fine, otherwise
        it's an error
    Return:
        the result of repository_ctx.execute(cmdline)
  """
    result = repository_ctx.execute(cmdline)
    if result.stderr or not (empty_stdout_fine or result.stdout):
        _fail("\n".join([
            error_msg.strip() if error_msg else "Repository command failed",
            result.stderr.strip(), error_details if error_details else ""
        ]))
    else:
        return result


def _read_dir(repository_ctx, src_dir):
    """Returns a string with all files in a directory.

  Finds all files inside a directory, traversing subfolders and following
  symlinks. The returned string contains the full path of all files
  separated by line breaks.
  """
    if _is_windows(repository_ctx):
        src_dir = src_dir.replace("/", "\\")
        find_result = _execute(
            repository_ctx,
            ["cmd.exe", "/c", "dir", src_dir, "/b", "/s", "/a-d"],
            empty_stdout_fine=True)
        # src_files will be used in genrule.outs where the paths must
        # use forward slashes.
        return find_result.stdout.replace("\\", "/")
    else:
        find_result = _execute(
            repository_ctx, ["find", src_dir, "-follow", "-type", "f"],
            empty_stdout_fine=True)
        return find_result.stdout


def _genrule(src_dir, genrule_name, command, outs):
    """Returns a string with a genrule.

  Genrule executes the given command and produces the given outputs.
  """
    return ('genrule(\n' + '    name = "' + genrule_name + '",\n' +
            '    outs = [\n' + outs + '\n    ],\n' + '    cmd = """\n' +
            command + '\n   """,\n' + ')\n')


def _normalize_path(path):
    """Returns a path with '/' and remove the trailing slash."""
    path = path.replace("\\", "/")
    if path[-1] == "/":
        path = path[:-1]
    return path


def _symlink_genrule_for_dir(repository_ctx,
                             src_dir,
                             dest_dir,
                             genrule_name,
                             src_files=[],
                             dest_files=[]):
    """Returns a genrule to symlink(or copy if on Windows) a set of files.

  If src_dir is passed, files will be read from the given directory; otherwise
  we assume files are in src_files and dest_files
  """
    if src_dir != None:
        src_dir = _normalize_path(src_dir)
        dest_dir = _normalize_path(dest_dir)
        files = '\n'.join(
            sorted(_read_dir(repository_ctx, src_dir).splitlines()))
        # Create a list with the src_dir stripped to use for outputs.
        dest_files = files.replace(src_dir, '').splitlines()
        src_files = files.splitlines()
    command = []
    outs = []
    for i in range(len(dest_files)):
        if dest_files[i] != "":
            # If we have only one file to link we do not want to use the dest_dir, as
            # $(@D) will include the full path to the file.
            dest = '$(@D)/' + dest_dir + dest_files[i] if len(
                dest_files) != 1 else '$(@D)/' + dest_files[i]
            # On Windows, symlink is not supported, so we just copy all the files.
            cmd = 'cp -f' if _is_windows(repository_ctx) else 'ln -s'
            command.append(cmd + ' "%s" "%s"' % (src_files[i], dest))
            outs.append('        "' + dest_dir + dest_files[i] + '",')
    return _genrule(src_dir, genrule_name, " && ".join(command),
                    "\n".join(outs))


def _get_python_bin(repository_ctx):
    """Gets the python bin path."""
    python_bin = repository_ctx.os.environ.get(_PYTHON_BIN_PATH, 'python')
    if not repository_ctx.path(python_bin).exists:
        # It's a command, use 'which' to find its path.
        python_bin_path = repository_ctx.which(python_bin)
    else:
        # It's a path, use it as it is.
        python_bin_path = python_bin
    if python_bin_path != None:
        return str(python_bin_path)
    _fail("Cannot find python in PATH, please make sure " +
          "python is installed and add its directory in PATH, or --define " +
          "%s='/something/else'.\nPATH=%s" %
          (_PYTHON_BIN_PATH, repository_ctx.os.environ.get("PATH", "")))


def _get_bash_bin(repository_ctx):
    """Gets the bash bin path."""
    bash_bin = repository_ctx.os.environ.get(_BAZEL_SH)
    if bash_bin != None:
        return bash_bin
    else:
        bash_bin_path = repository_ctx.which("bash")
        if bash_bin_path != None:
            return str(bash_bin_path)
        else:
            _fail(
                "Cannot find bash in PATH, please make sure " +
                "bash is installed and add its directory in PATH, or --define "
                + "%s='/path/to/bash'.\nPATH=%s" %
                (_BAZEL_SH, repository_ctx.os.environ.get("PATH", "")))


