# Copyright 2019 Google LLC. All Rights Reserved.
#
# 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.

# Creates an alias for SOURCE, called DESTINATION.
#
# On platforms that support them, this rule will effectively create a symlink.
#
# SOURCE may be relative to CMAKE_CURRENT_SOURCE_DIR, or absolute.
# DESTINATION may relative to CMAKE_CURRENT_BINARY_DIR, or absolute.
#
# Adapted from https://github.com/google/binexport/blob/master/util.cmake
function(create_directory_symlink SOURCE DESTINATION)
  get_filename_component(_destination_parent "${DESTINATION}" DIRECTORY)
  file(MAKE_DIRECTORY "${_destination_parent}")

  if (WIN32)
    file(TO_NATIVE_PATH "${SOURCE}" _native_source)
    file(TO_NATIVE_PATH "${DESTINATION}" _native_destination)
    execute_process(COMMAND $ENV{ComSpec} /c
        mklink /J "${_native_destination}" "${_native_source}" ERROR_QUIET)
  else()
    execute_process(COMMAND ${CMAKE_COMMAND} -E
      create_symlink "${SOURCE}" "${DESTINATION}")
  endif()
endfunction()

# Helper function that behaves just like protobuf_generate_cpp(), except that
# it strips import paths. This is necessary, because CMake's protobuf rules
# don't work well with imports across different directories.
function(sapi_protobuf_generate_cpp SRCS HDRS PROTO)
  file(READ ${PROTO} _pb_orig)
  string(REGEX REPLACE "import \".*/([^/]+\\.proto)\""
                       "import \"\\1\"" _pb_repl "${_pb_orig}")
  file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/${PROTO} "${_pb_repl}")
  protobuf_generate_cpp(_srcs _hdrs ${CMAKE_CURRENT_BINARY_DIR}/${PROTO})
  set(${SRCS} ${_srcs} PARENT_SCOPE)
  set(${HDRS} ${_hdrs} PARENT_SCOPE)
endfunction()

# 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 ${_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}/${_sapi_bin}_force_cxx_linkage.cc")
  file(TOUCH "${_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
            "${PROJECT_SOURCE_DIR}/sandboxed_api/tools/generator2/sapi_generator.py"
            "--sapi_name=${_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(TOUCH "${_sapi_force_cxx_linkage}")
    list(APPEND _sapi_SOURCES "${_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()