#
#  Copyright (C) 2016 Codethink Limited
#  Copyright (C) 2018 Bloomberg Finance LP
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU Lesser General Public
#  License as published by the Free Software Foundation; either
#  version 2 of the License, or (at your option) any later version.
#
#  This library is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
#  Lesser General Public License for more details.
#
#  You should have received a copy of the GNU Lesser General Public
#  License along with this library. If not, see <http://www.gnu.org/licenses/>.
#
#  Authors:
#        Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>
"""
BuildElement - Abstract class for build elements
================================================
The BuildElement class is a convenience element one can derive from for
implementing the most common case of element.

.. _core_buildelement_builtins:

Built-in functionality
----------------------

The BuildElement base class provides built in functionality that could be
overridden by the individual plugins.

This section will give a brief summary of how some of the common features work,
some of them or the variables they use will be further detailed in the following
sections.

The `strip-binaries` variable
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The `strip-binaries` variable is by default **empty**. You need to use the
appropiate commands depending of the system you are building.
If you are targetting Linux, ones known to work are the ones used by the
`freedesktop-sdk <https://freedesktop-sdk.io/>`_, you can take a look to them in their
`project.conf <https://gitlab.com/freedesktop-sdk/freedesktop-sdk/blob/freedesktop-sdk-18.08.21/project.conf#L74>`_

Location for running commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The ``command-subdir`` variable sets where the build commands will be executed,
if the directory does not exist it will be created, it is defined relative to
the buildroot.

Location for configuring the project
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The ``conf-root`` is defined by default as ``.`` and is the location that
specific build element can use to look for build configuration files. This is
used by elements such as autotools, cmake, distutils, meson, pip and qmake.

The configuration commands are run in ``command-subdir`` and by default
``conf-root`` is ``.`` so if ``conf-root`` is not set the configuration files
in ``command-subdir`` will be used.

By setting ``conf-root`` to ``"%{build-root}/Source/conf_location"`` and your
source elements ``directory`` variable to ``Source`` then the configuration
files in the directory ``conf_location`` with in your Source will be used.
The current working directory when your configuration command is run will still
be wherever you set your ``command-subdir`` to be, regardless of where the
configure scripts are set with ``conf-root``.

.. note::

   The ``conf-root`` variable is available since :ref:`format version 17 <project_format_version>`

Install Location
~~~~~~~~~~~~~~~~

You should not change the ``install-root`` variable as it is a special
writeable location in the sandbox but it is useful when writing custom
install instructions as it may need to be supplied as the ``DESTDIR``, please
see the :mod:`cmake <elements.cmake>` build element for example.

Abstract method implementations
-------------------------------

Element.configure_sandbox()
~~~~~~~~~~~~~~~~~~~~~~~~~~~
In :func:`Element.configure_sandbox() <buildstream.element.Element.configure_sandbox>`,
the BuildElement will ensure that the sandbox locations described by the ``%{build-root}``
and ``%{install-root}`` variables are marked and will be mounted read-write for the
:func:`assemble phase<buildstream.element.Element.configure_sandbox>`.

The working directory for the sandbox will be configured to be the ``%{build-root}``,
unless the ``%{command-subdir}`` variable is specified for the element in question,
in which case the working directory will be configured as ``%{build-root}/%{command-subdir}``.


Element.stage()
~~~~~~~~~~~~~~~
In :func:`Element.stage() <buildstream.element.Element.stage>`, the BuildElement
will do the following operations:

* Stage all the dependencies in the :func:`Scope.BUILD <buildstream.element.Scope.BUILD>`
  scope into the sandbox root.

* Run the integration commands for all staged dependencies using
  :func:`Element.integrate() <buildstream.element.Element.integrate>`

* Stage any Source on the given element to the ``%{build-root}`` location
  inside the sandbox, using
  :func:`Element.stage_sources() <buildstream.element.Element.integrate>`


Element.prepare()
~~~~~~~~~~~~~~~~~
In :func:`Element.prepare() <buildstream.element.Element.prepare>`,
the BuildElement will run ``configure-commands``, which are used to
run one-off preparations that should not be repeated for a single
build directory.


