# Copyright 2021 DeepMind Technologies Limited
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

#.rst:
# FindOrFetch
# ----------------------
#
# Find or fetch a package in order to satisfy target dependencies.
#
#   FindOrFetch([USE_SYSTEM_PACKAGE [ON/OFF]]
#               [PACKAGE_NAME [name]]
#               [LIBRARY_NAME [name]]
#               [GIT_REPO [repo]]
#               [GIT_TAG [tag]]
#               [CUSTOM_CMAKE [path]]
#               [PATCH_COMMAND [cmd] [args]]
#               [TARGETS [targets]]
#               [EXCLUDE_FROM_ALL])
#
# The command has the following parameters:
#
# Arguments:
#  - ``USE_SYSTEM_PACKAGE`` one-value argument on whether to search for the
#    package in the system (ON) or whether to fetch the library using
#    FetchContent from the specified Git repository (OFF). Note that
#    FetchContent variables will override this behaviour.
#  - ``PACKAGE_NAME`` name of the system-package. Ignored if
#    ``USE_SYSTEM_PACKAGE`` is ``OFF``.
#  - ``LIBRARY_NAME`` name of the library. Ignored if
#    ``USE_SYSTEM_PACKAGE`` is ``ON``.
#  - ``GIT_REPO`` git repository to fetch the library from. Ignored if
#    ``USE_SYSTEM_PACKAGE`` is ``ON``.
#  - ``GIT_TAG`` tag reference when fetching the library from the git
#    repository. Ignored if ``USE_SYSTEM_PACKAGE`` is ``ON``.
#  - ``CUSTOM_CMAKE`` path to a custom CMakeLists.txt file to be used when
#    fetching the library from the git repository. Ignored if
#    ``USE_SYSTEM_PACKAGE`` is ``ON``.
#  - ``PATCH_COMMAND`` Specifies a custom command to patch the sources after an
#    update. See https://cmake.org/cmake/help/latest/module/ExternalProject.html#command:externalproject_add
#    for details on the parameter.
#  - ``TARGETS`` list of targets to be satisfied. If any of these targets are
#    not currently defined, this macro will attempt to either find or fetch the
#    package.
#  - ``EXCLUDE_FROM_ALL`` if specified, the targets are not added to the ``all``
#    metatarget.
#
# Note: if ``USE_SYSTEM_PACKAGE`` is ``OFF``, FetchContent will be used to
# retrieve the specified targets. It is possible to specify any variable in
# https://cmake.org/cmake/help/latest/module/FetchContent.html#variables to
# override this macro behaviour.

if(NOT COMMAND FindOrFetch)
  macro(FindOrFetch)
    if(NOT FetchContent)
      include(FetchContent)
    endif()

    # Parse arguments.
    set(options EXCLUDE_FROM_ALL)
    set(one_value_args
        USE_SYSTEM_PACKAGE
        PACKAGE_NAME
        LIBRARY_NAME
        GIT_REPO
        GIT_TAG
        CUSTOM_CMAKE
    )
    set(multi_value_args PATCH_COMMAND TARGETS)
    cmake_parse_arguments(
      _ARGS
      "${options}"
      "${one_value_args}"
      "${multi_value_args}"
      ${ARGN}
    )

    # Check if all targets are found.
    if(NOT _ARGS_TARGETS)
      message(FATAL_ERROR "mujoco::FindOrFetch: TARGETS must be specified.")
    endif()

    set(targets_found TRUE)
    message(CHECK_START
            "mujoco::FindOrFetch: checking for targets in package `${_ARGS_PACKAGE_NAME}`"
    )
    foreach(target ${_ARGS_TARGETS})
      if(NOT TARGET ${target})
        message(CHECK_FAIL "target `${target}` not defined.")
        set(targets_found FALSE)
        break()
      endif()
    endforeach()