def _get_python_lib(repository_ctx, python_bin):
    """Gets the python lib path."""
    python_lib = repository_ctx.os.environ.get(_PYTHON_LIB_PATH)
    if python_lib != None:
        return python_lib
    print_lib = (
        "<<END\n" + "from __future__ import print_function\n" +
        "import site\n" + "import os\n" + "\n" + "try:\n" +
        "  input = raw_input\n" + "except NameError:\n" + "  pass\n" + "\n" +
        "python_paths = []\n" + "if os.getenv('PYTHONPATH') is not None:\n" +
        "  python_paths = os.getenv('PYTHONPATH').split(':')\n" + "try:\n" +
        "  library_paths = site.getsitepackages()\n" +
        "except AttributeError:\n" +
        " from distutils.sysconfig import get_python_lib\n" +
        " library_paths = [get_python_lib()]\n" +
        "all_paths = set(python_paths + library_paths)\n" + "paths = []\n" +
        "for path in all_paths:\n" + "  if os.path.isdir(path):\n" +
        "    paths.append(path)\n" + "if len(paths) >=1:\n" +
        "  print(paths[0])\n" + "END")
    cmd = '%s - %s' % (python_bin, print_lib)
    result = repository_ctx.execute([_get_bash_bin(repository_ctx), "-c", cmd])
    return result.stdout.strip('\n')


def _check_python_lib(repository_ctx, python_lib):
    """Checks the python lib path."""
    cmd = 'test -d "%s" -a -x "%s"' % (python_lib, python_lib)
    result = repository_ctx.execute([_get_bash_bin(repository_ctx), "-c", cmd])
    if result.return_code == 1:
        _fail("Invalid python library path: %s" % python_lib)


def _check_python_bin(repository_ctx, python_bin):
    """Checks the python bin path."""
    cmd = '[[ -x "%s" ]] && [[ ! -d "%s" ]]' % (python_bin, python_bin)
    result = repository_ctx.execute([_get_bash_bin(repository_ctx), "-c", cmd])
    if result.return_code == 1:
        _fail("--define %s='%s' is not executable. Is it the python binary?" %
              (_PYTHON_BIN_PATH, python_bin))


def _get_python_include(repository_ctx, python_bin):
    """Gets the python include path."""
    result = _execute(
        repository_ctx, [
            python_bin, "-c", 'from __future__ import print_function;' +
            'from distutils import sysconfig;' +
            'print(sysconfig.get_python_inc())'
        ],
        error_msg="Problem getting python include path.",
        error_details=(
            "Is the Python binary path set up right? " + "(See ./configure or "
            + _PYTHON_BIN_PATH + ".) " + "Is distutils installed?"))
    return result.stdout.splitlines()[0]


def _get_python_import_lib_name(repository_ctx, python_bin):
    """Get Python import library name (pythonXY.lib) on Windows."""
    result = _execute(
        repository_ctx, [
            python_bin, "-c",
            'import sys;' + 'print("python" + str(sys.version_info[0]) + ' +
            '      str(sys.version_info[1]) + ".lib")'
        ],
        error_msg="Problem getting python import library.",
        error_details=("Is the Python binary path set up right? " +
                       "(See ./configure or " + _PYTHON_BIN_PATH + ".) "))
    return result.stdout.splitlines()[0]


def _create_local_python_repository(repository_ctx):
    """Creates the repository containing files set up to build with Python."""
    python_bin = _get_python_bin(repository_ctx)
    _check_python_bin(repository_ctx, python_bin)
    python_lib = _get_python_lib(repository_ctx, python_bin)
    _check_python_lib(repository_ctx, python_lib)
    python_include = _get_python_include(repository_ctx, python_bin)
    python_include_rule = _symlink_genrule_for_dir(
        repository_ctx, python_include, 'python_include', 'python_include')
    python_import_lib_genrule = ""
    # To build Python C/C++ extension on Windows, we need to link to python import library pythonXY.lib
    # See https://docs.python.org/3/extending/windows.html
    if _is_windows(repository_ctx):
        python_include = _normalize_path(python_include)
        python_import_lib_name = _get_python_import_lib_name(
            repository_ctx, python_bin)
        python_import_lib_src = python_include.rsplit(
            '/', 1)[0] + "/libs/" + python_import_lib_name
        python_import_lib_genrule = _symlink_genrule_for_dir(
            repository_ctx, None, '', 'python_import_lib',
            [python_import_lib_src], [python_import_lib_name])
    _tpl(
        repository_ctx, "BUILD", {
            "%{PYTHON_INCLUDE_GENRULE}": python_include_rule,
            "%{PYTHON_IMPORT_LIB_GENRULE}": python_import_lib_genrule,
        })


def _create_remote_python_repository(repository_ctx, remote_config_repo):
    """Creates pointers to a remotely configured repo set up to build with Python.
  """
    _tpl(repository_ctx, "remote.BUILD", {
        "%{REMOTE_PYTHON_REPO}": remote_config_repo,
    }, "BUILD")


def _python_autoconf_impl(repository_ctx):
    """Implementation of the python_autoconf repository rule."""
    if _PYTHON_CONFIG_REPO in repository_ctx.os.environ:
        _create_remote_python_repository(
            repository_ctx, repository_ctx.os.environ[_PYTHON_CONFIG_REPO])
    else:
        _create_local_python_repository(repository_ctx)


python_configure = repository_rule(
    implementation=_python_autoconf_impl,
    environ=[
        _BAZEL_SH,
        _PYTHON_BIN_PATH,
        _PYTHON_LIB_PATH,
        _PYTHON_CONFIG_REPO,
    ],
)
"""Detects and configures the local Python.

Add the following to your WORKSPACE FILE:

```python
python_configure(name = "local_config_python")
```

Args:
  name: A unique name for this workspace rule.
"""