Element.assemble()
~~~~~~~~~~~~~~~~~~
In :func:`Element.assemble() <buildstream.element.Element.assemble>`, the
BuildElement will proceed to run sandboxed commands which are expected to be
found in the element configuration.

Commands are run in the following order:

* ``build-commands``: Commands to build the element
* ``install-commands``: Commands to install the results into ``%{install-root}``
* ``strip-commands``: Commands to strip debugging symbols installed binaries

The result of the build is expected to end up in ``%{install-root}``, and
as such; Element.assemble() method will return the ``%{install-root}`` for
artifact collection purposes.
"""

import os
from . import Element, Scope
from . import SandboxFlags


# This list is preserved because of an unfortunate situation, we
# need to remove these older commands which were secret and never
# documented, but without breaking the cache keys.
_legacy_command_steps = ['bootstrap-commands',
                         'configure-commands',
                         'build-commands',
                         'test-commands',
                         'install-commands',
                         'strip-commands']

_command_steps = ['configure-commands',
                  'build-commands',
                  'install-commands',
                  'strip-commands']


class BuildElement(Element):

    #############################################################
    #             Abstract Method Implementations               #
    #############################################################
    def configure(self, node):

        self.__commands = {}  # pylint: disable=attribute-defined-outside-init

        # FIXME: Currently this forcefully validates configurations
        #        for all BuildElement subclasses so they are unable to
        #        extend the configuration
        self.node_validate(node, _command_steps)

        for command_name in _legacy_command_steps:
            if command_name in _command_steps:
                self.__commands[command_name] = self.__get_commands(node, command_name)
                self.keyorder.append(command_name)
            else:
                self.__commands[command_name] = []

    def preflight(self):
        pass

    def get_unique_key(self):
        dictionary = {}

        for command_name, command_list in self.__commands.items():
            dictionary[command_name] = command_list

        # Specifying notparallel for a given element effects the
        # cache key, while having the side effect of setting max-jobs to 1,
        # which is normally automatically resolved and does not affect
        # the cache key.
        if self.get_variable('notparallel'):
            dictionary['notparallel'] = True

        return dictionary

    def configure_sandbox(self, sandbox):
        build_root = self.get_variable('build-root')
        install_root = self.get_variable('install-root')

        # Tell the sandbox to mount the build root and install root
        sandbox.mark_directory(build_root)
        sandbox.mark_directory(install_root)

        # Allow running all commands in a specified subdirectory
        command_subdir = self.get_variable('command-subdir')
        if command_subdir:
            command_dir = os.path.join(build_root, command_subdir)
        else:
            command_dir = build_root
        sandbox.set_work_directory(command_dir)

        # Tell sandbox which directory is preserved in the finished artifact
        sandbox.set_output_directory(install_root)

        # Setup environment
        sandbox.set_environment(self.get_environment())

    def stage(self, sandbox):

        # Stage deps in the sandbox root
        with self.timed_activity("Staging dependencies", silent_nested=True):
            self.stage_dependency_artifacts(sandbox, Scope.BUILD)

        # Run any integration commands provided by the dependencies
        # once they are all staged and ready
        with sandbox.batch(SandboxFlags.NONE, label="Integrating sandbox"):
            for dep in self.dependencies(Scope.BUILD):
                dep.integrate(sandbox)

        # Stage sources in the build root
        self.stage_sources(sandbox, self.get_variable('build-root'))

    def assemble(self, sandbox):
        # Run commands
        for command_name in _command_steps:
            commands = self.__commands[command_name]
            if not commands or command_name == 'configure-commands':
                continue

            with sandbox.batch(SandboxFlags.ROOT_READ_ONLY, label="Running {}".format(command_name)):
                for cmd in commands:
                    self.__run_command(sandbox, cmd, command_name)

        # %{install-root}/%{build-root} should normally not be written
        # to - if an element later attempts to stage to a location
        # that is not empty, we abort the build - in this case this
        # will almost certainly happen.
        staged_build = os.path.join(self.get_variable('install-root'),
                                    self.get_variable('build-root'))

        if os.path.isdir(staged_build) and os.listdir(staged_build):
            self.warn("Writing to %{install-root}/%{build-root}.",
                      detail="Writing to this directory will almost " +
                      "certainly cause an error, since later elements " +
                      "will not be allowed to stage to %{build-root}.")

        # Return the payload, this is configurable but is generally
        # always the /buildstream-install directory
        return self.get_variable('install-root')

    def prepare(self, sandbox):
        commands = self.__commands['configure-commands']
        if commands:
            with sandbox.batch(SandboxFlags.ROOT_READ_ONLY, label="Running configure-commands"):
                for cmd in commands:
                    self.__run_command(sandbox, cmd, 'configure-commands')

    def generate_script(self):
        script = ""
        for command_name in _command_steps:
            commands = self.__commands[command_name]

            for cmd in commands:
                script += "(set -ex; {}\n) || exit 1\n".format(cmd)

        return script

    #############################################################
    #                   Private Local Methods                   #
    #############################################################
    def __get_commands(self, node, name):
        list_node = self.node_get_member(node, list, name, [])
        commands = []

        for i in range(len(list_node)):
            command = self.node_subst_list_element(node, name, [i])
            commands.append(command)

        return commands

    def __run_command(self, sandbox, cmd, cmd_name):
        # Note the -e switch to 'sh' means to exit with an error
        # if any untested command fails.
        #
        sandbox.run(['sh', '-c', '-e', cmd + '\n'],
                    SandboxFlags.ROOT_READ_ONLY,
                    label=cmd)