    # If targets are not found, use `find_package` or `FetchContent...` to get it.
    if(NOT targets_found)
      if(${_ARGS_USE_SYSTEM_PACKAGE})
        message(CHECK_START
                "mujoco::FindOrFetch: finding `${_ARGS_PACKAGE_NAME}` in system packages..."
        )
        find_package(${_ARGS_PACKAGE_NAME} REQUIRED)
        message(CHECK_PASS "found")
      else()
        message(CHECK_START
                "mujoco::FindOrFetch: Using FetchContent to retrieve `${_ARGS_LIBRARY_NAME}`"
        )
        FetchContent_Declare(
          ${_ARGS_LIBRARY_NAME}
          GIT_REPOSITORY ${_ARGS_GIT_REPO}
          GIT_TAG ${_ARGS_GIT_TAG}
          GIT_SHALLOW FALSE
          PATCH_COMMAND ${_ARGS_PATCH_COMMAND}
          UPDATE_DISCONNECTED TRUE
        )
        if(${_ARGS_EXCLUDE_FROM_ALL})
          FetchContent_GetProperties(${_ARGS_LIBRARY_NAME})
          if(NOT ${${_ARGS_LIBRARY_NAME}_POPULATED})
            FetchContent_Populate(${_ARGS_LIBRARY_NAME})
            if(NOT "${_ARGS_CUSTOM_CMAKE}" STREQUAL "")
              file(COPY
                "${_ARGS_CUSTOM_CMAKE}"
                DESTINATION "${${_ARGS_LIBRARY_NAME}_SOURCE_DIR}"
              )
            endif()
            add_subdirectory(
              ${${_ARGS_LIBRARY_NAME}_SOURCE_DIR} ${${_ARGS_LIBRARY_NAME}_BINARY_DIR}
              EXCLUDE_FROM_ALL
            )
          endif()
        else()
          FetchContent_MakeAvailable(${_ARGS_LIBRARY_NAME})
        endif()
        message(CHECK_PASS "Done")
      endif()
    else()
      message(CHECK_PASS "found")
    endif()
  endmacro()
endif()


#.rst:
# FetchPackage
# ----------------------
#
# Fetches a package from a Git repository in order to satisfy dependencies.
#
#   FetchPackage([PACKAGE_NAME [name]]
#               [GIT_REPO [repo]]
#               [GIT_TAG [tag]]
#               [PATCH_COMMAND [cmd] [args]]
#              )
#
# The command has the following parameters:
#
# Arguments:
#  - ``PACKAGE_NAME`` name of the package.
#  - ``GIT_REPO`` git repository to fetch the library from.
#  - ``GIT_TAG`` tag reference when fetching the library from the git repo.
#  - ``CUSTOM_CMAKE`` path to a custom CMakeLists.txt file to be used when
#    fetching the library from the git repository.
#  - ``PATCH_COMMAND`` Specifies a custom command to patch the sources after an
#    update. See https://cmake.org/cmake/help/latest/module/ExternalProject.html#command:externalproject_add
#    for details on the parameter.
#  - ``TARGETS`` (optional) list of targets to be satisfied. If any of these
#    targets are not currently defined, this macro will attempt to fetch the
#    package. If not specified, the package name will be used as the target.
#
# Note: This is a wrapper around FindOrFetch that sets EXCLUDE_FROM_ALL and
# USE_SYSTEM_PACKAGE to OFF.
if(NOT COMMAND FetchPackage)
  function(FetchPackage)
    cmake_parse_arguments(
      _ARGS
      "EXCLUDE_FROM_ALL"
      "PACKAGE_NAME;GIT_REPO;GIT_TAG;CUSTOM_CMAKE"
      "PATCH_COMMAND;TARGETS"
      ${ARGN}
    )
    if(NOT _ARGS_TARGETS)
      set(_ARGS_TARGETS ${_ARGS_PACKAGE_NAME})
    endif()

    FindOrFetch(
      PACKAGE_NAME ${_ARGS_PACKAGE_NAME}
      LIBRARY_NAME ${_ARGS_PACKAGE_NAME}
      GIT_REPO ${_ARGS_GIT_REPO}
      GIT_TAG ${_ARGS_GIT_TAG}
      CUSTOM_CMAKE ${_ARGS_CUSTOM_CMAKE}
      PATCH_COMMAND ${_ARGS_PATCH_COMMAND}
      TARGETS ${_ARGS_TARGETS}
      USE_SYSTEM_PACKAGE OFF
      EXCLUDE_FROM_ALL
    )
  endfunction()
endif()