# Copyright 2019 Google LLC
#
# 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
#
#     http://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.

# Embeds arbitrary binary data into a static library.
#
# NAME specifies the name for this target.
# NAMESPACE is the C++ namespace the generated code is placed in. Can be empty.
# SOURCES is a list of files that should be embedded. If a source names a
#   target the target binary is embedded instead.
macro(sapi_cc_embed_data)
  cmake_parse_arguments(_sapi_embed "" "NAME;NAMESPACE" "SOURCES" ${ARGN})
  foreach(src IN LISTS _sapi_embed_SOURCES)
    if(TARGET "${src}")
      list(APPEND _sapi_embed_in "${CMAKE_CURRENT_BINARY_DIR}/${src}")
    else()
      list(APPEND _sapi_embed_in "${src}")
    endif()
  endforeach()
  file(RELATIVE_PATH _sapi_embed_pkg
                     "${PROJECT_BINARY_DIR}"
                     "${CMAKE_CURRENT_BINARY_DIR}")
  add_custom_command(
    OUTPUT "${_sapi_embed_NAME}.h"
           "${_sapi_embed_NAME}.cc"
    WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
    COMMAND filewrapper "${_sapi_embed_pkg}"
                        "${_sapi_embed_NAME}"
                        "${_sapi_embed_NAMESPACE}"
                        "${CMAKE_CURRENT_BINARY_DIR}/${_sapi_embed_NAME}.h"
                        "${CMAKE_CURRENT_BINARY_DIR}/${_sapi_embed_NAME}.cc"
                        ${_sapi_embed_in}
    DEPENDS ${_sapi_embed_SOURCES}
    VERBATIM
  )
  add_library("${_sapi_embed_NAME}" STATIC
    "${_sapi_embed_NAME}.h"
    "${_sapi_embed_NAME}.cc"
  )
  target_link_libraries("${_sapi_embed_NAME}" PRIVATE
    sapi::base
    absl::core_headers
  )
endmacro()

# Adds a library target implementing a sandboxed API for another library.
# The first argument is the target name, similar to the native add_library().
# This function implements the same functionality as the Bazel version in
# sandboxed_api/bazel/sapi.bzl.
#
# SOURCES Any additional sources to include with the Sandboxed API library.
#   Typically not necessary, unless the sandbox definition should be in a .cc
#   file instead of the customary "sandbox.h" header. Bazel also has a "hdrs"
#   attribute, but CMake does not distinguish headers from sources.
# FUNCTIONS A list of functions that to use in from host code. Leaving this
#   list empty will export and wrap all functions found in the library.
# NOEMBED Whether the SAPI library should be embedded inside host code, so the
#   SAPI Sandbox can be initialized with the
#   ::sapi::Sandbox::Sandbox(FileToc*) constructor.
# LIBRARY The library target to sandbox and expose to the host code (required).
# LIBRARY_NAME The name of the class which will proxy the library functions
#   from the functions list (required). You will call functions from the
#   sandboxed library via instances of this class.
# INPUTS List of source files which the SAPI interface generator should scan
#   for function declarations. Library header files are always scanned, so
#   this can usually be empty/omitted.
# NAMESPACE C++ namespace identifier to place API class defined by
#   LIBRARY_NAME into.
# HEADER If set, does not generate an interface header, but uses the one
#   specified.
function(add_sapi_library)
  set(_sapi_opts NOEMBED)
  set(_sapi_one_value HEADER LIBRARY LIBRARY_NAME NAMESPACE)
  set(_sapi_multi_value SOURCES FUNCTIONS INPUTS)
  cmake_parse_arguments(_sapi
                        "${_sapi_opts}"
                        "${_sapi_one_value}"
                        "${_sapi_multi_value}"
                        ${ARGN})
  set(_sapi_NAME "${ARGV0}")

  set(_sapi_gen_header "${_sapi_NAME}.sapi.h")
  foreach(func IN LISTS _sapi_FUNCTIONS)
    list(APPEND _sapi_exported_funcs "-Wl,--export-dynamic-symbol,${func}")
  endforeach()
  if(NOT _sapi_exported_funcs)
    set(_sapi_exported_funcs -Wl,--whole-archive
                             -Wl,--allow-multiple-definition)
  endif()

  # The sandboxed binary
  set(_sapi_bin "${_sapi_NAME}.bin")
  set(_sapi_force_cxx_linkage
    "${CMAKE_CURRENT_BINARY_DIR}/${_sapi_bin}_force_cxx_linkage.cc")
  file(WRITE "${_sapi_force_cxx_linkage}" "")
  add_executable("${_sapi_bin}" "${_sapi_force_cxx_linkage}")
  # TODO(cblichmann): Use target_link_options on CMake >= 3.13
  target_link_libraries("${_sapi_bin}" PRIVATE
    -fuse-ld=gold
    "${_sapi_LIBRARY}"
    sapi::client
    ${CMAKE_DL_LIBS}
    -Wl,-E
    ${_sapi_exported_funcs}
  )

  if(NOT _sapi_NOEMBED)
    set(_sapi_embed "${_sapi_NAME}_embed")
    sapi_cc_embed_data(NAME "${_sapi_embed}"
      NAMESPACE "${_sapi_NAMESPACE}"
      SOURCES "${_sapi_bin}"
    )
  endif()

  # Interface
  list_join(_sapi_FUNCTIONS "," _sapi_funcs)
  foreach(src IN LISTS _sapi_INPUTS)
    get_filename_component(src "${src}" ABSOLUTE)
    list(APPEND _sapi_full_inputs "${src}")
  endforeach()
  list_join(_sapi_full_inputs "," _sapi_full_inputs)
  if(NOT _sapi_NOEMBED)
    set(_sapi_embed_dir "${CMAKE_CURRENT_BINARY_DIR}")
    set(_sapi_embed_name "${_sapi_NAME}")
  endif()
  add_custom_command(
    OUTPUT "${_sapi_gen_header}"
    COMMAND "${Python3_EXECUTABLE}" -B
            "${SAPI_SOURCE_DIR}/sandboxed_api/tools/generator2/sapi_generator.py"
            "--sapi_name=${_sapi_LIBRARY_NAME}"
            "--sapi_out=${_sapi_gen_header}"
            "--sapi_embed_dir=${_sapi_embed_dir}"
            "--sapi_embed_name=${_sapi_embed_name}"
            "--sapi_functions=${_sapi_funcs}"
            "--sapi_ns=${_sapi_NAMESPACE}"
            # TODO(cblichmann): Implement sapi_isystem
            "--sapi_in=${_sapi_full_inputs}"
    COMMENT "Generating interface"
  )

  # Library with the interface
  if(NOT _sapi_SOURCES)
    set(_sapi_force_cxx_linkage
      "${CMAKE_CURRENT_BINARY_DIR}/${_sapi_NAME}_force_cxx_linkage.cc")
    file(WRITE "${_sapi_force_cxx_linkage}" "")
    list(APPEND _sapi_SOURCES "${_sapi_force_cxx_linkage}")
  endif()
  add_library("${_sapi_NAME}" STATIC
    "${_sapi_gen_header}"
    ${_sapi_SOURCES}
  )
  target_link_libraries("${_sapi_NAME}" PRIVATE
    sapi::sapi
    sapi::vars
  )
  if(NOT _sapi_NOEMBED)
    target_link_libraries("${_sapi_NAME}" PRIVATE
      "${_sapi_embed}"
    )
  endif()
endfunction()